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
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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.Quote:
Originally Posted by blackburn mark
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?):
Attachment 3479
Cross section, note disk break arrangement:
Attachment 3480
Attachment 3481
Mounted on mill:
Attachment 3482
You're not the only one :)Quote:
Originally Posted by chip
Will doQuote:
Originally Posted by chip
hahha!!! sorry jonathan, you did... on my build thread... it looks so much smaller on your router i thought youd built another oneQuote:
I mentioned it somewhere else on this forum...not sure which thread though.
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 :)
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...Quote:
Originally Posted by blackburn mark
Yep, that's my plan ultimately - to be able to accurately switch between stepper and brushless motor drive.Quote:
Originally Posted by blackburn mark
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.
Attachment 3484
I'm 14 holes and one slot away from finishing :) Plus a bit of assembly and wiring I suppose.
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 shaftQuote:
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...
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
Surely a timing belt for the outer gear would have the wrong profile.Quote:
Originally Posted by blackburn mark
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.Quote:
Originally Posted by blackburn mark
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...
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 ...
Sorry but you are gonna be wasting your time using MDF and an accident in the making for sure.Quote:
Originally Posted by Jonathan
More bad advice The only thing MDF should be used for is a spoil boardQuote:
Originally Posted by Wobblybootie
Phil
i compleatly missed that,,, i think your rightQuote:
Surely a timing belt for the outer gear would have the wrong profile.
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)
Attachment 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 :)
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!Quote:
Originally Posted by M250cnc
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.
ill do a sketch if i find time.
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)Quote:
Why do you want such a high ratio anyway?
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
Jonathan any type of wood table is going to fail to sufficiently clamp metal to itQuote:
Originally Posted by Jonathan
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
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 :)Quote:
Whatever you are machining/clamping to the table has to be weaker than or equal strength to the table itself
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?Quote:
Originally Posted by M250cnc
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.)
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.Quote:
Originally Posted by blackburn mark
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.Quote:
Originally Posted by blackburn mark
Dad's still making legs for router - wooden frames are always his department. Going to go and help now...
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.
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
Double Post
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.Quote:
Originally Posted by M250cnc
I like the idea of threaded inserts, but they're not so versatile as T-slots.
Jonathan, you have a lot to learn.:whistling:Quote:
Originally Posted by Jonathan
Phil
ha!! i guess that means your just about done with learning phil :clap:Quote:
Jonathan, you have a lot to learn.:whistling:
right!!! im off to stick my hand int fire :heehee:
:confused: :confused: :confused: :confused:Quote:
Originally Posted by blackburn mark
Phil
Just what I was thinking.Quote:
Originally Posted by M250cnc
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.Quote:
Originally Posted by M250cnc
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!
ok ok,,, it must be a northern thingQuote:
Just what I was thinking.
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:
Some pictures...
Legs:
Attachment 3488
Gantry side:
Attachment 3489
One X motor, need to tighten that belt:
Attachment 3490
Gantry side again:
Attachment 3491
Yeah my workshop is in disarray now:
Attachment 3492
looks well tidy to me:) i could live in that workshopQuote:
my workshop is in disarray now
It's much tidier than it was yesterday! There was a layer of swarf on the floor.Quote:
Originally Posted by blackburn mark
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?
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'?Quote:
Originally Posted by 2e0poz
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 colletQuote:
What's the diameter of the shank of those 5mm cutters you pointed me to? Also flute length?
hahaha! your 18... its ment to look like you dropped a box of grenades in there :)Quote:
What do you mean by far 'too clean'?
indeed ! im exspecting you and your old man to build a flux capacitor to go in the delorean when your done :)Quote:
thats some work shop at your disposal lad.
shank=5mmQuote:
What's the diameter of the shank of those 5mm cutters you pointed me to? Also flute length?
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
Christ if i could keep my workshop as clean as yours is dirty i would be heaven................Where do you keep the tesla coil?
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.
Thanks for the info. I'll probably buy some.Quote:
Originally Posted by blackburn mark
Action shot, suspicious lack of swarf :confused::
Attachment 3496
View of gantry:
Attachment 3494
Z axis, extended to about 390mm:
Attachment 3495
Whole router, Dad snuck in on this photo (everyone suddenly appears in the workshop when it starts working!):
Attachment 3497
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
:rofl: thanksQuote:
Originally Posted by blackburn mark
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...Quote:
Originally Posted by blackburn mark
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)
Well done Jonathan and good to see you up and running :-)
Splendid!!!! im surprised how fast its cutting
thats a lot better than i would have thought :)Quote:
0.06mm
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
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 bizzarQuote:
Yes one X motor is much stiffer than the other. It's limiting my feedrate...
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
Quote:
Originally Posted by 2e0poz
Thanks, I'm glad it's working at last!Quote:
Originally Posted by chip
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.Quote:
Originally Posted by blackburn mark
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.
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.Quote:
Originally Posted by blackburn mark
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.
Hmm, I thought 3600mm/min was tedious :redface:Quote:
Originally Posted by blackburn mark
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.
cant help you there, im not into wood... im just going off what iv seen on the netQuote:
What feedrates do you/other people normally use with MDF?
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 sureQuote:
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
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
Quote:
Hmm, I thought 3600mm/min was tedious
your definitely 18 :)Quote:
Z still works at 10000