Motorized Height Gauge retrofit
08 Oct 2014 09:05 #51871
by gernoff
Motorized Height Gauge retrofit was created by gernoff
I recently acquired a Mahr 600mm motorized height gauge. Long story short it is dead.
I would like to retrofit it with a new/undamaged glass scale and reader head and would like to control the system with linuxcnc.
Has this been done already?
If not, what do you genius's think it would take to do so?
I have in mind a system with a touch screen interface and the same measuring abilities as the original gauge.
There is a long list of measurements the original was able to do, here are a few:
Measure height from above, below, hole diameter, protrusion diameter, distance between plane surfaces, distance between hole centers etc.
I would also like to be able to measure perpendicularity, this would require input from a second touch probe, mounted on the motorized carriage. The system would need to be able to store a lookup table for calibration of the linear scale as well as the ability to calibrate for the second axis as well as be able to null out the non-perpendicularity of the hardware's vertical axis to be able to do perpendicularity measurements.
As I envision the interface, there would be icons on the touch-screen one could tap, to begin specific measurement macros.
Who wants to jump in and build a single axis CNC measurement controller with extra inputs??????
I would like to retrofit it with a new/undamaged glass scale and reader head and would like to control the system with linuxcnc.
Has this been done already?
If not, what do you genius's think it would take to do so?
I have in mind a system with a touch screen interface and the same measuring abilities as the original gauge.
There is a long list of measurements the original was able to do, here are a few:
Measure height from above, below, hole diameter, protrusion diameter, distance between plane surfaces, distance between hole centers etc.
I would also like to be able to measure perpendicularity, this would require input from a second touch probe, mounted on the motorized carriage. The system would need to be able to store a lookup table for calibration of the linear scale as well as the ability to calibrate for the second axis as well as be able to null out the non-perpendicularity of the hardware's vertical axis to be able to do perpendicularity measurements.
As I envision the interface, there would be icons on the touch-screen one could tap, to begin specific measurement macros.
Who wants to jump in and build a single axis CNC measurement controller with extra inputs??????
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08 Oct 2014 11:49 #51874
by cmorley
Replied by cmorley on topic Motorized Height Gauge retrofit
This sounds more like a HAL thing then a linuxcnc thing.
Is Gcode appropriate for programming the moves?
The UI could be made with gladeVCP or Gscreen (depending on whether using pure HAL or linuxcnc)
I am not familiar with the piece of equipment so can't comment much farther.
Chris M
Is Gcode appropriate for programming the moves?
The UI could be made with gladeVCP or Gscreen (depending on whether using pure HAL or linuxcnc)
I am not familiar with the piece of equipment so can't comment much farther.
Chris M
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08 Oct 2014 17:46 #51887
by ArcEye
Replied by ArcEye on topic Motorized Height Gauge retrofit
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08 Oct 2014 19:16 - 08 Oct 2014 19:18 #51892
by andypugh
You would need a HAL file that loaded a custom Glade GUI rather than the usual one.
You probably do want to load motmod, but you won't need a G-code interpreter.
The Glade panel can then have individual controls that perform fixed actions.
I imagine mainly this would be using the interface doumented here:
www.linuxcnc.org/docs/html/common/python-interface.html
Reading that it seems that you would need to usecommands to move the head, but I think that there are more direct methods.
if you look at the remap "stdglue" file here: git.linuxcnc.org/gitweb?p=linuxcnc.git;a...0dde4bf3edaf67c5ce71
You will see various calls directly to emccanon, which basically sends basic motion commands to LinuxCNC. I believe (I haven't tried it) that you can call anything in cannon.hh (git.linuxcnc.org/gitweb?p=linuxcnc.git;a...0dde4bf3edaf67c5ce71 ) this way, including STRAIGHT_PROBE
Look at www.linuxcnc.org/docs/html/remap/structure.html especially section 9.5.4 for more info.
Replied by andypugh on topic Motorized Height Gauge retrofit
If not, what do you genius's think it would take to do so?
You would need a HAL file that loaded a custom Glade GUI rather than the usual one.
You probably do want to load motmod, but you won't need a G-code interpreter.
The Glade panel can then have individual controls that perform fixed actions.
I imagine mainly this would be using the interface doumented here:
www.linuxcnc.org/docs/html/common/python-interface.html
Reading that it seems that you would need to use
c.mdi(G38.2...)
if you look at the remap "stdglue" file here: git.linuxcnc.org/gitweb?p=linuxcnc.git;a...0dde4bf3edaf67c5ce71
You will see various calls directly to emccanon, which basically sends basic motion commands to LinuxCNC. I believe (I haven't tried it) that you can call anything in cannon.hh (git.linuxcnc.org/gitweb?p=linuxcnc.git;a...0dde4bf3edaf67c5ce71 ) this way, including STRAIGHT_PROBE
Look at www.linuxcnc.org/docs/html/remap/structure.html especially section 9.5.4 for more info.
Last edit: 08 Oct 2014 19:18 by andypugh.
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08 Oct 2014 23:34 #51904
by gernoff
Replied by gernoff on topic Motorized Height Gauge retrofit
I don't have any programming ability. Anyone interested in whipping up a servo control and measurement interface? A new encoder is needed so I can get whatever would be easiest to integrate. The gauge used a small dc motor for drive. What hardware would be needed for a single axis servo system? Is there a possible pc card solutions or even better something one could interface to via a tablet?
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09 Oct 2014 12:47 #51916
by sivaraj
Replied by sivaraj on topic Motorized Height Gauge retrofit
usually these measuring devices use force control while measuring.
Once probe is at approximate measurement location motor will start measuring procedure based on the type of measurement function selected.
Mostly these measuring devices use Exposed type linear scale .Enclosed glass scales/scanning head are not recommended because how best you do alignment it will have few micron error due to the scanner head spring mechanism contact with the glass.This is not desirable for measuring equipment.
Again whether the equipment is 1D or 2D.With 1D equipment you need to manually position for each location on height measurement
Once probe is at approximate measurement location motor will start measuring procedure based on the type of measurement function selected.
Mostly these measuring devices use Exposed type linear scale .Enclosed glass scales/scanning head are not recommended because how best you do alignment it will have few micron error due to the scanner head spring mechanism contact with the glass.This is not desirable for measuring equipment.
Again whether the equipment is 1D or 2D.With 1D equipment you need to manually position for each location on height measurement
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03 Jun 2015 12:47 #59365
by gernoff
Replied by gernoff on topic Motorized Height Gauge retrofit
The original glass scale was damaged....... I will be retrofitting it with a new 20 micron spacing exposed glass scale. The read head is rigidly fixed to the probe carriage of the gauge. I have the option of either quadrature or sine (synchro) output from the scale. Which would be the better option for linuxcnc interpolation of the 20 micron spacing?
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03 Jun 2015 16:16 #59367
by andypugh
LinuxCNC typically reads digital quadrature pulses. However the data is transmitted it needs to be digital by the time it gets to the software.
With sin/cos scales you will need some hardware that converts the position to digital. This could be a Heidenain EXE box or an ICHaus chip, or something else (maybe an Arduino and a serial link, or run LinuxCNC on something with analogue inputs)
What interface hardware do you have in mind?
.
Replied by andypugh on topic Motorized Height Gauge retrofit
Which would be the better option for linuxcnc interpolation of the 20 micron spacing?
LinuxCNC typically reads digital quadrature pulses. However the data is transmitted it needs to be digital by the time it gets to the software.
With sin/cos scales you will need some hardware that converts the position to digital. This could be a Heidenain EXE box or an ICHaus chip, or something else (maybe an Arduino and a serial link, or run LinuxCNC on something with analogue inputs)
What interface hardware do you have in mind?
.
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03 Jun 2015 22:32 #59378
by gernoff
Replied by gernoff on topic Motorized Height Gauge retrofit
I am still in the planning stage so can use whatever. The optimum would be hardware that allows interface via usb / Bluetooth....... I would like to use my lvdt based electronic test indicator as the touch probe.
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03 Jun 2015 22:36 #59379
by andypugh
You might need to re-think using LinuxCNC then. LinuxCNC requires real-time access to hardware, and USB can't do that (and Bluetooth is usually USB-interfaced)
Replied by andypugh on topic Motorized Height Gauge retrofit
The optimum would be hardware that allows interface via usb / Bluetooth..
You might need to re-think using LinuxCNC then. LinuxCNC requires real-time access to hardware, and USB can't do that (and Bluetooth is usually USB-interfaced)
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