Synchronising A lathe Spindle with a CNC milli spindle.

I am going to fit a 1 HP motor and inverter to my Duality lathe that fits on the table of the Tormach Mill.

Currently, with Path Pilot the motor does not synchronise with the mill, there is a speed sensor fitted to the lathe spindle but it is only there to tell the mill that the lathe spindle has stalled and the Emergency stop activated.

I am wondering if I can cheat the system by running the mill spindle while running a programme and have the lathe spindle synchronised with the mill.

Any Ideas?

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

Yes it can be done but you will need someone very conversant with path pilot to hack into the rigid tapping cycle.

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

Andrew,

I should perhaps have worded things differently. As it stands at the moment path pilot does not support the Duality lathe to give either constant surface speed or for that matter feed/rev. It s just a case of dialling in the lathe spindle speed and letting the mill provide the feed for the cutting tools that are mounted to a tool post on the Mill Spindle.

I think when Mach 3 was the operating programme the Duality lathe could be programmed for feed/rev but am not altogether certain of this.

The reason I suggested synchronising the mill spindle to the Lathe spindle was so that I could fit the speed sensor to the mill spindle and get a repeat of the mill spindle speed on the lathe via some black magic with the controllers.

Ideally what I am after is the ability to control the lathe spindle speed to enable screw cutting and Constant surface speed capability.

As I see it at the moment when using the duality lathe in path pilot the spindle of the mill is inactive so is there some way that the lathe spindle could be activated in it's place?

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.

Bob -

I have a couple of the Mesa 5i25 cards; the latest build (for my mill) uses a spindle sensor tied to the encoder inputs. (you have a Mesa card, if you have PathPilot)

Does the duality lathe have a spindle rotational sensor? Is it actually tied into something in the machine?

If I remember correctly, there is only ONE encoder input (quadrature, high speed capable - read by a FPGA) in the Mesa cards.

MachineKit/LinuxCNC is very adaptable, so the answer is "yes", but as the other JohnS mentions, you'll need someone who knows how to modify LinuxCNC/MachineKit lower layers.

I do not run PathPilot myself, but am tempted to get it running on my Mills and lathe.

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 Andrew,

I will maybe look deeper into things once I get the bigger motor fitted. At least with a bit more power the lathe itself will be more useable for some of the jobs I will be doing. If I had more room in my workshop I would probably buy and convert a lathe to CNC operation. Until I get rid of some more of my motorcycles that is out of the question.

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

BobHi Les,

I will delve into the ELS when I have a quiet few hours. Thanks for all the responses to may question so far.

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

Hi Martin,

yes I do have the 4th axis. Presumably you run the fourth axis to rotate continuously whilst traversing the table in the X direction and holding a form type cutter mounted in the tool holder on the spindle ?

Bob

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

That sounds good to me. I have put off fitting the 4th axis to the lathe because you have to remove the tool tray and half of the splash guard assembly but considering you can't use flood coolant on the lathe it's no great hardship. I also have the 4th axis rotary table too.

I think that with the lathe guard off I will still have room to fit a drive pulley to suit a 1 HP motor with variable speed drive.

I am working on some vernier ignition timing sprockets that require some internal threads for the extractor, once I get time and I have the bigger motor fitted I will give it a try.

I also have 4 front hubs to make for my vintage Humber restorations that will probably need some screw cutting too and they will certainly need the extra power of the motor.

Bob.