Today I ran into a new problem....  I started using ramping to start cuts - this typically means a 3-axis helical move.  But, on some of them, my Z axis servo is faulting!  If I run the offending lines in isolation, they NEVER fault, even when run repeatedly.  Also, if I reduce the X/Y acceleration to what the Z axis is set to, the problem also goes away.  I've been using this machine for over a year, and NEVER had a servo fault, except when I accidentally ran an axis into a hard stop.  I've also verified the supply voltage is holding well, never dropping more than about 1.5V from its nominal value.  I'm suspecting perhaps Mach3 or the SS is not respecting the MUCH lower acceleration setting for the Z axis when entering the 3-axis moves, as the fault occurs almost instantly, before the Z axis has moved hardly at all.

How do I find and fix the cause of this so I can get back to work??

Regards,
Ray L.

Hi, Ray

Post the G code your having problems with for a start.

Chip

Hi, Ray

Post the G code your having problems with for a start.

Chip

Chip,

Here's one example.  The faults occur *only* on the 3-axis helical moves, yet I can take those lines, and run them over and over with no problems at all.  It's only when run *with* the preceding moves that the fault occurs.

(Filename: Mount Plate Ramped.tng)
(Post processor: My Mach2 Post 090819.scpost)
(Date: 11/29/2009)
G20 (Units: Inches)
G40 G90
F10
(Part: Fixture Plate)
()
(Process: Spiral pocket, Lower Support Shaft Bore, T145: 1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145], 0.52 in Deep)
G00 Z1.5000
(1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145])
M06 T1 G43 H1 (1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145])
G00 Z1.5000
M00 ( Pulley: 4 Motor: H )
M966 P8
M03 S6120 (Spindle CW 6120 RPM)
M07 (Mist coolant on)
G00 X27.6000 Y9.1579
G00 Z0.0197
G01 Z0.0000 F4.896 S6120
G03 X27.8421 Y9.3947 Z-0.3750 I0.0000 J0.2421
G03 X27.6000 Y9.1579 I-0.2421 J0.0053 F29.376
G03 X27.7365 Y9.2000 Z-0.5200 I0.0000 J0.2421 F4.896
G03 X27.7365 Y9.2000 I-0.1365 J0.2000 F29.376
G00 Z1.5000
()
(Process: Spiral pocket, Lower Retainer Shaft Bore, T145: 1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145], 0.52 in Deep)
G00 X27.8000 Y5.4579
G00 Z0.0197
G01 Z0.0000 F4.896
G03 X28.0421 Y5.6947 Z-0.3750 I0.0000 J0.2421
G03 X27.8000 Y5.4579 I-0.2421 J0.0053 F29.376
G03 X27.9365 Y5.5000 Z-0.5200 I0.0000 J0.2421 F4.896
G03 X27.9365 Y5.5000 I-0.1365 J0.2000 F29.376
G00 Z1.5000
()

Regards,
Ray L.

Hi, Ray

Try this.

(Filename: Mount Plate Ramped.tng)
(Post processor: My Mach2 Post 090819.scpost)
(Date: 11/29/2009)
G20 (Units: Inches)
G40 G90
F10 ;------------------------------- F10 Set
(Part: Fixture Plate)
()
(Process: Spiral pocket, Lower Support Shaft Bore, T145: 1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145], 0.52 in Deep)
G00 Z1.5000
(1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145])
M06 T1 G43 H1 (1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145])
G00 Z1.5000
M00 ( Pulley: 4 Motor: H )
M966 P8
M03 S6120 (Spindle CW 6120 RPM)
M07 (Mist coolant on)
G00 X27.6000 Y9.1579
G00 Z0.0197
G01 Z0.0000 F4.896 S6120
G03 X27.8421 Y9.3947 Z-0.3750 I0.0000 J0.2421
G03 X27.6000 Y9.1579 I-0.2421 J0.0053 F29.376
G03 X27.7365 Y9.2000 Z-0.5200 I0.0000 J0.2421 F4.896
G03 X27.7365 Y9.2000 I-0.1365 J0.2000 F29.376 ;--------------F29 Set Hear

F10 ; Try this Hear -----------------------------------------F10 Hear may be hear


G00 Z1.5000
()
F10 ; Try this Hear -----------------------------------------F10

(Process: Spiral pocket, Lower Retainer Shaft Bore, T145: 1/2 Carbide, uncoated, 3-Flute, Aluminum Cutter, 1XSlotting [145], 0.52 in Deep)
G00 X27.8000 Y5.4579
G00 Z0.0197
G01 Z0.0000 F4.896
G03 X28.0421 Y5.6947 Z-0.3750 I0.0000 J0.2421
G03 X27.8000 Y5.4579 I-0.2421 J0.0053 F29.376
G03 X27.9365 Y5.5000 Z-0.5200 I0.0000 J0.2421 F4.896
G03 X27.9365 Y5.5000 I-0.1365 J0.2000 F29.376
G00 Z1.5000
()

M30
%

Chip

Chip,

I don't understand what that changes.  The knee will rapid all day long at 50 IPM with no problems. and the fault is occurring on the first and third G03 moves of each set, never on a single axis move.  X and Y rapid at 200 IPM, and also have never lost position.  What would those F10s accomplish?

Regards,
Ray L.

Hi, Ray

It was just a Quick Thought, Guess I Missed part of your Issue.

Chip

Looks like this IS a Mach3 bug.  Brian has just sent me a test version that will hopefully fix it.

Regards,
Ray L.

OK, Brian has just confirmed this *is* a bug in the Mach3 CV code, and he's working on a fix.  As for my situation, if I go to exact stop mode, the problem goes away.  Since I'm not doing 3D profiling, this shouldn't cause me any significant grief, so I'm off to make some chips.

Regards,
Ray L.

Brian,
    Could you please give us some details about what this bug is and in what verison it appears. I do alot of 3D machining and I have recently been chasing what appears what shows up as lost steps on Z. I've been assuming it was hardware related but maybe not. - Thanks - Tery

Well, the plot thickens.....   I *thought* exact stop mode would get me going, but it's not 100% reliable, so I'm still dead in the water.  I re-wired my controller so the Z axis is on a completely separate power suppply, breakout board, etc., to make sure there is no interference when all three axes are running.  This made no difference. 

I'm quite convinced at this point it is a Mach3 bug.  I can do slow helical interpolations between two points, and get it to fault a LOT.  I can do linear interpolations between the same two points all day long with no problems.  In fact, I can even do rapids between the same two points, with the Z axis acceleration set to 3X the normal value, and it never faults.  So, Mach3 seems to be violating the Z axis acceleration limit when doing circular interpolations.

Back to waiting for Brian to come up with a fix....

Regards,
Ray L.