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### Author Topic: Z axis drift during X-axis motion...  (Read 11177 times)

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#### Chet

• 58
##### Re: Z axis drift during X-axis motion...
« Reply #20 on: November 20, 2010, 01:30:52 PM »
Hood, thanks for the offer...
If you can work with a string with the problem action, I'll try to isolate a couple of hundred lines...
Give me a day or two...
I really appreciate your effort to help me find a resolution...
Chet

#### Hood

• 25,838
• Carnoustie, Scotland
##### Re: Z axis drift during X-axis motion...
« Reply #21 on: November 20, 2010, 02:52:00 PM »
Just a few lines of code that makes it happen is all I would need, so if you can get that it would be good as it would hopefully narrow down the problem.
Hood

#### Chet

• 58
##### Re: Z axis drift during X-axis motion...
« Reply #22 on: November 21, 2010, 06:23:00 PM »
Okay, Hood, I've attached a test code when Z-axis drift occurs...
If you start counting with the top line as 0 in the attachment,
the problem occurs on line 29.

Here's a snippet of the code:
26  X0.1657  Y0.626  Z-0.25
27  X0.0823  Y0.626  Z 0.0
28  G00  Z0.1
29  X9.9157  Y1.376  Z0.0 (THIS IS THE LINE THE Z-AXIS DRIFTS ON)
30  X9.9157  Y1.376  Z-0.25

The drift also occurs if you use Set Next Line to an earlier execution like line 26...
The Z-axis will drift while moving to the line 26 start point...

I look forward to your analysis...
Chet

#### Hood

• 25,838
• Carnoustie, Scotland
##### Re: Z axis drift during X-axis motion...
« Reply #23 on: November 21, 2010, 06:28:27 PM »
The previous Z height to that line is Z0.1 and that line then commands it to go to Z0 because the X and Y have a longer distance to go the Z will move slowly so that all axis reach their destination together. Is that what you are meaning? because that is a commanded move and should be happening.
Hood

#### Chet

• 58
##### Re: Z axis drift during X-axis motion...
« Reply #24 on: November 21, 2010, 07:57:55 PM »
Okay, Hood, if I understand you correctly, the software is causing the move...
So do I simply eliminate all such lines to stop the drift????
(would I eliminate just the z0.1 line or both the G00 and Z0.1???)
I'm on a steep learning curve here...
I'm not the author of the code, it was generated by Acme Profiler...
It appears I'll have to tweak the code after Profiler generates it...
Yes???????????
Thanks, Hood, for all your effort on my behalf....

#### GeorgeRace

• 53
• My Home Built Airplane
##### Re: Z axis drift during X-axis motion...
« Reply #25 on: November 21, 2010, 08:30:09 PM »
I have been following your problem and there seems to be no real solution in sight, at least for the moment.

I have an off the wall idea i would like you to try.  Press together, the CTRL ALT & DEL keys.  This will bring up the windows task manager screen.  It will stay on top of everything else on your screen.  Now run your program.  Watch the CPU Usage number at the bottom of the window.  If at any time to goes to 100% your CPU is over extended and program steps in progress can be gained or lost in the process.
If you seen it go to 100%, then click on the Processes tab at the top and look down the list to see what process is causing the CPU to go to 100%.

Like I said, kind of an off the wall idea, but sometimes can be very revealing with running a complex program.

George

http://www.mrrace.com

#### Hood

• 25,838
• Carnoustie, Scotland
##### Re: Z axis drift during X-axis motion...
« Reply #26 on: November 22, 2010, 02:24:05 AM »
Chet your code is fine as long as the axis is doing what the code is telling it to do. On line 28 the code is telling the Z to move to 0 and line 29 it tells it to go to 0.1 along with the X and Y moving. If the Z does what its being told to do then all is fine. Line 30 tells the Z to move down again to -0.25, it also has X and Y moves but as X and Y are already there they will not move.
Is the axis doing as described above?
Hood

#### Chet

• 58
##### Re: Z axis drift during X-axis motion...
« Reply #27 on: November 22, 2010, 09:15:21 AM »
Two observations:
First, I am not a computer programmer, BUT George it would appear that activating the ALT-CTRL-DEL sequence WILL be putting more stress on the CPU, thus affecting the outcome...
(this nearly verges on the esoteric topic of quantum states...  if you watch it, you change it...)
Second, it's also really obvious I'm not skilled at understanding g-codes...
Hood, I appreciate your line by line analysis...
I believe your conclusion is that the router is simply obeying its commands.
So, I think I may simply take individual lines and bracket them with parenthesis to turn them off and study the results.
I think Wikipedia's g-code explanation may become my leisure reading....

#### Hood

• 25,838
• Carnoustie, Scotland
##### Re: Z axis drift during X-axis motion...
« Reply #28 on: November 22, 2010, 09:18:51 AM »
Is there actually a problem? Is the Z not going back to where you think it should be after line 29? The code tells it to go to -0.25 on line 30, is it going there?
Hood

#### Chet

• 58
##### Re: Z axis drift during X-axis motion...
« Reply #29 on: November 22, 2010, 09:44:12 AM »
Yes, the problem is that the Z-axis drifts below Z=0.0 while moving to a new location on the X-axis only...
This causes a taper across the top of work...
It's removing material where it should not...