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Jonathan
04-09-2010, 12:14 AM
I wasn't sure if I should put this in the mill or router cattagory, so I've been ambitious and put it in mill since I'll be using it for metals.

Progress so far...
Base - check
X-rails - check but need rotating I think
Z-axis - got the bits
Y-axis - in progress

Today the 900mm/600mm supported 20mm linear rails and bearings arrived from Hong Kong. Barely adequate packaging caused the bearing blacks to be skuffed, negligible really. Seller despatch very slow but DHL very fast.

Also the 20mm aluminium plate for the X/Y axis arrived. It's certainly heavy stuff!

I went to a small local metals supplier and picked up a meter of 80x3mm aluminium box section for the Y rails to mount on, along with 1m of 3"x1"x0.25" alu angle since it was cheap and looked handy for mounting stepper motors and stuff. Also picked up (barely) a piece of 4"x2" steel channel for the gantry sides. Two meters far 10 and it's heavy stuff :)


I'll post some more pictures soon. Here a couple of the base and X/Y/Z axis' I made which will not be used for obvious reasons...

Drawing....disregard the plywood gantry sides as above.
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Frame without top 18mm MDF sheet. Screws are M20x2.5
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Didn't want to be spinning those 2m long screws, so antibacklash nut placed between two tapered roller bearings. Those pine side bits are temporary until I make aluminium ones.
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Er, not much here....am I right in thinking I should rotate the X rails by 90? At the moment the bottom one possibly doesn't really do much?
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Old Z-axis ... ditched that plywood idea! Do note the alternative to a nut i'm using for the drive on the screw though - bearing. More on that later.
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Mount for stepper on Z-axis (will still use this) and screw. Note thrust bearing etc...
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Jonathan
05-09-2010, 08:22 PM
Been busy making router today and Friday...some photos of progress:

Gantry...layout of the parts just to check it looked ok:
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Closeup of Y/Z axis'
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My milling machine...
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routercnc
05-09-2010, 10:20 PM
Some good progress there, keep it up . . .

Jonathan
05-09-2010, 11:49 PM
Some good progress there, keep it up . . .

Thanks :) I'm at home 24/7 atm (and in the workshop 10/7) so it shouldn't be long!

I'm using the PM752 drivers from Zapp at 70V with their 3N.m motors. Two motors on the X axis. 1Nm motor for 4th axis, but with same driver.

http://www.slidesandballscrews.com/pm752-microstepping-driver-p-312.html?cPath=44_97

ecat
06-09-2010, 12:58 AM
Looking very nice, I can't wait to see how the 2x X motors work out.

Jonathan
06-09-2010, 12:24 PM
Just got some M16 threaded rod for the Y-axis, thought I'd give a quick demo of the drive 'nut' as it's a little different...


http://www.youtube.com/watch?v=m6k8Jz_-WCk

I know I should probably use ballscrews, but I reckon using this method is almost as good - rolling friction, low backlash... I measured the backlash on the plywood Z-axis I made using this method and it was <0.005mm which I think is pretty good considering the cost!

I guess it'd be better to use trapezoidal and put an insert in the bearing to fit the thread better - I'll leave that for a later date though.

Wobblybootie
06-09-2010, 12:38 PM
Now that got my attention ... have you detailed it elsewhere?

irving2008
06-09-2010, 12:41 PM
What have you done there? Can you give some more detail


edit: *** must type quicker ***

Jonathan
06-09-2010, 12:44 PM
Now that got my attention ... have you detailed it elsewhere?

Haha, thought it might!

I've not detailed it elsewhere, shall I start a new 'thread' about this?

Jonathan
06-09-2010, 12:46 PM
What have you done there? Can you give some more detail

Er, not much more to say really? Standard thin section bearing with bore bigger than the thread (20mm here, but more would be better to get less axial load on the bearing) placed on the thread at an angle. I'll use a strong spring to pull the bearing against the thread so that it rides over any imperfections. That's what the tabs are for on the mount, to mount the spring.

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I'm toying with the idea of pressing a brass insert into the bearing lathed to better fit the 60 thread profile. It's tricky to work out the exact dimensions though...

routercnc
06-09-2010, 01:40 PM
Hi Jonathan,

Interesting idea, but it's got me a bit puzzled. If the thread rotates, and the bearing rotates with it, how does it progress along the thread? For a nut in a thread to progress, one part has to rotate whilst the other stays still. Yet in the video the bearing inner and the thread are both rotating. Is it perhaps vibrating it's way along? If so I'm not sure this will give reliable position control.

The only way I can see this working is if you removed the inner race (somehow) to create a pseudo ballnut. Or maybe I'm missing something here so please enlighten me!

Jonathan
06-09-2010, 01:48 PM
]
Interesting idea, but it's got me a bit puzzled. If the thread rotates, and the bearing rotates with it, how does it progress along the thread?

Er...it just does!
The bearing is rolling on the thread properly, not vibrating. It's difficult to explain and visualise. Try just getting a random bearing and screw and fiddle with it, you'll soon see how it works!
If you imagine the inner ring of the bearing was stationary then clearly it would still work...just like a normal nut. The inner ring rotating makes no difference to this, except of course giving rolling friction.

Sorry I can't really explain it any better!

One slight issue I can see with this is the bearing applies torque to the screw, trying to bend it. This could be solved with having two bearings angled opposite to each other but I think M16 is strong enough for this not to be an issue.

I'm in the workshop at the moment..lots of tapping, joy!

Wobblybootie
06-09-2010, 01:54 PM
Ummm like this???

routercnc
06-09-2010, 01:56 PM
Mulled it over a bit more and managing to visualise this now. Yes, it does work. Nice idea, and worth a look compared to the cost of ballscrews.

Jonathan
06-09-2010, 01:59 PM
Ummm like this???

Yes, exactly. I'm sticking with one bearing for now though as I think it will be ok.

Jonathan
06-09-2010, 02:03 PM
Mulled it over a bit more and managing to visualise this now. Yes, it does work. Nice idea, and worth a look compared to the cost of ballscrews.

Certainly worth a try. 8 for a meter of M16 threaded rod, plus a few quid for the bearing compares very nicely to the price of a ballscrew! Even a *standard* ballnut has some backlash whereas I can't really see how this could have any? Granted the pitch of the thread being slightly uneven with threaded rod isn't ideal ' but that could be solved by using ACME.

routercnc
06-09-2010, 02:08 PM
I think there will be a torque limit (from the stepper motor) which can be applied to the leadscrew, otherwise the bearing will want to jump over the teeth. Depends on the spring preload holding it against the teeth - higher is better for this, but then more bending load on the leadscrew which is less good. This effect will probably be the determining factor in the success of this idea, but good thinking!

Better tooth engagement from a brass insert, as you suggest, might help although there will still be a limit - you'll have to see how it goes. You might be able to arrange a locking up nut so that when the spring tension is developed you can lock it off at that position. Of course this won't compensate for small variations along the thread, but might be a fallback position if it keeps jumping.

Jonathan
07-09-2010, 07:59 PM
I can see bearing jumping could be a big issue with a long screw since for the bearing to jump the screw would need to bend a bit...

Locking nut on the spring is a good plan. Just thought instead of using a standard spring I could use a couple of belleville washers since the travel required is tiny. Can also adjust the spring constant by stacking the washers different ways etc...

Back to the main build.

I went into school today. Their laser cutter had arrived over the summer...it's huge! Only 80W but still useful I guess.

I milled the 600x160x20mm Z axis plate square and drilled and tapped a couple of holes to bolt the rotary table to it for when I want a 4th/5th axis, not that that's very likely since I can't afford the software.

I also cut and milled the steel gantry sides square which took much longer than anticipated. It's not a nice grade of steel to mill.... Started milling the surface flat on either end to make a better contact between the gantry cross piece and this. I'm putting a piece of 20mm aluminium plate in both ends of the 80x80 box section to make a good strong joint.

Photos coming soon!

routercnc
07-09-2010, 10:08 PM
Hi Jonathan,

I'd need to draw it out and look at the angles and forces etc. , but I suspect that the bearing jumping would occur on any length of leadscrew. If the bearing is mounted in a sort of gimble as you have shown and held against the screw thread via a spring, then if you push the leadscrew it will try to rotate (not spin) the bearing about the gimble pivot axis against the spring force, and ratchet the bearing over the screw threads. A bit like a handbrake ratchet on a car where the pawl runs over the teeth against the pressure of a spring.
If you zoom in close to the exact point where the bearing contacts the thread you'd see an inclined plane sliding under the angled face of the bearing. When the inclined plane of the thread moves forward (either you pushing it or the action of the stepper rotating the leadscrew) it will push the bearing upward and away. If it pushes the bearing far enough away it will jump a thread.

Anyway, I was thinking of a way around this and was thinking about a setscrew with a small rubber buffer on the end, but your belleville washer is similar and neater. Hope it all works out because it's a nice idea and will save some cash. I went with 3 ballscrews for the fit-and-forget method, but it was not cheap.

Look forward to your photos . . .

irving2008
07-09-2010, 10:15 PM
There's a big thread regarding this idea on CNCZone... seems some have used it successfully and theres a commercial offering based on the idea.

Jonathan
08-09-2010, 06:50 PM
There's a big thread regarding this idea on CNCZone... seems some have used it successfully and theres a commercial offering based on the idea.

Yes I spotted that. There's two threads, one quite short one about the method I'm using and one huge thread about roller screws which is another story entirely. I may well try making a roller screw if this method doesn't turn out so well.

These photos wore taken yesterday:
Pretty self explanatory - Z-rails are bolted down and really smooth.
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I milled the alu plate square at school, shiny! Never seen such a good finish on aluminium - must be the grade.
2962

Today I've milled the gantry sides flat at either end and drilled them. Also had to nip a few mm off the end of one of the Z rails. I was a bit worried with it being hardened, but it milled OK taking small cuts. Plenty of smoke...

Also started machining the M16 rod for the Y axis.

I'll post some more photos tonight.

routercnc:
I see what you mean with the bearing jumping now - that is a bit of a worry.

Jonathan
08-09-2010, 11:26 PM
Some more photos ...

This is how the gantry fits together.
2976

Detail of gantry sides. I've milled them flat etc. Unfortunately I drilled those 5 holes (for M8 bolts) in exactly the same place on both sides, forgetting that the other one is flipped over! Looks like I'm going to have to mill those 5 holes on one side to move them across by 6.5mm...dow!
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Just after milling block to fix box section to gantry sides:
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It fits!
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Pretty accurate too :smile: I sawed the plate to roughly 80x80mm then used a 20mm 4 flute endmill to cut it to size. I used 2mm cut depth and 1000mm/min - no problem at all! I'm sure I could have gone faster or cut deeper since it didn't get hot. I then did a single finishing pass taking off 0.2mm at full 20mm depth and 300mm/min.

I'm very pleased with the accuracy seeing as this is with trapezoidal screws and using backlash compensation. I guess the brand new cutter and having set the backlash compensation values to the nearest 0.002mm a few days ago helped.
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Shiny :)
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Just a shame I didn't measure the box section beforehand and relied on the sellers dimensions. Turns out it's more like 74.6mm, not 74. I think it'll be ok though...

I'll post a vid of that latest bit of milling when I've compiled it.

Jonathan
11-09-2010, 11:22 PM
http://www.youtube.com/watch?v=iC7lXNTPYrg

Some progress today. I made another of the above part and assembled the 50kg(!) gantry, then assembled it:

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Jonathan
14-09-2010, 11:56 PM
Success!

I made the mount for the angled bearing thingy on the Y-axis. I'm not using springs/belville washers at the moment since I don't have any...yet. Currently it's just a few bolts pushing the bearing onto the screw at the right angle, but it seems fine!

So about an hour ago I clamped the motor mount and just the bearing for the Y screw at the motor end onto the gantry using G-clamps and mole-grips :whistling:

Motor is half stepping, 42T pulley on motor and 28T on the 2mm pitch screw. Currently I can just get 3600mm/min rapid feed but I'm sure it'll be more if I use a smaller than 28T pulley and mount the bearing on the floating end of the screw. Still a respectable amount though I think?

Anyway....backlash: 0.006mm :exclaim:
I spend about an hour checking that figure so I'm pretty confident it's right. I was using a 0.0001" indicator and the reading averaged 0.25 thou.

I think I'll settle for that :rofl:

Jonathan
16-09-2010, 03:43 PM
Got the motor and bearings fixed down properly on both ends of the Y screw now.

Been experimenting with the pulleys. With 42:13 I could get 6000mm/min, but that's above the critical speed of the screw as calculated by Irving's spreadsheet, and yes it started whipping at that. So I tried 28:13 and got 4800mm/min (maybe 5000), which seemed pretty smooth. Acceleration currently 800.
I don't think I'll use the 42:13, Irving what do you think would be best if you don't mind working it out? I've got plenty more pulleys to experiment with. The motors are the 3N.m ones from Zapp moving an 18kg Z-axis.

I know it's a balance between high rapid feed and having sufficient torque for cutting, but it's difficult to work out where this point is since there's so many variables!

I measured the backlash again, and got 0.01mm this time...

I'm not sure wether to tension the screw or not. It wouldn't be too difficult to tap a hole in the end and use that to tension it with a thrust bearing, but is it going to make much difference if I stick with less than the current critical speed?

irving2008
16-09-2010, 07:54 PM
Jonathan,

I'd try the empirical approach.. decide on your required rapid speed. Setup for that. Then put a rope and pulley on the router so that movement of y lifts a weight... add some weight (stones in a bucket or something), about 4 - 5kg and see how fast it'll go without losing steps (use a DTI to measure that it returns to the same point after moves). I'd start with the 28:13 ratio as this gives a nice rapids at 4800-ish and see what you can manage with load... 3000 would be OK, 4000 would be good... then turn accel down a little and speed up... you'll soon find the sweet spot... plot a chart (speed along bottom, accel up side) and you'll get a line for a given weight... change the weight, different line. That way you can tune it for different materials as you'll know what its capabilities are.

Jonathan
17-09-2010, 01:53 PM
Irving,

Thanks for those instructions - I'll do that at some point when I've got the whole router together. Thought I'd done my last physics practical :lol:

Some photos...

'Nut' I may well add springs/Belleville washers.
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3115

3117

3118

Kenneth Paine
11-10-2010, 01:28 PM
Irving2008,



There's a big thread regarding this idea on CNCZone... seems some have used it successfully and theres a commercial offering based on the idea.



Would you be so kind so as to post the link to this thread? I am unable to find it.

Many thanks,

Kenneth

Lee Roberts
11-10-2010, 10:50 PM
Kenneth,

Irving is going to be absent for the next 3 weeks as he is on a trip to the states.

Lee

Jonathan
11-10-2010, 10:59 PM
Irving2008,



Would you be so kind so as to post the link to this thread? I am unable to find it.

Many thanks,

Kenneth

Here it is...

http://www.cnczone.com/forums/showthread.php?t=13593&page=26

I can't find the link to the shorter thread where the method I use is dicussed, but it's linked off that thread somewhere!

I may use the method discussed in the above link for the Z axis as I'm running out of space.

Kenneth Paine
12-10-2010, 02:22 PM
Lee, thanks for letting me know.

Jonathan, thanks for the link. Fascinating!

Kenneth.

Jonathan
12-12-2010, 03:39 PM
Been at university recently so have not had much chance for router building. I came back on a couple of weekends and made a few bits - stepper motor mounts for X-axis and bearing mounts also for X-axis. I decided to scrap the latter and buy two SBR25-2000mm rails, which have now arrived. No customs charges either :smile:

Also had a change of plan with the Z axis. I couldn't get the drive mechanism I've used on the Y-axis to fit at all easily, so I decided to go for the easy option and bought a RM1605 ballscrew at the same time as the above bearings. I got back for Christmas holidays on Friday :smile: and on friday/saturday CNC milled the bearing mounts and ballnut mount for Z. One angular contact bearing at the stepper end of the ballscrew, and a normal bearing on the other end.

Somewhat randomly I picked a 42T pulley for the stepper and 22T for the ballscrew, so effectively the pitch is now 9.545 mm. PM752 driver with 3Nm motor as with the other axis and I'm getting 10,000mm/min :smile::exclaim: with 1000 acceleration. That means only 2.5 seconds to travel the whole 400mm Z axis. I might try some other pulleys/ratios but that can wait until I've done the X-axis and found which of the pulleys I have is most optimal...
Backlash on Z is negligible. I've not measured it with the more accurate DTI yet, but the 0.01mm resolution DTI moves just over one division if I move the motor back and fourth one quarter-step (0.012mm)...To be expected really since the mass of the Z axis itself should eliminate the backlash.


All that's left now is to mount the spindle/router, mount the X-axis linear bearings and do some wiring. If I had the metal to mount the bearings I'd probably be 'making chips' by tomorrow morning. Can't wait :smile:

I'll add some photos soon.

blackburn mark
12-12-2010, 04:26 PM
10,000mm/min

holy sh** jonathan !! i guess thats what you pay the extra for... my best X axis rapid is 1500mm/min

Question: do i need to keep my axis rapid speeds the same as my Y will run at 2000mm/min ?

Jonathan
12-12-2010, 04:44 PM
holy sh** jonathan !! i guess thats what you pay the extra for... my best X axis rapid is 1500mm/min

Question: do i need to keep my axis rapid speeds the same as my Y will run at 2000mm/min ?

Indeed, I'm not regretting buying that ballscrew now - 50 well spent. I'm not sure how often that speed will be useful though...could maybe drill something really fast!

I've got all the axis' at different speeds on my milling machine, so no you don't need to keep them the same. I'm using about 1800mm/min for the X axis on my mill. It will go maybe 20% higher, but it's not reliable at that speed any more. Possibly the ACME screws are getting worn (backlash has certainly increased) but I'm not sure if that would reduce the rapids.

blackburn mark
12-12-2010, 04:54 PM
cheers jonathan :)
i did a couple of cuts in alli and delrin yesterday, nowt spectacular, small pocket with a 3mm single flute,,,,, tickled me pink though to see it work.... my optimisme shot through the roof
i may just get there yet :)

Jonathan
12-12-2010, 10:28 PM
Good to hear that yours is working. I've not tried a single flute cutter yet, perhaps I should. I did the bearing mounts with a 2 flute 5mm cutter using 1mm depth at 200mm/min. Took a while to cut through the 1" aluminium, however it didn't require cutting fluid which left me free to leave it running whilst I made other bits :)

I've finally bought the ER16 collet chuck and set of collets for my big brushless motor. I thought that it'd compliment a kress spindle nicely when I can afford one of those since this motor will do up to 6000rpm, and the kress from 5000 to 25000rpm.

[Meant to post this hours ago - helps if I remember to press 'post' after typing!]

blackburn mark
12-12-2010, 11:43 PM
I've finally bought the ER16 collet chuck and set of collets for my big brushless motor. I thought that it'd compliment a kress spindle nicely when I can afford one of those since this motor will do up to 6000rpm, and the kress from 5000 to 25000rpm.



i cant see you having any worries with that monster!! are you going to put more bearings at the nose?
i used my 700w motor to do my test cuts(0.6mm depth) the bind with using that at low revs is the amount at which the revs drop under load, it needs factoring in.
i really need to re-work my 2000w spindle housing to fit the 43mm spindle mount (i bought a boat load of hss 5mm 2 flute of ebay to try in it, nice and cheap)
im not sure the single flute cutters are that important if you can get your revs down, youll have no worries there
my take was that with plastic the bigger the chip the less chance of melting but i am doing a lot of guesstimaiting at the moment, ill give a few diffrent cutters a try and see how i get on (delrin is pretty nice to machine)

Jonathan
13-12-2010, 12:03 AM
I'm going to put one 12mm double row angular contact bearing in - same as I used on the Z axis. Do you think that'll be sufficient?

I still need to buy the ESC for this motor and a suitable power supply. 50V and lots of watts...expensive.

Were the 5mm cutters a one off? The reason I'd want to try a single flute cutter is it should clear the swarf easily. [and why isn't 'swarf' in the spell checker?]

I'll post some pictures in a bit - after the snooker!

blackburn mark
13-12-2010, 12:49 AM
I'm going to put one 12mm double row angular contact bearing in - same as I used on the Z axis. Do you think that'll be sufficient?


iv put a 10mm double row a/c in my 2000w spindle but iv not used it to machine yet so i cant say for sure but as far as runout or play goes they will out perform standard bearings by a long way and as your going to get a kress at some point it would make sense to bolt a 43mm housing on the front of your brushless so you can swap them out easily and throwing a double row A/C in there while your at it wont take to much effort

my 700w with the pre-loaded(belleview washers) skate bearing gave a nice finish, i cant see them lasting to long but they are cheap and easy to change

ebay search "5mm slot drills (pk of 10) hss slotdrill uk made" 17 including postage
iv read HSS works well with delrin so i bought two lots of these

Jonathan
13-12-2010, 01:22 AM
I might get those 5mm cutters, or maybe go for a pack with some different sizes.

You read my mind with the 43mm mount - I was just looking at how easily it would fit.

Lots of photos...

Gantry with Z mounted:
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Z ballscrew bearing mount:
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Bits left to fit + old Z and 4th axis:
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Top of Z axis with stepper, 42:22 pulley:
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Ballnut, can just about see the mount:
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Router bits from Aldi, very cheap:
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Another view of Z axis:
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Finally the whole router:
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blackburn mark
13-12-2010, 01:58 AM
that 4th axis looks posh, what bearings ??? stainless body??? what are you going to drive it with ??? what gearing ???

for a moment there i thought you were using a hi-tec harmonic gearbox but im gessing the hi-tec box i can see has shoes int it lol

Jonathan
13-12-2010, 12:40 PM
that 4th axis looks posh, what bearings ??? stainless body??? what are you going to drive it with ??? what gearing ???

for a moment there i thought you were using a hi-tec harmonic gearbox but im gessing the hi-tec box i can see has shoes int it lol

I mentioned it somewhere else on this forum...not sure which thread though.

They're a pair of L 68149/L 68110 taper roller bearings. It's all mild steel - shows the dehumidifier is working as it's ages since I machined it. I'll use a stepper motor via timing belt to drive it since there's no way I could afford a servo. Also putting a disk brake using solenoids to hold it steady whilst milling. When I want to use it as a lathe I can put the big brushless motor on it. 6000rpm at several Kw would make a nice CNC lathe. I made it mainly to use with the milling machine, but I may well use it on the router.
I've machined the shaft to fit an 80mm chuck, same as my C3 lathe, but I'll make an adapter to put a 5" chuck on it.

Using 4th axis to make 4th axis (or should that be 5th?):
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Cross section, note disk break arrangement:
3480
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Mounted on mill:
3482


looking forward to seeing it running jonathan

You're not the only one :)


get some videos up.

Will do

blackburn mark
13-12-2010, 08:59 PM
I mentioned it somewhere else on this forum...not sure which thread though.



hahha!!! sorry jonathan, you did... on my build thread... it looks so much smaller on your router i thought youd built another one

im still pondering the options for my fourth axis, im leaning towards a 50:1 harmonic with a stepper... it'll only be on light duties
youve got me thinking now though.... it would be nice to be able to isolate the gearbox and run it up to lathe speeds

think ill just sit back and see how you get on with yours :)

Jonathan
15-12-2010, 01:45 AM
im still pondering the options for my fourth axis, im leaning towards a 50:1 harmonic with a stepper... it'll only be on light duties


Could you use a timing belt inside the harmonic gearbox as the flexible gear thingy? Milling the inside out pulley would be fun. Probably do it in two semicircles...



youve got me thinking now though.... it would be nice to be able to isolate the gearbox and run it up to lathe speeds


Yep, that's my plan ultimately - to be able to accurately switch between stepper and brushless motor drive.

Made good progress on the router today. Milled and drilled aluminium box section and channel to mount X axis linear bearings. Also drilled and milled one side of gantry to fit that, and put slot in for timing belt to go through. Lots of smoke and blue swarf when drilling the steel. It's a 20mm wide slot so I chain drilled @ 16mm (biggest I have) to save time with the 20mm milling cutter. Will probably make more sense when I put photos tomorrow.

3484

I'm 14 holes and one slot away from finishing :) Plus a bit of assembly and wiring I suppose.

blackburn mark
15-12-2010, 07:22 PM
Could you use a timing belt inside the harmonic gearbox as the flexible gear thingy? Milling the inside out pulley would be fun. Probably do it in two semicircles...


haaha!!!! you read my mind this time :) iv already considered it, not really explored it deeply though, you would need a clever way to output the torque from your inside-out timing belt to your output shaft
the beautful thing about using a belt for the strain wave gear is its so flexble you could use two simple bearings or rollers for your wave generator and use a slightly larger timing belt for the outer gear and pre-load it with your simple two bearing wave generator....
im thinking it would take quite a bit of elegance to make it work... backlash might well be very small but with heavy cuts im thinking it will have quite a bit of give
errrrr..... i dunno ??? youve got me thinking on the issue again.... if i try to fit any more in my head i think one of my eyes might pop out :)

Edit: not sure why you would need to cut the internal in two halfs ?? i dont think you would need sharp corners at the root end of the pitch

Jonathan
17-12-2010, 12:53 AM
...use a slightly larger timing belt for the outer gear and pre-load it with your simple two bearing wave generator...


Surely a timing belt for the outer gear would have the wrong profile.



Edit: not sure why you would need to cut the internal in two halfs ?? i dont think you would need sharp corners at the root end of the pitch

Maybe we are talking on cross purposes. I suppose it depends on the timing belt you choose. If it's one with round teeth then you could CNC mill it easily without a 4th axis. If it's say XL then you'll want to mill it with a 4th axis, but clearly the chuck will collide with the other side of the pulley when it's milling the teeth, unless you did it in two halves...or more realistically thirds.


Finished all machining for router this morning! *Just* needs assembling - waiting on my dad to put some bigger legs under it since the previous arrangement was designed for a 10kg gantry, not >50kg!

Been thinking about how I can clamp stuff to the bed to machine it. It would be nice to have T slots like on my milling machine since then I could use the same clamps and easily put the vice/rotary table etc on it. I do have some HSS T slot cutters however I think cutting MDF will destroy them.
My plan is to buy two sheets of 18mm MDF. Glue/screw one down to the bed, get the router to cut the wider part of the T in that and level it, then put another sheet of MDF on top of that and cut the top of the T slot. That way I can use standard router bits...My only worry is if MDF is going to be strong enough?

Just been making collets for the cheap router I'm using. I'll post a video here soon...

Wobblybootie
17-12-2010, 09:22 AM
giving the MDF a few coats of thin epoxy should provide some strength ... thin enough to soak in at first but not too much otherwise the MDF will swell an alternative could be the single T slot strips from Axminster or Rutlands etc. secure them to the lower panel and infill the spaces with the upper panel ...

M250cnc
17-12-2010, 10:44 AM
Been thinking about how I can clamp stuff to the bed to machine it. It would be nice to have T slots like on my milling machine since then I could use the same clamps and easily put the vice/rotary table etc on it. I do have some HSS T slot cutters however I think cutting MDF will destroy them.
My plan is to buy two sheets of 18mm MDF. Glue/screw one down to the bed, get the router to cut the wider part of the T in that and level it, then put another sheet of MDF on top of that and cut the top of the T slot. That way I can use standard router bits...My only worry is if MDF is going to be strong enough?

Sorry but you are gonna be wasting your time using MDF and an accident in the making for sure.


giving the MDF a few coats of thin epoxy should provide some strength ... thin enough to soak in at first but not too much otherwise the MDF will swell an alternative could be the single T slot strips from Axminster or Rutlands etc. secure them to the lower panel and infill the spaces with the upper panel ...

More bad advice The only thing MDF should be used for is a spoil board

Phil

blackburn mark
17-12-2010, 10:55 AM
Surely a timing belt for the outer gear would have the wrong profile.

i compleatly missed that,,, i think your right

iv got another one for you to ponder... there is probably somthing obvious iv missed but if you use a double sided timing belt you might be able to exit the belt through the outer gear wall (using small rollers maybe) to drive an output pulley, that
might solve the main stumbling block to the idea and give you a sturdy output (if it could be made to work)

3486

it would make an interesting project but i think im going to admit defeat and try to get a second hand hi-tec drive :)

Jonathan
17-12-2010, 01:05 PM
Sorry but you are gonna be wasting your time using MDF and an accident in the making for sure.

Can you think of anything better to use that's not too expensive? Maybe plywood, but I guess that's not much better. Vacuum table isn't much good for metals. Bear in mind it needs to be about 800x1900mm ... so clearly I can't afford a nice piece of tooling plate that size!

I'm not sure about the epoxy idea either, wouldn't it just crack/crush?

Making collets for router:

http://www.youtube.com/watch?v=m98fPg-_vUU


Not quite sure with what you mean by exiting the belt through the outer wall, diagram?
I agree buying one is probably the safest option! If you're after a really big reduction then perhaps several timing belts and pulleys could work. If each one gives 1:4 (feasible I think) then you only need 2 belts to get close to 50:1. Timing belts don't have backlash, but I'm not sure about stretching. Why do you want such a high ratio anyway? My rotary table is 1:90 and it takes forever to rotate, even with the 70v stepper drivers.

blackburn mark
17-12-2010, 01:38 PM
ill do a sketch if i find time.



Why do you want such a high ratio anyway?

i want to cut holes and bearing recesses in a 50mm acetal cylinder and also engrave fine markings and im trying to avoid the complications of adding a disk brake... it feels like i might get the holding torqe i need at 50:1 (i should really do the maths)
i may well use timing belts and pullies, im not fully commited to one thing or another at the moment

with all the ice i managed to burn out my windscreen wiper motor so iv even pulled the old one apart to look at the worm gear as a possibility... thats 55:1 ratio, i think id struggle tameing the backlash on that though

M250cnc
17-12-2010, 01:38 PM
Can you think of anything better to use that's not too expensive? Maybe plywood, but I guess that's not much better. Vacuum table isn't much good for metals. Bear in mind it needs to be about 800x1900mm ... so clearly I can't afford a nice piece of tooling plate that size!

I'm not sure about the epoxy idea either, wouldn't it just crack/crush?

Jonathan any type of wood table is going to fail to sufficiently clamp metal to it

Whatever you are machining/clamping to the table has to be weaker than or equal strength to the table itself. So the minimum would be ali but it would be cheaper to use steel.

A steel plate with 50x15 bars with 70x15 bars mounted on top to form the tee slots your require, and steel would be my preferred material.

Steel wont warp when wet/different humidity you would have to set your X & Y Axis to run parallel to the plate, now you might think this is a disadvantage not being able to machine the bed to suit the X & Y

But you can only get a flat surface this way if the material is thin as a very thick piece will show any misalignment.

Phil

blackburn mark
17-12-2010, 01:50 PM
Whatever you are machining/clamping to the table has to be weaker than or equal strength to the table itself

iv heard this said a few times... im not sure i agree with that phil, surley the table only has to "equal and opposit" the cutting force and carry the weight of the job.... you could use blu-tac as long as it did just this :)

Jonathan
17-12-2010, 01:53 PM
Jonathan any type of wood table is going to fail to sufficiently clamp metal to it...
A steel plate with 50x15 bars with 70x15 bars mounted on top to form the tee slots your require, and steel would be my preferred material.

Steel wont warp when wet/different humidity you would have to set your X & Y Axis to run parallel to the plate, now you might think this is a disadvantage not being able to machine the bed to suit the X & Y


Surely it all depends on what size cutter / feedrate I'm using - if the cutting forces are not to high etc. I was thinking more using the T slots for clamping wood, and using them to clamp my large milling vice (6" jaw, opens up to about the same) to the table for when I want to machine metals. That's still limiting me to only relatively small bits of metal though. If I want to machine a big sheet of aluminium then it's not going to be more than 8mm thick (cost again), so a 6mm cutter would suffice. What's the cutting force on a 6mm end-mill on aluminium at a decent feedrate? Surely not so much that lots of clamps on MDF won't hold it?

I agree putting steel strips on the bed is a good plan, but again very expensive - unless you know of a better supplier than me! I could skim the existing 18mm MDF bed with the router before putting the steel on top. That should get it reasonably parallel. I guess I could afford to make a smallish steel bed.

(Sorry I probably could have made this post a bit less rambling, I'm just thinking aloud.)

Jonathan
17-12-2010, 01:57 PM
avoid the complications of adding a disk brake... it feels like i might get the holding torqe i need at 50:1 (i should really do the maths)

Could stick with a worm drive and compensate for the backlash on that, either in software or use a split wormwheel sprung to eliminate backlash. If you've got 3nm holding torque then clearly that gets 150Nm at that ratio. So say maximum radius of 75mm, that gets you up to 2kN cutting force ... plenty.


iv heard this said a few times... im not sure i agree with that phil, surley the table only has to "equal and opposit" the cutting force and carry the weight of the job.... you could use blu-tac as long as it did just this :)

Yes, double sided tape is great for holding some things, especially PCBs. Effectively I would have 54mm of MDF, with some slots in it...plenty to carry the weight of the job I should think. Could try and calculate the deflection. I'm worried more about if I could do the bolts up tight enough without crushing the MDF. If I put a thin sheet of steel under the top MDF layer that should solve that.

Dad's still making legs for router - wooden frames are always his department. Going to go and help now...

Wobblybootie
17-12-2010, 03:18 PM
Sorry, I had not read the whole thread, I assumed that with a bed of the size you have, you would be machining wood etc. Phil, there are plenty of machines out there using an MDF surface, the MechMate springs to mind and that is one serious machine!! Others use the threaded inserts in the lower board and epoxy to secure them with a drilled replaceable spoil board above. However I guess to machine metals you will be using some form of coolant in which case MDF is a total NO NO.

M250cnc
17-12-2010, 03:54 PM
The point is, this type of clamping just will not work for a machine vice 4th Axis etc.

The Tee Slot nut will just pull straight out through the MDF or you only clamp with finger pressure:rofl:

Phil

M250cnc
17-12-2010, 03:55 PM
Double Post

Jonathan
17-12-2010, 04:08 PM
The Tee Slot nut will just pull straight out through the MDF or you only clamp with finger pressure:rofl:


That's why I suggested in my last post putting a thin sheet of steel under the top MDF layer, so that T-nut is pressing on the steel, not MDF.

I like the idea of threaded inserts, but they're not so versatile as T-slots.

M250cnc
17-12-2010, 04:14 PM
That's why I suggested in my last post putting a thin sheet of steel under the top MDF layer, so that T-nut is pressing on the steel, not MDF.

I like the idea of threaded inserts, but they're not so versatile as T-slots.

Jonathan, you have a lot to learn.:whistling:

Phil

blackburn mark
17-12-2010, 05:59 PM
Jonathan, you have a lot to learn.:whistling:

ha!! i guess that means your just about done with learning phil :clap:

right!!! im off to stick my hand int fire :heehee:

M250cnc
17-12-2010, 06:32 PM
ha!! i guess that means your just about done with learning phil :clap:

:confused: :confused: :confused: :confused:

Phil

Jonathan
17-12-2010, 06:56 PM
:confused: :confused: :confused: :confused:

Just what I was thinking.


Jonathan, you have a lot to learn.:whistling:

I've got plenty of years to learn it :smile: Hmm, just worked out it's 7 years since I first used a milling machine - yikes I must be getting old.

Anyway, thanks for the advice so far. I'll leave the bed for a little while and have a think.

The legs will hopefully be done tomorrow, so all being well I'll have it running tomorrow night. Got to think of something to make with it now!

blackburn mark
17-12-2010, 07:15 PM
Just what I was thinking.


ok ok,,, it must be a northern thing
i was feeling you were coming across a bit patronising phil
im sure youd get mdf to work if money left you with no option jonathan, maybe phil has arms like legs and would keep tightening those clamps till something broke

maybe you could make phil a touque wrench on it when your done:smile:

sorry phil :whistling:

Jonathan
17-12-2010, 07:35 PM
Some pictures...

Legs:
3488
Gantry side:
3489
One X motor, need to tighten that belt:
3490
Gantry side again:
3491
Yeah my workshop is in disarray now:
3492

blackburn mark
17-12-2010, 07:44 PM
my workshop is in disarray now

looks well tidy to me:) i could live in that workshop

Jonathan
17-12-2010, 07:46 PM
looks well tidy to me:) i could live in that workshop

It's much tidier than it was yesterday! There was a layer of swarf on the floor.

I want to get a metal bandsaw, but I'm rapidly running out of space.

What's the diameter of the shank of those 5mm cutters you pointed me to? Also flute length?

Swarfing
17-12-2010, 09:16 PM
Jonathan

What is your real age? far too clean for 18

Jonathan
17-12-2010, 09:24 PM
Jonathan

What is your real age? far too clean for 18

18 is my real age :lol: What do you mean by far 'too clean'?

blackburn mark
18-12-2010, 12:16 PM
What's the diameter of the shank of those 5mm cutters you pointed me to? Also flute length?

im not at home at the mo dude,,, ill let you know... they are long enough for my er11 with the tread clear of the collet



What do you mean by far 'too clean'?

hahaha! your 18... its ment to look like you dropped a box of grenades in there :)



thats some work shop at your disposal lad.


indeed ! im exspecting you and your old man to build a flux capacitor to go in the delorean when your done :)

blackburn mark
18-12-2010, 05:16 PM
What's the diameter of the shank of those 5mm cutters you pointed me to? Also flute length?

shank=5mm
the blade is about 10mm with about 5mm clearance above that (15mm cut depth)
theres aprox 20mm of clean shank to grip onto
13mm of coarse (1.3mm pitch) thread 5.7mm diameter

check your er16 5mm collet to see how much shaft you need

Swarfing
19-12-2010, 09:37 AM
Christ if i could keep my workshop as clean as yours is dirty i would be heaven................Where do you keep the tesla coil?

Jonathan
20-12-2010, 12:52 AM
It works!!!

I'll add photos/vid shortly.

I did a relief thing, 200x200mm ... 1mm stepover with a 6mm cutter. Varied the feedrate and seemed ok at 3000mm/min. One of the X motors stalled, twice, so that needs looking into. The result doesn't look very good, but that's due to using a flat not rounded cutter since I didn't have one.

Jonathan
20-12-2010, 01:13 AM
shank=5mm
the blade is about 10mm with about 5mm clearance above that (15mm cut depth)....

Thanks for the info. I'll probably buy some.

Action shot, suspicious lack of swarf :confused::
3496
View of gantry:
3494
Z axis, extended to about 390mm:
3495
Whole router, Dad snuck in on this photo (everyone suddenly appears in the workshop when it starts working!):
3497

blackburn mark
20-12-2010, 12:57 PM
looking good jonathan (the router that is, you need a hair cut :)
hows it getting on with thet much Z ?
have you made a provision to drop the whole gantry down for your smaller /finer jobs ?
it is a good feeling when the thing springs into life :)

iv was having trouble with one of my X motors stalling, i had to back off on the speed, i swapped channels and the same motor stalled, im thinking there is slightly more drag on that side
i might swap the bearings for double row A/C bearings to make sure the drag is identical

Jonathan
21-12-2010, 02:19 AM
looking good jonathan (the router that is, you need a hair cut :)

:rofl: thanks


hows it getting on with thet much Z ?
have you made a provision to drop the whole gantry down for your smaller /finer jobs ?
it is a good feeling when the thing springs into life :)

It seems fine. There's a bit of wobble visible on the latest part (see below), but I think other factors are contributing such as the whole router wobbling madly due to the floor not being strong enough...

I have measured the Z deflection parallel to X. I can bend the Z axis by about 0.06mm if I push as hard as I can with little finger, so a reasonable force but not huge. It takes a lot of force to bend it more than that which makes me think it's the linear bearings that are a bit sloppy. Not much I can do about that.

I've not made it so I can lower the gantry, it's far to heavy to be doing that sort of thing. I think I'll make a raised bed and machine aluminium stuff on that. It's a compromise, but the gantry sides are very strong.

Yes one X motor is much stiffer than the other. It's limiting my feedrate...

Anyway, at last here's a video of it running:


http://www.youtube.com/watch?v=O035hmG6kDM

(I'll post the first test video tomorrow when I've edited it)

Swarfing
21-12-2010, 09:55 AM
Well done Jonathan and good to see you up and running :-)

blackburn mark
21-12-2010, 12:47 PM
Splendid!!!! im surprised how fast its cutting


0.06mm

thats a lot better than i would have thought :)
i had to try your scientific test, im getting about 0.03mm but i only have 120mm cutting space so your gantry sides were a good choice over plate


Yes one X motor is much stiffer than the other. It's limiting my feedrate...

i removed the drive from one side (in order to find the one that was stalling/binding) and it ran better on a single stepper than it did on both which i found pretty bizzar
i could only think that there was some kind of sympathetic (machanical) interference between the two with there being more drag on one side and because i was lazy when i fitted the the standard brearings (the fit is to tight) i cant back the pre-load off... the diffrence in drag between each side isnt massive but im hoping that its that causing the problems

my double row A/C bearings have turned up so ill give them a try at some point but for now ill stick with 1500mm/min

Jonathan
21-12-2010, 01:23 PM
Well done Jonathan and good to see you up and running :-)

congratulations lad

Thanks, I'm glad it's working at last!


Splendid!!!! im surprised how fast its cutting

What feedrates do you/other people normally use with MDF? I looked it up and found the chipload should be about 0.3mm. That would mean with my router at 11500rpm (lowest) it needs to be fed at roughly 6.9m/min ... which is huge! I wanted to get it fast enough to make chips, not dust, and in doing so reduce wear on the cutter.
I accidently cut all the way through 18mm ply with 6mm cutter at 2m/min last night. The cutter survived but the finish was poor/wobbly.


thats a lot better than i would have thought :)
i had to try your scientific test, im getting about 0.03mm but i only have 120mm cutting space so your gantry sides were a good choice over plate

Er, I wasn't testing the deflection of the gantry sides - the DTI was stuck to the side and touching on the back of the Z axis. I'll see how much the gantry bends today.

My problem with the X motors is one of the nuts is stiffer than the other, and the screws are a bit bent. I put them under tension to remove the bend, however that doesn't help when the gantry gets to the end of the bed since there's no give in it and as a result it often stalls.



my double row A/C bearings have turned up so ill give them a try at some point but for now ill stick with 1500mm/min

Hmm, I thought 3600mm/min was tedious :redface:
Y is happy at 5000, maybe more - not tried. The backlash seems to have increased slightly on Y. It's now 1/2 a step - 0.012mm.
Z still works at 10000, and X seems reliable at 3600mm/min...but not at the end of travel.
I think my toroidial transformer is too small now I've got an extra motor.

blackburn mark
21-12-2010, 05:04 PM
What feedrates do you/other people normally use with MDF?

cant help you there, im not into wood... im just going off what iv seen on the net



My problem with the X motors is one of the nuts is stiffer than the other, and the screws are a bit bent. I put them under tension to remove the bend, however that doesn't help when the gantry gets to the end of the bed since there's no give in it and as a result it often stalls

im assuming you slackened everything off at one end (nut housing and bearing housing) and ran the gantry to that end and nipped it up, then did the same at the outher end... back and forth a couple of times to make sure

i read somewhere that i might need to staighten my screws when they arrived, mine are only 750mm so i got away with it
i was thinking i would need a reasonably flat surface to find the curve and use my knee to ease it out
as long as its a nice lazy curve you should be able to get the worst of it out...... bit more of a problem if its a short bend, it would be pretty easy to make it worse



Hmm, I thought 3600mm/min was tedious



Z still works at 10000

your definitely 18 :)

Jonathan
21-12-2010, 05:16 PM
im assuming you slackened everything off at one end (nut housing and bearing housing) and ran the gantry to that end and nipped it up, then did the same at the outher end... back and forth a couple of times to make sure


Yes I did exactly that. I think I'll try it again.

I saw on you-tube a video about making ballscrews and they straightened it by putting the screw between two blocks, and pushing down in the middle with a lever to bend it.

blackburn mark
21-12-2010, 05:37 PM
I saw on you-tube a video about making ballscrews and they straightened it by putting the screw between two blocks, and pushing down in the middle with a lever to bend it.

sounds like a winner
just take your time untill you know how much pressure it takes to get it to move or youll end up going passed the sweet spot and youll be chasing muliple curves up and down it till new year :)

Jonathan
21-12-2010, 11:09 PM
I relieved most of the tension on the X screws and now it's much better. Seems happy at 3600mm/min over the whole bed. I'm using a 42T pulley on motor, and the 28T pulley I posted about earlier on the 2.5mm pitch screw.

Bed surfacing, not terribly exciting but it demonstrates the vacuum working reasonably well:

http://www.youtube.com/watch?v=Jb1TL84NZBo&feature=mfu_in_order&list=UL

3500

Jonathan
23-12-2010, 11:42 AM
Been doing a bit more testing, latest videos:

This is the video of the first ever test...
http://www.youtube.com/watch?v=ZrhZLrJv1Og&feature=mfu_in_order&list=UL

And here I tried machining some aluminum:

http://www.youtube.com/watch?v=b4NrS9wCE9c&feature=mfu_in_order&list=UL

Bit of a faliure! I think I'll try that again but with it mounted higher on the bed. I could see/hear the Z wobbling.

blackburn mark
23-12-2010, 07:26 PM
Owch !!!
a bit uggly on the aluminium :( im a bit gutted
i was over the moon with mine, 3mm single flute 3000rpm, cant remember the feed i also had a go with the engaving spindle at about 10000rpm cutting small fonts (low feed) and they both were lovely and crisp

if mounting the work higher doesnt work out to well id be really tempted to stick a block n tackle above your gantry and make provisions to drop it down by 3/4 for alli and any fine work

im confident you would be amazed at the diffrence it would make
i guess it depends on what you are going to do with the machine generally

Jonathan
25-12-2010, 01:43 AM
Owch !!!
a bit uggly on the aluminium :( im a bit gutted
i was over the moon with mine, 3mm single flute 3000rpm, cant remember the feed i also had a go with the engaving spindle at about 10000rpm cutting small fonts (low feed) and they both were lovely and crisp

That's a lot less aggressive than 3 flute 8mm ballnose with 1mm DOC and 2m/min I tried! Anyway I've since noticed the plywood router mount I made isn't as tight as I thought which should make a huge difference.

I think I will look into making it easy to lower the gantry.

Having said that it's working nicely with woods:
(Wind turbine blade mould section)
http://www.youtube.com/watch?v=93SSlH0ldC4

We got chickens recently, so I made an egg holding device for my Mum for Christmas, hopefully it will go down well:

http://www.youtube.com/watch?v=GZC_0PWQc3g

I'm certainly pleased with the finish on that.

blackburn mark
25-12-2010, 01:56 AM
3 flute 8mm ballnose with 1mm DOC and 2m/min

i wouldnt dare!! :)

the vid you posted isnt working
i could do with getting some vids up (might have to speed them up a bit to make it look like its actualy doing something)

Jonathan
25-12-2010, 02:01 AM
i wouldnt dare!! :)

the vid you posted isnt working
i could do with getting some vids up (might have to speed them up a bit to make it look like its actualy doing something)

One of the videos hasn't finished uploading. It'll be done in 5 mins...you were too quick!!

I often sped up the videos on my milling machine.
Better go, cat is drinking my tea again, sigh...

blackburn mark
25-12-2010, 02:24 AM
One of the videos hasn't finished uploading.

just watched them both :) splendid!! it is nice and quick
wind turbine blades!! can i order three for my paramotor :)

h4ppy-chris
26-12-2010, 11:23 AM
fanatic jonathan i read all your post and watched all your vids love it keep um coming :)

Jonathan
26-12-2010, 02:52 PM
fanatic jonathan i read all your post and watched all your vids love it keep um coming :)

Thanks for the kind words. I'm intending to get the 5th driver wired up for the 4th axis today so I'll take a video of that...


nice work jon,i,ll bet you mother was eggstatic,:redface: :smile:
enjoyed the videos and seeing it in action
what software were you using for the relief work peice you did?

:lol: yes she was. I just used CAMbam free edition for the relief. It's limited but should work if I use the right cutter next time...

Jonathan
26-12-2010, 08:32 PM
I'm intending to get the 5th driver wired up for the 4th axis today so I'll take a video of that...

Well...I got the 5th driver wired up, switched it on and just get a red LED. It's dead on arrival :cry: Tried connectors from other drivers which hold motor/power wires with it (and vice versa), and it still doesn't work. I've emailed Zapp, sadly it looks like I've got to test their customer support...:cry:

Jonathan
27-01-2011, 04:27 PM
Well...I got the 5th driver wired up, switched it on and just get a red LED. It's dead on arrival :cry: Tried connectors from other drivers which hold motor/power wires with it (and vice versa), and it still doesn't work. I've emailed Zapp, sadly it looks like I've got to test their customer support...:cry:

Good news, I sent the driver back and they replaced it a few days ago.

Currently I'm designing a stepper driver and thinking about how to make the machine more rigid.

I made a 1.6x0.25m wind turbine blade mould with it a few weeks ago out of MDF. It went well, leaving a nice finish. I will post a video of it at some point, though not all of it since it took a few hours!

Jonathan
21-02-2011, 09:30 PM
I've bought a 2.2Kw spindle from eBay along with inverter. It was 247 including postage - I saved a bit via best offer. Having said that customs also charged 19 (well, customs charged less but DHL STOLE some)... so 7.7% added which isn't bad I guess. The spindle will arrive home tomorrow, but I'm at University so can't see it yet :(
ER20 collets have arrived for the spindle, and I've won some 4" extractor tube to sort out the dust issues. Hopefully.

Not much has happened since with the rest of the router. I've made and mounted the brushless motor as spindle, as detailed in another thread.

On a related topic I'm currently designing and prototyping a 120v, 10A ish stepper driver. It's going ok so far. I started prototyping with a H-bridge IC (to prove the principle) and got microstepping working with that. Now I've made a PCB with two N-channel H bridges on with power MOSFETs and a good heatsink.
When it's done I'll replace my PM752s with it.

Jonathan
26-02-2011, 05:15 PM
I've come home for the weekend - lots of post, including spindle.

Setting up the VFD was no problem. I've got a little 8L/m submersible pump for the water cooling. I've just tried it with a bucket of water and an odd assortment of tubing, about a couple of meters in total, and I got 1.3L/m flowing. I think that's fine.

With 5l of water in a plastic bucket the temperature rose by about 0.25C/min. The spindle was only drawing 0.6A from the mains.

Going to make the mount later today and hopefully try cutting with it tomorrow :smile:

At 24,000 rpm is quiet enough to listen to radio and I can't hear it over the dust extractor...Also I can barely feel any vibration at that speed on the spindle body.

Jonathan
01-03-2011, 09:59 PM
ello jon,just wondering how you got on over the weekend? did you manage to get it cutting
im about to order mine from the same source .
wouldnt mind a look at the mount you made if you got that far:naughty:

No I didn't get it cutting. Went to my grandmas on Sunday so didn't get as much done as I'd hoped.

I got one mount done and started the top one. I've not got a photo of the finished mount, but you can get the general idea from here:

3807

3808

3809

The extra aluminum on the side will let me fit dust extraction.

Quick video:

http://www.youtube.com/watch?v=xciLCN2Dz08&feature=youtube_gdata

Jonathan
06-03-2011, 02:14 PM
Spindle is mounted and working!

Runout isn't great - 0.05mm ish.

But it seems good in all other ways. I just cut some carbon fiber with it, about 2mm thick at 450mm/min with a cheap diamond burr at 24,000rpm. It's cut well and left a decent finish.

I'll post some photos soon.

Jonathan
06-03-2011, 04:52 PM
Spindle mounted + VFD:
3818

Water cooling... crude but it works. My mum is wondering where her bucket has gone!
3816

Closeup:
3817

Trimming carbon fiber sheet. Having the spindle going off the end of the bed is dead useful:
3819

I intended mounting the VFD there to be temporary, but now I'm thinking I might leave it since it saves on cable. The extra mass on the Z axis isn't much compared to what's already there. If I switch the steppers off the Z axis now drops due to gravity. Before the detent torque of the motor was sufficient to stop this.

Jonathan
07-03-2011, 12:44 AM
I've finally got round to uploading the video of cutting a wind turbine blade mould, with my router, to youtube:

http://www.youtube.com/watch?v=Puge7MSYoZU

It's, quite a long video but I've tried to use only short clips of each stage so it's not too tedious.

I will edit this post and add some more tomorrow.

FatFreddie
07-03-2011, 03:36 PM
I intended mounting the VFD there to be temporary, but now I'm thinking I might leave it since it saves on cable. The extra mass on the Z axis isn't much compared to what's already there. If I switch the steppers off the Z axis now drops due to gravity. Before the detent torque of the motor was sufficient to stop this.

I'd be more worried about the effect of vibration on the VFD.

Jonathan
07-03-2011, 09:27 PM
I'd be more worried about the effect of vibration on the VFD.

Yes I thought that too. I mounted it using those foam sticky pad things which, thinking about it, should damp the vibrations a little. Another issue is dust getting into the VFD which would reduce the efficiency of the heatsink.

FatFreddie
08-03-2011, 01:00 PM
Carbon fibre dust is conductive...

FatFreddie
08-03-2011, 01:02 PM
Runout isn't great - 0.05mm ish.
What were they quoting for runout? I was looking at some that were quoting ten times better than that - just wondering how reliable the claims are.

Jonathan
08-03-2011, 02:37 PM
Carbon fibre dust is conductive...

True, and texalium which I'll machine at some point is going to be even worse. Apparently carbon fiber dust is worse than asbestos, so I will allways use the dust extraction with it anyway.

Jonathan
09-04-2011, 05:15 PM
What were they quoting for runout? I was looking at some that were quoting ten times better than that - just wondering how reliable the claims are.

Yes mine was indeed quoted at ten times better than than.


I've decided to make a welded steel frame for my router. This is my initial design:

3915

I will probably add a few more triangles to that, however I'd like to keep the front of the machine open.

In that drawing I've discarded the tall gantry sides and replaced it with a bit of 100x60x3.6mm steel box section, so now the 'gantry' is only 100mm tall, not several hundered mm. This should help with the stiffness.

Also I am intending to have the existing bed fit inside the frame and attach it to the 6 vertical pieces with a series of holes which will allow the bed to be raised and lowered depending on the size of the job. Most of the time I will have it as close as it will go to the gantry, giving only 100mm (ish) z-travel. I've not yet needed more than this so I think it's a good way of stiffening up the machine without compromising on working volume. It'll also gain a good bit of travel on the Y axis.

Jonathan
09-04-2011, 07:40 PM
looking good jon,this ones allways been a favourite of mine on the tube,very simular,works well.
http://www.youtube.com/watch?v=hAS3GRE61jY

That one does look good, except for the position of the X-axis ballnuts which will cause uneven loading on the X linear bearings.

I'm not sure that the 100x60x3.6mm steel box section I've used on the sides is going to be sufficient. That cross section is weak with forces parallel to the Y axis. I may get some aluminium profile to fit there. Chip, can you remind me where you got yours please? What you used for your gantry sides looks about the right size.

Jonathan
08-06-2011, 01:25 PM
Quick update. I've ordered the steel for the frame and it should be ready Thursday or Friday. I've now started dismantling the machine ready for the conversion. I'll post more here with pictures as it happens...


heres the place jon,http://www.aluminium-profile.co.uk/ i think it was 90mmx45mm i used.

Thanks for the link. I'm tempted to use it for the sides, but if I did I can't weld it. I think I will weld some steel sheet on to the ends of the box section to strengthen it.

Jonathan
14-06-2011, 05:31 PM
I got the steel on Wednesday. Adey Steel were very organised and helpful. They cut the steel to the lengths I specified. They did accidently not give the offcuts from cutting my steel that I requested, so I went back and got it plus they gave me some box section free of charge along with some 6mm plate to practice welding with!! I'll use some of the extra box section to make the frame stronger if required..

Since then I have used my metal bandsaw to cut the box section - it's cutting very close to square now. I'm currently drilling lots of holes in it which will be used to support the bed at different heights. I intend to motorise the bed, effectively making it an F axis, to minimise the overhang of the Z-axis for each job.

I've ordered the ballscrews for X and Y (RM2510 and RM1610) - the tracking says they should arrive in one week, so my aim is to have the frame done by then.

The basic shape of the frame is going to be the same as in post #113, with a few extra pieces to strengthen it. The front is 'missing' to allow the Z axis to protrude past it at the end of the travel. I've used 50mm and 60mm, 3mm thick box section and 120x60mm, 3.6mm rectangular in places where I wanted a bit more strength.

Here's a couple of photos:

4155

Jonathan
21-06-2011, 07:53 PM
Slow progress with the frame, I've been getting distracted making other bits - such as spindle mounts:

4173

I've drilled most of the holes required in the frame, just got a few more to work out. I think it's best to drill them all using the milling machine ... except I can't really do that with the holes for the linear rails as I'm not confident I will be able to weld the frame parallel enough. I'm using the bed support rails to clamp the three upright pieces of the frame in place to weld, not sure about the rest...maybe some sash cramps:

4174

Jonathan
22-06-2011, 12:08 AM
i,ll have to have one of those spindle mounts off you soon,when i get round to changing my z plates.

Excellent ... I'm hoping I'll be able to mill them on the router when it's done as that should be quicker, or at least easier, than milling them. I would still bore the 80mm hole on the lathe. I will also round off the two corners that look a bit thin.

4175

4176

I've just drilled fixing holes in the 100x60 box section for the bed jacking screw mounts. I just need to drill some more holes for the X axis ballscrew mounts and chamfer quite a few of the ends then the main frame is ready to weld.

Jonathan
22-06-2011, 06:11 PM
I've started welding it at last!
I clamped everything together with M12 studs and G clamps:

4177

First weld was fine:

4178

Didn't need the hammer to get the slag off...the wind did that for me!

4181

Some tacking:

4179

Then I got worse...

4180

Jonathan
22-06-2011, 10:45 PM
I've finished one side of the frame... took all day! It's nice and flat/square :)

4186

Got some tidying up to do now! ...

4185

I'm going to get the other side of the frame clamped up now, and weld it tomorrow. I think I'll clamp the other side to the side I've just welded.

Jonathan
23-06-2011, 10:20 PM
I have now welded the second side of the frame. I clamped it to the other side to get it flat etc:

4192

I then tacked it together and welded the horizontal joins ... then rotated it and did the same etc:

4193

My welding is getting much more consistent. Still probably should have chosen something simpler for my first welding project!

4189

Now I have positioned the remaining pieces to work out how to proceed:

4191

I decided to use some spacers from steel tube. I'll put a few more in and use them to clamp the in between pieces. Cats were interested...

4190

Any comments / ideas welcome.

Jonathan
24-06-2011, 04:03 PM
thats looking good ,when will it be finished?

Thank you..... as soon as possible! I've just moved the frame up into the workshop since I decided it's best to weld it in there. I'm going to get it clamped together now (just stopped for a tea break!) and weld tonight.
I think realistically another two weeks to get it running, and some more for it to actually be finished. When the frame is done I still have quite a few parts to make to mount the X and Y-axis ballscrews and rotating ballnuts.

Jonathan
25-06-2011, 11:14 PM
Frame clamped together then tack welded:

4196

Some welding, then rotate it...
4197

A weld:
4194

Done!
4195

Jonathan
28-06-2011, 10:37 PM
Finally got the gantry mounted. Started making the aluminium plates to mount the X-axis bearings on 50mm wide, then realised it needed to be 60mm so that was a waste :sad: ... anyway, picture:

4203

The important point is I now don't have very high gantry sides, so the machine should be much more rigid.

I spent all of today working out where to put these holes for the Y-axis ballscrew bearing mount:
4204

Jonathan
16-07-2011, 09:46 PM
Got it all together ... and it works!
4243
4242
4241
4244

The last photo was after cutting 3mm off the edge of a sheet of 18mm MDF in one pass at 6000mm/min.

Y-axis rapid speed is 16000mm/min, X-axis is 10500mm/min and Z is 8000mm/min. The Y-axis will do much more, but I've left it at that as I don't see much point having it twice as fast as the X-axis. I prefer to keep the resolution good...

I think I'll try cutting some aluminium now.

(More to follow shortly, + video)

Jonathan
17-07-2011, 12:25 AM
I tried cutting a sign ... the test one with V-carve:

http://www.youtube.com/watch?v=ThVYRnHs4wE&feature=youtube_gdata

I need to get a cutter which has a sharper point ... that one has a 3mm or so flat on the end which spoilt things somewhat.

Jonathan
17-07-2011, 03:55 PM
Just tried cutting aluminium ... no problem! I put a bit of cutting fluid in the slot as it went round at 800mm/min, 0.85mm depth of cut with 6mm 2 flute HSS cutter @ 9000rpm. A lot faster than I could have used on my milling machine.

The edges are reasonably nice, still room for improvement but not bad I reckon for a first attempt. Next time I will add a climb milled finishing pass. Better than the milling machine...

4246
4245
4247

Video:

http://www.youtube.com/watch?v=ossjjN2BVsI&feature=youtube_gdata

I'm happy now that the conversion was worth it ... I always wanted the machine to be able to cut aluminium at a decent feedrate. I might try a relief with aluminium and ball nose cutter next.

luke11cnc
25-07-2011, 05:31 PM
nice cnc you have there Jonathan are you going to paint it at some point ??

Jonathan
25-07-2011, 06:17 PM
nice cnc you have there Jonathan are you going to paint it at some point ??

Thanks... it's not going to rust where it is so I don't think I'll paint it. It's there to make things not look at :smile: Paint would also get annoying if I need to add bits to it.

luke11cnc
25-07-2011, 07:15 PM
Jonathan
Reading more and more post I find my self thinking o's##T what have I let my self in for

I really thought 20 mm rails for the bed would be more than ample to carry the weight of the whole cnc machine

two 20 mm rails (made from 304 stainless steel) and four bearings mounted on the 90 degree side of 40/80 profile aluminium extrusion
and a centre ball screw (centre of the bed) 0f 16 to 20 threaded bar


where on earth do you all get your aluminium from as I have ordered of ebay, it arrived today so bent it is unusable

James & Luke

Jonathan
26-07-2011, 12:21 AM
I really thought 20 mm rails for the bed would be more than ample to carry the weight of the whole cnc machine

They will be ample to carry the weight since each of the 20mm bearings is rated for about 880N. That's not as excessive as it might seems though, see what I posted here:
http://www.mycncuk.com/forums/showthread.php/2739-Calculating-forces-on-linear-bearings-...

The reason I advised using the bigger bearings is not directly due to the higher load ratings. It it because they have 5 rows of ball bearings, not 4. This seems to make them have a lot less play than the <=20mm bearings. So I'm not saying you have to get the 25mm bearings, just that it will probably be better if you do.


where on earth do you all get your aluminium from as I have ordered off ebay, it arrived today so bent it is unusable

I now use http://www.aluminiumwarehouse.co.uk/
Only issue with them is you have to buy 2000mm lengths. If there's something smaller you need let me know as I might have a bit...
What size did you buy out of interest, and who from so I don't make the same mistake?

Jonathan
05-09-2011, 09:24 PM
1000th post :eek:

So here's a video showing my router doing 1000mm/s (2362ipm) on the Y-axis:

http://www.youtube.com/watch?v=k3MG7ww49A8&feature=youtube_gdata

All I did was change the pulley to 42T so the pitch of the screw is effectively 35mm. It's well above the critical speed of the screw, but interestingly it seems fine.

The video also shows the rotating ballnuts going happily at 15000mm/min.

Jonathan
19-09-2011, 01:09 PM
I had a request for some more photos, so here they are in no particular order:

4572
4573
4574
4575
4577
4578

deannos
03-08-2012, 01:57 AM
Hi,
Jonathan what have you used on your Y axis, I can't quite make it out

Jonathan
03-08-2012, 02:06 PM
Jonathan what have you used on your Y axis, I can't quite make it out

Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

deannos
03-08-2012, 03:14 PM
Which part in particular?
It uses an RM1610 ballcrew, 3Nm stepper motor...nothing unusual.

Your gantry in particular, is it ali box section

Jonathan
03-08-2012, 09:58 PM
Your gantry in particular, is it ali box section

Yep:


I went to a small local metals supplier and picked up a meter of 80x3mm aluminium box section for the Y rails to mount on

It's mounted with 20mm aluminium plate milled to fit in both ends. It's adequate, but I would advise using something a bit stronger. Since the rails are on both sides of the box section it had to be aluminium since the width of steel box section is not accurate enough. Extrusion is a good option, but quite expensive.

Jonathan
11-09-2012, 07:12 PM
The first of many upgrades to come:

682568266827

I'll be fixing 20 meters of 2"x1/2" aluminium strip under the bed in a grid to make it a bit stronger, since it's only 20mm thick aluminium. I've got 6m of the aluminium angle to go round the perimeter to enclose flood coolant, which will be the next upgrade. I'll have the router drill an array of holes to tap M8 for clamping. I elected not to go for strips (to imitate T-slots) as the difference in price is not that great in the whole scheme of things and this should be stronger although either would have been sufficient. Need to get it at the right height too...

JAZZCNC
11-09-2012, 07:35 PM
That looks like an expensive piece of Ali make sure you don't Fubar .!! At least with strips if you do then it's a cheap repair.!

After fitting the strips are you going to fly cut it.?

Jonathan
11-09-2012, 07:55 PM
That looks like an expensive piece of Ali make sure you don't Fubar .!! At least with strips if you do then it's a cheap repair.!

Ascmetals are to blame for the good price. Not that bothered about marks to be honest - if I do mess up it's unlikely to cause more than aesthetic damage, which luckily I don't care about!


After fitting the strips are you going to fly cut it.?

Not sure yet since the issue is I can't reach the full area with the spindle in one go. Once they're fitted I'll height map it and see how close it is. I can always put some aluminium 'sacrificial' strips on top (which could even make T-slots), but I think I've spent enough.

JAZZCNC
11-09-2012, 08:07 PM
Not sure yet since the issue is I can't reach the full area with the spindle in one go. Once they're fitted I'll height map it and see how close it is. I can always put some aluminium 'sacrificial' strips on top (which could even make T-slots), but I think I've spent enough.

90% sure you will.? . . . When I did mine I height mapped it with 45mm grid and was surprised at the differences.!! Thou mine was an easy surface has I only had to do the strips.
I had the same problem regards cutting the whole area but actually it works out good because the shoulder it leaves acts has a parallel reference edge for X & Y.

Jonathan
11-09-2012, 08:16 PM
I tend to a agree with the 90%...

I reckon if the spindle on there, or the one I made, can support a big enough fly cutter I can easily get over both sides by moving the spindle to either side of the Z-axis especially since 2" wide around the border will be occupied by the aluminium angle unless I mill that down. The problem then is maintaining an accurate height between passes, but that shouldn't be too bad. On the previous bed it was very handy having the ridge left from surfacing for a parallel reference

TrickyCNC
12-09-2012, 12:01 PM
Very nice machine you have there Jonathon !did you get anywher

e with the 'twisted bearing' screw drive setup ?

Rich




Just got some M16 threaded rod for the Y-axis, thought I'd give a quick demo of the drive 'nut' as it's a little different...


http://www.youtube.com/watch?v=m6k8Jz_-WCk

I know I should probably use ballscrews, but I reckon using this method is almost as good - rolling friction, low backlash... I measured the backlash on the plywood Z-axis I made using this method and it was <0.005mm which I think is pretty good considering the cost!

I guess it'd be better to use trapezoidal and put an insert in the bearing to fit the thread better - I'll leave that for a later date though.

Jonathan
12-09-2012, 12:20 PM
Very nice machine you have there Jonathan

Thanks, but it's not that great really...quite a few things I'll be changing as the gantry is not strong enough for what I want to do next.


did you get anywhere with the 'twisted bearing' screw drive setup ?

Yes, I mounted it and it worked well with low backlash:
http://www.mycncuk.com/forums/router-build-logs/2288-1-7%2A0-74%2A0-4m-mill-router-building-6.html#post16838

It's clearly not as good as a real ball-screw, but as something to get started it's excellent due to the low backlash and very low friction.

I cut the first piece with the new bed last night - just a pocket in the back of an aluminium motor mount and the finish was much better than with the [edit] MDF bed and I didn't need to do a finishing pass to get that.

TrickyCNC
12-09-2012, 02:23 PM
Yes, I mounted it and it worked well with low backlash:
http://www.mycncuk.com/forums/router-build-logs/2288-1-7%2A0-74%2A0-4m-mill-router-building-6.html#post16838

It's clearly not as good as a real ball-screw, but as something to get started it's excellent due to the low backlash and very low friction.


I saw you have mounted it, what I could not tell from reading the rest of the thread, is if you kept it / still use it ? and if so, how it was holding up ?

Rich

Jonathan
12-09-2012, 02:35 PM
I used it for quite a long time, until changing to an RM1610 ballscrew. It was working well, although had caused some wear to the M16 rod (although not enough to be a problem) due to bearing inner ring being significantly harder than the screw, however I think if you used springs to push the angled bearing against the screw and/or used a trapezoidal lead-screw instead then it would last a long time.

JAZZCNC
12-09-2012, 03:44 PM
I cut the first piece with the new bed last night - just a pocket in the back of an aluminium motor mount and the finish was much better than with the aluminium bed and I didn't need to do a finishing pass to get that.

Surely that should read MDF bed.?

Jonathan
12-09-2012, 04:10 PM
Surely that should read MDF bed.?

Yes, thanks for pointing that out - fixed.

What size fly cutter do you use for surfacing yours?

I'm cutting the aluminium angle now to fit round the sides for the coolant barrier, then once I've got the bed aligned I'll get the router to cut a suitable hole in the bed at one end for the coolant to flow through and make a filter etc...

I seem to be able to cut 3mm per pass with the 6mm single flute cutter now :)

JAZZCNC
12-09-2012, 05:05 PM
What size fly cutter do you use for surfacing yours?

It's a special that someone made for me and it's widest is 60mm.


I seem to be able to cut 3mm per pass with the 6mm single flute cutter now :)

Yep surprising how much a nice solid bed changes how the machine performs and best of all it never changes it's shape when you put your cup coffee near it.!!

Jonathan
29-09-2012, 01:36 AM
Very, VERY impressive. :thumsup::thumsup:

Not really, anyone can put a big pulley on the stepper motor and lower the acceleration to get a high feedrate at the expense of resolution. Such a high feedrate would only make a negligible difference to machining time on a router used mainly for cutting metals. It's just for show...

WandrinAndy
05-10-2012, 12:04 AM
4578

Jonathan,

A quick question about your "box" type Y-carriage in this pic please... Particularly about the position in which the horizontal plates are bolted to the vertical plates....

The top plate is bolted slightly above the top of the vertical plates and the bottom plate is bolted slightly below the bottom of the vertical plates... If that makes sense.

Did you do this for a specific reason such as making the initial DIY build/squaring easier?

Cheers,
Andy

Jonathan
05-10-2012, 12:19 AM
Did you do this for a specific reason such as making the initial DIY build/squaring easier?

Yeah I ordered the wrong size aluminium plate!

To make it easier to square you should mill a shallow slot into the back of the Y-carriage plate which holds the Z-axis bearings. This can then align to one of the smaller plates on the Y-axis to get Z perpendicular to Y. You can just about see what I mean in this picture, circled in red:

7064

Which reminds me I never posted the pictures from when I changed the Z round rails to linear guides:
7065706170627063
Using the indicator made aligning the rails properly and getting it to run smoothly trivial. Fitting everything in the small available space was less trivial. Hard to say how much difference it made to the performance of the machine, since at the time the MDF bed was the limiting factor and I think my spindle might be on it's last elbows...

Jonathan
26-11-2012, 01:51 PM
I finally had chance to drill the array of M8 holes for clamping in my router bed. Here's the result:

745774587459

I used a carbide drill since the spindle speed required for a 6.8mm HSS drill is too low for the spindle to have enough torque to cut efficiently, if at all. I ran the drill at 9500rpm and 840mm/min with flood coolant, which according to the manufacturer's recommendations is quite conservative, but still plenty fast enough. I didn't see any point pushing it harder as that would only increase wear on the spindle bearings.

Here's a video showing the process. Possibly the most repetitive video I've uploaded to youtube so far...

http://www.youtube.com/watch?v=gFLwSYARcUU&amp;feature=plcp

The Z-axis motor, not surprisingly, got pretty toasty but other than that it went well. I had to move the bed out to reach the whole length, so it's currently 360mm from the normal position. Just need to make the router cut a drain in it, then I'll put it back.

Jonathan
26-11-2012, 07:54 PM
Forgot to say in the previous post...
Around the edge of the aluminium bed I've put 3x2", 1/4" thick aluminium angle. This acts as a barrier for the coolant, so to ensure it seals I put a strip of 1.5mm thick neoprene under each piece. I used my metal cutting bandsaw to cut the 45 angles, but the finish from this although not bad for a bandsaw, is still quite rough.

746974707471

Bit of an unusual set-up on the lathe so I videoed it:


http://www.youtube.com/watch?v=Xj1AYb41dQs&amp;feature=plcp

(Something wrong with the sound on the past two videos)

olalofberg
09-12-2012, 11:26 PM
Hello, looks like you've got a fine machine there Jonathan! Good work, It inspired me to go the way with the bed-box-gantry type mill, if I get started with one on my own.
Usage: pcb, wood, plastic engraving, possibly some easy metals, maybe 3d printing?, 3d scanning? Bigger polystyrene works. I like the idea of the adjustable bed height for different jobs. I already have three industrial dc motors+encoders and two ballscrews I was planning to use. I was thinking of a machine capable of moving 800*700*300mm.
A couple of questions came to mind:


1. Where do you get all parts? Is there a standard online place with good prices/service? Guides, ballscrew, bearings. Saw that Hong kong was mentioned.
2. I was thinking of moving the gantry with two rotating ballscrews and one motor. Long
gearbelt to sync the screws and have the motor directly on one screw. Whats your thought about this? I think I'm ok with a 1/10 or 1/20 mm milling accuracy. (I don't think I can build the complete works with greater tolerance)

Cheers

/Ola

Jonathan
10-12-2012, 07:40 PM
Usage: pcb, wood, plastic engraving, possibly some easy metals, maybe 3d printing?, 3d scanning? Bigger polystyrene works.

So just about everything!



800*700*300mm.

That size is very manageable, although you will have to make it quite strong to make good use of the large Z-travel. Are you sure you need that much? I guess it's for the 'bigger polystyrene works', in which case since you will use an adjustable height bed, the required rigidity is lower.



Where do you get all parts? Is there a standard online place with good prices/service? Guides, ballscrew, bearings.

The nearest you'll find to a cheap standard online place is the seller linearmotionbearings2008 on eBay. Many people on this forum have used him, myself included, and been pleased with the products and service. It works out cheaper to get the spindle from other eBay sellers, or even better ali-express.




I was thinking of moving the gantry with two rotating ballscrews and one motor. Long
gearbelt to sync the screws and have the motor directly on one screw. Whats your thought about this?

6 of one half a dozen..
If you use two motors the available torque is greater, so you should get higher acceleration and top speed, however it will work out a bit more expensive than one motor and a long belt. I don't consider one motor stalling and the gantry racking a valid concern since if your machine is tuned properly, and you shouldn't be running it if it isn't, then that should never happen. On my machine I had little choice since with the current gantry design it's impractical to route a timing belt to link both rotating nuts.


I think I'm ok with a 1/10 or 1/20 mm milling accuracy.

Not difficult.

In other news, I have made and installed the drain for the router bed so I've been cutting with flood coolant. I fount that one corner of the machine is ever so slightly lower than the rest, so I put the drain in that corner so the coolant flows. A week later I discovered the reason for this corner being lower - there's a crack in the floor and it's sunk down!

The drain is fairly basic, just two parts I made on the lathe to hold some fine mesh, which is easily replaced:

75717572757375747575

After running for some time:

7576

Video of cutting with flood coolant:


http://www.youtube.com/watch?v=gkGf5c9VQyk&amp;feature=youtube_gdata

ubiestmea
26-04-2014, 05:36 PM
Did you source or mill the aluminum support for the guide rail?

Thanks, Jeromy