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Author Topic: Losing Steps????  (Read 2882 times)

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Losing Steps????
« on: January 29, 2010, 02:55:23 AM »
I am having trouble with my mill, it seems that I am losing steps.  The mill is set up as per my signature.

I am using an indicator mounted in the spindle, I zero out the indicator on a bar clamped to the table parallel to the Y axis, making sure to remove any possible backlash.  I then make a G1 move in the X axis of -2.953" (75mm) and then insert a 75mm Jo block.  With the feed rate set to 4 IPM the indicator reads .000.  I then remove the backlash and rezero my indicator on the Jo block, remove the block and make a g1 move in the X axis back to 0.  The indicator will read -.0015.  I did this 3 time at this feed rate and had the same results.  When I increase the feed rate to 6 IPM, I get an indicator reading of -.001 on th first negative X axis move, but it is off --.035" on the move back to 0.  If I increase the feedrate to 10 IPM I get -.006" on the negative move and -.067" on the move back to 0.  If I do a G0 move it is off almost -.185" on the move back to 0.

I've do some limited testing in the Y and Z axis and don't seem to have any issue, the indicator reads within .0005" both directions.

Any idea what might be happening?

Thanks

Tom
« Last Edit: January 29, 2010, 03:05:08 AM by jagert59 »
1986 Hurco SM1 Stock ElectroCraft Servos and encoders, Larkin Viper 200 drives, Smoothstepper, CNC4PC C23 BOB, Dura Pulse GS3 VFD, Mach 3

Offline Hood

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Re: Losing Steps????
« Reply #1 on: January 29, 2010, 03:38:39 AM »
Check that you have no loose pulleys, failing that I can only think it is a problem with tuning or a drive.
Hood

Offline Jeff_Birt

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Re: Losing Steps????
« Reply #2 on: January 29, 2010, 05:42:46 AM »
How are you 'removing backlash'? Sounds to me like you have a problem with your testing proceedure.
Happy machining , Jeff Birt
 
Re: Losing Steps????
« Reply #3 on: January 29, 2010, 05:53:33 AM »
Check that you have no loose pulleys, failing that I can only think it is a problem with tuning or a drive.
Hood
Checked the encoder attachment set screws they were ok, no pulleys it's direct drive, swapped drive with the Y axis drive, no change.  could I have a defective encoder, I have another one, would it make sense to swap it?

Tom
« Last Edit: January 29, 2010, 05:56:40 AM by jagert59 »
1986 Hurco SM1 Stock ElectroCraft Servos and encoders, Larkin Viper 200 drives, Smoothstepper, CNC4PC C23 BOB, Dura Pulse GS3 VFD, Mach 3
Re: Losing Steps????
« Reply #4 on: January 29, 2010, 05:55:26 AM »
How are you 'removing backlash'? Sounds to me like you have a problem with your testing proceedure.

By 'removing backlash', I meant that I made a small move in the opposite direction to 'take up" the backlash ~.0015" that the X axis has.  I did this so that the backlash wouldn't effect my measurements.

Tom
1986 Hurco SM1 Stock ElectroCraft Servos and encoders, Larkin Viper 200 drives, Smoothstepper, CNC4PC C23 BOB, Dura Pulse GS3 VFD, Mach 3