here is the tap file and auto cad file. On the auto cad file the flat problem is at 0,1.7097 and 0,-1.7097. Any help would be appreciated.

David

David, I think you may just be seeing the result of backlash. I haven't studied the code much but the dxf looks fine to me. Can you post a picture of the cut?

Brett

I tried to do something simply from the circle wizard. This is the tap file and the picture of the cut.

Yup, looks like backlash to me. Have you checked it yet? Do you have a dial indicator?  Checking your backlash should be no problem if you have an indicator. Put the indicator on something solid. Jog your axis until you move the indicator to a reading of about half of its travel. Write down the reading on the indicator. Jog the axis in the other direction by a set amount, say .010" and see how much difference the indicator shows. If the indicator says you moved .005 and Mach says it has moved .010 then you have .005" backlash.

Brett

I was watching some videos on you tube and I seen this one (Mach 3 Backlash Compensation )
it looks it might be a fix to your problem.
hope it helps

I appreciate the help I was messing with the backlash and it does seem to make things look better. So I guess what I need to do is find a dial indicator.

David

If you do not have a dial test indicator, a set of digital calipers will do the job.

With Backlash compensation OFF :-

Start with your mill at 0,0: On the MDI type G0X1 and measure the position of the table (or cutter, whichever moves) from some suitable point in line with the axis. Zero your calipers. If you then type G0X2, followed by G0X1, in theory the table will have returned to where it started and your calipers should read 00 again. (If you want to be really accurate do a G1 with a slow feedrate F4 say)

They will not, and the amount on the calipers is your backlash. This is the movement lost by the axis as the gearing is getting itself into the right position to shove the other way. On a circle (depending on where you start) each axis changes direction once, and sometimes twice, so the flat bit you get on the circle is say the Xaxis changing direction (and not moving for a short time) whilest the Y axis carries on regardless.

Enter this amount in the backlash compensation table, repeat for the other axis, and turn on the compensation.

The way Mach 3 applies compensation is a little disconcerting (although the speed of it can be adjusted) but it is accurate.

okay,  i have been measuring the x- axis with a dial indicator.  after zeroing the indicator and the axis.  i moved the x to g1x.1f4 and the indicator reading .097(  the computer reading .1)  i move it back to zero and it ends up on .025 (the computor is reading .00).  without re-zeroing anything, i move the x axis again to g1x.1f4 and the dial returns to .097.   is there a way to correct this  in MACH 3... I  have been playing with the backlash, but this seems to be a different issue all together....

Is there a spot in the Mach 3 that will move the machine a certain distance and then allow me to input the actual distance the machine moved in order to calibrate?

Where is X and Y in relation to the flat spots?