Improbable Construct S2 buildlog

[Improbable Construct]

I finally got myself settled in after the move and caught up with work so I decided to finally put my Shapeoko 2 #3926 together.
I made a video of the initial build.



I did not install motors because I had another plan for driving this machine.

I had some NEMA 23 non-captive stepper motors made. They are 2.1 amp, 106 oz/in with a TR10x2 thread pattern. I wanted them in a 3/8" ACME thread but for a small quantity they we not willing to make them for me.

I made some brackets loosely based on the brackets for the bottom bearing bracket for the ACME upgrade to hold the ends of the TR10x2 screws.
The nice thing about this setup is that it does not require the screws to be turned down.

My initial test with only one Y side motor seemed to be pretty good. So I went for it and installed two Y motors and one X motor.

Top reliable speed is 1000mm/min I think it would do better with either more powerful motors or a multi start screw.
Right now I am running 1x microstepping. The screw is 2mm per revolution so a 200 step motor = 100 steps per mm.
For my first trial I ran a pocket cut in HDPE.

HDPE is not a good material for this kind of thing, but I had a few scrap pieces and to be honest I did not have high hopes for a perfect outcome on the first run with a comleatly new setup. It turned out really well for a pocket in HDPE. I used a 1/32" 2 flute endmill. 2mm pass 100mm/min feed. Total cut time was ~18 minutes. I did not actually do any squaring of the machine. I just slapped it together and used my calibrated eyeballs to square it up. I will take some time in the next few days to square everything up properly and surface the spoil board before trying it again in Delrin.


I also installed a prototype belt drive Z axis bracket.

It has a 2:1 ratio and really speeds up the Z axis. I am running a 175oz/in motor at 2000mm/min it seems to work really well and it allows more clearance for the spindle.

[Improbable Construct]

[akhlut]

Beautiful. Absolutely beautiful.

I saw these and had a similar idea.

Where did you get those captive nut TR 10x2 steppers? 200 step? Any noticeable backlash?

100 steps/mm @ full step should give you 0.01mm positional accuracy, +-0.0005mm. And fast.

Do you think that a machine like this (if reinforced enough), coupled with a DW611 and a large enough bit could cut mild steel?

[Improbable Construct]

Beautiful. Absolutely beautiful.

Thanks. I have been trying to implement this design ever since I first found out that noncaptive motors existed.

I saw these and had a similar idea.
Where did you get those captive nut TR 10x2 steppers? 200 step? Any noticeable backlash?

I had a supplier in China custom make them for me. Getting the motors was the hardest part of the whole build. I really wanted them in a 3/8"-12 ACME thread but they were unwilling to make a small quantity of them for me. I have a feeling that if I wanted 10,000 then they would make anything I wanted but for 3 I had to take what they would make. Although TR10x2 is not normal for these motors it was as the best I could get and still have easy access to the screws.
They are 200 step and have a lower holding torque than I requested but again it was a trade off for a small quantity. I don't see any noticeable backlash. They seem to have less backlash than the stretch is ee in the belts on my big machine.

100 steps/mm @ full step should give you 0.01mm positional accuracy, +-0.0005mm. And fast.

To be honest they are not as fast as I would like. I rapid my big machine at speeds up to 10,000 mm/min. The best I have been able to get out of this machine is 2,500mm/min but it is not reliable at that speed. 1,000mm/min seems to be reliable and for rapid and feed.

Do you think that a machine like this (if reinforced enough), coupled with a DW611 and a large enough bit could cut mild steel?

I do not think that this, or any shapeoko based setup, will ever be able to mill steel. You need to have something stronger than what you are trying to mill and aluminum extrusions will never be stronger than steel.

[akhlut]

Still, super cool.

You have given me some ideas. That is usually hazardous to my wallet. D:

But freakin' awesome job! You should take this sucker to makerfaire...

[dataway]

Great setup IC....will you be offering this setup has a kit soon ?

[Signals]

I love the setup of the Z-axis, as my Bosch Colt hits the bottom of the motor plate. Not a big deal right now, but would be nice if it cleared it like yours does.

[Improbable Construct]

Great setup IC....will you be offering this setup has a kit soon ?

Possibly.
I need to figure out if it adds enough value to justify the cost.
The Z axis will probably happen, but the non captive motors are another story.

[groguard]

This is excellent! A friend of mine that is just getting into the CNC world was looking at doing this to his shapeoko. He wants to go with 1mx1m rails, but he could run into a few issues with something like this because of the size. Not sure if the added length would be an issue. Excellent work!

[CheapSquier]

I like the setup you posted, but I'm curious about a couple of things.

First, I'm new to CNC, so I apologize in advance if I don't know something that should be obvious.

It seems like non-captive steppers are kind of hard to come come by. You mentioned "I had some NEMA 23 non-captive stepper motors made"? I understand why you went with a screw drive instead of the standard Shapeoko belt-drive, but why did you choose the non-captive motors vs captive motors with a motor shaft coupler to the screw? I guess maybe your configuration is a little simpler since the screw is fixed? A trade-off between easily available parts and getting a clean build?

It sounds like you got the resolution is excellent. Have you checked the repeatability? You mentioned you would like the feed rate to be faster. What would you change to improve that?

Something else that I didn't realize until I started looking closely at your build. I didn't realize that Shapeoko has a motor on each Y rail Many of the desktop CNC systems I've been looking at use a single screw under the gantry, right down the middle of (underneath) the table. (Ex: http://www.cncrouterparts.com/benchtop- ... p-313.html) That way they only use one motor for the Y. So I was going to ask you how you kept the two Y motors from getting out of sync, but I guess Shapeoko already figured that out somewhere along the way. You just had to recalibrate for the different step size.

Thanks!