Messages

81

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 07:04:42 PM »

To Vmax549, Thanks for your input.  See the above post.  The machine is pretty tight, but smooth.  We rescraped the ways and refitted the gibs about 2 years ago when w got it and prepared it for the retrofit.  There is about .0005" mechanical backlash in each axis.  If it was staying within that and not creeping off in one direction I would be fine.  I haven't hooked up any REF switches yet...  To lazy.  BTW, the small bronze handwheels were installed to prevent accidents, shuch as bruized legs, blown parts, etc.  They were raw castings I turned.  Sorry about the clutter on the table.  Don

82

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 06:57:22 PM »

no problem.  I've tried changing the active state of the Dir pins and the result is that when I start the program that moves + first, When it gets done...  It still moved positive.  It seems to be about .0005" each time I run the repeatability test.  Yes it is cumulative.  Running the test with the accel at .1 just now after 6 runs, I've accumulated about .0032" error.  This agrees with the Dial on the right end of the leadscrew.  It is a standard Bridgeport type.  This is a very frustrating anomaly.  I haven't had this happen before until just this last week.  Could adding the 4th Axis possibly be related?  It was added about 2 weeks ago.  Pretty straight forward.  Thanks for the help, Don

83

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 06:13:30 PM »

Yes, I have tried accel values as low as .1 (ramps up very slowly) and got the same results as accel. 4 which is what I'm using now.  Don

84

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 05:54:25 PM »

I reversed the X axis in Homing/Limits then ran the mirrored version of the program with the result that the table is still slipping to the left.  Sounds like something other than the computer?  Don

85

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 05:29:36 PM »

Hi, again.  Breakout board is a PMDX 120.  Steps per unit is set to 10000.  Kernal speed is 45Khz.  I should be able to post/attach a picture of the control setup now.  the cable in front of the BOB is the E-stop sense input from the BIG RED BUTTON.  Computer is off image to left. Gecko powersupply is upper left.  800VA 70V.  The Current set resistors are set per Geckodrives calculation formula and the motor spec.  The signal cables to the G212s are 4 conductor Shielded Com cable.  The shield is grounded to the aluminum plate at the Geckos only.  The SJOOW wires at the bottom are the outputs to the motors.  I've been using this machin for about 2+ years now and just recently reinstalled the Windows, and Mach.  Yes, It has been "optimized" per the Mach Support instructions.  Thanks, Don

86

General Mach Discussion / Re: My X-Axis is losing steps!

« on: December 21, 2008, 05:08:38 PM »

First a clarification. The x Axis is slipping to the positive direction only.  If I se the program to go negative it behaves and repeats perfectly.  The Y-Axis is also doing it only it only goes toward the negative direction...  The MPG when set to .001 inc. repeats perfectly on both axes, but when set to .0001 inc. doesnt repeat in X.  Again, it loses steps to slip toward the positive in X.  Making repeated back and forth moves yields mor and more error. The indicator is mag base mounted on the head and touching the fixed jaw on the mill vise.
Step is active low for all axes.  Direction is active low only for the X Axis.  Could this be a mechanical problem?  I will try to post pictures of my setup. This may take another post since my card reader is finiky. Thanks, Don

87

General Mach Discussion / My X-Axis is losing steps!

« on: December 21, 2008, 02:10:49 AM »

I'm having a problem with my X-Axis losing steps Or is it microsteps and not returning to zero.  The mach3 says it is back to zero but I lose about .0005 or so each time I run this program:
F20
G20G90
M98P1234L3
M30
O1234
G1X4
G1X0
M99
  System consists of the following...  Computer 1.83Ghz Athlon, 1Gig memory, PMDX 120 Breakout board, Geckodrive G212, Homeshopcnc 1200 oz.in. Stepper motor, 1:2 timing belt, 5 TPI ballscrew on 9x42" table.  
  When I run the above program with a dial test indicator zeroed on a block fixed to the table, it reads a lower number at the end of the program run, ie. the machine is slipping toward the positive direction.  I don't know what is causing this as changing the feedrate, acceleration, step pulse timing, etc. has not helped.  I have gone through the Windows Optimization procedure, and that didn't help.  What should I try?  I'm not even sure it is software or hardware related...  Thanks for any help or suggestions you might have, Don