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Author Topic: Weird rotary axis issue???????????????  (Read 8791 times)

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Offline Tarak

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Weird rotary axis issue???????????????
« on: April 24, 2016, 06:41:27 AM »
Hi All, been awhile since I've been back at the forum, may I pick your brains for some ideas with this rotary issue I'm having?
Question1.)
I've been using this machine for a few years now, it's basically a cylindrical grinder, it works in the same manner as a lathe.
Xaxis is diameter, Zaxis is left and right and A axis is the rotary head (indexable axis not a spindle).
Ever since I can remember, if I run code like the following:

G90 G0 X20. Z0.
G91 G1 A1440. F2000
      G0 X20.;***********

X axis will jump out and lose position, tripping out the servo on the line with the**************
I managed to get itto work by entering a really slow feedrate instead of G0, e.g G1 X20. F20 (very, very slow though).
I'm guessing it's to do with the fact I am trying to use the indexable axis as a spindle type arrangement, any ideas why it might be doing this?????????.

Question2.)
A few years back I attempted to use the A axis as both the indexable axis and also a spindle that I could just turn on and off, but I couldn't get it to work.
I tried setting the pins of the spindle to the same as the step and direction on the A axis, but I just got errors about duplicating pin assignments, could someone possible explain exactly how I could get this to work?

Tarak
« Last Edit: April 24, 2016, 06:48:39 AM by Tarak »

Offline rcaffin

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Re: Weird rotary axis issue???????????????
« Reply #1 on: April 24, 2016, 10:54:24 PM »
I don't know, but I wonder whether it was the G0 X20 which was really the problem? Sometimes it seems to me that Mach3 highlights the adjacent line.

Looking at your code sample, I see the X axis should already be at X=20, so the X axis servo should have nothing to do. Of course, could it be tripped if the power supply rail dropped too far?

I would start by checking the speed and acceleration on the A axis. To try to spin it at F2000 seems to me to be really asking for a lot. That would explain why the servo was tripping if both the A axis and the X axis shared a common supply. A simple check might be changing the F2000 to F100 say.

Cheers
Roger

Offline dude1

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Re: Weird rotary axis issue???????????????
« Reply #2 on: April 25, 2016, 02:40:13 AM »
rodger a F2000 for A axis is normal on some machines I run mine at 2340 if the x,y or Z are running at 1250 if I did a F100 it would lake a long time.

Tarak it should work how you wont it to you will just have to weight to one of the other boys comes along who knows how to set it up

Offline rcaffin

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Re: Weird rotary axis issue???????????????
« Reply #3 on: April 25, 2016, 02:43:56 AM »
To be sure. I was simply suggesting a diagnostic.
Cheers
Roger

Offline dude1

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Re: Weird rotary axis issue???????????????
« Reply #4 on: April 25, 2016, 03:12:20 AM »
I

Offline Tarak

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Re: Weird rotary axis issue???????????????
« Reply #5 on: April 25, 2016, 04:54:29 PM »
Thanks guys,
rcaffin, even though it is programmed to F2000, it only rotates at approx. 100-200 rpm, it's a deceptive value.
Also you will notice it goes from absolute to incremental, so it should rapid out 20mm.
I can run programs all day with no issue, but as soon as I try and rotate A axis for numerous turns in the one spot (in a program), it always jolts on the line after and trips out.
It's one of the strangest issues with Mach3, I've just never figured out??

Offline rcaffin

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Re: Weird rotary axis issue???????????????
« Reply #6 on: April 25, 2016, 06:17:28 PM »
Odd. But if the servo trips out, can you blame Mach?

I am assuming that the servo drive is faulting - right? I would ask why. Is there a power supply problem, or is the servo drive getting a follower error, or is the encoder playing up?

Cheers
Roger

Offline dude1

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Re: Weird rotary axis issue???????????????
« Reply #7 on: April 25, 2016, 07:59:12 PM »
a few question what version of Mach are you using, what is driving the machine PP or external controller, what is specks of your computer.

Offline rcaffin

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Re: Weird rotary axis issue???????????????
« Reply #8 on: April 25, 2016, 09:09:23 PM »
Dell box fairly new, W7, Mach .062, ESS w fairly current driver, Homann MB-02 BoBs, Gecko 320X servos on X, Y & Z, Gecko 203V stepper on A axis, SHG-25-50 HD, stock stepper, some reduction between stepper and HD.
Most machining takes about 5% of the CPU or less. NO internet connection.

There's a long series of articles on CNCZone at http://www.cnczone.com/forums/linear-and-rotary-motion/261174-cnc-engineering.html about the A axis I built.

Cheers
Roger

Offline dude1

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Re: Weird rotary axis issue???????????????
« Reply #9 on: April 25, 2016, 09:22:06 PM »
Tarak reply 7 is for you