Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: charliev on March 08, 2013, 11:28:48 PM

Title: MAXNC and linear motion (G00 and G01)
Post by: charliev on March 08, 2013, 11:28:48 PM

I have my MAXNC CL10 working with MACH3 and I did some cutting today, yay!

I have a mystery that I hope a MAXNC user can help me with... it appears the the MAXNC treats the G00 and G01 code the same (unless I am totally missing something since I am a newbie...)

Here's my setup...
1. With a piece of plexiglass in the vice, I brought the endmilll down within 0.0375 of the TOP of the piece (used a 0.0375 feeler gauge)
2. Zero'd X/Y/Z on MACH3
3. Turned on the spindle and set spindle speed and issued this command: G01 Z-0.0375 F4.0
4. Endmill now is basically on the TOP surface of the piece
5. Next, issued this command: G01 Z-0.50 F2.0

Here's my issue... I expected Z to be -0.50 away (relative) from the last command, instead it went to an absolute Z distance of -0.50 (what is was expecting was an absolute distance of -0.5375)

a) Am I using the wrong G code to accomplish a relative position? Have I got the wrong idea what the G01 code does? If so, what is the linear motion code that moves RELATIVE to the current position?
b) Does the MAXNC controller not recognize the G01 (or relative position code) and interprets it like a G00?

Thank you for your help!

Title: Re: MAXNC and linear motion (G00 and G01)
Post by: Hood on March 09, 2013, 05:14:16 AM
Should have moved to z-0.5 at 2 units per min. so from what, I think, you are saying it moved correctly. What I suspect you are doing wrong is you entered Zero into the Z DRO when it was 0.0375 above where you want the offset zero to actually be. If you had entered 0.0375 into the DRO then that would have meant commanding a Z0 would take you to the surface, z-0.5 to 0.5 below the surface etc etc.
 You can use absolute or incremental moves in Mach but most often absolute is used.
Title: Re: MAXNC and linear motion (G00 and G01)
Post by: jimthefish on March 09, 2013, 08:03:10 AM
Read the bit on Absolute and Incremental codes in the G code tab on the main Mach page, it looks as if you have misunderstood their application. I think Mach always defaults to absolute unless you tell it different in the first line of your program. Looking at your explanation your machine is in absolute but you a thinking and programming in incremental. if the top of you component is Z zero and you are in absolute what you program in is what your machine will move down. Incremental moves a distance from your last programmed position. Best policy is to always use Z zero as the top of you componet, when your learning CNC it makes life easier, and saves a lot of broken tooling.
Incremental programming can be a nightmare when you first start programming.