[catabolic]

I cannot figure out how my drawings are being scaled down before milling. In autodesk/autocad mech. the units are set correctly and they match up in cambam /mach3 as well. But upon cutting on my machine everything is being scaled down by a factor of ~11/32. In other words a drawing that is 8 inches wide in cad/cam comes out 2.75 inches after cutting. I jog the g-code drawing and the machine coord's/units are correct as well in mach3...I see "scale" next to mach3's machine coord's, should this be edited?

Is it because my power settings are set at 1/2 step, 75% current settings? I'm checking units/ and measuring, but am drawing a blank. Hopefully it's something small I've overlooked. Advice? Thanks

[ger21]

Post some sample g code for a simple 6" square.

[catabolic]

I can edit scale on the machine coord's, but want it to show cutting to real time scale. Scaling up would take the machines movements off the boundaries of my table?

[catabolic]

will do, one moment

[catabolic]

( Made using CamBam - CamBam CNC Software )
( samplesquare 7/11/2011 6:51:51 PM )
( T0 : 0.0 )
G20 G90 G64 G40
G0 Z0.0
( T0 : 0.0 )
T0 M6
( Engrave1 )
G17
M3 S1000
G0 X-3.0 Y-3.0
G1 F10.0 Z-0.01
G1 F30.0 X3.0
G1 Y3.0
G1 X-3.0
G1 Y-3.0
G0 Z0.0
M5
M30

[catabolic]

No cutting, just as if the bit was replaced with a pen tip.

[ger21]

Mach3 problem.

What are your Default Units?
If they are inches, then you're steps/unit are probably wrong.

[catabolic]

yeah, my native units are in inches...what is the fix/problem? Thanks

[ger21]

What kind of screws are you using, and what are your steps/unit set to in motor tuning?

[catabolic]

I think I see it now that you mention it... 12 tpi acme screws, 1600 steps 79.98 vel./ 40acc on x axis. I spent so much time trying to decrease stepper noise/running smoothly that I didn't pay attention to scale (as I have fairly small parts that I am trying to mill and engrave). So I'm going to have to go full step power setting and 200 steps/per for tuning and just deal with the noise (I posted about this issue in another forum thread recently)? Or is there a better way that you can suggest...

[ger21]

Should be 4800, not 1600.
12 * 2 * 200 = 4800

[catabolic]

sorry, you're dealing with a new guy here... I did put 4800 at one point, but I guess I got confused with power settings/noise from the stepper. So dialing in 4800 should fix it?

[catabolic]

what do I tune my motors to I'm trying different ranges and they are stalling out?

[ger21]

what do I tune my motors to I'm trying different ranges and they are stalling out?

Set the accel to about 5, then slowly increase velocity until it stalls, then back off about 20%.

Then you can start increasing the accel until it starts to stall again, then back that off 20%

[catabolic]

I think I've got it had to adjust screw holds on machine, will test later as lightning storms are moving in...thanks for all your help.

[catabolic]

Thank you for all your help and advice... I will definitely try it as I need to re-tune everything now...I will be in touch, you've helped me out of a simple jam that I would have other wise over looked. Thanks Again ger21

[catabolic]

Drawing a blank, units aren't translating to cutting table; still being scaled down to half their intended size 6" comes out ~3"...?

[catabolic]

I finally figured it out. 4800 is the correct steps it is just I wasn't calibrating the units to those steps with my cnc machine (i.e. matching the units with my table's axis distance). I had to go to settings (alt-6) "Set Steps per Unit" for axis calibration right above the RESET button in that interface. Then calibrate each axis and double check measurements. Everything is running smoothly now. Thanks Again