RE: [rp-ml] FW: Geometric Accuracy of RP parts

From: Good, Jim <>
Date: Wed Dec 29 2004 - 15:54:26 EET

Yes, I agree. This is why our first iteration is to establish the system to
scan layer-by-layer to inspect all features, internal and external. That
would be the best set-up.


-----Original Message-----
From: Anshuman Razdan []
Sent: Tuesday, December 28, 2004 11:45 PM
To: Good, Jim;
Cc: Marshall Burns;;
Subject: RE: [rp-ml] FW: Geometric Accuracy of RP parts

Either the inspection system must measure as the part is being built or once
its built you cannot measure the internal structure with surface scanning
methods. Then MicroCT must be employed, which has its own issues ...


-----Original Message-----
From: [] On Behalf
Of Good, Jim
Sent: Tuesday, December 28, 2004 7:15 AM
To:; Anshuman Razdan
Cc: Good, Jim; Marshall Burns;;
Subject: RE: [rp-ml] FW: Geometric Accuracy of RP parts

The inspection system must provide the required data to determine if the rp
part is geometrically acceptable for its intended purpose. Additionally, we
would want real-time inspection to verify the part-build, as each layer is
produced. Is this feasible? Can we make it work? Is it over-kill? Those
are things we will explore. Maybe we only need a post-build inspection.
Either way, this part must be verified before the astronaut, or robot,
attempts to replace the part within a system.

Ernst, I agree with your comments.


Muniz Engineering Inc.
In Situ Fabrication and Repair (ISFR)

-----Original Message-----
From: []
Sent: Tuesday, December 28, 2004 6:00 AM
To: Anshuman Razdan
Cc: Good, Jim; Marshall Burns;;
Subject: RE: [rp-ml] FW: Geometric Accuracy of RP parts

Hello RP's,

The RP system has to have a reasonable cost of ownership to be successful.
If the build process of a RP system has to be based on a built in scanner
to receive accurate, reliable and consistent parts, this RP system has no
chance on the market.

The problem comes if the part is removed from the RP system, has to fit
into the existing assembly and perform the needed functionality. Then a
measuring system can define the deviations between the build versus the
designed form or define the modifications needed to perform the needed
For simple parts, a CMM is a good solution. If the part is complex, with
free forms, warped or bended, a scanner is usually preferred to understand
the problem (3D color plot with selected deviation flags) and get it fixed.

Then depending on the selected measuring technique, the specific
preparations have to be done to get data fast and in good quality (e.g.
built a fixturing for the part on a CMM or dull shiny or transparent parts
for scanning).

I do not fully agree with the statement: "it depends on the tolerance", it
depends much more on the part, the available time and the application.

We wish you a happy new year, with best regards

Ernst Müller
GOM International AG
Bremgarterstr. 89b Tel. ++41 56 631 04 04
CH - 8967 Widen, Switzerland Fax:++41 56 631 04 07

             Anshuman Razdan
             Sent by: To
             owner-rp-ml@rapid Marshall Burns
    <>, "Good,
                                       Jim" <>,
             28.12.2004 05:48 cc
                                       RE: [rp-ml] FW: Geometric Accuracy
                                       of RP parts

It depends on the tolerance. Laser is good, but requires dull surfaces for
best results. Any sharp angles or shiny metal will throw it off. There are
other metrology techniques but they are not fast. Speed vs accuracy is the
age old problem.


      -----Original Message-----
      From: [] On
      Behalf Of Marshall Burns
      Sent: Monday, December 27, 2004 7:57 PM
      To: 'Good, Jim';
      Subject: RE: [rp-ml] FW: Geometric Accuracy of RP parts


          This is a very important idea you're looking into. I don't have
      specific recommendations of scanners for you, but just thought I'd
      chime in about the concept. Even in a terrestrial application, it's
      this kind of thing that will provide the feedback to ensure that a
      fabber is on track, and let it make mid-course corrections. It's
      obviously that much more critical in a remote application, like

          I'd be interested to learn more about your project as it

      Best regards,
      Marshall Burns

      -----Original Message-----
      From: [] On
      Behalf Of Good, Jim
      Sent: Monday, December 20, 2004 13:45
      Subject: [rp-ml] FW: Geometric Accuracy of RP parts
      I thought I would throw this out. I am looking into inspection
      equipment that will verify the geometric accuracy of my RP part,
      after fabrication, and actually during fabrication. I've looked at
      laser scanning and got some good input already. I'd like everyone's
      opinion on what system they are using and what they believe to be the
      best system to verify geometric accuracy. The ultimate goal is to
      build a fabricator that contains an integral inspection station.
      This system would be used in space for repair and fabrication of new
      parts. Any thoughts?


      Jim Good

      Muniz Engineering Inc.
      In Situ Fabrication and Repair (ISFR)
Received on Wed Dec 29 14:42:37 2004

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