Messages

131

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 10:04:53 PM »

When you say you didn't have the A-axis "Hooked up" do you mean? You had the motor unplugged or what?
Unplugging the motor could damage the drivers. Maybe not Gecko's but a definite don't do for other lesser drivers.

Sage

132

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 08:35:10 PM »

Don't forget there are two of us experiencing this.
I don't recall which Z moves (+/-) failed but the steppers screatched and the Z-axis was messed up.
I've used my machine for a few years now and never had a problem until I ran the code presented. I would never have such crazy F values in my programs so this issue could have gone un-noticed.

I'll test it thoroughly tomorrow as well.

Sage

133

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 06:33:23 PM »

For me:
Box un-checked
A axis radius 0.0
My A axis is a standard rotary table at 90:1

Sage

134

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 04:55:27 PM »

Perhaps it has someting to do with how the different configs of MAch deal with such a high feedrate command.
I don't no the congif pages so well as to have an idea what might be adjusted to fix it.

I'm surprised none of the "experts" have chimed in here.

Definitely a problem here though.

Sage

135

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 04:42:16 PM »

I haven't looked at the whole program carefully but, at first glance the Z commands are the ones immediatly after the crazy F feedrates.
The G0 in front of them does take effect eventually I guess (proven by single step) and apparently makes it ok for the following X move.

N280 A62.222 F1357.7
N290 G0 Z.542    <---------- G0 doesn't seem to take affect for this Z move.
N300 X-.16 A-62.222

I don't have time at the moment but try putting an X move where the Z is and see what happens. Perhaps like this.

N280 A62.222 F1357.7
N290 G0 X.1.5
N300 X-.16 A-62.222

See what happens. I suspect the X will screw up instead.

Obviously the Z IS being affected because it isn't resonding to the fast step pulses and not positioning properly. You probably don't hear anyting (like I do) perhpas because they are so fast the motors don't even respond. I have NEMA 42 sized steppers and Geko drives at full power 7Amps so they see sometihng but can resppond.

I'll try it myself in a while.


You might also try putting the G0 on a separate line for each of the offending commands and see if it helps - like this:

N280 A62.222 F1357.7
N290 G0
N295 Z.542
N300 X-.16 A-62.222

You might also try removing the F commands altogether becasue I don't see why you need them. G0 should be full speed set in configuration. So try removing them or subbing them for a G0 like these examples.

N280 A62.222
N290 G0 Z.542
N300 X-.16 A-62.222

or

N280 G0 A62.222
N290 G0 Z.542
N300 X-.16 A-62.222


Let me know what happens
Its a Mach bug as far as I can tell.



Sage

136

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 12:44:16 PM »

Derek:
The program was written for inches (G20). Therefore 1300 in/min. A crazy speed of 21 inches per second. (or in metric 550mm /sec)
I suspect for the A axis that might be interpreted as DEG per minute which is 21 deg per second a (somewhat) manageable number. My A axis has no problem with it (surprisingly since my motor is small) so it must be deg/min.

also

The moves in X,Y and Z as you mention, are locked together is speed only if the commands are on the same line. In the example programs the Z moves are on a separate line from the A moves with a G0 in front which should revert the Z moves to whatever the config says for maximum speed for the Z axis. (as far as I understand it anyway). It works fine single stepped.

Sage

137

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 10:44:08 AM »

Ok. I ran it again and had problems with the first program as well this time. On all the Z moves after the high feedrate A moves.
The Z axis screams, misses steps and the Z axis is not what the MACH DRO says.
I can tell this easily becasue I have a physical DRO on my Z axis and the Mach DRO and my real DRO are off after the missed steps.

So, there does seems to be a problem with the high feedrate for the A moves not being cancelled by G0 for the Z moves.

*** This may not show up as a problem for anyone who can tolerate a feedrate of 1357 - not me for sure.

BUT THEN:
I single stepped through both programs and they work fine so that's a clue.
The Z axis G0's seem to take affect fine and the Z-axis moves fine when single stepped.

Very strange  

BTW
Not that it matters but:
I'm not sure what you mean by "incremental" in the second program because you have specified G90 a couple of times and that's absolute. But it makes no difference the result is the same.

Waiting for the experts to shed some light on this one  

Brian


Sage

138

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 10:10:06 AM »

I ran your code and the absolute version ran fine. (not sure why - read on)

Whe I ran the incremental version,  I think I saw problems.  It's hard to tell where becasue of the look ahead but possibly on lines like this:

N280 A62.222 F1357.7
N290 G0 Z.542

After doing the A positioning I heard what sounded like gears stripping in the Z axis.
I can only guess the Feedrate you have of 1357.7 for the A axis causes some sort of issue with the following Z command even though the G0 in front of the Z move should cancel it. The noise I heard was (I presume) missed steps due to the high feed rate requested.

This would explain your observations of the DRO showing the correct value but the Z axis actually being wrong. My (big) Z motor tried to oblige but - no way, just a very loud buzz.

A feedrate of 1357.7 is crazy fast and I can't see why it's necessary?
A G0 in front of your A moves should be enough to go at whatever you have the maximum speed for the A-axis set for in the configuration - No?

So I somewhat retract my earlier comment that this is not a Mach problem becasue I think the G0 in front of the Z move whould override the previous F command (I think) but apparently it doesn't.

I'll play with it some more.

Sage

139

General Mach Discussion / Re: 4th axis question, possibly configuration ?

« on: May 15, 2011, 09:38:48 AM »

What hardware (BOB,Stepper drivers etc) is on the offending machine? Since this is likely where the problem lies. I doubt it's a Mach issue since so many have working A axis'. Me included. Perhaps some sort of noise or cross talk on the step signals?
 

Sage

140

General Mach Discussion / Re: Gantry Slack

« on: March 31, 2011, 08:21:31 AM »

Provided you had screws into that piece of plywood from the sides as well, I would have thought that should take care of your problem. Surprising. 

Whatever works I guess.

Sage