Electronic Lead Screw

[WobblyHand]

You are right on. The proof of the pudding is how the lathe performs. I struggled with a way ro evaluate that perfo4rmance because there was no previous metric on the actual force needed to make a particular cut. An experiment to that effect would be in order. I would set up some stock and a depth of cur and increase the feed rate until the stepper stalled. The number will be dependent upon the diameter of the stock as that is proportional to stock removal rate and to spindle speed as the stepper torque is dependent upon stepped speed. A family of curves would be generated for a particular material and tool.

At a 5mm feed rate (the highest my ELS will go), that is screaming at 300 rpm. 50 rpm is more reasonable. In that case my lead screw is turning at 6x the spindle or 300 rpm. The stepper is turning at 2x that or 600 rpm. From the torque curve for my stepper, it is generating about 1.4Nm of torque.

I could do a 5mm pitch(feed), which is really fast, maybe even an 8mm pitch. I have cut a 4 TPI (6.35mm pitch) and it was exciting, since my minimum lathe speed is 100 RPM. I can't say that was chatter free, or even spindle stall free, but on the other hand the work piece was deflecting since the part diameter (1") was far too small for 4 TPI thread.

Grizzly never claimed this 10 x 22 lathe was capable of 4 TPI as they don't include gearing for it, nor a setting on the gearbox. The largest metric pitch is given as 3.5mm. So doing 5mm, or even 4 TPI was considered outside of the range for this machine. Going far beyond the design point of the lathe is inviting failures. Maybe if you are a YouTuber and your views paid for the lathe, but not me.

A decent test within the range of the machine might be 3.5mm pitch or 8 TPI on some decent diameter steel. I'd use a 60 degree tool for this test, set up for threading. Because at that "feed rate" you are really threading. Short sections of thread at various DOC might be illuminating. Find when it stalls.

 

[ttabbal]

You guys are doing some great stuff here. I love seeing more development on ELS in general. I really like mine, and am happy to have taken the time and money to build it.

I have been looking at those higher speed servos. I think that will likely be the direction I go if I change it out and will likely include a higher gear reduction as well. More for the requirement to power off for a time before I can use it again than to have much more torque really, and to match the torque/speed curves of the motor better. Honestly though, it might be a while before I bother with it. It's working quite well with only the occasional issue, which is inconvenient but doesn't damage anything. Fooling with the motor specs always brings the possibility that I might need to repair something that breaks.

 

[WobblyHand]

Just as a follow up, @ivel03 cut an 8 TPI thread in steel today with no issues (as expected). The weather was a little warmer then his last tests, in full disclosure. In any case, he's feeling a lot more comfortable with his ELS set up. Makes me happy too.

 

[ivel03]

Thanks for everyone's input and especially @WobblyHand for working through the troubleshooting process with me. Here's a link to my build if anyone is interested:

ELS Conversion on Weiss 1127

I have started the conversion of adding an ELS onto my lathe. Here are some pics of the progress: I'm happy with the stepper motor mount - it is very rigid. I plan on doing a bit more fit and finish on the stepper mount. The encoder mount i'm redoing b/c the bracket kicks slightly...

www.hobby-machinist.com

There are a lot of categories on this forum so maybe i should have posted here instead of in the Asian lathe area.