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Soft Limit Warning
« on: June 10, 2009, 04:23:10 PM »
I have recently upgraded my Sheetcam program from Standard to TNG.  I am using virtually the same post processor (a modified version of the standard Mach2 post processor).

I have taken an existing job and re-run it through the SheetCam TNG program and generated the GCode.

When I load the new gcode, it loads without error, however, as soon as I click Cycle Start, I receive a Soft Limit warning.

I can bypass the error message and it appears to execute correctly.  I receive no additional warnings.

I have compared the code generated from the SheetCam Standard and SheetCam TNG programs, and can find almost no difference.  The primary difference is the TNG program eliminates some of the Z moves.

For example, in SheetCam standard, you might have the following sequence of commands:
G00 Z1
x2 y4
Z0.0197
G01 z0 f90
x-0.03


On the TNG program you might see:
x2 y4
z0.0197
g01 z-.03 f90


Other than that, the code is virutally idendical

Has anyone else experienced this type of problem???

Offline Hood

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Re: Soft Limit Warning
« Reply #1 on: June 10, 2009, 05:11:16 PM »
What version of Mach, there were softlimits warning problems with earlier revisions but it was a long time ago.
Hood
Re: Soft Limit Warning
« Reply #2 on: June 11, 2009, 07:21:14 AM »
I am running version 3.042.020.  I believe this is the latest lockdown.

Offline Hood

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Re: Soft Limit Warning
« Reply #3 on: June 11, 2009, 07:25:11 AM »
Can you attach your xml and the two  code files please.
Hood
Re: Soft Limit Warning
« Reply #4 on: June 11, 2009, 08:10:00 AM »
Ok - here it is.

#1 was generated using SheetCam Standard
#2 was generated using SheetCam TNG

The post processor for used to generate both files are virtually identical. 

Thanks
Re: Soft Limit Warning
« Reply #5 on: June 11, 2009, 09:54:47 AM »
It's hard to tell from the XML what the Soft limit parameters of your machine are set at (I think that info is stored in a different Config file and I dunno which one).  What are the specs on your machine?  How much travel do you have available?

The G-Code has a comment line that says that the total depth of cut is 12.?? in a positive value but the G01 Z commands are all in Negative numbers (which is correct) but not being familiar with your CAM package this is nothing more than an observation of inconsistency on my part perhaps you could verify that the PP is in fact processing correctly?

In any case the there is some conflict between your code and the settings on the machine- I suggest you load your code and go to the Toolpath screen.  It shows the "Extents" of the the code and you will see immediately what Z axis command is calling a soft limit conflict.  That will help to narrow things down a bit.

It's really gotta be one of two things - The soft limit settings on the machine are not correct or the code is calling for something out of range

HTH,
Sid
Re: Soft Limit Warning
« Reply #6 on: June 11, 2009, 10:51:12 AM »
Sid,

On my machine the soft limits are set as follows:

X   Min 0   Max 103
Y   Min 0   Max 49.5
Z   Min –12   Max 0

Yes, there is an inconsistency between the comments and the G code.  The comments are in absolute values and describe the actual distance between the top of the board being cut and the bottom of the collet.  But, to use that distance with a machine that homes at 0 (full up) and travels down 12”, I have to enter a negative number.  Hence the G52 offset of Z-12.5625

As suggested, I loaded both programs into the toolpath screen and both show identical results:

X – 0 to 6
Y – 0 to 6
Z – 0 to 2.5

However, when I execute the programs, only #2 creates the soft limit error (at the start of the program).  No error is ever generated in the body of the code while it is executing - nor does the program ever exceed the -12 soft limit set by the program.

But, you questions have caused me to do some additional testing.  I changed the Z limit to –12.75.  That eliminates the warning message.   Although this isolates the problem, it does not fix the problem.   The machine can only travel to an absolute distance of –12.

The G52 command sets the offset to –12.5625 (which is over the limit), however, the G43, tool length offset, adds 1.5” to that which results in a net travel of  –11.0625.

What is interesting is that both programs display the same numbers on the toolpath screen, but only #2 creates the soft limit warning.  And along that line of thinking, the “absolute z” values are 0 to 2.5 – but 2.5 is outside of the soft limits of the Z axis.  By that logic, I would think that both programs would generate a warning.

Suggestions?
Re: Soft Limit Warning
« Reply #7 on: June 11, 2009, 11:41:29 AM »
I also regularly see soft limit problems with the .027 Mach release. You'll get a warning on first run that I know isn't correct as the code has been run before in the same configuration, and if you ok through the warning the program will run without problems. On next run the warning doesn't occur, its always on the first run for me.

Paul T.
Re: Soft Limit Warning
« Reply #8 on: June 11, 2009, 11:57:43 AM »
I get these errors also.  Probably a bug of some sort.
Re: Soft Limit Warning
« Reply #9 on: June 11, 2009, 12:06:28 PM »
As a further note, I receive the error every time I run code #2.