Messages

31

General Mach Discussion / Re: Strange axis skew - maybe a Mach machine profile bug?

« on: July 30, 2012, 08:51:25 AM »

I also ran through a diff of the 2 files. A couple of points.

I thought the mh-540B was pre-enabling backlash comp but apparently backlash was enabled in it.

mh-Millie has a lot of config for spindle and flood control that I had upgraded on my machine and in the process of debugging this issue, disabled in the profile but some of the config is still there.

cheers,
Michael

32

General Mach Discussion / Re: Strange axis skew - maybe a Mach machine profile bug?

« on: July 30, 2012, 08:06:16 AM »

Thanks Hood.

mh-540B  is the old file that works
mh-Millie is the current file that skews on Y

cheers,
Michael

33

General Mach Discussion / Strange axis skew - maybe a Mach machine profile bug?

« on: July 29, 2012, 08:15:24 PM »

My X2 minimill has been running like a champ for a couple of years cutting 1000s of parts for my fly fishing reel kits. A few weeks ago, I decided to to do some upgrades and repack the ball nuts with oversize bearings to remove some backlash. I had enabled backlash comp last year (.002" on X and .003" on Y) to help a bit.

Long story short, after the upgrades and bearing repack I had a problem where the Y axis would slowly skew over the course of a run. I tried several programs that I had used 100s of times and they all failed to varying degrees. I checked all the mechanicals, backlash, make sure backlash comp had been disabled, etc. For several weeks I have been out of commission. I can not hear missed steps when running. I slowed my rapids down from my normal 125IPM to 75IPM and accel from 25 to 5. Still no change. I even ordered and installed a much bigger stepper on Y and the problem persisted.

Today, I went back to basics. I first wrote a little gcode program to exercise the mill. Here it is:

Code: [Select]

M98 P01 L50 (call subroutine 1)
G0X0Y0
G4P4
M98 P02 L50 (call subroutine 2)
G0X0Y0
G4P4
M98 P03 L50 (call subroutine 3)
G0X0Y0
G4P4
M98 P04 L50 (call subroutine 4)
G0X0Y0

M30

O01 (subroutine "01")
(simple short distance movement on Y)
G0Y0
G0Y.1
M99 (return)

O02 (subroutine "02)
(small rectangle on X & Y)
G0Y0
G0X.1
G0Y-.2
G0X0
M99 (return)

O03 (subroutine "03")
(diagonal movement on X & Y)
G0Y.1X.2
G0x0y0
M99 (return)

O04 (subroutine "04")
(small triangle on X &Y)
G0Y.1
G0X.2
G0X0Y0
M99 (return)

%
When I run this, only subroutine 4 introduces the skew along Y. The others do not. In 50 calls, the Y skews about 1/8" (eyeballed). I then switched my X & Y stepper cables to see what I might learn. Now the skew shifts to the X axis and in the same magnitude. If I run 100 cycles, the skew is about 1/4", 150, 3/8" etc - so its cumulative.

Thinking about the amount of skew: my Y "steps per" are roughly 10,000. So, to skew 1/8" would require 1250 (missed) steps, which would be 25 (missed) steps per call to the triangle path! I do not hear anything indicating missed steps. And, the diagonal and back-forth movements on Y do not result in this skew. I re-ran at 7.5 IPM and the same amount of skew occurs.

Then I realized that my previous .003" backlash comp on Y * 50 cycles = .150" - in the ball park of the eyeballed 1/8" skew. I double checked backlash comp and although the checkbox was unchecked to disable it, the X and Y values were present. So I zeroed them and restarted Mach (actually rebooted the PC too). The skew still occurs.

Then I remembered that I have a saved profile from last year before I enabled backlash comp. I loaded it and ran. No skew! It ran flawlessly. I even ran it 10000 cycles and saw no skew! I then restarted Mach and loaded my current profile and again the skew appeared. Restart with the old profile, no skew.

I suppose the easiest thing will be to rebuild a new profile from scratch but this is nagging at me! Anyone have any ideas or configuration parameters that I can check?

cheers,
Michael

34

General Mach Discussion / Re: Odd spindle speed hesitation problem

« on: July 23, 2012, 08:56:36 AM »

Thanks Peter. Here's more info.

When I disconnect the flood relay and disable it in Mach the spindle still hesitates periodically when "complex" sections of gcode execute - it seems only at the beginning of the line of code for arcs. If I run the spindle manually it is stable during this same code segment.

(the flood motor is a little aquarium pump)

cheers,
Michael

35

General Mach Discussion / Re: Odd spindle speed hesitation problem

« on: July 22, 2012, 10:36:48 PM »

Forgot to mention, the flood relay is one I bought from you maybe 2 years ago that I just got around to using. I did not install the diode as my understanding is the G540 does not need it.

regards,
Michael

36

General Mach Discussion / Re: Odd spindle speed hesitation problem

« on: July 22, 2012, 10:28:34 PM »

Thanks Peter. I don't notice any issues with the step/dir lints. As for the other possibility the hesitation is intermittent (doesn't happen every time I turn on/off flood) and more importantly, it sometimes happens when turning the flood off. And also, the situation that when cutting arcs also causes the hesitation so it isn't isolated to just turning flood on/off. In fact, once the program is running, flood is turned on at the start and off at the end so that probably wasn't the source that was causing my initial observation that led me to diagnose this.

Unfortunately, I don't have a scope.

cheers,
Michael

37

General Mach Discussion / Odd spindle speed hesitation problem

« on: July 22, 2012, 09:56:07 PM »

I just upgraded my X2 minimill to enable spindle speed and flood coolant control. I'm using a Gecko G540. I immediately started experiencing a strange issue when running a program. The spindle periodically decreases speed momentarily. It doesnt completely stop, just slows for a split second. When I run the spindle from the original speed control pot it Is steady.

Then I tried control from the mdi. I entered an M3 S5000 on the mdi and the spindle spins up and is rock stable - just like when I use the pot manually. Then, I clicked the coolant on button and the spindle momentarily hesitated. Turning the flood on and off sporadically does this but not every time. Then I excersised movement with G0 command and that worked fine. Then I loaded a program and cut air with the coolant off. For most movements, the spindle was fine but for some arc moves (I cut a lot of disks and rings) I occasionallY get hesitations when the line of code executes.

If I run the spindle from the pot and turn the flood on and off there is no change. So it appears not to be an electronic issue I think but maybe a Mach issue. My kernel speed is at the lowest although the machine most likely culd support greater. I was going to try that but Mach warns that all axis will have to be recalibrated if I change the kernel speed. I have a lot of parts to cut in the next week so I can't mess with that right now.

What do you think about the above behavior? I wouldn't think that turning the flood on would take that much processing pow to cause a momentary stall on the spindle. As I write this I realize that flood has a 3 second pause to allow time for it to flow. I will turn that off (to 0) and see if that has any effect.

Cheers and thanks for the help.

Michael

38

FAQs / Re: steps per won't change from 1000

« on: March 13, 2012, 09:16:21 PM »

Very odd, I am having the same problem on an A axis set up to move an extruder for a 3d printer. I can set the steps per from 1 to 10000 and it moves the filament exactly the same amount. It's driving me crazy! I'll try the built in calculator. But it would be interesting to know if others have experienced this.

Cheers,
Michael

39

General Mach Discussion / Re: How do I clear a fixture?

« on: November 21, 2011, 12:29:01 PM »

As silly as that sounds, that is basically what I did. I'm weaning myself go the habit to press that button. So far, 100s of parts and no accidental tool breakage.

cheers,
Michael

40

General Mach Discussion / Re: How do I clear a fixture?

« on: November 11, 2011, 08:49:49 AM »

Thanks ger21. I haven't messed around with editing screens so maybe that's what I'll do.

In thinking about it some more, I think I default to using Goto Z because I do not have home switches and that seemed like a reasonable place to go. Maybe I should create a replacement button that takes me to a safe Z and x=y=0.

Thanks all,
Michael