I think BR549 is right. I just did some tests myself and one of the 2 axises will always be incorrect. I guess maybe Mach cant do it???

You MIGHT could do it with 2 versions of mach running independantly of each other and some FANCY plugin work.  I would give Scott S a call and discuss it with him.

(;-) TP

Sure you can do this with Mach. As DaOne said before he lost faith, this is only a three axis job, you just need to bend your mind a bit to see it.

Let's forget the "pre-trimmer" - this is just a dumb tool dragged along by the X axis. Also forget the fact that the stock is spinning - that's of no interest to Mach.

So, that leaves us with the X axis with the 2 tools attached. The first tool is the Y axis and the second tool is the Z axis. To help see this, in your mind just rotate the second tool round the X axis by 90 degrees.

Now the real mind bender. Imagine a toolpath for the Y axis - it's just a profile of the job but so is the Z axis but staggered to the left and rotated by 90 degrees so standard CAM can handle it. Then you generate an engraving path. I used Rhino for the pic attached. It's supposed to be a baseball bat - hey give me a break it's not bad and it's late and the beers are doing just fine. 

Cheers

Ian

What you need is some custom CAM software.
It looks to me like you have X, Y, and Z, with Y and Z the tools, like Stirling said.
What I'd do, is draw my roughing and finishing paths in AutoCAD, and choose an X axis resolution, maybe .002-.005", maybe bigger?
Then parse through the paths, and put the Y and Z values into arrays.
Then, for X = 1 to however many steps needed,
Y= Y(X)
Z = Z(X- tool spacing)

So you'd end up with a series of X,Y,Z moves, with X incrementing  by the chosen resolution amount for each line of g-code.

Seems like it should work.

Thanks guys for the help. Ian, could you post what the g-code wold look like for that drawing? Gerry, I am sort of following what you are saying but I am not sure what you mean by " parse through the paths, and put the Y and Z values into arrays.".  But it seems to me that even with the 3 axis's I don't understand how the y and z moves can happen at different points along the x axis. I am trying to figure out what the g-code would even look like. Do you think you could do a couple lines of code showing how it would be.

Thanks again for the help
Tom

Ok, it looks like it will work. You just need to be sure your X and A axises are fast enough to keep up with the feed of Z. Just like I said before its all about timing the 2nd tool (whatever the offset between them and the feed rate). Programming this by hand will become a mind bender for sure. Its just like 3 axis 3D profiling. That you just don't do by hand as well.

I don't understand how the y and z moves can happen at different points along the x axis. I am trying to figure out what the g-code would even look like.

They move at the same time when they are on the same line...

G1 Z-.001 X2. A2.
G1 Z-.002 X1.9 A1.95


Basically lots and lots of lines.... The higher the resolution = more lines of code.

You need to figure out when to start feeding A into the part based upon where X is.

Actually without the pretrimmer you would just break up a bunch of wood. Its main purpose is as the steady rest to support the wood. BUT it is not a programmable feature.

I have seen these CNC copy lathes run before but never really studied them as to controller function.

I am all good for learning something new(;-)

Lets get the axis convention straight, I see it as a lathe    Z/X and U where U is the second X axis ??

(;-) TP

Sure you can do this with Mach. As DaOne said before he lost faith, this is only a three axis job, you just need to bend your mind a bit to see it.

Yes I simulated it and opened my mouth a bit too fast. Its actually quite simple when you look at it. Just lots of detailed feeds... one line at a time. (same as doing 3D profiling) Whatever your resolution is will determine just how big the file is gonna get. Your fingers will become quite sore without some kind of cam software. Will most likely require a custom post as well.

Lets get the axis convention straight, I see it as a lathe with live axis   Z/X and U where U is the second X axis ??

You can set it to any letter you want. I went with "A" because there are lathe screen sets out there with a "A" DRO. All my live tools are B & C axis on the big boys. The only thing that will matter what letter it is will be the post you use. That can be easily edited in most CAM software.