[Bob La Londe]

I think its time. I have done conversions and worked with several Mach 3 based machines. I'm still wrapping up a Hurco conversion to Mach. I decided its time to build a machine with LinuxCNC in mind.

I'm starting simple with a 2 axis mini lathe. I'll just go with gang tooling on this one. If I do another I may add a live toolpost, but this one is going to be simple.

I'm going to start with a standard LPT port, but I'm not against going with something like a 5i25 card if the port turns out not to be upto it.

All of that being said... I'll want to be able to do single point threading on it, so can somebody point me to the basics on setting that up with LinuxCNC. Please, no need to recap. Point me to other conversations and references. I am glad to read up. In the mean time I'll start doing some searches and see what I can find on my own too.

Thanks for any help.

[alan_3301]

LinuxCNC Documentation Wiki: SpindleSynchronizedMotion

as far as I can tell, you just need to have a spindle speed/position sensor.
the functionality should all be there in the gcodes g33 and g76.

As far as the sensor, some reading will be required, but I think you can get away with just 1 pulse per rev, although more are ok too..

Hopefully one day I'll be able to cnc a lathe also. Sounds like fun.

[alan_3301]

It seems that 100 ppr quad + index is a good balance if you are going through the trouble to mount an encoder, and using the parallel port to get those pulses into linuxcnc.

here is a fairly cheap one that I found. (5000 max rpm) TRDA-2E100BD | Incremental Encoder: 1/4 inch solid shaft, 100 PPR, 12-24 VDC

and here is a nice diy alternative.
Lathe Spindle Encoder

There are probably some good deals on ebay also.
I think finding something that fits well to the existing machine would probably be important.


Are you building from scratch or do you already have a minilathe?

[Bob La Londe]

I already have a mini lathe. I decided I had stripped my last plastic part on it over the weekend, and I want to get rid of all the gears on the head. Just go straight CNC with it. I have another slightly bigger lathe I'll keep for manual work.

Will LinuxCNC be able to provide a closed loop configuration for the spindle motor? It sounds kinda like it if it requires both an index and an encoder input.

[samco]

You can do threading with a single index like mach - but linuxcnc allows you to use a quadature encoder + index. As alan stated - if you are going to use the printer port - a 100 count (400 quad) encoder with index works great. If you are going with a mesa 5i25 - then you are less limited as the 5i25 does the encoder counting (also pwm and step generation).

This also allows you to rigid tap, (you need a quadature encoder with index to rigid tap)

sam