Help - G-Code Circular Motion for CNC Milling

[Rafi A]

don't you have to use mastercam to export it to the machine?

[sanddrag]

Originally Posted by Pixel_Perfect

don't you have to use mastercam to export it to the machine?

I don't think so. Can't you just make an NC file and save it one a floppy. The machine has a floppy drive for importing and exporting files.

Anyway, can we get back to how to bore a bearing hole in 1/4" plate. Katie said how to do the circle, but I need to know how to go down at the same time. Any help?

[indieFan]

Sanddrag,

Any chance you can get your hands on a reamer of the correct size? If so, the initial downward cut shouldn't make a difference. If not, I suggest that you try dropping the z in increments. You might be surprised at the results if your speeds and feeds are correct and your tool is in good shape.

Also, I would check out the HAAS website for their operator manual. That might have information on what you want. The other website to check (including their Q&A section under "Resources") is www.cncci.com. The guy who does most of this site has written several books on CNC programming, including the issue of parametrics.

indieFan

[sanddrag]

I think I have finally found what I need. I just realized that the answer probably was in my HAAS Programming manual so I decided to take a look. What I found was a code called G12. It seems to be just what I need but I have one question. Will it ramp downward?

Here's the sample code the manual gives:

N1 T1 M06
N2 G90 G54 G00 X2.5 Y2.5 (position to X Y center of cirular pocket)
N3 S1900 M03
N4 G43 H01 Z0.1 M08
N5 G01 Z-0.5 F30. (to feed Z axis slower, or faster, than what's in the G12 line
N6 G12 Z-0.5 I0.5 D01 F11. (1.0 Dia. x .5 deep circular pocket)
N7 G00 Z1. M09
N8 G53 G49 Y0. Z0.
N9 M30

My question is does line 5 run the cutter down into the part? That would seem a bit odd to me. Another version of the code does not have line 5 and I guess only makes 1 revolution before getting all the way down.

See what I think I want to do is make it go around and around several times constantly ramping down very slowly. Is that right? How do I make it do that? Someone please help.

EDIT: I think I may have a solution. What if I incrementally went down to rought out a little bit smaller hole, and then I absolutely went around to just enlarge it slightly and to get a nice finish. Would that work?

[Matt Reiland]

Sanddrag,


I think you are getting really close. Couple of things. First, you should be able to download a free version of FlashCut CNC Offline and play around with it.

www.flashcutcnc.com

This is the software that my Smithy CNC runs on at home. It will directly import your .DXF file and convert it to G Code for you. As for bringing down the Z while cutting a circle. Make sure your controller is capable of 3 axis circular interpolation. Mine can only cut 2 axis at a time. Therefore I bring the Z down into the part like your line above then start to cut the circle. If you want you can slightly undercut it then make a final circular path to get a smooth dimension. Now would be a good time to find out about the backlash of the machine you are on also since ANY backlash will show up quickly when you cut circles on a CNC mill since your x & y change direction 4 times in the circle. I got so fed up on mine that I just had new ballscrews made and am putting them on this weekend which should clean up a bunch of slop.

Also the Flashcut manual is available for download which has all of the G codes listed and how they work.