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Author Topic: Dynamic milling, slipping axis/missing steps?  (Read 253 times)

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Offline sx3

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Dynamic milling, slipping axis/missing steps?
« on: March 12, 2019, 04:42:19 PM »

We're using Mach 4+ESS (latest stable, official release, 3804 i beleive) with ESS plugin 220.
The machine is a 1986 years DynaMyte 4400 with stepper motors that are rated 2000 Velocity, however we don't have official values for acceleration from Dyna.

We have tested with 2000vel/500acc, and machine starts to loose steps, so we've reduced to 1500/150 and this what we currently are running on.

The machine is configurated with backlash compensation, the backlash is within 0,01mm during tests. The compensation is set to 0,0135

We have milled a moped crankcase using dynamic milling, which is a quite aggressive form of milling. Now that the crankcase is finnished we notised that tha halfs are offsetted by 0,4mm from eachother, which is quite alot. During milling we never noticed axis slippage, but apparently something have went pretty wrong. It's only the Y-axis that's affected, the roundness of bearing seat is within 0,01mm, but the offset between pieces are 0,4mm

Our first thought is that BC might be the culprit? Noticed that some fixes have been made in recent ESS release, but don't know what the issue was?
Our other thought, is that dynamic milling is too much for either the machine or ESS during some tight turnarounds at the end of each cut?

Any one else experienced such problems? shouldn't 1500/500 be safe when 2000/500 was the point when we notices axis slippage during calibration and Dyna states 2000 to be possible.

This is one of the Dynamic mills we ran.[video]https://www.youtube.com/watch?v=EoO38Bt-wcg[/video]
Re: Dynamic milling, slipping axis/missing steps?
« Reply #1 on: March 12, 2019, 06:22:31 PM »
I run Adaptive Clearing (Autodesk's version of Dynamic Milling) on a mill at work with the ESS on Mach4; it now has servos on it, but I was running it with steppers and it ran just fine. 
In your video, it didn't sound like there was too much strain on the machine or steppers.  Turn off the backlash comp and see if you are still having issues.  I don't use BC on my mill, so I don't know how well it is working.  I know there has been a lot of discussion about BC and the ESS before, maybe someone else will respond as well and give more insight. 
I would give that a shot though, disable BC and run a test piece, some holes and boss' and see what they measure.
Chad Byrd