Mach3 lathe spindle pulleys problem

**John11668** · 15-01-2021

Background .
I converted a Boxford TCL lathe to Mach 3 but retained the DC Spindle motor, and Lenze controller with Iso Board.

Had a bit of trouble getting the spindle index function sorted but thanks to some help from folks on here (you know who you are) I now have a very accurate "true spindle " readout which corresponds well with a mechanical tachometer .
And with spindle speed set to 2000 the analog signal generated by the pwm output is 9.6 v and reduces more or less in proportion to selected spindle speed so that looks fine .

Now I know that this is actually the motor speed , and the true spindle speed will vary according to the pulleys in use at any time , and that I need to select a number for the pulley setting along with the ratio of the selected pulley combination.
But if I change the ratio in spindle pulleys (and I have tried varying ratios from 1 to 8) but this has no effect at all upon true spindle speed .
In addition whatever spindle pulley number I select the display continues to show S1

I have looked for other related settings but dont see any which are relevant. I have read the manual and although there is a section on pulleys and the need to specify the ratios I dont see any guidance on other settings
What might I be missing.
Suggestions anyone ?

**m_c** · 15-01-2021

IIRC the spindle pulley settings didn't work correctly in turn, especially if you were not using the parallel port. Certainly the closed loop spindle control just didn't work.

The Mach forum is probably your best bet at finding a definitive answer though.

**John11668** · 15-01-2021

Using UC100 for connection to BoB
Have left the same query on Mach support forum so will see what comes back.

**hanermo2** · 16-01-2021

Also mostly as others said later.
The spindle feed / speed like threading depends on the plugin and hw you have.

So my csmcio-ip-s results will not be the same as yours, or the centipede I had in the past, or the smoothstepper early version.

And inputs from analog sources may be accurate, as regards relative spindle speed, but equally may not be accurate.
I tested this really well with Sergey who developed the centipede.
We proved very clearly that most index signals, single pulse, are not too good and reliable and crisp.
He developed a specific board for that, to make a single crisp reliable pulses.
This was several years ago.

My lathe now uses industrial servos at 1:3 belt drive, HTD 8 MM x 30 mm, 1:3.
The controller csmcio-ip-s can read them, from servos with 10.000 counts/turn.
The readout fluctuates +/- 1 rpm, which is an error in csmcio plugin.
It´s still extremely accurate.

The spindle speed is still extremely accurate.
About 0.01 rpm accurate in fact.

This wont be of much use to You, as mach results depend on the controller and or hw you have.

Originally Posted by John11668

Background .
I converted a Boxford TCL lathe to Mach 3 but retained the DC Spindle motor, and Lenze controller with Iso Board.

Had a bit of trouble getting the spindle index function sorted but thanks to some help from folks on here (you know who you are) I now have a very accurate "true spindle " readout which corresponds well with a mechanical tachometer .
And with spindle speed set to 2000 the analog signal generated by the pwm output is 9.6 v and reduces more or less in proportion to selected spindle speed so that looks fine .

Now I know that this is actually the motor speed , and the true spindle speed will vary according to the pulleys in use at any time , and that I need to select a number for the pulley setting along with the ratio of the selected pulley combination.
But if I change the ratio in spindle pulleys (and I have tried varying ratios from 1 to 8) but this has no effect at all upon true spindle speed .
In addition whatever spindle pulley number I select the display continues to show S1

I have looked for other related settings but dont see any which are relevant. I have read the manual and although there is a section on pulleys and the need to specify the ratios I dont see any guidance on other settings
What might I be missing.
Suggestions anyone ?

**John11668** · 16-01-2021

This lathe is a Boxford TCL acquired for £350 and I have used the existing structure , steppers and motor drive / control..
Effectively just added a pair of cheap drivers and a BoB and a bit of my own time (Which I dont count ) so total outlay on the machine is still around £400.
Cant really justify outlay on exotic motors so just something to play with until I get the confidence to invest in something better.

With regard to spindle indexing, the original Boxford spindle sensors did not stand up to the process, and with some unsuccessful experimentation and with some well considered advice from a friend, a different type was chosen which has turned out to be well up to the job. Correlates well with the measurement using a mechanical tacho so i am happy to use this and accept the reading which it gives me on the screen . Fluctuations seem to be only a digit or two in a thousand so good enough for my purposes.

I was always told that I would not be able to thread successfully with Mach but it looks like I will just need to discount pulley ratios too.
Will just play a while with what i have then look at changing to linux. I chose to keep Mach 3 cos i was familiar with it , but looks like it falls short on a 64bit operating system.

Thanks for inputs anyway.

**m_c** · 16-01-2021

Originally Posted by John11668

I was always told that I would not be able to thread successfully with Mach but it looks like I will just need to discount pulley ratios too.
Will just play a while with what i have then look at changing to linux. I chose to keep Mach 3 cos i was familiar with it , but looks like it falls short on a 64bit operating system.

Thanks for inputs anyway.

Mach 3 can produce perfectly acceptable threads.
Only thing that won't work on 64bit, is the parallel port driver. Mach itself still works perfectly fine, you just need to use an external motion controller.

**John11668** · 16-01-2021

I use an external motion controller (UC 100) so am still exploring the options here .
Trying the wizard but it it comes up with an error message saying that no lead is specified in the G76 commend so am looking into that now .

My PC is 64 bit with windows 10 and connected via the UC100 controller to USB port .
Are you saying I should still be able to change spindle pulley ratios and cut reasonabe threads with this rig . If so what settings do I need .