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Quickly moving from complex prototype to CAD model to finished product is the key to competitiveness.
Larry Carlberg Published: 07/07/2009
You have a carefully crafted clay prototype made by a top design artist. Each detail is exquisite and you want to make sure every last one is molded into the finished article. Contact measurement isn't an option, because the piece is too complex and too malleable for touch probes. You need computer-aided design (CAD) data of the entire part so it can be reproduced as soon as possible. How can you quickly and accurately digitize your intricate free-form shape and then fabricate it on a condensed timeline?
One problem all product designers and engineers face is how to manifest their design vision in physical form, and how to do it as time efficiently as possible. While designing products in the many CAD programs available may work for some types of parts, others require a good old-fashioned prototype that can be held, tested, and “tweaked” in the real world before taking on its digital version for today’s computer-driven manufacturing processes.
However, these one-of-a-kind prototypes or models are difficult to digitize quickly, accurately, and cost effectively with traditional contact-measurement methods. To compete in our fiercely competitive economy, coupling laser scanning with rapid manufacturing is one method of fabrication that can skew the odds of success in favor of its user, slashing days, weeks, or even months from the manufacturing process. It offers a quick, low-cost way to make usable parts from a one-of-a-kind prototype for testing purposes, mass customized items, or short-run production cycles, and is quickly gaining popularity with designers and engineers in many industries where the first-to-market advantage may be the difference between product success and failure.
Rapid manufacturing definedRapid manufacturing (RM) is an additive fabrication process in which parts are built from the ground up rather than cut or milled away to create the shape. This means that complex geometries can be produced without the limitations of conventional molding or manufacturing processes. Some surface finishing work may be done after the build depending on how the finished piece will be used. RM systems have improved significantly in the last several years with larger build volumes. More progress is expected in the future, with accuracies and strength of RM parts becoming comparable to molded plastic parts.
Another process considered RM is computer numerically controlled (CNC) machining, which is a subtractive rather than an additive process. A solid block of plastic is milled or cut into the finished shape on a CNC machine. This method of RM produces the strongest parts with the best surface finish because it starts with a solid material, not additive layers.
The operational word in any rapid manufacturing method is, of course, “rapid.” Because nearly all manufacturing processes, including RM, currently require a CAD model of the part, prototypes must be quickly digitized to benefit from the competitive advantage RM can bestow. Working hand-in-hand with RM systems to capture the part’s shape digitally is ultra-fast 3-D laser scanning.
Laser scanning speeds RMNoncontact laser scanning is especially well suited to scanning complex, free-form shapes, and organic, amorphous geometry often found in prototypes made from clay, foam, wood, and other soft materials. Laser scanning’s noncontact nature eliminates any distortion a touch-measurement method would introduce.
The laser scanning system projects a line of laser light onto all of a part’s surfaces while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along, greatly reducing the problems of missing data on irregularly shaped surfaces. The laser line moves back and forth over the part until the entire area is captured. The system measures details and complex free-form geometry so the object can be exactly replicated digitally in a point cloud of data points. Laser scanners measure articles quickly, picking up to 75,000 coordinate points per second. They generate a large quantity of data points without the need for special templates or fixtures.
Laser scanning is ideal for reverse engineering complex parts into CAD models because the whole surface of the object is scanned, not just a limited sample of discrete points, as with contact measurement. Parts can be modeled “as is” for exact replication or the original design intent of the prismatic shapes can be extracted even if the as-built prototype part is warped or misaligned. When taken into a solid modeler software package, the history of the model is available to designers, so any version may be referred to at any time in the remodeling process. Design changes or variations can then be easily made and documented.
After the laser scan is complete, the point cloud of millions of data points is converted into a polygon mesh STL file which can be fed directly into the RM system to create the high-accuracy part in a very short timeframe. Scan files can also be directly programmed into CNC machines to create toolpaths. Using laser scanning to capture and digitize a prototype shape into CAD creates a seamless manufacturing process from design to modeling to fabrication.
Companies that specialize in the RM technology known as 3-D printing use engineering quality materials for fabrication, so the rapid prototypes are functional. Although many quality improvements have been made to the end results over the years, RM is usually feasible only for prototypes and short manufacturing runs. Using another process, CAD models can create a “negative” of the part to cut molds for making cost-effective short-run prototypes via CNC machining and rapid injection molding.
A major benefit of using RM for the prototyping and product-development process is that it does away with most of the time-consuming and expensive manual labor. Only one model is hand crafted and it's quickly laser-scanned to create a CAD model. Physical iterations and recrafting steps are eliminated.
If any modifications are needed before going to the rapid prototyping or testing phase of the physical object, they can easily be made in the CAD modeling software. The product that comes out of the RM process incorporates all the changes and improvements that were made digitally, but were impossible to fashion in the hand-made prototype model.
Mass customization: An early adopter of Laser Design’s laser scanning systems was the hearing aid industry. Hearing aids are all similar in size and shape, but each one has unique details to fit an individual’s ear canal. Hearing aids are made from distinctive ear impressions, which are created in the field by audiologists and sent to a hearing aid maker. In the past, the final product was manufactured using a very labor-intensive manual process.
With the fully automated Laser Design laser scanning system, the ear impressions of hearing aid users are scanned in minutes. The system sets automatic scan parameters since the ear impressions’ size is quite uniform and then uses specialized software to process the scan data of the impressions into the digital model of the ear shell in a fraction of the time it used to take. The model is fed directly into the rapid prototyping (SLA or FDM) machine to manufacture the ear shell for each unique hearing aid, in effect, mass customizing the product.
This noncontact process significantly improves the fit of the aids inside the ear canal. A better, more comfortable fit resulting from automated, yet customized laser scanning reduces the chronically high return rates for the devices, which saves the hearing aid company many thousands of dollars every day.
As additive RM machines become more advanced, many more such custom applications will be developed, saving companies time and money while maintaining quality. Industries where complex individualized parts are the norm, such as medical, dental, consumer products, and many more, will especially benefit from this rapid fabrication technology.
Toolmaking: Manufacturers have also starting adopting RM to produce aids to the fabrication process such as fixtures and assembly guides. Because the cost of rapid-manufacturing parts is low, financial risk is minimized when companies decide to retool or redesign their lines. New RM parts can be made quickly and inexpensively, and if needed, redesigned and easily remade.
Need for speed: In a pinch, RM parts are sometimes used if an assembly needs to be complete and deadlines loom, or if only a few parts are needed, as tooling for long-run items is very expensive. While not yet at the same level of strength or durability as traditionally manufactured parts, RM parts are gaining ground. Of course, laser scanning can quickly generate the CAD data needed for rapid part production keeping projects on schedule and costs under control.
Many industries, such as the military, automotive, and aerospace, have already adopted RM methods for layer-based manufacturing of large and small products from plastic resins, metals, and composite materials. Medical, dental, consumer electronic devices, and many more small product manufacturers have also begun to take advantage of the speed and cost-effectiveness of RM. Laser Design has laser-scanned many items, large and small, for these applications. With the seamless integration of laser scanning output to the RM system, no other method of CAD generation is more efficient.
Rapid manufacturing delivers customized products with speed and accuracy. Prototypes, individualized items, and small volume runs are the perfect application of RM, and when combined with laser scanning, the time efficiency can’t be surpassed. With the constant need to innovate and be first to market with new products and inventions, RM through laser scanning model generation can give manufacturers a truly competitive edge.
Larry Carlberg is general manager of GKS Inspection Services. He has a B.S. in Civil Engineering and 30 years experience as a pattern and model maker. Product development has been a major part of his entire career, including patterns, molds, and RP models for the medical, aerospace and consumer products. Carlberg joined GKS Inspection Services in March of 2002, integrating the unique combination of laser scanning technology with rapid product development services. Larry offers companies key advantages by using GKS Inspection Services to gain a competitive edge, cutting product design & production costs.
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