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Machine hesitates then loses position
« on: January 20, 2013, 12:52:46 PM »
Hello everyone,


I have been having a problem for the past 2 weeks with my machine running a program while doing a finishing cycle on some pickup cavities on a guitar body. It will run along just fine then the machine hesitates then continues do run the cycle, however mach3 thinks it never hesitated and therefor it loses position. The strange thing is when I home the machine out, my offsets for the fixture are still what they were before the machine did that hesitation. I have scrapped a few bodies out because it appeared as though the machine just wanted to do its own thing.

I have been running without a hiccup for 2 years and it just started to do this to me. The only thing that has changed was I attached my home switches to my machine 2 weeks ago. Before they were taped to my desk and I would tap them when an axis was close to its travel when starting up mach. Now that I have a consistent home position this problem started.

After I attached those home switches, I changed my look ahead to 100 lines instead of the default 20 and that's when I started seeing the issues happen. I changed it back to the default and it helped but now its hanging up in another section of the piece. Prior to changing my look ahead back to default it was hanging up in the exact same position over and over. Now that its back to default it is able to run the cavity at the first depth but hesitates during the second depth cut.

I unhooked my limit switches and set all config settings back to default and I still have issues. I had thought maybe my home switches were causing noise interference due to the fact the wire is unshielded but during my test I discovered that as not the case.

I know this is very confusing to read, and I can take a video if you would like.

I am still running the same version of mach3 that was originally downloaded several years ago.

Would uninstalling and reinstalling do anything?

I am at my wits end with this.

Specs are as follows if it means anything?
Gecko G540
P4 2.6 GHz processor
1GB of ram
nothing else on the computer, dedicated CNC computer.

Please help.
Chris
Re: Machine hesitates then loses position
« Reply #1 on: January 20, 2013, 07:20:45 PM »
Chris,

A video may give someone a clue.  It is a little confusing since you say it loses position, but also that it zeros back to the fixture.  Strange.  As a wild guess, are you running your gcode file from a drive other than your hard drive?

John Champlain
Re: Machine hesitates then loses position
« Reply #2 on: January 23, 2013, 06:03:00 PM »
John,

http://www.youtube.com/watch?v=-DwrXKvqqOY

There is a video showing what the machine is doing.

Like I said earlier, everything was working and performing as it should have until about 2 weeks ago. I know my motor wiring and mach settings are good, however I will attach my xml file for you guys to proof read if need be.

My only change was physically attaching my home switches to the machine. Before they were wired up setting on my desk and I would activate them when an axis was close enough. I wanted to start using fixtures so I needed a consistent machine zero and that's when I drilled and tapped some holes. The home switches do not have any shielded wire, but I unhooked them from the power supply over the weekend and the machine was still losing steps/stalling.

There are no binds on the Y axis to cause the motor to stall and my acceleration and velocity settings have been the same for a year.

I can try swapping parallel cables to see if that helps but I doubt it will.

Videos speak louder than words.

Any help is greatly appreciated.
Chris

Offline Hood

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Re: Machine hesitates then loses position
« Reply #3 on: January 23, 2013, 06:24:17 PM »
Can you attach your xml.
Hood
Re: Machine hesitates then loses position
« Reply #4 on: January 23, 2013, 07:48:01 PM »
I'm also running V3.042.040 for what its worth.

Thanks,
Chris

Offline Hood

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Re: Machine hesitates then loses position
« Reply #5 on: January 23, 2013, 08:01:14 PM »
Ok I see you have the kernel set to 60KHz but the most you need is 42KHz so could you try setting to  45KHz and restarting Mach.
Also can you tell me what the Time in Int and Frequency are before you change the kernel please.
I probably wont get your reply until the morning as its late, or rather early, here.
Hood

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Re: Machine hesitates then loses position
« Reply #6 on: January 23, 2013, 08:09:04 PM »
One other thing, can you disable backlash comp to test and see if it improves.
Hood
Re: Machine hesitates then loses position
« Reply #7 on: January 24, 2013, 05:20:42 PM »
I am going to create a new profile and change the kernal to 45Khz so I can revert back if need be.

Current Time in Int is +4.2 but it cycles up to 7.5

The numbers move so quick its hard to see what it is, but +4.2 is the lowest it goes and +7.5 is the highest. Frequency is 62442

I will start doing some changes while you guys instruct me on what to do next.

Thanks,
Chris

Offline Hood

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Re: Machine hesitates then loses position
« Reply #8 on: January 24, 2013, 05:28:02 PM »
Ok Time in Int should be ok but your frequency is a bit out although it sounds like its stable.
Might be worthwhile looking while you are running code however to see what its like. Also have a look at CPU usage when running code and see what its like (Ctrl Alt Del)
Definitely disable backlash and see if that helps.
Run the driver test (with Mach closed down) and try it at 60KHz and see if there is a nice flat line, also try at 45KHz and see what its like.
Hood
Re: Machine hesitates then loses position
« Reply #9 on: January 24, 2013, 05:57:36 PM »
Disabled backlash compensation and the problem has gone away. Everything works like a champ now.

I ran a driver test before I set it at 60KHz over a year ago and I was green across the board and everything seemed to check out.

I will make a new profile using 45Khz and maybe it will be even more stable.

But I am so happy that I ran without one issue and the machine sounded much smoother.
I think I enabled backlash compensation before I attached my home switches thinking that it was the reason my circles were not coming out perfect. I think my feed rate was too fast and that's why the small circles weren't coming out good. I was using a 1/16 end mill to profile 3/32 and 3/16 holes at 60IPM.

Thank you Hood for helping me out!
Chris