Need Help. Machine not cutthing to size, Tool Offsets ???

Hello there

I am having a hard time with my machine, it been cutting around 0.030" under size,
I double checked the x and y axes and backlash with my dial indicator and everything is pretty much perfect.
I made code using Inventor and Aspire also did one by hand to cut a simple 2"x2" square and they all end up pretty much the same, 0.030"-0.035" under size

Is there setting in Mach that has something to do with this ??
I made sure the tools table offset are all set to zero
Any one have any ideas ???

Thanks

1st things 1st.... is your machine moving the correct distance ?
ie mark at X0,Y0 move 10" in X and measure... do the same for Y

if correct then look to your program... what strategy do you program to ?
ie is the toolpath the actual finish profile of your job ?.... tool offset cannot be = zero. it should be either the tool radius or tool diameter.
If toolpath is offset from the part profile by the tool radius, then tool offset is theoretically = zero
.... but you must use the tool diameter as programmed
.... if you use a tool smaller than programmed the a -ive value is placed in the appropriate offset number. To make the tool pass closer to your work shape.
.... if you use a larger tool, a +ive number is used... but this opens a field of problems, most common being the cutter cannot process an internal radius smaller then the tool being used.

what tool size did you use ?
... guessing it was a 1/16"
... if you use the part profile method, then the offset should have been 0.0315
put up your nc code for the 2" square

Hi There

Yap i double checked everything on the machine and everything is good
I am using 1/4" cutter
I tried something simple like this
G01 X2.25
G01 Y2.25
G01 X0.0
G01 Y0.0
and using Aspire or Inventor i get the same results
i posted the code Aspire did

Try doing a climb cut, and measuring the size. It'll probably be larger.

Quote:

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Originally Posted by Biggermens

Hi There

Yap i double checked everything on the machine and everything is good
I am using 1/4" cutter
I tried something simple like this
G01 X2.25
G01 Y2.25
G01 X0.0
G01 Y0.0
and using Aspire or Inventor i get the same results
i posted the code Aspire did

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well... it's not tool offest values...
your program is not using G41 D1 or G42 D1, nor has a G40 to cancel cutter comp.
D1 being the stored value you put in for the amount of compensation...
CAUTION.... some controls have only 1 field per offset number. don't make the mistake of calling a tool length instead of a radial offset

Your discrepancy must come from a different reason... Gerry is suggesting flexing through the tool or spindle
Are your tools reasonably sharp ?

I feel a bit stupid but i found the problem, my machine is a pile of junk, it flexes everywhere if i take light cuts then my parts are to size.

now i have to figure out how to make this thing stronger hehe

Thanks everyone