Mass Production Out, Mass Customization In

Aug. 21, 2008
New software and rapid manufacturing foster custom products on demand.

Who, what, where
ISIQU Orthopaedics
By Kenneth Korane [email protected]

Mass production has been the lifeblood of manufacturing for the last hundred years but it may have outlived its usefulness, according to officials at Delcam plc, a CAD/CAM software developer based in Birmingham, England.

“In many cases, there is an oversupply of similar products,” notes the company’s Peter Dickin. “Design ideas are easily copied, and companies can be drawn into price wars, where quality is sacrificed to reduce costs.

“Add to that the rise in individualism. Customers have become more affluent and demand more choices — they want to be treated as individuals, not part of a crowd. Mass production struggles to keep up with changes in fashion,” he adds.

In the past consumers may have had little choice but to accept what was on the shelves, but technology is changing the rules of the manufacturing game, says Dickin. 3D CAD has made complex design easier and quicker. Rapid prototyping makes one-off parts practical, in many different materials and often overnight. Advances in high-speed machining mean speedier production of parts and tooling. And five-axis machine tools produce complex shapes in a single setup, he says.

As a result, a growing trend is mass customization, which aims to give manufacturers more flexibility without losing the cost benefits of mass production. Among the many possibilities:

  • Cars and motorbikes built on a common platform but with individualized design details.
  • Sporting goods matched to the player for ultimate performance.
  • Orthotic, orthopedic, dental, and surgical products tailored to the individual.
  • Different logos and decorations on the same consumer product.

Software tools
Delcam has tailored its software to facilitate mass customization. The company’s design tools include PowerShape, a surface and solid modeler; CopyCAD for reverse engineering; and ArtCAM for decorations, textures, and other custom details.

The problem in the past, says Dickin, was engineers had to work with three separate programs. “We’ve now integrated the products so they’re easier and quicker for the designer,” he says. It combines three capabilities in one package, which Delcam calls “tribrid” modeling.

Surface modeling generates complex shapes, but is traditionally difficult to use, explains Dickin. Solid modelers came along because they’re faster and easier to learn, but a bit restricted in the geometry they can handle. “Hybrid modeling combines the flexibility of surfaces with the speed of solids, and is pretty much an industry standard these days. Tribrid modeling adds a third element which is much more unusual, triangle modeling,” says Dickin.

Tribrid modeling lets users reverse engineer custom elements of a design and add them to solid CAD models. Basically the process takes details specific to an individual and combines them with a standard product where a high percentage of the features, perhaps 90%, are common in all versions.

This lets designers move data captured with reverse engineering into designs more easily and quickly than in the past. However, tribrid modeling does not simply patch together existing programs, Delcam officials stress. The company has also enhanced several key operations.

For example, improvements have been made to the sculpting and model-repair tools previously available in CopyCAD to edit triangle files. The tools let engineers make high-quality models from poor-quality reverse-engineered data, or from damaged or defective physical components. For instance, it can smooth uneven surfaces, fill gaps in the data, and add extra points in areas where only sparse data has been collected.

Most importantly, combining PowerShape and CopyCAD capabilities generates more-accurate CAD surfaces from triangle data. Users still control the data that govern component features and surfaces. But each area can now be converted to CAD data by generating a network of curves and then projecting it onto the mesh of triangles.

PowerShape’s Smart Surfacing function then analyzes the curves and determines the most appropriate way to generate a single surface that includes the complete set of curves.

The other key benefit of integrating triangle modeling into Power- Shape is the ability to create “perfect” geometry in areas where reverse engineering would give only approximate results. “For example, reverse-engineered fillets always have variations in radii along their lengths. PowerShape lets users quickly replace them with consistent, smooth fillets. The key is being able to make perfect models from imperfect data,” emphasizes Dickin.

There are also many cases where engineers need a combination of techniques to complete a design. A typical example is in the plastics industry, where initial prototypes are often hand-modeled in solid material. Reverse engineering from such models only produces the external surfaces. However, PowerShape can offset these surfaces by the material thickness to generate internal surfaces. Extra geometric features, such as reinforcing ribs and fixturing bosses, can then be added to complete the model.

A similar approach can be taken when developing new parts that are, in fact, variations on existing components that were developed without CAD data. It is often quicker to digitize existing parts and limit CAD work to the desired modifications, instead of completely recreating entire parts with CAD.

Custom products
In surgical applications, ISIQU Orthopaedics, Cape Town, South Africa, is using tribrid modeling to replace cancerous limbs as an alternative to amputation.

The company starts with a digitized 3D scan and basic dimensions of the affected area to guide design decisions. The process converts a CT bone scan to an STL file and then imports it into reverse-engineering software that converts it to a surface model. This generates a digital model of the skeletal part that will be replaced with an implant. Surfaces from the software, or dimensions from X-ray or MRI scans, are imported into CAD software to complete the implant’s design. The final design goes to CAM software that generates NC toolpaths, and the custom part is produced on a five-axis DMG machine. The entire process takes only a couple days, according to ISIQU officials.

Delcam also is working with Ducati, Bologna, Italy, on custom motorbike seats that reportedly offer more comfort. Scanning equipment measures the rider “in the appropriate area,” says Dickin; the data is used to develop a CAD model for a custom seat; and individualized cushions are manufactured with rapid-prototyping equipment. A similar effort involves motorcycle helmets that are said to maximize comfort and safety.

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