Need Help!- EdgeCAM Mach3 Sherline Compatability Issues

[enigmatech]

I bought EdgeCAM and a Sherline 4axis CNC Mill, am running Mach3 and have been having some problems with losing the home and origin positions during machining. I am cutting an organic shape that has been laser scanned. The Laser scan and resulting CAD model are fine. It's the EdgeCAM to Mach3 to Sherline process that is causing some problems. I am losing my home position by 0.015" in the x axis, 0.020" in the y axis and 0.010" in the z axis. I set the home before machining using an edge finder, run the program, and when I check the home following machining I am out the values listed previously. The problem occurs irregardless of speed, so I'm not going to too fast (22in/min as recommended by Sherline). If I run the program a second time, then the error is cumulative and thus worsens.

I've checked backlash and repeatability on each axis and I am within tolerance (0.001"). The issue arises when I run complex 3D profiles as most of these organic shapes are.

I am cutting in 3 axis mode and have manual code written for a 180 degree indexing operation to machine the bottom side. I am using a Mach3 post for EdgeCAM that I found on this forum. I am running Mach3 confgured for Sherline as downloaded from the Sherline website. I am cutting modeling board which is light weight and using brand new cutters.

The whole reason I bought the Sherline was for precision. My TechLine CNC router is more precise right now. The TechLine runs a different Mach xml, but G-code is generated by the same Mach3 post for EdgeCAM.

Can anyone please help or offer suggestions? I am just about ready to return the Sherline and have many thousands invested.

[rider23]

Can you show us the program ? (just the first 50 lines). Is there a g10 or a g91 command anywhere ?

[tummen]

We had a step motor controlled design mill fråm roland some years ago and there was quite often a problem with loosing the position because the plastic we cut overloaded the stepmotor holding force.
it count sometimes pull z down 50mm just by touching material if the mill was steeply cut.
do you get the same result if you run the code without material and at 10% of the speed?

[enigmatech]

Originally Posted by rider23 Can you show us the program ? (just the first 50 lines). Is there a g10 or a g91 command anywhere ?

No G10 or G91 from what I can see.

Here are the first 50 lines:

%
O0001
N10 G20 G90 G40
N20 (PROFILING OPERATION)
N30 G0 X-0.5303 Y-0.614 S2800 M3
N40 G43 Z0.7283 H00
N50 Z0.6543
N60 G1 Z0.4543 F22.0
N70 G17 G2 X-0.4112 Y-0.707 R0.8212
N80 X-0.3648 Y-0.7806 R0.2575
N90 X-0.4124 Y-0.8702 R0.0697
N100 X-0.5008 Y-0.8616 R0.1312
N110 X-0.6628 Y-0.7627 R1.2715
N120 X-0.7834 Y-0.6481 R0.3691
N130 X-0.8097 Y-0.5744 R0.1961
N140 X-0.707 Y-0.5082 R0.0708
N150 G1 X-0.6628 Y-0.5312
N160 G2 X-0.5303 Y-0.614 R2.888
N170 G1 X-0.5273 Y-0.6094 Z0.4293
N180 X-0.3863 Y-0.707
N190 X-0.324 Y-0.7557
N200 G2 X-0.2858 Y-0.8101 R0.2593
N210 X-0.301 Y-0.8985 R0.0759
N220 X-0.3977 Y-0.9218 R0.1103
N230 X-0.5155 Y-0.8808 R0.5864
N240 G1 X-0.5327 Y-0.869
N250 G3 X-0.6628 Y-0.7777 R0.9191
N260 G2 X-0.7659 Y-0.702 R0.7427
N270 X-0.8394 Y-0.6039 R0.3588
N280 X-0.861 Y-0.5302 R0.1909
N290 X-0.7954 Y-0.4521 R0.0688
N300 G1 X-0.7806 Y-0.4518
N310 G2 X-0.7059 Y-0.4851 R0.1798
N320 X-0.5892 Y-0.5678 R1.5144
N330 G1 X-0.5302 Y-0.6076
N340 X-0.5273 Y-0.6094
N350 Z0.4043
N360 G3 X-0.3825 Y-0.7065 R3.9179
N370 G2 X-0.2444 Y-0.8101 R0.7138
N380 X-0.2237 Y-0.8837 R0.0872
N390 X-0.2946 Y-0.9561 R0.0973
N400 X-0.383 Y-0.9441 R0.1897
N410 X-0.5231 Y-0.8837 R0.9045
N420 G1 X-0.545 Y-0.8685
N430 G3 X-0.6912 Y-0.7659 R0.7124
N440 G2 X-0.869 Y-0.5872 R0.5176
N450 X-0.8969 Y-0.5155 R0.27
N460 X-0.8951 Y-0.4566 R0.1337
N470 X-0.8101 Y-0.4137 R0.0699
N480 X-0.7512 Y-0.4403 R0.1511
N490 G1 X-0.7282 Y-0.4566
N500 G3 X-0.5273 Y-0.6094 R3.7101

[enigmatech]

Originally Posted by tummen We had a step motor controlled design mill fråm roland some years ago and there was quite often a problem with loosing the position because the plastic we cut overloaded the stepmotor holding force. it count sometimes pull z down 50mm just by touching material if the mill was steeply cut. do you get the same result if you run the code without material and at 10% of the speed?

I am only taking 0.010" or less cuts with a 0.125" ball nose cutter out of fairly lightweight material.
I certainly haven't seen anything like what you have observed with pulling force.
I ran the prgram at 10in/min in air (no material) instead of 22in/min and got the same result.
Thanks,
Rob

[rider23]

Is there any tool changes in the program? If so could you post the lines on the forum? If you ran only half the program them stop it is the shift still there? Is there any G92 or G52 codes in the program? do you cancel the old tool offset length when you change tools or is it automatically done by the machine G49?