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Arcs and cutter comp
« on: March 30, 2013, 09:41:19 PM »
OK, My 1st program. 

In regards to making arcs, is I and J incremental or absolute in Mach3?  What if I am in G90 mode? 

I plan on cutting a path by programming the points of the outline and using both G41 and G42.  You see, I have a .375" cutter and I am going to for the first pass, G41 and use a P variable of .375 ( .750" diameter cutter), get to the end of the pass and then switch to G42 w/ a P of .3125, go back up that path but in reverse.  I want to go back and forth getting closer each time to the final dimension until I use a final P of .1854 as this whole operation has been a roughing cut in 4140 PH.  I will not be making any tool changes so I won't be using D variables.  From what I understand, I don't need any lead in moves when hitting the end of the path and changing between G41 and G42.  My question is this, will I need to include lead in moves because I am changing my P values?

       

Offline BR549

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Re: Arcs and cutter comp
« Reply #1 on: March 30, 2013, 09:52:20 PM »
Arcs, IJ mode? you can have it either way it is covered in the manual

Not a great idea to "try "and use the toolcomp offset to do your machining that way. Just program the moves as you need them. Go down the line move over a step over amount and go back to the beginning, Repeat until you are at the final value.

Just a thought(;-) TP

Re: Arcs and cutter comp
« Reply #2 on: March 30, 2013, 10:33:22 PM »


Not a great idea to "try "and use the toolcomp offset to do your machining that way.
Just a thought(;-) TP


Please elaborate?  I used to make mock programs by drawing paths around my parts in CAD, that grew tedious and tiresome, especially if there is a function that can take care of that for me.  I also used to program using tool center paths and a buddy of mine that actually has experience doing this told me, learn cutter comp.  is cutter comp in mach not reliable? 

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Re: Arcs and cutter comp
« Reply #3 on: March 30, 2013, 11:12:52 PM »
To use Cutter Comp you still program as tool centerline and you use the Comp to offset the toolpath by the value of the tool radius. BUT you have to use a leadin/out to bring the tool into play or out of play for the moves.

Best get a GOOD gcode manual to study as describing it in full here could take HOURS of typing(;-) Also note that MACH3 may have nuaisences that other favors of Gcode do not. So the basic's apply but the fine tuning may be MACH3 specicfic. Should be covered in the manual(;-).

(;-) TP
Re: Arcs and cutter comp
« Reply #4 on: March 31, 2013, 01:07:38 AM »
OK, My 1st program. 

In regards to making arcs, is I and J incremental or absolute in Mach3?  What if I am in G90 mode? 

I plan on cutting a path by programming the points of the outline and using both G41 and G42.  You see, I have a .375" cutter and I am going to for the first pass, G41 and use a P variable of .375 ( .750" diameter cutter), get to the end of the pass and then switch to G42 w/ a P of .3125, go back up that path but in reverse.  I want to go back and forth getting closer each time to the final dimension until I use a final P of .1854 as this whole operation has been a roughing cut in 4140 PH.  I will not be making any tool changes so I won't be using D variables.  From what I understand, I don't need any lead in moves when hitting the end of the path and changing between G41 and G42.  My question is this, will I need to include lead in moves because I am changing my P values?

Hi Mountainman,
   Too funny, I just noticed your post right after I posted a very similar question and have been beating my head trying to understand G02 and G42 for a few hours.  I think we may have similar questions, but also you seem to have a question that I have just learned the answer to I think.

   Go to the "Config" pull down menu and select "General Config...".  There in the middle you'll see "IJ mode" and you can select relative or absolute.

   For some reason this is "absolute" by default I think.  And it would seem that doing G02's with relative IJ's is way easier to code by hand.

   Anyway, I got that working fine, but see my other questions here:

http://www.machsupport.com/forum/index.php/topic,24178.0.html
Re: Arcs and cutter comp
« Reply #5 on: March 31, 2013, 10:02:24 AM »

Hi Mountainman,

   Go to the "Config" pull down menu and select "General Config...".  There in the middle you'll see "IJ mode" and you can select relative or absolute.

   For some reason this is "absolute" by default I think.  And it would seem that doing G02's with relative IJ's is way easier to code by hand.

   Anyway, I got that working fine, but see my other questions here:

http://www.machsupport.com/forum/index.php/topic,24178.0.html


I use CAD in order to figure out the points of my cutter path.  I just set my datum on the workpiece where I want it and then I just transpose my points to the G code, so for me, absolute mode seems easier, no need to subtract anything.  So bottom line, we have the arc question answered, it does not matter if I am in G90 or G91.  What determines if I am using absolute or incremental IJ is in the general config menu.

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Re: Arcs and cutter comp
« Reply #6 on: March 31, 2013, 10:45:40 AM »
actually you need to read the manual(;-)

G90 set abs motion
G91 set inc motion

G90.1 set abs IJ arcs
G91.1 set inc IJ arcs

The Gen config setts are just the defaults that Mach3 starts up with.

Just a thought, (;-) TP
Re: Arcs and cutter comp
« Reply #7 on: March 31, 2013, 02:05:45 PM »
actually you need to read the manual(;-)

G90 set abs motion
G91 set inc motion

G90.1 set abs IJ arcs
G91.1 set inc IJ arcs

The Gen config setts are just the defaults that Mach3 starts up with.

Just a thought, (;-) TP

I'll remember to add G90.1 at the header of my programs so I don't have to worry about config settings.  Thanks, but what I really need help on is if knowing whether a lead in move is necessary when changing the P value in cutter comp? 
Re: Arcs and cutter comp
« Reply #8 on: March 31, 2013, 05:30:43 PM »
It works ok, I see that lead in moves are not perpendicular to programmed path, so I see why lead in/out moves are used as to not disturb the material that should not be cut.  For my intenst and purpose it looks fine.  I tested it all out by fixturing some paper and chucking in a pencil. 

I also learned that my G code, the values that should have been - were all + and vise versa.  Then when I fixed it all up, the part was shown on teh screen as a mirror image.  My X axis seems to be in the wrong direction, how do I flip that? 

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Re: Arcs and cutter comp
« Reply #9 on: March 31, 2013, 06:00:54 PM »
IF the Mach3 too lpath is showing the mirrored image then your Gcode is mirrored. IF the display is correct and it cuts mirrored then the motor is backwards.

The lead in / out  is ONLY there to give MACH3 room to do the tool radius comp move. IT is up to YOU to make sure the profile is fully cut(;-) as part of your programming in Gcode.

Just a thought, (;-) TP