[sci.electronics] Profileometers?

piner@pur-phy (Richard Piner) (12/01/89)

A couple of days ago I got a call from a chap down in Indy who
has an interesting problem. He needs to measure the shape of
a molding in three dimension to within 0.025". And he needs to
do it fast. What they want to do is take a molding of a piece of
human bone and machine an implant from the molding. He says
that the CNC milling machine can do the cutting in under an
hour. The problem is getting the digital information to program
the mill.

So, does anyone know of a commercial system that can measure
the shape of an object in three dimensions and do it quickly.
Most machine vision systems are not fast enough or accurate
enough. Anyone know of a 3d profileometer system that is up to
this task?
					R. Piner

greg@sj.ate.slb.com (Greg Wageman) (12/06/89)

Opinions expressed are the responsibility of the author.

In article <2826@pur-phy> piner@pur-phy (Richard Piner) writes:
>
>A couple of days ago I got a call from a chap down in Indy who
>has an interesting problem. He needs to measure the shape of
>a molding in three dimension to within 0.025". And he needs to
>do it fast. What they want to do is take a molding of a piece of
>human bone and machine an implant from the molding. He says
>that the CNC milling machine can do the cutting in under an
>hour. The problem is getting the digital information to program
>the mill.

Quite true.  Back when I worked at Computervision (now owned by
Prime), writing Numerical Control Postprocessors, one of our customers
was doing exactly that for replacement knee joints.  They were
matching the replacement part to the existing bone-end for a more
comfortable fit.

>So, does anyone know of a commercial system that can measure
>the shape of an object in three dimensions and do it quickly.
>Most machine vision systems are not fast enough or accurate
>enough. Anyone know of a 3d profileometer system that is up to
>this task?

Sure, they're called "Coordinate Measuring Machines" (CMM's).  Like NC
machines, you program them to move around your part.  Instead of a
tool, however, the head ends in a ball-end probe of a known accurate
radius.  When the probe touches the part, the current coordinate of
the machine can be stored.  Like NC machine tools, they're very
expensive, very heavy, and very accurate.


Copyright 1989 Greg Wageman	DOMAIN: greg@sj.ate.slb.com
Schlumberger Technologies	UUCP:   {uunet,decwrl,amdahl}!sjsca4!greg
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        Permission granted for not-for-profit reproduction only.

eln485g@monu1.cc.monash.oz (Rick Alexander) (12/13/89)

In article <2826@pur-phy> piner@pur-phy (Richard Piner) writes:
:
:A couple of days ago I got a call from a chap down in Indy who
:has an interesting problem. He needs to measure the shape of
:a molding in three dimension to within 0.025". And he needs to
:do it fast. What they want to do is take a molding of a piece of
:human bone and machine an implant from the molding. He says
:that the CNC milling machine can do the cutting in under an
:hour. The problem is getting the digital information to program
:the mill.
:
:So, does anyone know of a commercial system that can measure
:the shape of an object in three dimensions and do it quickly.
:Most machine vision systems are not fast enough or accurate
:enough. Anyone know of a 3d profileometer system that is up to
:this task?

A high accuracy non-contact three dimensional shape measurement 
system has been under development at Monash University over the 
past few years and is now commercially available via MonTech Pty.
Ltd., the commercial arm of Monash University. The system measures
the 3-D coordinates of up to 64 by 128 points on a surface in about
35 seconds (on a 20 Mhz 80386 system) with a precision of about
1:12000 of the major dimension of the surface area being measured.

The measurement principle used by the system is active triangulation.
The system uses a specialised white light projector and CCD camera
interfaced to an AT compatible.