Re: Message by Mark K. Smith
Rapid Prototyping and Reverse Engineering
Mon, 2 Dec 1996
I would like to introduce myself to you and the rest of the RP-ML
My name is: Gerald K. Stevenson Sr.
GKS Inspection Services, Inc.
37100 Plymouth Rd.
Livonia, MI. 48150
Phone: 313 953 9696 Fax: 313 953 9635
I have been providing Inspection and what you would call “Reverse
Engineering “ services for industry for over 15 years.
I am currently waging a one man campaign to change the above term to
“FORWARD ENGIEENRING”. In every case with out exception I am moving
my clients forward in the product or process development cycle.
I’ve taken the liberty to divide the process of Forward Engineering
into two basic categories. The first is CMR or Cad Model
Refinement. This covers creation or adjustment of an existing CAD
model by transfer of information from a 3D artifact to a 3D CAD
The second is PVA Product or Process Verification and Analysis. In
this mode we compare an existing 3D artifact with a valid 3D CAD model.
Each transformation consists of four steps.
Data Collection, Point Processing, Model Refinement, Verification of
Data Collection, Point Processing, Comparison to Model, Analysis of
At our facility we us a plethora of devices for the collection of
discrete usable points. For example we us a 5 axis CNC line laser
digitizing system to scan large components within it’s 5 X 8 ft
volume. We have achieved rates as high as 4.5 million points per hr,
with the average being about half of that figure. We also have a CNC
point digitizer that we program complex paths from an existing CAD model
(but out of date) to scan specific areas of concern to our client.
Small components with complex internal geometry maybe processed on our
Automatic Cross Sectional Scanning System. The working volume is
relatively small but it is capable of collecting very dense data sets on
highly complex parts. Other devices such as CMM’s and CNC Vision
systems are also utilized by our staff as well.
Data is processed at GKS with three different software packages.
Some times it is necessary to use all three concurrently and have our
staff developer create additional code to speed up the process.
At this stage many things happen to the data which are too numerous to
detail here, mostly to do with organization, reduction and definition.
Typical outputs are: Toolpaths, Polygonal Meshes, Nurbs Curves, and
At this point the output from point processing is sent to the owner of
the CAD model and the appropriate changes are made.
Verification of Result:
Once the CAD model has been changed the original scan data set can be
compared with the updated CAD model to verify continuity through out the
measurement process. ( Yes we are measuring !)
Comparison to Model:
Product verification is accomplished quit well once the scan data sets
have been aligned by what ever method, best fit or other wise. We
have even done correlation studies between these new measuring systems
and established methods such as CMM’s with contact probes.
Analysis of Result:
This is the most important area of product verification, where decisions
are made to change a product or process. We work very closely with
the client to establish an understanding of what he’s trying to
accomplish. This is necessary so we can present the data in the best
format enabling the customer to clearly understand his own product or
I hope this gives you some idea of what is involved in Forward
Engineering. This my first day as a visitor to the RP-ML. I have not
had time to read the entire archive yet. I apologize if I have been
redundant or tend to get long winded, how ever I am willing to share as
much information as you can tolerate with respect to dimensional
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