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Problems with offset cuts and stock orientation
« on: October 15, 2014, 10:59:08 PM »
Long time listener... first time caller.  ;D

I've got a bit of a problem with my CAD->CAM->G-Code->Mach3->Cut process... and I'm not sure where in the chain I'm going wrong, but I'll do my best to explain. Hopefully someone has seen this before, and knows what I can do to fix it. I've spent days staring at this, and I suspect the answer is right in front of me.

Anyway... here's what's going on:

I'm cutting a heatsink out of a small block of 6061 aluminum. It's set up fine in Autodesk Inventor 2014, I have all the toolpaths generated in HSM Express, the simulations look great, I get some pretty clean looking Gcode out of the Mach3 post processor, that code looks great in the CutViewer simulator as well, and after I load the code into Mach3, set my work zero, and regen the toolpath there, it also looks just fine.

Then I run cycle start. The machine starts to cut a pocket, but the pocket isn't centered on the workpiece like it was in simulation. It's offset by a fair amount. The block is 3.64" wide, 2.69" deep, and 1.02" tall, and this ~2.2" square pocket is sitting right against the Y0 boundary, and at least 0.25" too close to the X0 boundary.

My work offsets are correct, the DROs are in fact registering the correct position of the tool as I move it around manually, and the machine consistently and repeatably returns to 0,0,0 when asked. Everything looks OK. This is where I ran out of ideas... until I started considering the dimensions of my stock. On a whim, I swapped the dimensions for X and Y in the CutViewer simulator (to 2.69" for the width and 3.64" for the depth) - and low and behold, the cut that was simulated was EXACTLY what my machine is doing to the piece of aluminum in the vice. Somewhere along the way, I think I either entered the wrong dimensions for the wrong axis, or I've been zeroing the X and Y axes incorrectly this entire time.

Thoughts? What am I doing wrong?
Re: Problems with offset cuts and stock orientation
« Reply #1 on: March 27, 2015, 04:42:28 PM »
I have a similar problem. I used Cut2D to generate code, which I loaded onto a Shireline mill running Mach3. First I pocketed a square and an island which were centered on the piece. Then I manually changed the tool from 0.125" to 1mm and the origin shifted 0.5mm to the left. Can't figure out where the offset comes from. Cut2D and Mach3 simulation look centered.