New Machine Build- First build! 3-Axis Gantry-style CNC

[TheBakachan]

Hey everybody!

I'm finally building a CNC machine to further my goals of world domination!

I'm a complete nüb when it comes to this stuff, and am going to have some questions, but I'm a fairly smart guy and a fast learner.

I have a rough idea of the design worked out in 3D, but I have to finish nailing it down today now that I have all the components in-hand.

For its guts it has a Keling Inc 3-axis package with KL-4030 drivers and 425oz-in NEMA23 steppers.

Its construction consists of a bunch of 80/20 extrusions that I got good deals on from their eBay surplus store.

The linear motion is 1/2-10 Acme screw, and precision steel shafts with linear bearings.

The (maybe temporary) brain is a very old Athlon 1800+ machine running the custom Ubuntu EMC2 linux distro.

The spindle is a Bosch 1617 in a mount from K2CNC.

Hopefully this will turn out really well. You can look forward to my detailed status reports (And lots of pictures!) as things progress.

[ger21]

Do not use 1/2-10 acme with those motors, you'll get poor performance. Use something that gives 2 to 4 turns per inch max for best speed.

[TheBakachan]

Originally Posted by ger21 Do not use 1/2-10 acme with those motors, you'll get poor performance. Use something that gives 2 to 4 turns per inch max for best speed.

Thanks, I'll keep that in mind in case it doesn't run as well as I'd like.

For now though, what's bought is bought. Based on my currently limited understanding of this stuff, I was going for high positional resolution, with a pitch that offered nice round numbers to deal with. Speed isn't really my top priority.

I am not free of concerns regarding the design however. For instance, I think I might need a second stepper and screw for the Y axis...which frankly I don't have the money for right now, heh.

We'll see

The last components arrived today, so I can really get to work on the design. (I'm very hands-on, so I wanted to have the parts and really see how everything goes together before I tried to get more specific with the design.)

[FandZ]

I think what Gerry is saying is that with those motors and driver you won't be able to hit the sweet spot since the driver won't be able to provide enough juice to drive them at their optimum. You may end up, buying new screws and nuts, downgrading your motors, or a new driver and power supply. All three are kinda pricey. Since you havn't used them yet, perhaps you should exchange the package for one that better suits your needs.

The only reason I'm pointing this out is I wanted the same motors. But CR talked some since into me.

[TheBakachan]

Hmm, that DOES sound rather problematic. What would you recommend for motors instead? Though I'm not sure I understand how the driver and power supply wouldn't be able to 'provide enough juice'. The rated draw for the steppers fits well within the specs of the drivers and power supply.

Speaking of the steppers though, I was wondering, should I have them wired in series or parallel? If I've been reading correctly, I probably want Parallel. Series and Parallel both offer the same torque, but Series will stall sooner.

[FandZ]

Originally Posted by TheBakachan Hmm, that DOES sound rather problematic. What would you recommend for motors instead? Though I'm not sure I understand how the driver and power supply wouldn't be able to 'provide enough juice'. The rated draw for the steppers fits well within the specs of the drivers and power supply. Speaking of the steppers though, I was wondering, should I have them wired in series or parallel? If I've been reading correctly, I probably want Parallel. Series and Parallel both offer the same torque, but Series will stall sooner.

I'm still learning myself. So I wouldn't be the right person to ask. There is a guy named Crevice Reamer. Send him a PM and tell him your setup. He'll be able point you in the right direction. He really gave me some solid advice.

[ahren]

Ger didn't say anything about the motors -- your motor package is fine. What he's saying is that you should use multi-start ACME screw. I agree with him on this. For the hobbiest, multi-start acme is the sweet spot -- higher efficiency, higher linear speed for lower rpms (which keeps steppers in the lower rpm, higher torque range), and less chance of screw whip due to the lower rpms. All this for a modest increase in price. I did this on my machine (using 5-start ACME), and it was by far the best upgrade I made.

Best regards,

Ahren
www.cncrouterparts.com

[TheBakachan]

Hopefully the choice in screw won't be a problem in just getting the thing up and running. Speed isn't really a concern. The intended uses of the machine are rather varied. For example; routing/cutting large pieces of flat material (Like say MDF or something), cutting and drilling sheets of carbon fiber composite, milling and drilling PCBs, machining small parts from various materials including billet aluminum, and really anything else I might want to do.

The screws are turned down to 5/16" at each end for mounting into bearing blocks. (And again to 1/4" on one end for coupling.) The couplers are the flexible shaft couplers from Keling Inc and will be housed in a motor mounting block with the stepper mounted on the one end, and capped with the bearing block on the other. The nuts are machined Delrin, from the people who did the screws, bearing blocks, and motor mounts.

On another note, after testing the motors in both series and parallel, I'd say parallel is the way to go. The 2.8 amps per axis-- versus 1.4 for series --is still well within the bounds of my power supply.

Once I finalize the design of the machine itself, I'll post some pics.

Right now, the big question is whether or not the Y axis needs two drives instead of one. But I'm fairly confident that my choice of bearings will make the gantry glide with relatively little effort.

[TheBakachan]

So I have the design for the X half of the X/Z stage worked out. (Minus whatever is going to attach the X-axis nut to it) This is a VERY accurate representation of the parts, considering I modeled everything basically freehand in a 3D animation package instead of a CAD program. (My trusty Lightwave 3D)

Bah. Picture exceeded size acceptable, so just click here.

[FandZ]

Can't argue with that Z axis. Nice job. Nice rendering too. Are all the parts for it orderable or will you have to fab any of them?

[TheBakachan]

Thanks.

I have every part pictured, with the exception of maybe one length of hex cap screw. (Which I'll have after my next smallparts.com order)

The delrin nut, bearing blocks, and motor mounts were machined by the folks at Precision Tech Machining and bought off their eBay store. (Along with the acme screws which they turned down to match)

The clamps for the 12mm steel shafts were purchased from VXB.com, along with the 20mm ones used for the other axis.

The 20mm pillow blocks with linear bearings (Along with the 12mm ones that will be on the tool half of the Z stage) and the 12mm steel shafts were purchased from Misumi USA.

The extrusions were purchased on the cheap through 80/20's surplus and overstock shop on eBay. (Along with a bunch of aluminum blocks and flat stock to try out the machine on.)

The 20mm shafts for X and Y axis, motor shaft couplers, as well as the electronics and steppers, were purchased from Keling Inc.

The router mount was purchased from K2CNC along with an 1/8" collet adapter.

The Bosch 1617 was purchased on Amazon.

And as I alluded to earlier, all the screws and other fasteners and hardware are from smallparts.com

That about covers it.

[stevespo]

Great looking Z axis. I'm looking forward to updates on your build, and I always enjoy seeing the creative uses for 8020. This is a great project and you'll have a lot of fun with it.

I totally agree with FandZ, Gerry, and Ahren on the motors/screws issue. I wish I had sought more advice before I put my machine together. Don't get me wrong, I love my machine - but I'm definitely not using it to it's full potential.

You might be completely happy with 45 - 90 IPM rapids - hard to say. Perhaps you'll get more, but I think the screws/motors are going to hit a wall about then. I'm not familiar with EMC2, but the computer hardware may also factor in. Get it running and you can always improve it later on.

Steve