Benchtop Lathe Conversion Project, A few Glitches

[BTremain]

Hi Folks

I have been a member here for some years but only just recently started getting into some CNC build projects of my own.
I have a lathe conversion project and a cnc router/ mill project underway.

The topic of my post here is the Lathe conversion.

The lathe in question is a Chinese HD250 Lathe (250x550), I believe I is the same as/ similar to the American Lathemaster HD250.
I have had the lathe for a while but early on I broke some of the mechanism on the change gears for the leadscrew.
One can possibly live without the ability to thread on the lathe but not to be able to autofeed was not an option for me.
For a year or so I have been using a 290OzIn Nema 23 stepper driving 20 to 40t tooth geared belt reduction onto the leadscrew and driven by a pulse/direction generator and this has been very successful.

Just this weekend I have been starting with a full CNC conversion that I have been planning and gather parts for some time.
The CNC is driven by LinuxCNC via a Chinese DB25-1205 Parallel Port Interface.
I have been successful in reading spindle speed with a Melexis 90217 Hall effect sensor counting teeth and in automating the Z axis on the original leadscrew but I seem to be having some glitches where I can hear the motor 'pulse' or 'shudder' and I am loosing steps.
The driver is a Chinese FMD2740A running at 48V. I have even removed the motor from the lathe to take mechanical load out of the equation.
All of the wiring is prototype and not shielded at the moment. Is it possible/ likely that I am losing pulses due to un shielded cables between the interface and driver or driver and motor?

Any advice would be much appreciated.

Regards

Bruce

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[asuratman]

Do you have some pics?

[DICKEYBIRD]

I had a similar problem on my ORAC lathe conversion and it turned out to be a short between 2 of the stepper motor wires at a splice joint between the controller & motor. Took ages to find but as usual, it's the simple stuff that bites you!

[BTremain]

Hi Guys, I'm pretty sure I'm on the right track now. My feed rates and motor/ gear ratios while correct could not attain the default rapid rate in LinuxCNC.
I have played around with settings and been able to observe going from a smooth feed to a glitch feed to a point where the motor just sits there buzzing.
I was also able to improve the sharpness of the step waveform by putting a resistor across the step terminals at the driver.
Nothing really to take pics of at this point but happy to post a build log and progress as I go along if people are interested.
Have tried both my Nema23 and Nema34 motors on the bench and both exhibit similar behaviours.

Thanks for your help

Bruce

[DICKEYBIRD]

Yes, please do post a build log. There's way too many mill threads in the forum & far too few few lathe threads to suit me.