Reverse Engineering In Practice

Last month, I described reverse engineering as a process in which parts are carefully measured and tolerances are developed prior to generating CAD drawings. The most common application for reverse engineering is the reproduction, or modification, of an existing part for which there is no formal drawing.

Columns From: 3/1/1998 Modern Machine Shop,

Last month, I described reverse engineering as a process in which parts are carefully measured and tolerances are developed prior to generating CAD drawings. The most common application for reverse engineering is the reproduction, or modification, of an existing part for which there is no formal drawing.

NVision in Irving, Texas, has reverse engineered many products for its customers. In its reverse engineering process, NVision has employed multiple scanning methods to capture part geometry. By using high-end point cloud processing software, NVision personnel convert scanned data into an IGES surface model. The surface model can be directly imported into a CAM program, or it can be converted to a solid model in CAD applications.

One of NVision's customers needed to quickly modify and reproduce existing drill forgings that were designed without CAD models. NVision staff laser-scanned and surface-modeled the company's wooden drill forging models to a tolerance of less than 0.001 inch. The surface models were run through a CAM system to convert the data to solid models, which were used to create forging dies. The customer was then able to reproduce drill bits quickly and efficiently.

Active Applications, located in Macon, Georgia, has been using reverse engineering techniques to help its customers for many years. Company president Ron Turpin says that his associates "get completely outside the box" when trying to help customers design or modify parts.

In one instance, Active Applications dealt with a local textile manufacturer that was having trouble with a faulty seal on a piece of heavy machinery. The Active Applications team reviewed the seal design and recorded all dimensions. Once they accurately captured the key features of the seal, the team analyzed the operation of the machine and set out to modify the seal so it would not break under operating conditions. With a CAD model to work from, Active Applications redesigned the seal and provided the textile manufacturer with a complete design specification. The new seal was 30 percent cheaper, more reliable and much easier to manufacture.

Gaspardo and Associates, in Batavia, Illinois, has found a niche in delivering reverse engineering services to its customers. The company uses a special milling machine to face-mill thin slices from a part. As the milling machine cuts these slices, it scans dimensional information and creates a point cloud. According to Gaspardo's Eric Poss, this machine allows them to capture internal and external features very accurately because the machine provides a very dense point cloud.

"When we have needed a large amount of detail, we have cut parts in increments as small as 0.001 inch," says Mr. Poss. "Typically, however, the face mill cuts are between 0.010 and 0.050 inch."

Gaspardo has used this milling machine to reverse engineer a variety of products including valves, impellers, eyeglass frames and tennis shoe soles. Mr. Poss claims that his company's reverse engineering process offers many advantages to customers. For one, the process provides a simple report that is actually a color map analysis of the part. This is much shorter (usually two pages) and easier to understand than a CMM report.

At the Center for Manufacturing Systems (CMS) at the New Jersey Institute of Technology in Newark, New Jersey, we have used reverse engineering techniques to assist small manufacturers in developing formal part specifications. One small machine shop had been making a part for one of its customers for so long that it no longer had a formal blueprint on the premises. The machine shop's customer did not have a copy of a blueprint either and needed one as part of the documentation requirements of ISO 9000. What the machine shop did have was an accurately machined sample part.

The CMS staff took the part and used a CMM to determine all critical dimensions. Required tolerances were then calculated with the assistance of the machine shop's chief machinist. The part drawing was completed using solid modeling software.

Not everyone can afford high tech equipment; however, if you have accurate measuring tools and a basic CAD system, you can offer reverse engineering service to your customers.

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