how to reproduce a irregular shape ?

[pit202]

hi ,

is there a way to scan a shape with a probe on cnc machine ? i need to make a copy of a thing that does`t have a blueprint , this isn`t 3D , this is simple 2D shape , one way I have in mind is to use a computer scanner , but i fear i don`t reach the 0.5mm accuracy

[Donkey Hotey]

I've used a manual mill with a digital readout for capturing dimensions. The problem that I see using a probe is that the probe doesn't know the approach direction. In other words: if you're probing an edge that is 45 degrees from the machine axis, it only knows that it bumped into something, not where the true edge is.

Now that you've asked this question, I see a use for something that I just bought: a 3D Taster.

http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=67848317

Here's what it does:
It works like a combination of a centering indicator and dial indiator. The probe tip goes in and out like a normal dial indicator. It also deflects in any direction and has a cam like a centering indicator. Both movements cause the needle to deflect.

Here's why it would be uniquely suited to what you're trying to do. The ball diameter is matched to the indicator. When you bump far enough into the part for the needle to read 'zero', the centerline of the gauge is exactly over the edge.

So there is no edge calculation needed like with normal edge finders. It works at any angle, from any direction--bump into the part, get to zero on the gauge and record the dimension.

I just found one on eBay:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=190197926532

Here is another brand of the same kind of indicator. They also have a couple of videos showing how it's used:
http://www.haimer.de/english/taster-universal.php

If you don't need that kind of resolution, you could also use a pointer in the spindle and just carefully dial to each location and record the numbers.

Do you know how to zero and set the Operator coordinates display on your Haas control?

[pit202]

thanks , this is a way too, but is there a way to combine a touch probe with dnc to make it automaticly ?

[PBMW]

Spline it.
Aerosapce has seen fit to ues this technique for many years
Lay it out on a surface plate. Use regular intervals in one direction, measure from a datum at those intervals in the other direction.
A probing system will cost you thousands unless you already have it. If you're akign this question....you ain't got probing, cause you'd already have it done.
You may want to take some courses in layout work. If such a thing even exists any longer.

[Mike Stevenson]

I have a method I use to digitize any irregularly shaped parts I might like to make. I clamp the piece down on a cnc mill table. Then I use a .200 diameter edge finder and manually take points all around the contour. Then I take the pattern of .200 diameter circles and either make a spline through them or make a series of arcs tangent to 3 of the .200 dia circles at a time until I go all away aroung the part. Any bad corners I might end up with I create a Blending Spline that smoothes away any sharp corners. I make Guitars and this technique works well.

[Vern Smith]

PIT202,

You can use the Renishaw probing system to reverse engineer to a degree, which I think is what you are asking. Go to their web site and download the manual, it's a .pdf file. It lists all the macros that come with the system. There are a bunch of them and several will find angles as well as corners, bore diameters and centers, and boss dimensions.

[Geof]

I don't use drafting programs so maybe this question/suggestion is not well founded.

I have read about programs that do raster-vector conversions that can be using for scanning pictures for engraving. Once the information is in vector form it can enter a normal CAM program.

You want 0.5mm precision which should be possible just by tracing around the shape onto paper with a fine pencil. Then scan the tracing into a computer and pass it through the conversion to vector form and do the CAM output.

But maybe this type of software is prohibitively expensive?

[pit202]

thanks all , i try with succes with the 3D Taster , it isn`t very complicated , time taking not so much and quality - don`t know yet I attached a partial scan , you can see points and finaly the line , I jog at hand jog , and send positions with G102 at MDI , next I rewrited points to solidedge manualy anybody know a better idea to make points from .txt file to a cad software ?

I also know how to make use of touch probe , the point is I need to write a complicated stepping macro that could steps at the edge and plunge coords. over serial port , maybe in the future ..... far far away ... ;-)

thanks again.
Piter

[dannystooblue]

Have you considered scanning a picture then using rhino to create geometry? It may not be to scale but after the geometry is created you could take a couple measurements and adjust the scale to the whole part. For a 2-d shape would think it could work pretty well depending on the resolution of the photo.

Danny

[pit202]

yes I have , but I did not know a software that could do that till now , i`ll try, thanks.

[Mike Stevenson]

In SolidWorks you can, "sketch a JPG" which I find very useful too.

[pit202]

maybe call me lazy man , but I done a auto shape probe and macro , I attached a self made touch probe to IO board, see pics , the first attemp was succesfull, its fine scanned a circle and second shape , but when I taken a photo camera to take a short video it all ends working , I have try to make more securities to the macro , and discover what is wrong , it appears that reading the X axis position is the whole error , I don`t why reading the same way "Y" axis is 100% true and correct, the "X" seems to be readed to early, as you see in macro I tryd to make use of G103 and/or G04 but without succes , one time it works, next time without changing macro it is not working , I traced a whole program and it still get problems with reading "X"pos. and the whole next math is useless.
don`t ask me for precision, I have taken only 2 scans , and I didn`t have time to calibrate it - it could be possible if the macro get working.

the circle at the 123 file is a scan from a bearing outside, and the second one is that one from previous photos.