LASER scanning

[Karl_T]

I bought a LASER displacement sensor off eBay with the idea of scanning parts. This sensor outputs the very common 4-20 milliamp. A galil board needs 0-10 volts. I started with a very simple resistor for the conversion but found a ripple in the voltage reduced accuracy. So a EE friend designed the attached 4-20 milliamp to 0-10 volt converter. Also attached is a graph of this Omron sensor performance.

Next I wrote code for my mill's .cbk file. See the attached text file. This code uses G101 to record LASER displacement sensor values to a file. The format of this Gcode is G101 X_ Y_ I_ F_ X,Y,F work just like G1 in any Gcode. I is the increment between laser readings. To scan a part, write a Gcode file to run the laser over as many passes as needed. Parametric programming (looping and incrementing X or Y) can keep this program fairly small.

So far, I've scanned as fast as 4ipm with readings every 0.002" with good results.

Enjoy

Karl

[Adamj12b]

Very Interesting. Do you have a link to the sensor that you used? Was it expensive?

As for the 0-10V output, what is the purpose of this? Dose it have something to do with height.

Also, What kind of machine are you running this on.

-Adam

[Karl_T]

Originally Posted by Adamj12b Very Interesting. Do you have a link to the sensor that you used? Was it expensive? As for the 0-10V output, what is the purpose of this? Dose it have something to do with height. Also, What kind of machine are you running this on. -Adam

http://www.omron247.com/marcom/pdfcatal.nsf/PDFLookupByUniqueID/46021884A762C2E086256A31006B2E69/$File/D02Z4MWR0401.pdf?OpenElement

Promise not to call the sheriff? I stole it - $80.

Laser displacment sensors like this one put out an analog value proportional to the distance or Z height in this setup

Camsoft control on an Excello knee mill

[XYZADave]

Hello,
Any chance you could post some results, (pics)???
Thanks Dave

[Karl_T]

Here's a macro to laser displacement scan arcs.

My concept: Scanning a grid of readings to a file just gives a point cloud that is complex, at best, to turn into a CNC program to replicate a scanned surface.

I have found that with a little study a CNC program can written for the X and Y coordinates on how a replicated part surface should be machined.

1) I write this program and test.

2) Then change all G01 to G101, all G02 to G102, all G03 to G103. Run the Laser displacement sensor programs to get the Z depths.

3) Rewrite the program in 1) with Z depths. Machine part.


This goes really fast, no complex design time. I've done a couple parts, only downside is careful inspection for error readings is needed. Edges are giving the most trouble.

Karl

[Farmers Machine]

So you are using your mill as a CMM to reverse engineer your part?
Does it record the measurments into your CNC control or into a seperate CAM package? are you using the Cam Soft 3000 or something different. I saw the laser on there web site and was thinking about building a measurment machine. but mounting the laser to the mill takes care of a lot of issues.
Thank You
Farmers Machine

[Karl_T]

Originally Posted by Farmers Machine So you are using your mill as a CMM to reverse engineer your part? Does it record the measurments into your CNC control or into a seperate CAM package? are you using the Cam Soft 3000 or something different. I saw the laser on there web site and was thinking about building a measurment machine. but mounting the laser to the mill takes care of a lot of issues. Thank You Farmers Machine

Yes, poor man's CMM. Exceptional accuracy if you pay attention to detail.

The data is recorded to a text file as a series of X Y Z coordinates.

You quickly end up with a HUGE number of points, or point cloud. A package called Rhino can handle the data and turn it into a model that is in turn imported to a CAM package. This is NOT my area.

I found a shortcut for the parts I needed to copy. Carefully plan your X and Y moves to machine the part; write this Gcode file. (Note that my G101 is linear laser read, G102 is CW laser read, G103 is CCW laser read). Spend some time thinking exactly where you need Z readings. Now modify the Gcode (add 100, put in read increments) to read your Z values off the part and run laser program. Input your Z values into the original program(I automated this step) and you are ready to machine.

Karl