Losing steps after circles

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10-19-2017, 06:12 PM
CollectorCNC

Losing steps after circles

Hi

Ive got a 97 multicam 48plus that was converted to a stepper machine by someone else. It has a dedicated pc running win7 64bit, a pdmx-126 rev c and the usb smoothstepper. Runing gecko drivers each with its own 48v psu. Steppers are nema 34 long body and both x and y are rack and pinion.

Im having a strange problem when cutting small circles and then coming back to pocket the tops for screwing in 6mm inserts. The machine has great repeatability even on full length travels with both x and y moving at 750ipm

When I set up hole patters everything is great until the path for pocketing the circles gets run. The circles come out round, but after all the deep 7mm holes get pocketed, the 10mmx2mm shallow pockets are all off center. When the machine returns to 0 the mill is off by 1/16" to the x negative. To make matters worse. If i ref all home and the try to return to the 0 offset saved as a fixture, x is still off. If i shut the machine down and restart, its back to dead on.

Ive gone through and set everything up per the instructions for the USS in mach, verified gecko settings, and as of the last failed test, installed all pulleys and pinions using loctite 638 to ensure no slipping is happening and reset the pinion to rack mesh as tight as i can without causing binding.

Any suggestions if the mechanical fixes don't help? Im not sure what else it could be causing the off cuts.
10-19-2017, 07:03 PM
coherent

Re: Losing steps after circles

Could be a number of things. The first thing I'd do is slow it down the acceleration and cut/travel speeds and see if the error goes away.
10-19-2017, 07:16 PM
CollectorCNC

Quote:

Originally Posted by coherent

Could be a number of things. The first thing I'd do is slow it down the acceleration and cut/travel speeds and see if the error goes away.

Hi thanks for the response. The issue only happens when there are circle paths in the job. Cutting any shapes that dont have the circular pockets are all well within .01 of the desired cut. I get the same result at 900ipm as at 600ipm.
10-19-2017, 08:38 PM
coherent

Re: Losing steps after circles

If that's the case are you using Mach 3? I remember seeing some previous posts over the years about Absolute/Incremental IJ mode settings in Mach causing some cut issue with arcs and circles. I'm sure a little searching would offer more information.
10-19-2017, 11:30 PM
CollectorCNC

Quote:

Originally Posted by coherent

If that's the case are you using Mach 3? I remember seeing some previous posts over the years about Absolute/Incremental IJ mode settings in Mach causing some cut issue with arcs and circles. I'm sure a little searching would offer more information.

Ive read tons if posts on that as well. I just figured age of the posts and updates to the software would have remedied that kind of bug.

Ill try change that and see if it improves. Can you think of any mechanical items that should be checked, that i havent listed in the OP?