Cutting outside the line!

[GaryM]

I need some help. I have a simple shape to mill out, it's a dxf. The problem is my cnc cuts on the line, I need it to cut outside the line. I am using Mach3. Could someone give a dumby a helping hand?

Gary

[mxtras]

You can either use cutter compensation (give the cutter a diameter in the code generator) or offset your data for the tool diameter.

Scott

[GaryM]

Thanks mxtras, I'll check that out!

Gary

[GaryM]

I am still at a loss of how to cut on the outside of this shape. I have attached the dxf file if someone could look at it and maybe explain how to do it. I am using Mach3, and turbocad.

Thanks

Gary

[ger21]

First of all, not a single pair of endpoints lined up in your drawing, so I had to do a lot of editing on it. The ends of every arc didn't touch the endpoints of the adjacent lines.

Here's how I do it. When you draw the part, add a leadin line and a leadout line. This is where cutter compensation is applied and removed. Join the entire object into a single polyline, and make sure it's drawn in the cutting direction. (Not sure how to do this in TurboCAD).

Then, convert the polyline to g-code the way you normally would, and add the G42 and G40 lines to your code. The G42 goes between the first and second point, the G40 before the last point.

In the example code, I assumed a 1/8" tool. The P value in the G42 line is the tool radius.

Make sure in Mach3, you have advanced compensation turned on. (Ports and pins>mill options I think)

[ger21]

I just looked at it in Mach3, and noticed you may have to slow the feedrate way down for it to display correctly, because it goes too fast.

[paulC]

You need to create a tool path by creating an offset in your cad/cam software, then use this offset to generate your gcode. The offset is normally half the bit size.
Paul

[GaryM]

Thanks guys I'll check it out!

Gary