Messages

1521

General Mach Discussion / Re: Mach3, G31 probe on Z axis, and variable 2002

« on: April 27, 2020, 03:44:30 PM »

Hi,

Why does everyone focus on this one thing? 

Whatever.

Mach4 has a logging feature which offers a very granular diagnostic potential, for example the attached pic.
You wanted to know if Mach4 had better documentation, it does but more importantly it does have superb diagnostic
logging.

Craig

1522

General Mach Discussion / Re: Mach3, G31 probe on Z axis, and variable 2002

« on: April 25, 2020, 06:33:27 PM »

Hi,

Does Mach4 have either better documentation or stick better to ansi standards?

Mach4 documentation is much better than Mach3, having said that it tends to lag the latest developments. Probing
(there are four probe channels in Mach4) is of course very mature and so the documentation is pretty good. In particular
there is an excellent description of the sequence of signals between Mach4 and the motion controller with a g31 code.
And by the way if you read it you will discover that a g31 does not retract....contrary to your belief, the retract requires
a second gcode move.

Probing
Motion plugin probing procedure.
The probe moves are really just G01 moves in exeact stop mode with the addition of being marked as EX_PROBE in the execution_t struct from mcMotionCyclePlannerEx().

When executing a G31, the core considers the move as an exact stop move and therefore will request a motor stop report. It waits on one of two conditions:

A probe strike condition where the motion plugin calls mcMotionSetProbeComplete().
An end of move condition where the motion plugin reports the motors as being still.
Until either of these conditions are satisfied, the core will generate no more moves after the EX_PROBE marked moves. In other words, all you will get out of mcMotionCyclePlannerEx() will be EX_NONE type data. In the event of a probe strike, this makes it safe to clear the planner and be sure that future moves are not removed by accident.

A motion plugin should implement probing in the following way:

Upon seeing the first move marked as EX_PROBE, the plugin should arm position latches on the hardware.
Then consume the EX_PROBE marked moves as normal.
If the probe stikes, the plugin should:
Cancel any MSG_REPORT_MOTOR_STOP requests. (see g. VERY important!)
Report the latched positions via mcMotionSetProbePos() for each motor.
Clear the hardware of any additional moves.
Call mcMotionClearPlanner() to clear the Mach planner of any unretrieved EX_PROBE moves.
Update Mach with the hardware's current position via mcMotionSetPos().
Call mcMotionSetProbeComplete().
If a MSG_REPORT_MOTOR_STOP has been received, do not acknowledge it. mcMotionSetProbeComplete() does this for you and a position sync as well.
If no probe strike, then the move continues to it's end point as if it is a regular move.
The plugin should ack the MSG_REPORT_MOTOR_STOP messages with mcMotionSetStill().
The positions latches should be disarmed (if needed) when a MSG_PROBE_DONE is seen.
In the event that the probe move is aborted, the plugin should:
Call mcMotionClearPlanner() to clear the Mach planner of any unretrieved EX_PROBE moves.
Call mcMotorSetPos() for each controlled motor.
Call mcMotionSync.
Call mcMotionSetStill() for each controlled motor.
Probe Operation Overview.
Upon executing G31, the core will mark those moves as EX_PROBE in the data stream.
If the probe strikes before the end of the G31 move, the plugin aborts the rest of the probe moves as described above. If a probe data file has been opened via mcCntlProbeFileOpen(), then the positions recorded by the motion plugin are inserted into the probe data file in the specified format.
If the probe doesn't strike and the G31 move reaches its end point and a probe data file has been opened via mcCntlProbeFileOpen(), then the end point positions are inserted into the probe data file in the specified format.
Using the probe data file routines.
int mcCntlProbeFileOpen(MINSTANCE inst, const char *filename, const char *format);
The format argument is a printf style format with expanding macros for the axis values. AXIS_X, AXIS_Y, AXIS_Z, AXIS_A, AXIS_B, AXIS_C. It is used in the following manner:


mcCntlProbeFileOpen(inst, "myProbeFile.csv", "%.4AXIS_X, %.4AXIS_Y, %.4AXIS_Z");
This will produce a probe file in CSV format like so:



1.0000, 2.0000, -1.4356
1.0100, 2.0000, -1.4343
1.0200, 2.0000, -1.4324
...

A format of "X%.4AXIS_X, Y%.4AXIS_Y, Z%.4AXIS_Z" would yield:



X1.0000, Y2.0000, Z-1.4356
X1.0100, Y2.0000, Z-1.4343
X1.0200, Y2.0000, Z-1.4324
...

A format of "X%.4AXIS_X\tY%.4AXIS_Y\tZ%.4AXIS_Z" would yield a tab delimited file:



X1.0000 Y2.0000 Z-1.4356
X1.0100 Y2.0000 Z-1.4343
X1.0200 Y2.0000 Z-1.4324
...

int mcCntlProbeFileClose(MINSTANCE inst); Closes the probe data file.

Mach4 is generally ANSI compliant, but more importantly is made to be Fanuc 21B compliant, which is the template for ANSI.

I've been using Mach4 for five years and regularly probe parts and surfaces and have had no problems whatever.

Craig

1523

General Mach Discussion / Re: Mach3, G31 probe on Z axis, and variable 2002

« on: April 24, 2020, 11:40:28 PM »

Hi,

When I run g31 with the current position minus one inch, it works fine, it stops (but does not retract any which the specification says it should),

Thats not my understanding.

The machine will move toward the specified end point, at the same time it is looking for the probe input to be activated. When the probe input is activated the current position is recorded to # variables according to the table below and motion is stopped. The recorded position can then be used to calculate tool offsets, work offsets, measure parts, etc.

It does not say anything about retracting. When you have a probing routine it takes two Gcode instructions, a G31 which
does the probe move per the description above followed by a G0 which retracts the Z axis.

Craig

1524

General Mach Discussion / Re: Add 2nd DRO for Y axis

« on: April 23, 2020, 06:15:14 PM »

Hi,
if you had an encoder on the stepper then yes the second DRO would record the actual position so you
could see the difference between commaned and actual positions.

The expense and complication of doing that would be better invested in fixing the fault that causes lost steps.

I use Vexta steppers and Vexta drivers, they are great, not hugely powerful but because they have low inductance and the voltage
of the driver is a whopping 150VDC they really sing. I have not lost a step in five years.

Craig

1525

General Mach Discussion / Re: Add 2nd DRO for Y axis

« on: April 23, 2020, 03:46:29 PM »

Hi,
even if you add another DRO it would display the commanded position only. If a stepper loses steps Mach dosen't
know. So the commanded position could be '2000' say butthe stepper has lost five and is actually at position '1995' but
the DRO is still going to say 2000. What does a second DRO gain you?

Craig

1526

Mach4 General Discussion / Re: Mach4 use with XHC card

« on: April 22, 2020, 03:40:18 AM »

Hi,

There is a poor communication with Chinese factory, but they do respond.

By all means try them. We really need to know how they have set up the servo, how many pulses per rev.
Ballscrew ptch and gearing would mean that you don't have to stri the machine.

Good luck
Craig

1527

Mach4 General Discussion / Re: Mach 4 on a Millright Mega V: What do I need?

« on: April 22, 2020, 12:28:05 AM »

Hi,

Just curious - customize in what way?

Lets take a fairly simple example. Lets say you have a large VMC and the operator Estops it.
Because of the weight of the Z axis it slumps down under gravity, which would be VERY dangerous to the operator.
A machine builder might customize the control program such that before the power is disconnected from the Z axis
motor the brake is engaged.

Another example might be that you have an independent axis that rotates a part in discrete amounts. A machining
operation is performed and then the part is rotated another 30 degrees say before the maching operation
starts again. You could of course do that with a fourth axis but it is possible to do it with an Out-of-Band axis, of
which Mach4Hobby is allowed six. So you could have multiple OB axes manipulating parts say, or jigs or clamps...
The last feature for instance is likely to be important to a machine builder whom needs a flexible control for his new
machine....prehaps less so to you.

1) Reliable controller
2) Ability to restart a job partway through if I have to stop it for some reason
3) ability to do tool changes (manual at first, auto later maybe)
4) Has to handle homing/limit switches
5) has to support a touch probe
6) ability to control spindle speed through VFD
7) ability to turn coolant on/off
e-stop that shuts off the spindle along with the rest of it.

All of this is pretty much bog standard for any CNC solution and yes Mach4 can do it all.

Craig

1528

Mach4 General Discussion / Re: Mach4 use with XHC card

« on: April 22, 2020, 12:01:32 AM »

Hi,
given that it is a servo machine calculating the 'steps/unit' from first principles may not be that easy.

You are correct we would need to know the pitch of the ballscrews, any gearing between the servo and ballscrew
but would also need to know the pulses per rev of the servo. This last item may not be available to you. Many
servos have 'electronic gearing' programmed into them and most likely you don't have that information nor
will the machine builder provide it.

All is not lost however. You can do it manually.

Lets say you MDI a a command g0 x100, you would expect the x axis to move 100mm right? If however you measure it and find
it moves only 91mm then you have a problem.

If you do the calculation 100/91=1.0989, then you open the x axis motor tuning page to see what the current 'steps/unit'
are, then you need to increase it by a factor of 1.0989.

For example lets say the current 'steps/unit' are 2450, then 2450 x 1.0989=2692.23. Substitute the new number, restart
Mach to have the new setting be propagated through the machine and try again.

When you MDIed a 100mm move, measure how far it ACTUALLY moves. The more accurately you can do this the better.

Using this 'suck it and see' appraoch means that you don't have to know anything like screw pitches etc.

Craig

1529

Mach4 General Discussion / Re: Mach 4 on a Millright Mega V: What do I need?

« on: April 21, 2020, 04:56:07 PM »

Hi,
Mach4 is a highly flexible CNC solution, it can be programmed to do many things.
As a straight out CNC user I would not expect Mach4's flexibility to be significant to you.....
but you never know. Many people here thought they would never customize their machine
and yet a few months later thats exactly what happens,

Craig

1530

Mach4 General Discussion / Re: Mach 4 on a Millright Mega V: What do I need?

« on: April 21, 2020, 02:35:41 PM »

Hi,

All you will need is a motion controller, Smoothstepper, or CSLabs or one of the many others out there it all comes down to your budget.

There are a number of posts on this board (Mach4 General Discussion) that talk about the shortcomings of the CSlab
products with Mach4. The hardware quality is good and the Mach3 plugin is fully developed but the Mach4 plugin is
buggy and CSLabs, contrary to their reputation, have not been botherd to fix it. Given the cost of the CSMIO boards
hard to recomend for Mach4.

Craig