probing profile on the lathe and then...

Hi Guys!

i'm facing the following problem: the workpiece chucked in the lathe has to be digitized to get its profile and then the digitized data have to be interpolated (to smoothen the profile) and then a skimming pass has to be made to resurface the item.

I found it not an easy job for me! The assumptions i made so far are:
1. i can use 'smartprobe.ngc' to digitize the profile
2. i can then open log file in excel-like spreadsheet program and use linear interpolation (somehow) to create new, smooth profile. The reason i'm thinking about interpolation is there might be some minor dents in the workpiece so i assume that linear interpolation should mitigate them. Should it?
3. here there should be some kind of lead-in and lead-out profiles added to the main profile to introduce the cutting tool into the workpiece at the beginning and clear safely the workpiece after skimming.
4. now i have to apply an OFFSET - that is how much material is to be skimmed of.
5. final action would be the skimming itself - using newly generated profile.

Do you guys know how to setup linuxcnc to perform actions described above? Is it possible to make all this steps (1-5) in linuxcnc?
I think linear interpolation of probed data would be the hard part as well as the lead-in/lead-out add-ons.

I was googling around to find some other type of probing/digitizing. I'm thinking about making the following touch probe: couple the linear slide with rotary encoder or linear glass scale encoder. Moving part would be spring loaded to make sure the probe stylus has a good contact with workpiece. Then linuxcnc should read the encoder data during slowly travel along the lathe's Z axis to log workpiece profile. Can it be done it this way? I think i know how to hook up encoder channels A and B do LPT port but how to modify HAL and INI files to store probing data properly?

Please let's start some discussion on this subject here.
Thank you!
Bogi

no, i have to recondition steel rollers from sheet metal rolling machine. As the sheet metal is progressivelly formmed there are many different shapes. The roller diameter can change but the profile has to be the same. I think the same way can be applied for skimming alloy rims!

Have you seen this from Dewey Garrett...


Rick G

thank you for reply Tommy,

"I asked since i was asked to build machines that do alu rim skimming several times, but i never did since here where i live that would imply me to go teach them to use it, and knowing most of them can not follow a simple procedure for starting and homing Linuxcnc, i had to decline."


tolerances are not an issue here as far as i do not know how to make a usable gcode from digitizing *.txt file. I have nine columns containing XYZAB.... coordinates. The code have to pick the coordinates up. Lead-in/lead-out portion of the final profile have to be written manually or find some way to apply maths based on first and last point coordinates and add, say, a circle, or parabollic shape, or ramp, or just mirror extreme parts of the digitized profile and put them up side down (hope you get what i'm trying do picture).

If i choose small enough increments during digitizing and prepare the workpiece (fill in any dents) i can get pretty accurate reading. Accurate enough to skip linear interpolation part. Right?

This would cause digitizing very slow as probe points count would be very high. And here my idea comes to play: spring loaded constant touch probe. I can put encoder reading component to the base thread in linuxcnc, add some position counter and dump its reading to user #500 - #5000 parameters every xxx steps during scanning travel of the lathe/router carriage/spindle. This should be quite fast and as accurate as linear scale used in probe is. The question is - is it possible to add encoder/position counter to the linuxcnc's servo thread that is not connected to any axis?

I've just printed all the documentation about linuxcnc (getting started, users manual, integator and HAL manual) and studying it:)

Rick G - it looks amazing! Does it look like something i need? Now - how to do that?

is Mr. Dewey Garrett a member of this forum?