Reference for C-axis

[sinha_nsit]

While this is not important for an axi-symmetric job, I was wondering where C0 position is.

[gbowne1]

The ones I've been around, and I'm rather new at this, you go into C axis mode via M code, then it programs via call letter C in degrees from there. When not in C axis mode, it responds to the spindle S command.

There are also different interpolation modes. Polar coordinate and cylindrical are the most common.

Polar is for working on the face of the part, ie. milling features that are not on center line. Basically you program as if you were looking at the end of the part straight on program just like on a mill except you substitute C for Y.

Cylindrical is for working around the diameter of a part, ie engraving on the OD. It's a little harder to explain but you take the profile you want to mill and unroll it so that it's flat on a cartesian plane. The Z axis is vertical and the C axis is horizontal.

Polar is very handy but cylindrical is easy enough to duplicate in normal C axis mode. On Fanuc controls the feed rate in normal C-axis mode is specified in degrees per min. Makes it interesting when you mix C moves with linear X or Z moves, makes for lots of F changes.

I would guess there are as many ways to program it as there are machine builders.

You may also need to switch between planes (G17, G18, G19) for your G02s and G03s to work. Basically you have to tell the control which plane its supposed to use for interpolation.

Remember too that some FANUC's with conversational mode let you treat the end of the part with XY. So it's polar coordinates, but you program in XY not XC at least from what I read thats how I understand it.

And for many common operations, like making Hexagon flats, on newer controls, you can just describe the feature and the control will G code it for you.

I think that's a long winded way of saying at least some conversational programs have decent support for C-axis tasks. I don't know if all do.

Yes, there is a home position. Most newer C-axis lathes have absolute encoders in the spindles. On Mori Seiki lathes, M45/M46 engages/disengages the C-axis. "G00 C0" homes the axis.

The work offset table allows you to store C-axis offsets alongside the X, Y, Z, and B axis offsets.

The one I played with you don't have to home the C axis. It automatically knew the position. On my friends' Kia, you call the C axis into action then go into a polar mode via a G12.1 (Polar Interpolation On) and Polar Off with G13.1
This is as much as I know.

Greg

[dcoupar]

I don't understand your question.

C0 is the position that the C-axis rotates to when you command G28 H0 or G28 C0.

[sinha_nsit]

Which position does it rotate to?

[sinha_nsit]

Originally Posted by gbowne1 ... This is as much as I know. Greg

Good information. Thank you.

Is the home position of C-axis related to M19 or marker pulse?
What happens when there is incremental encoder?

I was wondering if it is possible to do a rework involving C-axis.
Possibly, we can put a mark on the spindle indicating C0 position, and would hold the workpiece with reference to this position for further machining, though it cannot be very accurate.
Or, we just clamp the workpiece, turn the spindle to some particular angular orientation, and define a new C0 position.

[angelw]

Originally Posted by sinha_nsit I was wondering if it is possible to do a rework involving C-axis. Possibly, we can put a mark on the spindle indicating C0 position, and would hold the workpiece with reference to this position for further machining, though it cannot be very accurate. Or, we just clamp the workpiece, turn the spindle to some particular angular orientation, and define a new C0 position.

Hi Sinha,

If the work was being held in bored soft jaws, or by some other accurate means so the part will set up again accurately, you can rework using the C axis the same as any other machining axis.

The C axis has a machine Zero position the same as the X and Z axes and has work offsets G54 to G59 like the other axes. If there is a feature on the part to be reworked that can be dialed in with a dial indicator being traversed with the X axis, then any error in the replacement of the part can be compensated with a work offset.

Regards,

Bill

[dcoupar]

Originally Posted by sinha_nsit Which position does it rotate to?

C-axis usually has 360,000 positions. I think the builder determines where C0 is, and it probably isn't the same from one machine to the next. And I don't necessarily think C0 is the same as M19 orientation position... it CAN be, but it ain't necessarily so.

[gbowne1]

Well, that information I came across while reading more about the C axis through several threads on related forums all over the internet. This is what I found on the C axes when I was looking for more definition of the axes beyond X, Y & Z. While it's not much, I scribbled down some notes on it based on my findings figuring I might need it someday, and hoping someone would fill in the missing bits of information.

Not sure about axes rework or what you want to do, but it might be possible.

Greg

[stevo1]

Sinha as stated above the C-axis is like any other axis. It can have an absolute encoder on it so it knows 0 is or it can have incremental encoders and have a home switch.

Now depending on what you want to refer to as 0. Reference position and home position are 2 different things. Most of my C-axis I have to change the reference position so that when I program C0 it will go to the center of one of the T-slots.

Stevo