I checked teh DXF file it is fine , I checked the Gcode file it iooks ok, I converted the Gcode file back to a dxf and verified it is fine as well.

That eliminates the drawing and the Gcode.

That leaves the machine and mach3. Mach3 is NOT known to be wrong in its geometry. Are you running any FORMULAS in MACH3??

That leaves out of square machine, lost steps, Cutting deflection, Slow ACCELL for feedrate causing CV to compensate.

BUT you say you have veried the square and deflection and exact stop cuts the same.

NOW they ALL can't be right and it still cut wrong (;-). I would go back and check everything machine related step by step until you find the problem.

(;-) TP

I have re checked square and all is ok. I don't know how to find out if i am running a formula, could you advise...

Check here.

Please explain HOW you checked square.

(;-) TP

Hi,

No formulas enabled. I checked square by machining a cross into MDF bed that runs the full length of x & y then putting a straight edge along one of the lines and a square against the straight edge, lined up with the machined line along the other axis. We are having the same problem across two machines bought 2 years apart so would not expect the same machine build problem to have gone unnoticed (hopefully!).

I was thinking about the loosing steps comment earlier. When i have machined something and returned to home and machined again it has followed the same path does this verify that this is not a problem? - it follows the same path what ever shape i cut and whether it is from the mahine home as x 0 y 0 or an offset somewhere else on the bed...

thanks

luke.

IF you have home switches then after a program run you can do VERIFY and mach will return to the home switches to verify you have not lost steps.  

HOW fast do you normally cut ??  What are your Motor tuning values   Vel?  accel?   We are down to MACH3 CV altering the path due to slow acceleration vs Feedrate. It will be MORE prevalent on curvy stuff rather than Straight sided stuff such as squares.

HOW far OFF is the cutting?  tenths, hundreths, thousanths ?

IS it always to BIG or to small?

BUT let me re verify the problem. You cut the guitar body out then Flip it over and set it into a fixture to  cut other features and it does not fit in the fixture ? How did you cut the fixture to hold it?

SHooting in the dark, (;-) TP

 

OK will try that.

Normally cut around 1000 mm/m up to 1500.

Motor tuning values as shown in attached pic. (velocity 1500 acceleration 750)

when we try and flip it fits perfectly one way but the other way up the part is between 0.5mm & 1mm out from fitting always in the same place.

To verify, we cut the body. then fix 4 MDF blocks securly to the bed and run another cut which allows for the 4 tabs around the body to slot in which shoudl locate the body facing up or down. do you want me to put a pic up of the process?

Thanks

Just ran a cut around the outside of the guitar body and  the VERIFY gave these readings

X = 0.02000 Y = 0.0000 Z = 0.0160

Hi Guys,

I have just re modelled the guitar body with a slightly different outline but with the tabs that locate it in the same place these are the same size as before. The cut followed the tabs as before and the curvy part of the body outline changed as it had on the new model.

Any furthur input would be greatly appreciated.

I don't have any allowance for backlash, and don't know how to measure if this is a problem can you suggest something?
 Luke.

Back to the backlash, I'd check to see if there is any on the X and Y.
Several methods are posted, a search will reveal.
Russ