Vertical 4th axis contour machining?

[Un4givn]

Hi,

I recently got to work on a job that was too big for my HAAS VF4, but I soon got around this with a 4th axis that i put flat on the table so that it rotates on the Z axis. Because the job is a big round ring I could program it by hand using only the A, X and Z axis, leaving the Y axis out because the job would crash into the machine.
This went well for a while until I opened up a new drawing the engineer gave me. It wasn't round any more...well, almost round except for a few places along the circle where there were simple profiles.
Now I know it is still possible to cut it using only the AXZ axis, the problem is I can't program it by hand, it's gonna be way too complicated for the limited amount of time I have.
After trying long and hard on CAMworks, I couldn't get anything done, using 4 axis machining turns the cutter to cut perpendicular to the surface I'm cutting. All I want is to cut a contour without using Y axis. I tried MasterCam too, no go there also. I can't imagine that I'm the only one who ever wanted to cut in this way, so that means I must be missing something...Could anyone help?

[Kiwi]

Can you post a sketch of the contour and give the Y position of the tool relative to the centre of your A.
Just trying to understand what you require.

[cncbayer16]

Use a G68 inyour G18 or 19 plane along with your g2 or 3 add a z move for some Favorrrr!

[HuFlungDung]

What comes to my mind is that you'd need something like Mill/Turn functionality because you've got polar coordinate programming to deal with. OneCNC now has this sort of functionality available, obviously meant for lathes with a live 4th, but I can at least imagine hacking a post to make it run on a mill

[Un4givn]

Here is a rough sketch, it's bad quality but you can get the general idea. Y axis stands still on Y0.0 in the center of the job. That's also where my A axis rotates.

I know it doesn't look like much but those curves are critical, and right in the middle of the little profile is a flat part for 35mm.

[Kiwi]

My suggestion would to generate a tool path with G01 steps.
Open NC file with Excel and calculate Angle and X

[Un4givn]

I thought of the same thing this morning while driving to work. That ring you see is 900mm in diameter though, so I'm going to need a way to calculate about 250000 steps to get within 0.02mm between steps. Have you got any idea how I can calculate that fast?

I saw the pic you sent but my excel knowledge is somewhat limited. If that is the answer I'm looking for could you just explain a bit more in detail?

This is the way though, I just need to calculate those coordinates.

[Kiwi]

.....so I'm going to need a way to calculate about 250000 steps to get within 0.02mm between steps.

I saw the pic you sent but my excel knowledge is somewhat limited. If that is the answer I'm looking for could you just explain a bit more in detail?

When the path is on a constant radius, only one line of code is required, but when machining the flats and the small arcs, I believe you need many short movements to maintain accuracy.

The method I'm suggesting has a number of steps to get what you require, but I don't have a 4th axis CAM program to advise using one.

Please supply some details of your drawing and I will supply some code with details on the method I'm using.

[cncbayer16]

I want to Buy a 20" swing lathe (not to require that it is cuts to that dia) just need it to be fadal or the Kentucky thourghbreed, A MAZAK, either way I m a lookin @ all ,, Thanks

[Matt@RFR]

You don't need to make it complicated. Position the tool where needed and feed A until you get to the first radius going into one of the tabs. Stop the A right there and lead out along that radius. Then reenter the cut and interpolate the step without moving A. Reposition so Y is on centerline with A again and keep cutting until you encounter the next tab.

If you're programming manually, just make the above into a local sub and loop it in Z until you're through, then change your D number for that tool and run the finish pass. No biggie.

[Kiwi]

You don't need to make it complicated...........

I like your approach but this may only be possible if the Y travel doesn't crash the job into the machine.

........ leaving the Y axis out because the job would crash into the machine......

[Matt@RFR]

Thanks Kiwi, I missed that part somehow. Those tabs on the part look small so hopefully he's got enough room to move Y by that much. If not, that is one tight fit!