Would LIke to incorporate Laser Distance Sensor as Variable

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31 Aug 2023 18:18 #279500 by kotlikm
I am not sure if anyone has done this in the past, but for I am looking for a solution to support a custom application I have for my LinuxCNC controlled 3-axis router.

I have an application, where I need to perform a drilling like operation with a tool to install a widget into a panel at a given set of X,Y coordinates. For these installs, they are going into a sheet good type material, imagine like a polystyrene foam sheet. The installation height is critical that my install tool stops at the surface of the sheet, and does not advance into the material at all. This becomes a challenge as the sheet material can have a slightly varying thickness across panel due to manufacturing tolerances.

In order to solve this, I would like to incorporate a laser distance sensor that measures each X,Y coordinate, and allows me to use the outputting value from the distance sensor as a variable to adjust the finished Z height for my installation macro. Below is the link for the sensor type that I am considering. The outputting value from this sensor is a voltage, that would need to be calibrated, which would then allow for the conversion to be performed from voltage to distance. I know I would also have to incorporate some routines to tie the end of the tool and a value from the distance sensor, but at this point, I need to figure out how to get the values in from the sensor as a variable to LCNC that I can use in macros and programs.

www.automationdirect.com/adc/shopping/ca...ring_sensors/opt2006

Has anyone seen a similar system incorporated into a LinuxCNC run machine? Would anyone have any advice on how to handle solution like this?

Thanks,

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31 Aug 2023 18:53 #279506 by andypugh
It might be worth investigating a digital-ouptput sensor (though I don't know if anyone has integrated, for example, IO-Link with LinuxCNC yet. www.automation24.co.uk/laser-distance-se...c-oid200-oidlcpkg-us )

There are, however, some options for analogue input with LinuxCNC.

I think that you could use the sensor in conjunction with "external offsets" to adjust the Z axis position.

linuxcnc.org/docs/html/motion/external-offsets.html

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31 Aug 2023 20:38 #279511 by rodw
Also consider the way a cnc plasma cutter probes to find the surface on every pierce via mechanical means. Some people use an air ram to lower a seperate probe  and sometimes they have it so it encircles the tool. Setting the height  can then be done with normal tool offsets.
a touch off routine can be called at every hole position  by editing your post processor. Your challenge is how to mechanically probe a soft surface :)

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31 Aug 2023 23:51 #279523 by kotlikm
Thanks for the feedback. I have considered a mechanical foot system similar to the type you mention with the plasma cutters. I was hoping to avoid physical contact with the panel surface. I had also considered a laser switch like Andy linked, but I would like to avoid having to drive the z-axis up and down to find the surface point. 

I wonder if there is anyway to read a voltage output through a mesa board and treat it as a variable, I might reach out to them and see if they can think of any way to incorporate it. 

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01 Sep 2023 00:19 #279525 by rodw
The most accurate way to measure analog voltage would be to use the Mesa THCAD  attached to an encoder input. 
The THCAD is a voltage to frequency converter so the frequency is scaled in HAL to a voltage (or more likely distance in your case)
You can choose 0-10v or 0-5 volt ranges on a THCAD2. I was able to see the voltage ramp up over 0.04mm as the probe contacted the plate in a 24 volt circuit. refer to ohmic.comp component

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