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1

General Mach Discussion / G2 - G3 Command Bug with G68

« on: October 22, 2010, 12:06:18 PM »

All,
I seem to have sumbled on a bug that has some very odd behavior.  While the following code is exactly the same line for line two different circles are created.  My IJ is set to incremental.  I'm attempting to cut a spiral hole so I don't burn up my endmill drilling straight down in .25 stainless.  I need the G68 as I'm milling a single part and will be reversing it for every other part cut so as to use my stainless in the most efficient manner possible.  I've removed all other part G-code to ensure it wasn't causing an issue.  The two pieces that appear to conflict are the G68 and G2/G3.

First my original code that revealed the issue.  You'll notice that the only difference between line 4 and 5 is deeper Z.  But instead a different and much larger hole is created:
G68 A0 B2 R180
G0 x0 y0 z0
G1 X.280 Y.432 F.6
G2 x.280 y.432 Z-.15 i.036
G2 x.280 y.432 Z-.25 i.036
G2 x.280 y.432 Z-.35 i.036
G40
M30

Second a block of IDENTICAL lines of code that create two different size holes.  Each identical line of G2 code creates an alternating different size hole.
G68 A0 B2 R180
G0 x0 y0 z0
G1 X.280 Y.432 F.6
G2 x.280 y.432 Z-.15 i.036
G2 x.280 y.432 Z-.15 i.036
G2 x.280 y.432 Z-.15 i.036
G2 x.280 y.432 Z-.15 i.036
G40
M30

Any assistance would be greatly appreciated.
Thank you,
Jeff

2

General Mach Discussion / Parrallel Port Help Request

« on: May 16, 2010, 07:24:42 PM »

I just completed a 2'X6' CNC table and am having a parrallel port issue (I believe).  I initially installed Mach3 to an IBM T40 (1.4ghz) notebook and was fairly easy to get all three axis working ok.  A little problem though.  I could only get 30 RPM (3 Inch Per Minute w/ 10 pitch screws) as a maximum speed.

I moved a desktop to the garrage to see if the faster computer would work better (Intel Q9400 2.66ghz - Quad core processor).  The Y and Z axis work ok, but ONLY when I set the speed at 10 inch per minute and the X axis just hums and jerks back and forth no matter what I do (core speed set to 100).  Through trial and error I've found that the X axis output (likely LPT?) is out of sync with the rest of the outputs.  The computer had everything build onto the system board accept the parallel port.  I had purchased an add on card with the computer ($19 card off the shelf that works fine with my old laser priner). 

A secondary issue I'm having is the two axis that do work only work at the 10 inch per minute speed.  If I adjust the speed up or down the motion becomes VERY jerky or won't operate at all (just humms and jerks back and forth).

Is there a recommended add on parrallel port that is known to work good? (or a used brand / model of computer that is known to work) 

OR - Is there a way to get more than 30 RPM from the T40? (best solution).  The LPT check program that comes with Mach3 says the 25k core speed is the only speed it will work at.

Any assistance is much appreciated!

Thank you,
Jeff