Could this be done with Mach

[kencor1]

I am thinking about trying to build a Wood Lathe controlled by Mach. But I would need 2 cutters that are about 1.5 inches spaced apart following the same z axis but the 2 X axis would happen at different times. The 1st cutter would be a roughing cutter and would leave approx. .25 from the final dia. the other cutter is a finish knife that will take it down to the finish dia. They would both be tied to the same Z axis. This is how one of the commercially made lathes are. I have racked my brain but I don't think that Mach can do this. Can anyone think of a way that this might be done

Thanks,
Tom

Here is a link to a video of a commercial machine doing what I am trying to accomplish
http://www.youtube.com/watch?v=eEt6dFmcZYU

[budman68]

Hi Tom,

I have no idea if Mach can do this, but I'm just curious looking at the video, isn't there actually 3 cutters?

One to turn the blank to a given diameter, then the rough and then the finish knives?

Dave

[DaOne]

Yes this can be done with Mach. It is simply a 3 axis machine. You will not be able to show the correct toolpath simulation in Mach however. The way I would set it up depends on the post processor that you intend to be using. A simple way would be a simple 2 axis lathe setup with X as the rougher and A as the finisher. If you having an issue wrapping your head around this just think about 3D ball milling on a 3 axis mill. All 3 axises are driven simultaneously. Where it become complicated is in creating the G-code.

[kencor1]

Dave, yes the video shows a pre-rounding cutter. I would not need to use a pre-rough cutter because my turnings would have square and turned areas.

DaOne - do you have any ideas on how the g-code would be created? Or what the code would even look like?

Thanks,
Tom

[DaOne]

Well since your Z is always the same on both tools you need to figure out the time it takes between the tools to be in the same spot to start using the finishing axis (A) and the give it the commands with X. It basically just a simple delay based on the feed rate of Z. You can always post out the roughing... then the finishing. Figure out timing point (offset) to graft them together. Like I say the G-code is the issue not Mach. Mach with just do what its told.

[kencor1]

Thanks DaOne, do you have any suggestions on how I would set up a post, or how I would "graft" the tool paths together, would I have to manually do it? Lets say the delay is 1 second between tools.

Tom

[DaOne]

I wish I could. Its all about math and will probably take some trial and error to get it just right. If It was me I think a single cutter (each axis would have its own pass) would be much easier to use. I would just do it in 2 passes. I am not familiar with wood lathe cam packages to recommend anything. 

Wes

[BR549]

HUM I don't see that happening with mach3.  The problem is running two independant axis's in sync with z to do the 2 profiles at the same time.

I don't see any way to Gcode that with Mach3.  Could be wrong though(;-)

What I would do is do a standard lathe setup with a tool changer and multiple passes.

(;-) TP

[kencor1]

Thanks for the replys, the problem with running 2 tool paths is that with a wood lathe the work piece has to run through a steady rest, so after the 1st cut there will be no stock left on the work piece to be supported by the steady rest and the finish pass will produce a lot of chatter and the finished work will need way too much sanding. Hopefully someone else may have am idea on how to make this work.

Tom

[BR549]

That is WHY they used a rigid precutter in the vid it serves 2 purposes prerounds the square  AND helps support the work(;-)

Let us know what you find, (;-) TP