CNC Mill Project
So it begins.
As I post this the frame is just about complete, with the last side rail under semi-precision layout work right now in the home shop.
I'll post some pics of the actual work going into cutting/drilling one of these rails soon, before I paint it and fit it together.
Pics to come!
- regular NC threaded rod to be used
- ugly backlash eliminator to be designed machined & applied.
- 280 oz steppers from xylotex&board to be purchased
- Mach2, MC9.1(school version, of course)
- 2" square tubing galore outside from my dad's scrap pile
- cold rolled steel for the bearing surface
(photo: z axis incomplete, will take some bench work to fab it.)
Last edited by justCNCit; 02-03-2006 at 08:52 PM.
and if this makes any sense:
so I've decided to go with ballscrews(almost completely decided, that is)
now that I've realized that a CNC machine will/would lose almost all accuracy with even only the slightest bit of backlash, I see no other choice.
I'm sure these options have been endlessly explored already on this board, but if anybody wants to save me some time can they tell me if:
- it is feasible to eliminate backlash, or compensate effectively enough for it in an ACME screw driven system
- a belt system is the way to go, (expenses? complexity?)
- how badly priced are ballscrews, I'm willing to spend a reasonable price on them. ?
- are ballscrews the god of all screws?
It is hard to tell from your pics and drawings as to the size of this router. Ball screws are probably going to cost you a bundle. You have not given us a budget or expectations. Seems from your posts that you are leaning toward the cheaper side, and that is OK, but it makes a difference as to what to recommend.
If I got it right, your long axis is riding with skate bearings on unsupported rod (even if it is cold rolled). I would worry more about this than backlash. Backlash can be easily controlled with Acme screws or ball screws. Acme will be a lot cheaper and zero backlash nuts can be made by you or purchased from Dumpster.
Tell us more what you want to accomplish.
Fairly cheap and affordable, but to work reasonably well.
I've been meaning to update the CAD pic that is found first thing in this post. At school I can't do that but I can describe a few changes to the design.
The design you see doesn't show everything in the plan. There will be holes drilled in the frame rails beneath the cold rolled shaft, with larger access holes directly beneath where adjustable support bolts will be mounted.
Hm, as for budget and expectations. . . well here is a rough estimate that I think would work:
- Misc. steel and aluminum (parts of the gantry alum, cold rolled shafts)
$200~ probably quite a bit less
- Steppers & control system, $430 CND shipped(xylotex system, 280oz)
- $80 ($5 a piece) 26OD 10ID bearings (one in photo)
- $30~ paint
- plenty of steel out back that can be used for general framing.
and of course, once it's built a $100 copy of Mach2 and BobCad/cam.
This is going to be a hobby machine, at least in the beginning. The machine will be used to route out complex contours and horizontal Z roughing paths. I already have a controller PC.
It's just that the way I see it, even a small amount of backlash is enough to kill your accuracy when controlled by stepper motors. Will check out that link.
oh, and for a size, I think the length of the frame in the pic is about 64". The width must me somewhere around 30", it happened to be the size of the steel that was already there.
Trying to get ahold of some steel through school, began work on the X axis the other day. Completed the Y axis rod blocks already and 3/4 done them on the X axis.
Material for the X axis has been cut to size, will need to drill holes in them properly spaced and order aluminum 2" square tubing for the crossmembers.
pics to follow, of course.
Ran into a design problem, the way the rod bracket's bolt into the frame the bolts are not only unaccessible, but are too big for the rod to fit through.
Ended up doing this today when I checked and confirmed this problem:
welding nuts to the holes so that they can be bolted from inside the frame rails.
Settled on inside Hex bolts too, because you can't get a wrench into most places on this machine. So much for all those 10mm bolts/nuts I bought, stock now.
Mocking up gantry, there is more work to do before these vertical rails can be welded to their bases. Have to cut bolt access holes into the sides with the new die grinder & discs I bought.
Pic of corner of shop
radiant floor heat. 92 jeep cherokee
Ball screws vs asme thread
I'm just a newbie, have to confess an older newbie, and don't know too much about CNC routers yet. But I do know that the backbone of lathes, mills, cross feeds, etc is the acme thread. This tells me that it is very capable of extreme accuracy!!
Couple months work in rhino(now and then)
Going to get a couple (6) pieces laser cut, maybe even 12 depending on $$.
An order is coming in from Dumpster(www.dumpstercnc.com) & Ahren (www.cncrouterparts.com) is receiving it and sending it with some of his product. These parts have been incorporated into this design.
Last edited by justCNCit; 08-09-2007 at 06:03 AM.