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1

PoKeys / PoKeys57CNC, feedrate in Mach4 incorrect

« on: March 29, 2017, 05:39:27 PM »

Here is something for the lathe thread cutters and mills:

Now everything (except of probing with G31 on my mill, but that is a different topic) runs with PoKeys57CNC. Motion is very smooth, limit switches working, PWM, ... but the feed rate on both of my machines runs never as commanded. When I command in the G-Code (metric, G21) G1 X10 F10, it will run the x-axis with 6.40 mm/s instead of 10 mm/s. I also tried it with inch settings, but with the same result. Weird!

The FRO is set to 100% (sure, I can get the feedrate to the desired 10 mm/s if setting the FRO to 156%, but that is not the point).

This behavior is totally reproducable and independant from settings like exact stop, css or whatsoever. I clocked the motion with a stopwatch and indeed, it takes this strange factor of 1/0.64 = 1.56 longer as desired to drive (any axis) a certain distance.

This is very annoying, especially when I want to cut threads on my lathe (because during threading, the FRO is locked to 100%).

And, yes, I could work around with generating G-Code which commands the CNC always this 1/0.64 factor faster than desired, but that is obviously not the way to do it.

Has somebody seen the same or an solution for that?

Regards,
    Carsten

2

PoKeys / PoKeys57CNC, spindle speed measurement jumps like hell

« on: March 18, 2017, 08:12:16 PM »

Hi folks,

I'm new to the forum, but got a decent (and probably not easy to solve) issue: I've got a PoKeys57CNC and just converted my lathe from an parallel port interface. For spindle speed measurement, I use a CNY 37 with an index disc, directly mounted on the spindle. This setup worked quite well with the parallel port interface so far (including threading on my lathe under mach3).

Now, after re-wiring everything, I've got signal levels from on the output of the CNY 37 between 0.04 V (low) and 2.3 V (high). It is wired to the index input to the PoKeys57, Pin 13 (Encoder I). Those signals look quite nice on the oscilloscope, right frequency. When looking at the PoKeys diagnostic screen, Pin 13 is turned on and off when turning the spindle by hand - fine so far. I've configured the spindle speed measurement in the Plugin configuration as "Index (lathe)" with 1 tick per rev. Threading support is turned on. Spindle feedback ratio is set to 1

Now to the strange thing: When (and only when) the spindle is turned, at exactly each pass of the index hole, the measured and in the DRO "True RPM" displayed value for the true spindle speed jumps like hell between totally arbitrary and quite large values. That is true for all rpms from nearly DC (turning by hand) to its max speed of 2000 rpm.

Those speed measurement values are so large that when turning with constant surface speed, the axes of the lathe always run at full speed - which for sure is no option for working with it.

Anyone got a good idea how to solve this jumpy behavior of the index? I've got already a low-pass-filter infront, but that does not help.

Attached are some pics, also a youtube video: https://youtu.be/7k_iY3MVh2Y

With best regards,
    Carsten