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jcb121
24-07-2011, 01:08 AM
So, my name is Jesse.
I'm going into college next year to do 3d design for two years.

I enjoy modding motorbikes and Pcs!

I've been wanting to build a CNC machine for a year at least and I've now ran into some money to do my motorbike bike test and build a CNC machine!

I've got some designs, I'm going to be using linear bearings on 16mm steel rods and will probably use leadscrews with nema 23 steppers.

All put together on some extruded Alu. The budget of this is going to be as low as possible!

my Local Metal supplier is great! as long as I go around there with a pack of biscuits and when the boss is out he just makes up a number in his head for bits I need!

I'll be CNCing Aluminium mainly so I was looking at a kress 800watt spindle.

I'm hopefully going to get a working machine! I've already purchased some linear bearings so they can't go to waist now!!

If anyone knows any good places to get things like Leadscrews, Housed bearings etc, then that would be a great help. I've just been looking on ebay.

I'm looking forward to being an active community member not only getting help, but giving it too :)

Thanks

Jonathan
24-07-2011, 01:53 PM
So, my name is Jesse.
I'm going into college next year to do 3d design for two years.

Hmm, that implies you're about the same age as me...


I enjoy modding motorbikes and Pcs!

...so does that!



I'm going to be using linear bearings on 16mm steel rods ... If anyone knows any good places to get things like Leadscrews, Housed bearings etc, then that would be a great help. I've just been looking on ebay.

I hope that's supported 16mm rails, not just round bar. It depends how big the machine your building is and what you want to do with it, but in general supported will be better (less deflection & vibration) and not too expensive if you get it from linearmotionbearings2008 on eBay.


All put together on some extruded Alu. The budget of this is going to be as low as possible!

I think steel box section is the most economical material to use for the frame. Aluminium extrusion is strong, but expensive. Having said that if you're paying with biscuits that may not be a problem :smile:


I'll be CNCing Aluminium mainly so I was looking at a kress 800watt spindle.

Definately use supported rail then if you want to be able to machine it accurately at a decent feedrate.


I'm hopefully going to get a working machine! I've already purchased some linear bearings so they can't go to waist now!!

Looks like it might be too late... I should have read the whole post first.

jcb121
24-07-2011, 02:16 PM
Pretty close age wise.

The mill I'm building is A4 Size, I've looked at many machines this size like this one (http://www.worldofcnc.com/products.asp?recnumber=212)

I haven't paid for them yet, I was holding off until I had completely finished my drawing and I have now, almost. I'm in that process of making the numbers nice to work with.

Extruded Alu for my A4 Cnc comes to a cool 60 excl P+P from Zapp and I'd say my design will be on par strength wise with the one I've linked.

I may go full supported rail, but it's really expensive!

i2i
24-07-2011, 04:53 PM
Hi Jesse, i have a set of leadscrews that i removed from a working router that you're welcome to. I'm based in Cardiff as well, so you can collect them if you want.

jcb121
24-07-2011, 05:09 PM
Thanks but what lengths are they?

I managed to cancel my order for the closed linear bearings. I will be buying Some 20mm supported rail, 600x600x300.

While walking the dogs I saw my neighbor (who works at the metal shop) and they said under 10 for 1000mm of extruded box section Alu! That was off the top of their head though....

So I'm thinking I'm going for linearmotionbearings2008 20mm supported rail kit, 50x50mm box section Alu and a 1000watt Spindle.

Should be a beast! Plenty of 10mm Alu thrown into the design as well, for good measure Ofc!

I'll be starting a build log soonish. I would respond quicker but the Mods have to monitor my posts! :( :(

i2i
24-07-2011, 07:04 PM
820mm, 670mm and 250mm, with nuts and bearings. If your picking them up you can have a nose at the router as it's currently being modded.

Jonathan
24-07-2011, 08:11 PM
If you can afford little bit more on the rails then get the 25mm (at least for the X axis) as it has one more row of balls than the 20mm rail. On my machine I used 25mm and 20mm and the 25mm clearly has less play in it. Might be a bit over the top for an A4 size machine...

So it's just aluminium box section, not aluminium profile? It must be for that price...if it is just box section then how are you intending to fix the ends together? Steel+welding would be easiest.

Have you considered getting one of the water cooled spindles that are available on eBay? I was going to get a Kress but decided/was persuaded that the water cooled one is better as it's quieter, less runout, stronger in general and won't wear out as fast. The collets are also a lot cheaper than Kress. I got the 2.2kW version since it takes 1/2" collets.

Have you got a milling machine to cut the 10mm aluminium? If not I can help you there ...

jcb121
24-07-2011, 09:23 PM
My budget is around 800~, Though I wouldn't like to spend this all On a CNC Machine as I need to buy ALU, motorbike parts and my Mod1+2

My current criteria are:

Supported Rails
A3 workable area

I plan to:
Mill Aluminium.
Acrylic

What would you recommend as you guys know best? is the LC spindle really needed over a cheaper alternate such as the kress.

is 40mm Alu Profile ok to build a machine of my needs with?

is making the leap to 25mm supports really needed for a A3 machine?

what Force Nema 23 motors will I get away with?

Thanks.


PS. I have a Drill Press, Some Cobalt bits, Files and Lots of time so I souldn't need anything CNC'd for me to make it :)

but if I do, You'll have a PM,

Jonathan
24-07-2011, 10:32 PM
What would you recommend as you guys know best? is the LC spindle really needed over a cheaper alternate such as the kress.

The Kress is in the end still a router, not a proper spindle. It will have more run-out, be noisier etc and won't last forever. The minimum rpm is 5000 ... whereas you can go lower with the water cooled spindle. That's good for cutting metals.
Maybe get a really really cheap router to start with then save up for the spindle? I started out with a router for about 6 from the car boot sale ... one of the ones from Aldi. This is what I have now got:

http://cgi.ebay.co.uk/2-2KW-WATER-COOLED-SPINDLE-MOTOR-ER20-INVERTER-DRIVE-/250748327119?pt=LH_DefaultDomain_0&hash=item3a61c3d4cf#ht_7977wt_1139

For an A3 size machine the only reason to get the 2.2kW version is because it takes bigger collets. The extra power wont be required.


is 40mm Alu Profile ok to build a machine of my needs with?

Do you have a drawing of it, or better know its second moment of area?


is making the leap to 25mm supports really needed for a A3 machine?

It's not needed, but every little helps. The more rigid the machine is the faster you can cut whilst still maintaining a good finish. I regret not getting 25mm for the Y and Z axis, but then my machine is much bigger.


what Force Nema 23 motors will I get away with?

These 3Nm ones are popular/economical:

http://www.ebay.co.uk/itm/3-X-3Nm-Stepper-motor-CNC-Milling-machine-router-/220733820503?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item3364c2ce57#ht_1617wt_905

You could use less, but the price per Nm goes up if you do. The main thing is to look for motors with a low inductance and run them on a high voltage as that gets more torque at higher rpm. With those motors 70V will work well, which means you'll spend about 40-50 on each driver.

jcb121
24-07-2011, 10:47 PM
So would these Stepper motors (http://www.ebay.co.uk/itm/3-X-3Nm-Stepper-motor-CNC-Milling-machine-router-/220733820503?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item3364c2ce57#ht_1801wt_804) with these Stepper drivers (http://www.ebay.co.uk/itm/4-2A-50V-Stepper-driver-CNC-Milling-machine-router-/220795461105?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item33686f5df1#ht_825wt_804) hooked up to this breakout board (http://www.ebay.co.uk/itm/Breakout-board-CNC-Stepper-Motor-5-Axis-Spindle-Relay-/120751785894?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item1c1d5e07a6#ht_680wt_804) with this 48v PSU (http://www.ebay.co.uk/itm/600W-PSU-48V-12A-CNC-Power-Supply-Stepper-Motor-Milling-/110718245260?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item19c752598c#ht_500wt_814) or this 36V PSU (http://www.ebay.co.uk/itm/400W-PSU-36V-11A-CNC-Power-Supply-Stepper-Motor-/120748967665?pt=UK_BOI_Industrial_Automation_Contr ol_ET&hash=item1c1d3306f1#ht_500wt_814)

and that would be the electrical side done apart from the spindle?

Jonathan
24-07-2011, 11:56 PM
Steppers good and drivers are ok but you will find equivalent much cheaper on eBay internationally and 75 volt would be nice.

The breakout board you have chosen is opto-isolated which would be good except the drivers you have chosen are already opto-isolated ... that makes it slightly more difficult to wire up and can lead to issues so it's best and also cheapest to use a breakout board which is not isolated or even just connect them directly.

The 48V supply is ok, but again 70V would get higher torque. It's also very expensive ... so go for this one if it's still availably and you stick with the 50V drivers:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=380071301709#ht_1179wt_1139

Though it looks like Zapp might have bought the lot to sell them for three times the price:

http://www.zappautomation.co.uk/ep002g1-50v-power-supply-p-11.html?osCsid=05c0e6d325fd327267b64aaf46d5274f

I dislike the way they are making so much on those bye claiming it's a good price by saying the RRP is 280.

jcb121
25-07-2011, 01:52 PM
are there any benefits to having the cutting bed move along the x axis?

I know it will take more room in my workshop but surely it's more stable?

i2i
25-07-2011, 01:57 PM
you have a more rigid y and z axis

Jonathan
25-07-2011, 01:58 PM
Swings and roundabouts...

Moving bed is bad if the part you are machining is heavy, or if you've got a heavy vice etc as the steppers have to accelerate that mass quickly. If however the mass of what your machining+bed+clamps is less than the gantry then moving the bed will get better acceleration/speed.

How rigid the machine is depends on how you configure either option, so it's difficult to compare. Having the gantry stationary is good in that you can make it as strong and heavy as you want want ...

Not sure what other pro's/con's there are as I never really considered it ... other than space as you say.

jcb121
25-07-2011, 03:12 PM
what do you guys think so far? the cutting are from the outside of the 10mm bit is 420x290

so just under A3. this is with 20mm clearance on each side of of gantry when moving in all directions.

so the actual cutting are is 40mm bigger both ways.

I need to re-think my Z axis though, it's too big and won't give the spindle enough depth.

I'll be limited to the thickness of the sheet not be the length of the supported bar.

Jonathan
25-07-2011, 03:41 PM
The way you've orientated the X-axis linear bearings will make them difficult to align parallel - you would have to cut the frame they attach to extremely accurately or have some adjustment. If you rotate them by 90 then it's easy to align them as you can fix down one and use it to get the other parallel.

Having the Y-axis ballscrew close to the bed is a good plan as that reduces the overhang... which will reduce deflection parallel to the Y axis. Similarly to the X-axis you've not got a way to adjust the spacing in the Z direction of the Y axis bearings. That orientation is good .. you just need to have the plates in the YZ plane bolt to/overlap the plates in the XY plane. Look at how I did it on my machine if that's not clear.

Where's the X-axis ballscrew(s)?

Putting the rails on the moving part of the Z-axis is stronger than having the bearing blocks moving when it's at the upper limit. Be careful with making the Z-axis too long. It will make the machine much less rigid. I had that problem (400mm Z axis!) so I ended up eliminating the gantry sides:

http://www.mycncuk.com/forums/showthread.php/2288-1.7%2A0.74%2A0.4m-Mill-Router-building.../page11
(only need to look at the last few pages...)

Mounting the stepper motors on posts has poor torsional stiffness. A 'solid' mount would be better.

luke11cnc
25-07-2011, 05:13 PM
jcb121 welcome you seem to know a lot more than me so I will be an eye on this post

James & Luke

jcb121
25-07-2011, 06:03 PM
Ha, sure. I was going to start a proper build log, maybe when I get my stuff :)

I was going to ask if you wanted to order stuff from china together, but then realized that rugby was not in wales. I genuinely thought it was in wales and you could come and pick it up :)

42724273

How's this lads?

luke11cnc
25-07-2011, 08:48 PM
how do I mark this post to keep an eye on it ??

James & Luke

jcb121
25-07-2011, 08:53 PM
Thread tools at the top right. click subscribe. I'll be making a new thread in the next few days.

I'm guessing this thread silence means you can't see anything wrong with my drawing? :)

Jonathan
25-07-2011, 08:54 PM
how do I mark this post to keep an eye on it ??

Subscribe to the thread... use the 'Go Advanced' button when you next post and tick 'Subscribe to this thread and notify me of changes:'

jcb121 - I think what you've just drawn looks better.

i2i
25-07-2011, 08:55 PM
how do I mark this post to keep an eye on it ??

James & Lukeas you've posted in the thread you should be notified when a post is made.

Jonathan
25-07-2011, 09:06 PM
I'm guessing this thread silence means you can't see anything wrong with my drawing? :)

Possibly... :smile:

Driving the ballscrews via timing belts allows you to change the ratio - ultimately getting a higher feedrate. True it's more expensive, but if you want to use the motors to their full potential I think it's the way to go. You will of course loose a bit of resolution if it is geared up, and vice versa.

You still have the Z-axis bearings mounted to the Y-axis, not the rails. I'm pretty sure that putting them the other way round makes it stronger in general.

The aluminium extrusion should be strong...steel box section should be cheaper for the same strength. Consider putting an aluminum plate on the bed (maybe 10mm thick) to stiffen it up and give a good surface to hold stuff.

(I just typed this 3 times ... first time I accidently clicked close, next two times the cat closed it for me...)



as you've posted in the thread you should be notified when a post is made.

Yeah I'm getting flooded with emails!

jcb121
25-07-2011, 09:25 PM
The Ballnut on my drawring is tightly placed between the two bearings to reduce the size. switch the bearings onto the other side would lock the ball screw in between the bearings making it useless!

unless I did a re-design. would take maybe 5-6 minutes of my life, but it's dinner time and I'm bloody starving!

all the items in Sketchup I made, would it be worth having a sketch up section on here so that people can download them into there CNC machines within sketchup?

I made all mine my self apart from the spindle, would of shaved a lot of time off the design.

jcb121
25-07-2011, 10:06 PM
http://www.damndirtyrino.com/wp-content/uploads/2011/03/cat_plotting_4.jpg
http://26.media.tumblr.com/tumblr_l0ggn7mjan1qzfehio1_500.png

:)