Topics

1

General Mach Discussion / Spindle speed control - serial port

« on: October 02, 2011, 11:36:44 AM »

Hi I have just bought a Texas Microcircuits serial port speed control board (apparently developed by SoundLogic) I have loaded the plugin and using the XML suggested.....nothing narda zip ... an M3 command does nothing at all... Any ideas folks??

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General Mach Discussion / Lathe threading - I Love Brian!!

« on: September 04, 2011, 03:42:21 PM »

This is just a thankyou to all who created this program - After a year of failing to be bothered I set up my late spindle index properly (who would have thought a TTL signal needed a ground.....) The result perfect threads - I am soo happy. I forgot to cook dinner - the family have gone for a take away and .....I don't care!!!!!

So Brian (whoever you may be) Thanks!

3

General Mach Discussion / Index/rmp/threading issues

« on: November 10, 2010, 06:00:10 AM »

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

4

General Mach Discussion / Still being driven mad by arcs

« on: October 09, 2010, 09:54:30 AM »

My problem is that my lathe loses position when I use any code with either a G2 or G3 command. I think that there is something in the pulse train in curves that confuses the servo drive. I have tried the following tests. I have written a test program that runs an S shape (G2 then G3) 50 times in rapid. At the end there is an error on each axis +0.8mm Z and -1mm X. I can run a test on either axis running 200 rapid moves backwards and forwards  - no error. I can run 200 moves backwards and forwards with both axis moving together in a straight line - again no error.

The errors are repeatable. I do not think that it is noise, a weak port signal, or my rather old pc (although I could be wrong).

The servo drive needs the Dir pulse to lead the Step pulse. My problem is that I do not know what that means! I have step set in Mach3 at 3 and Dir as 10. I have tried loads of values but seen no change.

Is the Dir signal pulsed in the same way as the step or does it only change between 0 and 1 on a direction change?

As far as I can measure (which is good enough for me) I have no problems with any moves other than curves. I have been working at this for 2 months now and may just burn down the shed!

I have servos 2000 line encoders, 16x multiplier, 200/250 steps per mm and a dual axis servo drive.

5

General Mach Discussion / Help Please! arcs in Mach turn

« on: July 19, 2010, 05:14:41 PM »

Hi
I have retrofitted my lathe and all is fine. Simple x and z cuts seem very accurate. But...I have hand written code to produce a pawn shape (No that was spelt correctly!) I am using a series of subroutines with G2 and G3 cuts using the I K system. My all dimensions are in mm to 4 decimal places. After 30 loops the position has drifted significantly by around 0.5mm per axis. What am I doing wrong??

I am on Servo motors with 2000 resolution encoders.

I have adjusted Gibs, backlash in the belts, the ballscrews seem fine.

I have slowed down velocity and acceleration to a fraction of what the servos can cope with.

I have broken each arc down into a separate subroutine in order that the errors do not add up - minor improvement

I have broken arcs that intersect axis lines (causing the motors to reverse) into separate sections.

I could get around the error multiplication by resetting zeros before a final cut but that seems very crude.

Are arc moves generally inaccurate or is it me?