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Author Topic: My X-Axis is losing steps!  (Read 24009 times)

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Offline Hood

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Re: My X-Axis is losing steps!
« Reply #30 on: December 22, 2008, 03:59:29 PM »
Wiring looks pretty good to me :)
Hood

Offline RICH

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Re: My X-Axis is losing steps!
« Reply #31 on: December 22, 2008, 05:33:55 PM »
Don,
When you get home, the testing of the stepper awaits you.
Till then.......pay,pay,pay or no play! ;D
RICH
Re: My X-Axis is losing steps!
« Reply #32 on: December 25, 2008, 11:51:35 PM »
Hi, again, and Merry Christmas to you all.  I've had a chance to play a little and checked some things with my breakout board...  The breakout board is a PMDX-120 ( www.pmdx.com) and it has a feature called Step and Direction Conditioning Modes.  Mode "0" is no conditioning. Each of the other modes regenerates or retimes the step pulses or latches the direction signal to either the rising or falling edge of the step pulse.  I found that modes 1 and 2 both doubled the error.  None of the other modes did anything different than mode "0".  Mode 1 provides step regeneration on the rising edge of the incoming step pulse, and No direction latch.  Mode 2 latches the direction signal to the rising edge of the incoming step pulse, but does nothing to the step pulses.  I am wondering if this means something???  Thanks, Don
Re: My X-Axis is losing steps!
« Reply #33 on: December 26, 2008, 12:48:44 AM »
Hi, again.  Brain is still cogitating on this problem and I was reading thru this thread again:
Here is a similar topic.   http://www.machsupport.com/forum/index.php/topic,7364.msg47127.html#msg47127
I am wondering a couple of things...  Does anyone know what symptoms a bad Buffer IC would exhibit?  Reason for My asking is that the PMDX-120 B.O.B. has a step and direction buffer that is socket mounted in case there are any "mishaps". The buffer is a SN74ACT254.  I am wondering if replacing it might be worth a try...  Might take a while to get one, but if it is a breakout board issue, it sure would be nice to fix.  If anyone has any experience with these devices, I would appreciate it, Thanks Don
Re: My X-Axis is losing steps!
« Reply #34 on: December 28, 2008, 04:03:29 AM »
Hi, Again, Guys.  I think I've finally solved this one...  I downloaded and installed the latest version of Mach3 from the website, and Lo and Behold---  The test programs work perfectly!  :)  I thought I was in for a defective mobo or BOB but it was just something in the software...  Repeated testing in all axes and both directions are showing perfect repeatability.  I quess there have been some major improvements in the Lockdown version of Mach3. I guess the moral to the story might be to always use the updated version of the software.  Good work,  Thanks, Don :)

Offline RICH

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Re: My X-Axis is losing steps!
« Reply #35 on: December 28, 2008, 09:16:22 AM »
Good for you Don,
For closure one more question. What Mach version was used before and after?
RICH
Re: My X-Axis is losing steps!
« Reply #36 on: December 29, 2008, 04:24:56 PM »
Arrgh!  Its Back!  Tried to run the repetitive program last night and at first it seemed all right. tried upping the feed from 4ipm to 20ipm but at F8.0 it lost steps again.  I tried acceleration set as low as .16667 (default from entering .01) and up to 20 but it loses the same number of steps each time...  So, I shortened up the amount of X travel to .100 to save time and adjusted the feedrate until I determined that the lost steps occur at anything over 7.5887ipm.  At 7.6ipm feedrate no steps are lost at any acceleration setting.  So, I shortened up the X-travel while leaving the acceleration at 2 and the feedrate at 2 and found I was losing steps again.  Shortened up the X to .0002" and the machine just vibrates over the .002" of lost steps.  Now the wierd part.  My machine has a max resolution of 10000 steps per inch.  I set line 6 of the program to .000005 - half the minimum travel resolution of my setup. when I ran the loop program, the machine almost smoothly moves positive .002".   ???  Is this a software issue?  Is this a computer issue?  Is this a breakout board issue?  I was leaning toward the BOB but theoretically, the machine shouldn't move any where if the commanded movement is smaller than the resolution of the machine and its software settings, shouldn't it?  At any rate, new sn74ACT245 buffer should arrive next Monday.  I did try this program both in Constant Velocity and Exact Stop modes.  It made no difference.  When I got done running all these tests, I reset the distance to X .100 and feedrate 2 and now it was losing steps at those settings too. :'(  Did something warm up and puke, or was I imagining things at first...  Thanks for any help you can provide, Don

Offline Hood

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Re: My X-Axis is losing steps!
« Reply #37 on: December 29, 2008, 04:36:15 PM »
I remember a long time ago people having problems with similar issues and the Geck Servo drives that had the step multipliers, well at least I think I do but my recollection is hazy. I am sure the cure was to take the chip out and just use as the normal servo drive, Can you do that as a test?
Hood
Re: My X-Axis is losing steps!
« Reply #38 on: December 29, 2008, 04:42:02 PM »
I dont have the other component that plugs into the Gecko mainboard, but still wonder why the computer would send out signals to the drives that are smaller by 1/2 than the resolution limit of the Mach3 Motor tuning setup?  Also the Gecko on this axis is now the one I recieved only a few weeks ago.   ???
Re: My X-Axis is losing steps!
« Reply #39 on: December 30, 2008, 01:49:35 AM »
Hi,

I am have a terrible time with lost steps. My Machine has been working perfectly for a long time now.  But out of the blue - lost steps.

I have been chasing my tail for over a week with little joy until now. I have checked everything printer ports, power supplies, mechanicals, static electricity,wiring, software, gcode - all ok!

The one thing I have changed prior to the problem becoming evident was : I upgraded from mach3 version2.63 to version R3.042.020.

This appears to have caused the missed steps.

I have reverted to R2.63 - no more missed steps!

Still testing!

Hope this helps.  Or maybe its muddled things up. but I has fixed my problem.

Cheers

Bruce