Bob, you can run the 4th axis only if the Path Pilot has that additional function capability, from your question seems you have the lathe spindle interlocked with the mill stop circuit only, not the program.

Emgee

Bob: I can't quite get my head around why you'd want to synchronise the mill and lathe spindles? I can see why spindle to axes sync is useful but not spindle to spindle. GIven that both are driven by asynchronous electrical machines it is impossible to synchronise without some form of independent speed measurement and control of at least one of the VFDs.

Andrew

I think you will need to ignore the mill spindle and get sync pulses from the lathe spindle into Path Pilot. I believe that the latter is based on LinuxCNC? Usually with CNC threading the CNC motion control software (/hardware) synchronises the cut to the spindle rather than vice-versa.

As noted previously, it's a distinctly non trivial challenge to get Path Pilot running on a non-Tormach machine. You probably know that, JAS, but for anyone else (like me) who believed it might be fairly simple, there are some notes on the LinuxCNC forum telling you how to do it. It's a work in progress and hopefully will become more straightforward in time.

Bob: I've mostly forgotten what I read on the operation of the Duality lathe, and it's theory only as I eventually decided against ordering it.

Given that PathPilot doesn't support the Duality lathe I'm not sure how you could slave the Duality motor off the mill spindle, since the mill spindle won't be doing what you want? In principle CSS should be fairly simple in that you only need a base speed and the radius of the tool from the axis of rotation. I don't know how you'd get that information out of PathPilot. Screwcutting might be a bit trickier as you need position of the Duality spindle as well as speed. If I recall the original Duality had a once per rev pulse that was used to locate the spindle position and also to make a crude estimate of speed to match the feed for screwcutting?

I guess that the key is to find out what, if any, information can be extracted from PathPilot.

Andrew

Hi Bob,
An alternative to syncronising the lathe spindle to the X axis of the mill would be to do it the other way round by syncronising the X axis of the mill to the lathe spindle. This is what the "Electronic leadscrew" does. There is a forum related to this here. I notice that there is an article about it in MEW 239.

Les.

Edited By Les Jones 1 on 23/03/2016 08:32:32

As I understand the set up the duality lathe can have a harmonic drive to act as a fourth axis. A thread is a helical groove and what you want to do is helical milling. Do you have the 4th axis option? It will allow you to do what you want quite easily, maybe not as fast as you want.

Martin

Bob: Correct, here's a setup for milling a worm:

I am using rotating cutters, but no reason why a fixed form tool shouldn't be used. The G-code for the worm was hand written. The basic code is very simple, just G01 with arguments for X and A. Feedrates with Mach3 were a disaster area. They didn't work properly, and I ended up using G93 inverse time feedrate. I would hope that PathPilot is a bit more sanitary in this area. The standard says that when G01 has linear and rotary values any feedrate should be interpreted as mm/min. The finished worms:

Andrew