Any CNC machinists around (C-axis milling with lathe)

Dowly · 07-30-21, 08:57 AM

Hola, we got any machinists here that could explain the principle behind C-axis milling using a lathe? Need to do some milling on Monday, but have never needed to program C-axis before.

The task itself is simple enough; six flat sides on the end of a 68mm axel with the length across two flats being 62.8mm.

Something like this:

Catfish · 07-30-21, 10:54 AM

My cnc capabilities are virtually inexistent.
C-axis is the theoretical center line running along the wire?
I guess you will have to know the exact thickness of the wire, too. Unless they want you to solve it mathematically by angles

I would clamp or (mount?) the thick wire so it is exactly in the center and turns without vertical (to the axis) deviation. Then arrest it in one position.

Then, from the other side (where the flats shall be located) let the machine horizontally (parallel to the center or to the outside of the wire) chip away one flat telling it to go this x millimetres from the outer diameter. Let the machine rotate the wire 60 degrees and repeat to chip off the next circle segment. Do this five times in all.

Dowly · 07-30-21, 12:55 PM

C-axis is the turn of the chuck. Sorry, should have labeled my pic a bit better. That is the front/end view.

Catfish · 07-30-21, 02:15 PM

If the transition from the six-sided end to the rest of the wire may be smooth, you can of course use grinding instead of lateral chipping, with the axis of the grinder being at 90 degrees to the c-axis.
Just don't ask me how to translate this and get it into a cnc terminal.

ET2SN · 07-30-21, 02:23 PM

Normally, I would urge spending several weeks reading the manuals of the CNC machine, its interface(s) to the computer, plus some research into the material you'll be machining.

But, this is SUBSIM. Just wing it.

If anything breaks, make sure you have someone else to blame.

For the record, I have a lot of background in programming but pretty much no experience in CNC. Take my advice for what its worth.

Buddahaid · 07-30-21, 04:49 PM

I'm no machinist but you may find what you are looking for on the Autodesk Fusion 360 YouTube channel tutorials. You should also be able to get a free hobbyist license for Fusion 360.

Dowly · 07-31-21, 11:13 AM

After digging around, I think I have figured it out.

Thanks for the suggestions.

EDIT: I suppose I should explain how it works in the unlikely case someone has the same problem or finds this thread via google.

In normal operation the position of the C-axis is shown in degrees as it is the rotation of the chuck. Using the G112 command changes the operation of the axis to work more like X/Z, so instead of degrees it is now in millimeters. Now, it is a simple task of figuring out the corner points of the hex and the machine does the rest.

07-30-21, 08:57 AM	#1
Dowly Lucky Jack Join Date: Apr 2005 Location: Finland Posts: 25,052 Downloads: 32 Uploads: 0	Any CNC machinists around (C-axis milling with lathe) Hola, we got any machinists here that could explain the principle behind C-axis milling using a lathe? Need to do some milling on Monday, but have never needed to program C-axis before. The task itself is simple enough; six flat sides on the end of a 68mm axel with the length across two flats being 62.8mm. Something like this:

07-30-21, 10:54 AM	#2
Catfish Dipped Squirrel Operative Join Date: Sep 2001 Location: ..where the ocean meets the sky Posts: 17,766 Downloads: 38 Uploads: 0	My cnc capabilities are virtually inexistent. C-axis is the theoretical center line running along the wire? I guess you will have to know the exact thickness of the wire, too. Unless they want you to solve it mathematically by angles I would clamp or (mount?) the thick wire so it is exactly in the center and turns without vertical (to the axis) deviation. Then arrest it in one position. Then, from the other side (where the flats shall be located) let the machine horizontally (parallel to the center or to the outside of the wire) chip away one flat telling it to go this x millimetres from the outer diameter. Let the machine rotate the wire 60 degrees and repeat to chip off the next circle segment. Do this five times in all. __________________ >^..^<*)))>{ All generalizations are wrong.

07-30-21, 02:15 PM	#4
Catfish Dipped Squirrel Operative Join Date: Sep 2001 Location: ..where the ocean meets the sky Posts: 17,766 Downloads: 38 Uploads: 0	If the transition from the six-sided end to the rest of the wire may be smooth, you can of course use grinding instead of lateral chipping, with the axis of the grinder being at 90 degrees to the c-axis. Just don't ask me how to translate this and get it into a cnc terminal. __________________ >^..^<)))>{ All generalizations are wrong. Last edited by Catfish; 07-30-21 at 02:25 PM.*

07-30-21, 04:49 PM	#6
Buddahaid Shark above Space Chicken Join Date: Jun 2008 Posts: 9,320 Downloads: 162 Uploads: 0	I'm no machinist but you may find what you are looking for on the Autodesk Fusion 360 YouTube channel tutorials. You should also be able to get a free hobbyist license for Fusion 360. __________________ "However vast the darkness, we must provide our own light." Stanley Kubrick "Tomorrow belongs to those who can hear it coming." David Bowie

07-31-21, 11:13 AM	#7
Dowly Lucky Jack Join Date: Apr 2005 Location: Finland Posts: 25,052 Downloads: 32 Uploads: 0	After digging around, I think I have figured it out. Thanks for the suggestions. EDIT: I suppose I should explain how it works in the unlikely case someone has the same problem or finds this thread via google. In normal operation the position of the C-axis is shown in degrees as it is the rotation of the chuck. Using the G112 command changes the operation of the axis to work more like X/Z, so instead of degrees it is now in millimeters. Now, it is a simple task of figuring out the corner points of the hex and the machine does the rest. Last edited by Dowly; 08-01-21 at 03:26 AM.

07-30-21, 12:55 PM	#3
Dowly Lucky Jack Join Date: Apr 2005 Location: Finland Posts: 25,052 Downloads: 32 Uploads: 0	C-axis is the turn of the chuck. Sorry, should have labeled my pic a bit better. That is the front/end view.

07-30-21, 02:23 PM	#5
ET2SN Ocean Warrior Join Date: Oct 2017 Posts: 2,652 Downloads: 60 Uploads: 0	Normally, I would urge spending several weeks reading the manuals of the CNC machine, its interface(s) to the computer, plus some research into the material you'll be machining. But, this is SUBSIM. Just wing it. If anything breaks, make sure you have someone else to blame. For the record, I have a lot of background in programming but pretty much no experience in CNC. Take my advice for what its worth.