Lathe c-axis on wrong side

We have a Fanuc x-z axis lathe with live tooling. When we make c-axis contour programs in mastercam we post it out using the generic c-axis slant bed post.

The problem we are having is that the lathe wants to cut it to the opposite side. Instead of engaging the material at +x it engages at -x.
This isn't too much of a hassle for face contouring, we have to cutter comp the whole diameter of the tool we are using though.
The main problem is that when we do cross holes the tool rapids to the start position as -x therefore it would rapid through the part and start cutting through the bottom of the part into air.

I don't know if this is a Mastercam setting, a post setting, or a setting on our lathes but I know this isn't right.

I have attached a crude picture of what it is doing.

Any ideas and/or suggestions to fix this is greatly appreciated

Is poitioning normally when you are turning?

Litlerob,

I'm not quite sure what you are asking.

Positioning is normal for when we are turning, it is only the c-axis and live tooling operations that are not normal.

Looks like G41/G42 selection is backwards if this were a mill. Never programmed C-axis lathes with Mastercam so this is just a WAG.

That is a post issue.

Philabuster - That's what we thought as well but Mastercam only lets me post one direction of cutter comp (left). If I change it it flips my toolpath to the other side.

Wheelieking - Is this a simple post issue or a big one? Do you know the exact issue? Could you walk me through it?

litlerob1 said:

Is poitioning normally when you are turning?

Click to expand...

Jemop430 said:

Philabuster - That's what we thought as well but Mastercam only lets me post one direction of cutter comp (left). If I change it it flips my toolpath to the other side.

Wheelieking - Is this a simple post issue or a big one? Do you know the exact issue? Could you walk me through it?

Click to expand...

Sorry about my question combo of typing fast and poor spelling. It is a post issue, and it sounds like a programming issue, and a control and or machine def issue. The part needs to be in front view and the toolpaths as well.

For the machine def, go into machine definition and make sure all the axes are right there should be a simple layout of the axes in the machine definition. The machine def the control def and the post processor need to be integrated with one another. Example; if the machine def thinks the control def is using a lower turret machine, or vise/versa everything gets all fucked up right? Or if the machine and control are integrated but you are using the wrong post processor then the code you get will be all fucked up.


What version of MC are you using? CAM software is definately not touch and go, as much as the salesmen like to make it seem that way.

OTOH try picking a different post, if it isn't a jacked copy then you should have like 50 to pick from.

Robert my ±2

Rob,

We are running X6.

Our vendor only gave us a few posts (or at least we've only kept a few over the years).
I am taking on the steep task of learning post processors so that we can adapt the generic ones to our machines.

We may have found a solution,
Where the toolpath enters the geometry relative to the X and Y axes (from the "Right" WCS) seems to affect it.
If it enters at a +X and +Y position than it works fine.
If it enters at a -X and -Y position it does what I described earlier.

This confuses me because I thought that with c-axis interpolation it would just rotate to that relative position and be fine.

I know on mine you can't travel through x0,y0, you may have to do intermediate move to like
g0 x.1 y1
x-2 y0

Jemop430 said:

Rob,

We are running X6.

Our vendor only gave us a few posts (or at least we've only kept a few over the years).
I am taking on the steep task of learning post processors so that we can adapt the generic ones to our machines.

We may have found a solution,
Where the toolpath enters the geometry relative to the X and Y axes (from the "Right" WCS) seems to affect it.
If it enters at a +X and +Y position than it works fine.
If it enters at a -X and -Y position it does what I described earlier.

This confuses me because I thought that with c-axis interpolation it would just rotate to that relative position and be fine.

Click to expand...

They are easy enough to get as long as it's licensed, ask the Cad/Cam subforum here at Practical Machinist, explain what's going on, or on Emastercam.com (a forum specific to MasterCam professioanals). If someone deleted all the posts that came with the license they are dumb, just cut the ones you don't use into a different folder on your PC. For C-axis work it will always be from a side, NOT top or front. Go back to cutter comp and change it from "left, right cutter comp" to to wear. You looking at your model is the same as you opening the door of the lathe and staring straight at the back of the machine, left, right, top, front, bottom. Plus like I said you definitions need to match. If by mistake you picked up a post that is for a swiss machine, your in for a headache until you get it figured out, if you accidentally picked a post for a CNC laser, right you get the point.

Robert My ±2

Rob, That makes sense, I do also have this topic up on emastercam (covering all bases).
Our post works pretty great for everything on the lathe this was just confusing.
I think mastercam wanted it to go to a -x value, and thereby overtravel, before going into c-axis mode. Seems like a flaw on their part but now that we know about it we can avoid it.

Thank you for all your advice.