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Topics - nicad

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I'm not sure where to start with but I need to start somewhere! :)
The need: I'm chucking a tube in a lathe with C-axis control. The tube is round on the OD and the ID, but the ID can be off-center by up to 0.01".
I'm needing to grind a short section of the OD to be concentric with the ID. I need this process to be automated as each tube is slightly different and I'll be doing hundreds.

I'm envisioning some procedure where a probe is run into the tube, then over to check the ID at angle 0, then rotate the C-axis to angle 90, probe again, then angle 180, etc.. to get 4 readings to know the center of the ID.
Then the fun part-- still automated within G-code or macro or brains-- slowly rotate the C-axis while grinding the OD true to the ID by moving the X-axis back and forth in a sine wave to "follow" the ID bore based on the probing data. The offset in the Y-axis as it rotates is not critical as it's not off far enough to make enough difference.

A good example I've found is this: https://www.youtube.com/watch?v=FpP7iTKuWpw
I'll be grinding so the spindle C-axis rpm can be as slow as it needs as the X-axis keeps up.

Any ideas how to accomplish this??

I am needing to make a macro to:
A) Read a 3-position switch
B) Set a value to a variable in my G-code based on which position the switch is in.
What I have so far:
I am using a G100 for I/O. I have my switch wired to 3 of the digital inputs. This works so far.
I assume I need to assign each of the 3 inputs to an "OEM Trigger" under Ports/Pins.??

What do I then need to do in my macro to read the condition of each of these 3 inputs?
And the, how do I set a variable to a value accordingly so that my G-code can then use the set value? (it will be for a G1 Y xx call, where "xx" is the value)


I have an application that is very much like a lathe, where I have a servo motor with a 500 count encoder driving the spindle, powered by a G320.
I would like to know if I can switch Mach modes from "velocity" mode to "position" mode from my Gcode, so that I can also use the spindle as a "C" axis for indexing the stock in the spindle for live tool machining, from within my program.

For normal spindle mode, I know Mach can run a "spindle" with steps or PWM. I would use steps, since it is going to a G320 servo amp.
Then for angular control, I know Mach can output step and direction, and is a normal rotary "C" axis.

I need to know if I can switch between these two modes dynamically from my Gcode program? I understand that absolute position would be lost while in spindle mode, but that would be OK..


Mach3 and G-Rex / Mach3 Dev. Version 1.90.065 w/grex bugs.
« on: July 20, 2006, 12:03:48 AM »
I don't know if this is the right place for bug reports??

just installed Mach3 Version 1.90.065 w/Grex on a 4-axis system.

If I zero the A axis, all is well.
If I zero the Z axis, A axis will set to a huge number (machine ABS).
If A axis is zero'd and I zero the X or Y axis, Z axis will set to a large number (machine ABS) AND A axis will set to a huge number (machine ABS).
If A axis is left at the huge number and I zero the X or Y axis, all is well.
Happens on all screens.

Also, some of the images for the buttons on the "program run" screen are corrupt. The ESTOP on all screens, if flashing, is also corrupt.

Is it just me?
That is all so far. :)

General Mach Discussion / Mach + Grex + Pendant w/MPG
« on: July 19, 2006, 05:54:21 PM »
I love the Grex/G100, but one thing I have found hard to adjust to is the delay in axis movement when jogging from the keyboard in Mach.
I am wanting to build a pendant with MPG control (encoder wheel), axis select (X, Y, Z, A), and distance set (1, 0.1, 0.01, 0.001).

I am not sure if the current Mach3/4 (Grex firmware?) will support this, since the pendant will be using inputs on the Grex.
I would assume the pendant controls should directly drive the Grex, otherwise if the inputs from the Grex are fed to Mach, which then will try to step the Grex.. I would be back where I started with the delays in jogging axis movement, correct?

Anyone have any information on doing this?

I have been trying to run Mach2 and 3 on a Dell Inspiron laptop 1ghz P3(mobile) and an Intel P4 1.7ghz desktop system.
Both are running winXP Pro, and stripped down according to the optimization documents.

In Mach3 the Pulse Frequency will be mostly stable but sometimes, at random, it will drop lower by about 30 hertz. Everytime this happens, and if an axis is in motion, that axis BUMPS very hard in its motion... sometimes twice in a row, but only and always while the Pulse Frequency drops. It only lasts for a second or two.. Sometimes if the axis is moving somewhat quickly, the BUMP will fault out the Gecko 320's and the machine stops!!! Very annoying.

It could happen a few times in a minute, or only once per 20 minutes.. very random.
This happens on both computers and in both mach2 and 3. I am running the kernel at the lowest 25000hz. At higher kernel speeds the frequency drops and bumping are even worse.. almost always catastrophic to the axis in motion..

Also the "Dbl Plse" in Mach3 is flying with changing numbers ALL the time. numbers so big they are longer than the text box for them.

Any Ideas? I know the "Dbl Plse" is for debugging for Art, but should it be spinning with huge numbers?
I have tried with and without the "Enhanced pulsing" option-- no change.

Mach3 and G-Rex / Mach4 - couple of quick questions for Art.
« on: February 15, 2006, 04:47:21 PM »
As I understand it, Mach4 outputs "curves" at a rate (1/64 sec?) that results in prominent vectoring of the curve at anything above a slow feedrate. If I am post-processing all my curves into very short line-segments (~0.002"), will Mach4 + Grex be able to output this smoothly at a quicker rate?

Also, The Grex has a USB and an Ethernet port. The USB is for flashing of the firmware only and the ethernet is for motion control commands (correct?). Will this always be true? It would seem that a direct USB link would be more "fail proof" than an ethernet network.. but I am just thinking out loud here.. :)


I have asked about this in the past via email... You had made a "change" to one of the mach2 6.11x versions, but it didn't help any.

The problem that I see is that Mach is calculating accel rates based on a unit/sec^2, which is fine if all of the axis were the same units.
Yep, you guessed it. I am talking about simultaneous  rotary + linear motions accelerations.
If Mach calculated accel rates based on STEPS/sec^2, it would remove units from the equation.

my setup:
X/Y/Z axis resolution: 16,000 steps/unit (unit = INCH)
X/Y/Z axis accel: 17 units/sec^2

A axis resolution: 400 steps/unit (unit = DEGREE)
A axis accel: 500 units/sec^2

When a move involves both the A and one of the linear axis, I know mach defaults to the slowest accel on all the axis involved. This results in ~ 30 TIMES slower accel on all axis (500 is used in place of 17 to be "safe"). I agree with the "safe" algorithm, I do not agree with the numbers it is looking at.

IF Mach used steps/sec^2, I would have:

X/Y/Z axis resolution: 16,000 steps/unit (unit = INCH)
X/Y/Z axis accel: 272000 STEPS/sec^2

A axis resolution: 400 steps/unit (unit = DEGREE)
A axis accel: 200000 STEPS/sec^2

This is the exact same config, but using steps instead of units (same accel and resolutions). The accel calcs would operate properly all the time. (272,000 is VERY close to 200,000) Which would perform as it should.

This is killing me. It it taking at least 10x longer time to cut the same part because of it.

Please help! :) :)

(yes I have set my "rotation diameter".. it does not fix it) :-/

G-Code, CAD, and CAM discussions / G92 does not always take.. why??
« on: February 05, 2006, 05:56:47 PM »
I have observed this problem in Mach 2 6.11 and now just happened to me today with Mach3.

G92 command randomly gets ignored. G92 should change the designated axis to the value given (no movement).

G0 Z1
G92 Z0

Most of the time Z will be 0 after this, but sometimes, randomly, Z will still be 1.


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