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Author Topic: Mach3 Turn G95 feed rate changes by itself intermittently  (Read 3778 times)

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Re: Mach3 Turn G95 feed rate changes by itself intermittently
« Reply #10 on: September 28, 2016, 01:52:18 PM »
Ok, so I enabled spindle relays and routed them to unused pins on my breakout board. So as far as Mach is concerned it thinks it's turning on a physical relay. Unfortunately, no change in the issue.

I also tried deleting my linearity.dat file as I know this is related to spindle speed and let mach rebuild the file on the next restart. This didn't work either.

I reverted the machine to ver 062 from 066, however I don't think I did a 'clean' uninstall. I thought I would have to copy my xml and macros back into the mach3 folder and this was not the case they were still there. I need to do some more forum research on how to revert to a previous version. So, it's possible it is still an issue. I just used the windows 'uninstall a program'.

But for now, anytime 'use spindle feedback in sync mode' is checked I don't get the requested program feedrate. actual feedrate is always much lower. At least I can 'uncheck' it and make parts while I try and figure it out.

I'm hoping it's just a corrupt file somewhere in the mach installation and a clean re-install will fix it but I'm really stumped. I've not seen this symptom anywhere on the forum after a few hours of searching. I've been considering moving away from the parallel port to motion controller (and probably Mach4 as well), but I'm not even convinced that is what is causing my troubles. Thanks again for your help.

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Re: Mach3 Turn G95 feed rate changes by itself intermittently
« Reply #11 on: September 28, 2016, 02:44:46 PM »
All you need to do to install an older version is run the installer, no need to delete anything.
If using a default profile and you have custom macros in that xml's macro folder then you will lose them and the settings in your xml as they will be overwritten. If however you are using a custom profile then it will remain intact and also any custom macros for that profile will be untouched.

I saw  this problem a long time ago on the big lathe when I had the gearbox and the speeds stepped up in sequence, If I commanded a higher range it would take a few seconds to get to speed and if I had zero spin up delay then Mach would see the slow spindle speed and start moving the axis at that rate, next feed call would correct. Adding a spin up delay cured it for me and now I have a servo spindle so no problems even with zero delay.

I think your problem may be the Index input and for some reason Mach does not see the correct RPM when it starts to look for it, maybe try a G4P2 after the spindle call and before your first feed call.

Re: Mach3 Turn G95 feed rate changes by itself intermittently
« Reply #12 on: September 29, 2016, 01:01:41 PM »
You were exactly right, the G4 fixed it.

For whatever reason there is a delay in the index input so that Mach sees a much lower RPM (probably 0 or close to it) when it calculates how to execute G95. I feel like it was ignoring whatever I put in the 'CW delay spin up' parameter, even once I enabled relays but I'm not going to worry about it, as I had tried spin up delay of like 4 seconds with not noticeable effect.

A simple G4 P2000 (milliseconds in my case) gives everything enough time to stabilize so that once a G95 Fx.********* is called it is executed correctly. That also explains why my symptom only appeared in the beginning of a program. If I changed feed rates later Mach of course saw the correct RPM as everything was stable by that point.

Thanks again for walking me through some troubleshooting. The solution makes sense, though I would have never thought of it.