With much help I have got most of my lathe working properly (thanks all). I had a dodgy multiplier in my servo drive causing inaccuracy. I now have a machine that is slow but accurate - that will do! But......

I cannot cut threads. I have a single slot disc and a C3 index board. I have lowered debounce and have a broadly accurate RPM reading but it flickers up and down around the correct reading.

When I try and cut a threat the lathe waits for an index pulse (I think) jerks but stops then jerks then stops until I panic and press stop. I have tried very slow speeds - no change. The DROs remain accurate. It looks like my index signal is unreliable. The slot in the disc is ab0ut 8mm on a 125mm diameter (enough according to the manual). I have switched active high and active low.

In diagnostics the led lights up when I turn the spindle by hand but when I run the spindle on the motor there is just an occasional flash.

The sensor is 2m from the board but the cable is shielded and not too close to any nasty cables.

Any thoughts?

John

First question is do you have a licence and if you do make sure it is there by looking at the Help menu then About Mach........
Reason is threading does not work in Demo versions.

Next thing is to go to General Config page and choose spindle speed average, that should sort out your slight variations in speed.

Can you post the code you are using for the tests and also your xml would be good.

Hood

Hi Hood - many thanks as usual - it was your help that got me up and running!

I am such a good boy that having bought an industrial pc with Mach3 loaded and discovering that it was a hacked copy - i bought a proper licence! I am fairly sure Mach3 knows that because at your suggestion I have upped the kernal speed - my wonky little pc has a fit over 35k!

I have checked spindle speed average but it made no difference - at 750rpm it will occasionally drop say 70rpm and then revert - it does this every 5 seconds or so.

I used the simple threading wizard to generate the code - it is tricky for me to post it or the xml as the industrial pc has no usb/floppy/cd attached (I must do something about this as I get into trouble when I trail it through the house) 

750rpm it will occasionally drop say 70rpm and then revert - it does this every 5 seconds or so.

That is not good....
You need a stable rpm. Fix that first or you will never get a quality thread.

RICH

Agree with Rich regards the  steady RPM but with regards the hacked version of Mach, delete that totally, also delete the pulsing engine from device manager and then install Mach afresh, best would actually be to format and reinstall the operating system though.
Hood

Thanks guys

Hood - I have done what you suggested - I formatted and reloaded - I only preserved my XML file.


Does my slot size seem about right? Any idea how I could improve the signal?

John

The slot should be enough, I used to use 10mm on 100mm dia but 8mm should be fine, suppose it depends on the opto though.

Just double check that you definitely see that it is registered in your name by looking at the About Mach.... if it says your name then yo are fine, if it says demo then the licence is not being seen.
Hood

Thanks Hood - I will do that tonight - I will see what I can do with the signal as well.

The other thing to consider is the speed of the input pin on the bob, some are designed for limits (SLOW) and some are designed for high speed.

I also use a C3 index card and get a good speed reading all the way up to 3K