I don't think 3.042.20 is the problem. In fact I just cleaned off everything and it was a fresh install along with
the SS latest plug in. Could be wrong, but, if there is some poop i usualy have the knack to step in it!
RICH

Thanks Hood, they look rather nice! I can achieve that but with VERY gentle cuts - 0.03mm diametrical depth per cut at about 400rpm. What depth and speed did you use?

Do you think running SmoothStepper makes any difference to this potential issue?

Thanks Rich, I'm tending to agree at the moment!

Woody.

I did these threads in 5 or 6 passes but then again my lathe is a bit bigger than yours and Rich's, I could do a thread in one pass (if the tip would stand it ) and the spindle wouldnt slow,  the spindle servo is 12.5Kw.
  I did threads before with the parallel port, heres a  pic of two with the pp and 2 with the SS when I was testing the Beta plugin for threading with the SS.
 The SmoothStepper is definitely more responsive than the PP for threading but the PP  can do very nice threads.

Hood

Has a solution to this problem ever been found?  I am using .020, and it is giving me very similar problems.  If during a cut the spindle slows down very much at all the z speed compensates just fine, but the next pass is cut very unusually.  The next pass will be cut at what appears to be a constant taper with the z axis very slowly moving from a depth that is outside of the thread to the final depth that the pass should have been cut at.  This movement can be seen both physically, and on the DRO.  I have also had a problem where the next pass after a slowed down pass will be completely outside of the thread in the air.  I am not losing steps, and the pitch is always spot on, but the depth is very messed up.  I have run a test piece of code posted elsewhere in this forum that is a g-32 code that has a very shallow thread cut in 80 some passes.  I have run it three times, and the results are perfect, and repeatable. 

I am very confused as to what is going on here.  I don't have a very good understanding of what the g76 is commanding while it cuts at all the diffirent depths to achieve a thread, but something seems to be amiss.  I am pleased to hear that you can change the output from the threading wizzard to a g32, or what I would understand to be a longhand version of the code, I will try that as soon as possible to see what happens.  Thanks

Hi TrevorH,

I still have the same problem, but like you no missed steps and no errors coming up anywhere in Mach3. But, when the spindle slows more than about 5%, the "X" axis is then messed up in the next cut. Z axis is fine for me. Its 100% repeatable which makes me think it is in the coding somewhere. The solution for me is lighter cuts, with which I can then make perfect threads, even with "normal" spindle speed change.

So, I believe there are now four people posting with a similar issue with this Mach3Turn version. I still have more experiments to do when I get time and I will post them back here.

Looking through the G76 macro, I can't see how that is a problem, all it does is repeatedly call G32 and work out the correct parameters for each call. It can't make any direct X axis movement requests. So, I think there is a problem with the G32 macro with some setups.

However, others do not see this problem, esp with smoothstepper. So it could be a combination of settings or setup which then allow this error to occur.

Hmmm... Any ideas out there? No matter what the setup, the X axis should not move with a non tapering thread!

Cheers,

Woody.

Woody, and others if you haven't allready check out another thread titled"Problems threading on the lathe"  For some reason it seems to have alot more interest, and some great discussion took place yesterday.  Last night I posted the reaults of some test cuts that I did, and I am awaiting feedback and suggestions.  Thanks