"Scan" feature to move around maximum boundaries

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14 Oct 2018 20:06 #118794 by lars
Hello.

I would like to implement a "scan" function to move the spindle along the XY-bounding box of the loaded G-Code file. I thought I would get the boundaries, add a MDI_COMMAND that I can link to a pyVCP button or a button on a XHC-pendant.

I found forum.linuxcnc.org/41-guis/29080-boundaries-pin-in-axis which allows me to get the boundaries into HAL pins. But how can I access these pins from G-Code?

On forum.linuxcnc.org/22-pyvcp/30976-readin...n-values-from-python someone used a command like "G0 X#<_hal[boundaries.xmin]>", but when I try this I get an error that the variable does not exist.

How can I access the pin values? Or can I write the boundaries to named or numbered parameters in .axisrc? Or is there another way to get values from the python code in .axisrc to a MDI_COMMAND?

Thank you for your help,
Lars

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17 Oct 2018 12:04 #118938 by andypugh
For this application you should be OK to use G-code access to HAL.

linuxcnc.org/docs/2.7/html/remap/remap.h...i_file_configuration

(You can be forgiven for not finding that, it is documented in a very odd place)

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17 Oct 2018 18:22 #118948 by lars
Thanks a lot. Works great.

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17 Oct 2018 20:58 #118955 by tommylight

lars wrote: Thanks a lot. Works great.


Would you mind elaborating ?
Thank you.

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17 Oct 2018 21:43 - 18 Oct 2018 08:04 #118960 by lars

tommylight wrote: Would you mind elaborating ?


Sure. Sorry. I didn't think there was any interest.


This is to check if the coordinates and the fixtures are all setup correctly before starting the actual job. It moves to the bounding box (XY only) of the loaded program, goes around once and then returns to its old position.

It was a feature I liked in bCNC which I used with GRML before switching to LinuxCNC on my new machine.

This is my .axisrc
if hal_present:
    boundcomp = hal.component("boundaries")
    boundcomp.newpin("xmin",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.newpin("xmax",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.newpin("ymin",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.newpin("ymax",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.newpin("zmin",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.newpin("zmax",hal.HAL_FLOAT,hal.HAL_OUT)
    boundcomp.ready()
if vars.metric.get():
    conv = 1
else:
    conv = 1/25.4

# this function is called at [DISPLAY]CYCLE_TIME interval
def user_live_update():
    min_extents = from_internal_units(o.canon.min_extents, conv)
    max_extents = from_internal_units(o.canon.max_extents, conv)
    boundcomp['xmin'] = min_extents[0]
    boundcomp['xmax'] = max_extents[0]
    boundcomp['ymin'] = min_extents[1]
    boundcomp['ymax'] = max_extents[1]
    boundcomp['zmin'] = min_extents[2]
    boundcomp['zmax'] = max_extents[2]

and this is goes in $SUBROUTINE_PATH/boundaries-scan.ngc
O<boundaries-scan> SUB

(-------------------------------------------------------------------------------------------------------)
#<_UseInches> =           0     ( set to 1 to use inches here, or 0 to use millimeters )
#<_TravelFeed> =     3000.0     ( feedrate used to travel to and along the boundaries )
(-------------------------------------------------------------------------------------------------------)

M70                   ( save current modal state )
G[21 - #<_UseInches>] ( use inches or millimeters as required here, units will be restored on return )
G30.1                 ( save current position in #5181-#5183... )
G90                   ( use absolute positioning here )
G40                   ( turn cutter radius compensation off here )
G94                   ( use feedrate in units/min )
G61                   ( follow exact path, don't round corners )

( Move to first corner of bounding box )
G53 G1 F#<_TravelFeed> X#<_hal[boundaries.xmin]> Y#<_hal[boundaries.ymin]>
( Drive around the block )
G53 G1 F#<_TravelFeed> X#<_hal[boundaries.xmin]> Y#<_hal[boundaries.ymax]>
G53 G1 F#<_TravelFeed> X#<_hal[boundaries.xmax]> Y#<_hal[boundaries.ymax]>
G53 G1 F#<_TravelFeed> X#<_hal[boundaries.xmax]> Y#<_hal[boundaries.ymin]>
G53 G1 F#<_TravelFeed> X#<_hal[boundaries.xmin]> Y#<_hal[boundaries.ymin]>

G53 G0 X[#5181] Y[#5182]  ( return to where we were in X Y)
M72                       ( restore modal state )

O<boundaries-scan> ENDSUB
M2

Then I created a new line under [HALUI]
MDI_COMMAND = O<boundaries-scan> call
which I have mapped to a button on my pendent.
Last edit: 18 Oct 2018 08:04 by lars.
The following user(s) said Thank You: tommylight

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17 Oct 2018 21:59 #118962 by cmorley
i bet this would be very useful for plasma or oxy cuttimg machines to see if you have enough material... It would make a great macro program.
Too bad it's so akward to get boundary info to linuxcnc.
I wonder in boundaries shouldn't be standard variables?

Chris M
The following user(s) said Thank You: tommylight

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18 Oct 2018 08:01 #118981 by lars
Yeah. I also thought it would be easier to get the boundaries. But it's just a feature of the GUIs to parse the loaded program and calculate the boundaries, so I don't see how this could be a standard variable of the LinuxCNC core.

Although it would be nice if the GUIs exported this in a more easily accessible way.

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18 Oct 2018 09:20 #118982 by andypugh
Maybe it would be easier to use a standalone HAL component (it only needs to be a HAL component so it can be wired to a button press)

It could get the file name from the linuxcnc.stat().file
linuxcnc.org/docs/2.7/html/config/python...ding_linuxcnc_status
The run through each of the lines of G-code noting the max and min X and Y values.
(this might be inaccurate for arcs)
Then it could send the moves by MDI.

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18 Oct 2018 10:44 #118985 by lars
I'm definitely not an expert at this, but I see some problems there:

1. What happens if the file changes? The boundaries should only be updated when the GUI reloads the file. How would an external component detect that?
2. The coordinate system offsets may change. I think this would be possible to detect from the component but it would not be really trivial.
3. Just getting min/max X/Y values from the G-Code also neglect cutter compensation and maybe other things? I think the values should be precise when they are used to ensure that the program won`t go through your fixtures.

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18 Oct 2018 11:21 #118986 by andypugh

lars wrote: 1. What happens if the file changes? The boundaries should only be updated when the GUI reloads the file. How would an external component detect that?


Nothing changes. When the component sees the "do your thing" trigger it then loads a copy of the current G-code fie into it's own parser and works out the extents.

2. The coordinate system offsets may change. I think this would be possible to detect from the component but it would not be really trivial.

The module can either work in the current coordinate system, or get all clever and have the parser consider the offsets (read from linuxcnc.stat() and calculate absolute sizes.


3. Just getting min/max X/Y values from the G-Code also neglect cutter compensation and maybe other things?.

Yes, including arcs. But I was imagining starting simple and then making the parser more sophisticated as required.

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