Update on sherline CNC lathe

Machine Shop
#21

Thanks @Raymond @jphelps for getting this up and moving! I fired up the lathe and played with it a bit tonight to get a feel for how it’s working.

I noticed how hot the motors got and it seems to me the X is hotter than the Z. Another thing I noticed is there is a difference when jogging the axis’s with Mach4 versus cranking the handle in manual mode. Handle mode sounds much better and that leads me to believe the servos need some type tuning on the CNC side of the circuit. I’m not familiar with how to do that, just noticed the behavior.

Also, .1/div and .01/div in handle mode are fairly smooth where as .001/div seems a bit choppy. Not sure what that signifies but it is a difference.

I verified the lathe will move with G code from MDI, so running a program should work fine.

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#22

There’s an acceleration mode that can be activated and a velocity setting that says how fast to move the servos under the motor profiles. That is fully tunable in Mach4.

There’s also a setting for motor pulse duration that I think was set to 20ms. That can be revisited to see if it can be tweaked down a bit… IIRC, that was the setting found online as what to use on the Sherlines.

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#23

I would think the driver gain is he same for manual or CNC. Perhaps it’s some of those other settings Raymond mentioned. There’s also heatsinks, a very cheap bit of insurance we might want to go with regardless, given our typical usage pattern and members being somewhat hard on gear anyway.

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#24

So myself & @Chris_Wischkowsky were trying to run a program to do some test turning. While working on getting set up, we found that the Z axis stepper getting hot. By hot I mean 140-150f. Then we noticed that the X axis had too much play in it, we adjusted that right. Well then we started noticing that the X axis stepper was letting hot. Basically one would get hot then the other. Trying to troubleshoot why, we changed steps to see if that took care of it. Ultimately what ever we did, we could not keep the steppers from getting to hot. During this time of testing we noticed the Z was acting strangely. The stepper would stall easily, no matter the configuration we went with. So we swapped the outputs on the back of the controller, This ended up moving the problem. In other words we have a bad/weak driver for the Z axis.

@Chris_Wischkowsky has some suggestions on some ways to proceed. This is not my area of expertise by any means.

  1. Replace like for like, less money but potentially looking for future issues. Chris said he has used these drivers before but had issues with them.

  2. Replace both drivers to upgrade.

  3. Rebuild with better components, including drivers, motion controller, power supply & steppers. He suggests Dynomotion for the motion controller, closed circuit steppers, misc terminal blocks, & grounding.

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#25

So I thought on it overnight, I think we are getting hot because the steppers are uni-polar. The specs on the Toshiba driver don’t appear to support uni-polar steppers. I think this is what may have caused the driver to weaken.

I don’t know this for sure, it’s speculation. I’m sure there are others that could chime in.

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#26

It’s more work but option 3, a rebuild, would be an interesting learning experience for me.

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#27

I know I want to see momentum build on getting the machine squared away. For that effort, I will be willing to pony in some money or buy some materials, if we go with 3. We saw these last night that have the driver built into it. They certainly look interesting. https://www.automationtechnologiesinc.com/products-page/hybrid-servo-system/kl-5056h/

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#28

I think the committee has funds for it. Thanks for offer. Just need to knoe what to buy. If under $500 Nick can authorize.

#29

I had one thought there’s a setting in mach3 for half-steps. perhaps the half steps are leaving something in an undesired State that’s causing the extra heat?

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#30

Yes I think we should be able to fund it. The alternative is to buy the CNC retro fit kit directly from Sherline

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#31

IIRC that controller has another axis for Y. Can we use it and tell Mach3 the difference?

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#32

It was on half steps originally. Then we tried all sorts of combinations. We were showing X & Z in Mach

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#33

I would suggest upgrading the motion controller ($250), moving to a pair of nema23 closed loop steppers with built in drivers ($320), externalizing the PSU and adding some proper DIN terminals to the inside.

With both the power supply and the stepper drivers now outside of that control box, it will really give that case some much needed breathing room.

An alternative to the Closed Loop Steppers we could just get a new set of standard steppers, ($40) and a pair of drivers ($220), but I see a real benefit of eliminating the drivers from the control box and having them be closed loop (especially on a metal lathe).

I would be happy to overhaul it myself as I think it would be really great to have a CNC lathe that could be reliable and cut serious work.

As for CAM software I think we should have no problems using Fusion 360, unfortunately me and Tim were unable to test it because of the stated reasons above.

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#34

Bump on this. I dont want it to fall out of thoughts. I would like to see it run sooner than later.
@Chris_Wischkowsky what other power supply did you have in mind?

How shall we proceed with parts?

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#35

I’ll put together a spreadsheet.

We might consider something like this.

#36

Did this project migrate to a private messaging thread or does it need a bump? I could start putting in a bit of time on this.

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#37

We haven’t ordered any parts for it yet since Chris has his hands full. We talked about it in a few Machine Shop meetings briefly. We can order the parts if you have the time Jay.

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#38

We also need to order whatever type is wrench is needed to disassemble lower spindle so we can replace the pin inside that prevents collets from rotating. Plus the pin itself.

#39

I’m game. Going to be easing back into spending some more time making and volunteering again and a project like this would be good.

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#40

We will find the parts list & get that stuff ordered. We have that list somewhere.

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