Initial Prototyping

3M began this phase by creating stereolithography (SLA) patterns with its in-house SLA equipment. Overflow SLA work was sourced to Vista Technologies. The SLA prototypes were used by engineers and industrial designers to check fit and form. The same prototypes were used by 3M packaging engineers to create conceptual mock-ups of product packaging. They also made excellent tools for ergonomic and usability studies.

To mimic the soft under pad of the sanding tool, Vista used PolyJet(TM) rapid prototyping technology. PolyJet was chosen because it can use either of two soft-durometer (a hardness measurement) materials that can be run to gain similar quality parts as SLA technology. TangoBlack, a material with a score of 61 on the Shore A durometer scale, was the best fit. Within days Vista was able to supply 3M with their simulated soft-durometer under pads for more testing.

The bottom pad for the hand sander was prototyped using TangoBlack material from the Polyjet technology. This material is a 61 Shore A material that mimics the properties of santoprene.

At the same time, a gripping/tensioning mechanism for the sanding media was being developed. At this point, the sub-assemblies were merged into a refined set of CAD databases. Additional SLA parts were created to evaluate the new mechanisms. With each new prototype, the team was able to investigate new features in the design. Because these rapid prototype parts could be created cost-effectively in a matter of hours instead of days or even weeks, the team had the ability to study complex forms and details in a manner not possible using traditional machining and fabrication techniques. In some cases multiple iterations were generated in one or two days.

On the left is the hand sander from the prototype tool and the hand sander on the right is from the production tool.

Second-Generation Rapid Prototypes: More Realistic Simulations
In the second generation of the prototypes, 3M needed the hinge function and material properties to be simulated more realistically. After a few design changes were made to the CAD data, Vista Technologies supplied 3M with a Fused Deposition Modeling (FDM) prototype.

The FDM part, made from extruded black ABS, allowed for more robust testing and provided similar specified material properties in weight and strength as the final part would have. This prototype was able to handle a variety of tests that allowed 3M to modify their design before production tooling was released.

Rapid Tooling Takes Over

Once 3M completed its work with prototypes, it was time for rapid tooling. Vista Technologies quickly created aluminum tools. Milled at 42,000 rpm with high-speed milling technology and a proprietary fixture system, these tools were made for quick turns and quick modifications.

A core and cavity of a 1+1 family tool of the hand sander top handle. The mold finish is as machined.

The aluminum tools could be modified, polished, textured, welded on, and were capable of shooting 10,000-plus parts. Vista Technologies supplied injection-molded parts within two to three weeks of usable CAD data. By getting specified material parts in hand, 3M could complete their required testing.

A computer rendering of the hand sander concept before prototyping.

The rapid tools supplied by Vista Technologies were for multiple parts that made up the sanding products. The parts were made in family tools–meaning several related parts were made in the same tool. By adding runner shut offs to the tools, 3M could turn on or turn off certain parts of the tool–thereby making only the parts they needed. This kept costs down while minimizing wasted material in extra mold inserts. The molds were made with hand pick-outs and manual slides to capture several undercuts in the part design.

3M chose the rapid tooling approach because it allowed them to quickly evaluate different part features and molding parameters. Tooling changes could be completed and parts resampled for evaluation in just a few days. This was a tremendous advantage to 3M.

From an engineering standpoint, they were able to sample several materials for strength and repetitive testing. They were also able to compare the functionality of various latch mechanisms and to check material flow and gate locations (points where material is injected into the tool).

A close-up of a production 3M hand sander. Many methods of rapid prototyping and rapid tooling were utilized before production tooling was released.

A 1+1 aluminum mold showing the handles molded in different colors for marketing review.

From a marketing standpoint, along with sampling different materials, they also were able to mold parts in a variety of colors to get important feedback from focus groups. By the time databases were released for production tooling, the mold designs had been optimized and the material and color strategies were in place.

By using rapid tooling, 3M discovered many things in the functional prototypes before cutting production tools. The gating was changed on the production tool, the snap-fit features were redesigned, the handle was modified and ultrasonic energy directors were added for sonic welding of parts in final assembly.

Summary

As rapid prototyping and rapid tooling technologies become more sophisticated, the importance of picking the correct technology for product applications can be critical to gaining a competitive edge. As 3M found, a combination of RP and RT technologies and materials helped them save money, speed development time and establish a foothold in the marketplace.

Owner of Mold Making Technology

Advisor to Rapid Tooling

Article Source: http://EzineArticles.com/?expert=Dan_Mishek

For those involved in product development, engineering, and other form-giving applications, rapid prototyping (RP) technology can offer an excellent deliverable for various applications. Prototyping can be used for concept generation, ergonomic testing, test fitting, functional testing and even small-batch production.

There are various rapid prototyping technologies available for use including Fused Deposition Modeling (FDM), Stereolithography (STL), Selective Laser Sintering (SLS), and 3D Printing. Each of these technologies has advantages and disadvantages.

Fused Deposition Modeling technology is marketed commercially by Stratasys, which also holds a trademark on the term. Like most other RP processes FDM works on an “additive” principle by laying down material in layers. A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion nozzle which can turn on and off the flow. The nozzle is heated to melt the material and can be moved in both horizontal and vertical directions by a numerically controlled mechanism, directly controlled by a computer-aided design software package. In a similar manner to stereolithography, the model is built up from layers as the material hardens immediately after extrusion from the nozzle.

Stereolithography is an additive fabrication process utilizing a vat of liquid UV-curable photopolymer “resin” and a UV laser to build parts a layer at a time. On each layer, the laser beam traces a part cross-section pattern on the surface of the liquid resin. Exposure to the UV laser light cures, or, solidifies the pattern traced on the resin and adheres it to the layer below.

Selective laser sintering is an additive rapid manufacturing technique that uses a high power laser to fuse small particles of plastic, metal, ceramic, or glass powders into a mass representing a desired 3D object. The laser selectively fuses powdered material by scanning cross-sections generated from a 3D digital description of the part on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.

3D printing is a unique form of prototype creation that is rooted in traditional rapid printing technology. A three dimensional object is created by layering and connecting successive cross sections of material. 3D printers are generally faster, more affordable and easier to use than other additive fabrication technologies. While prototyping dominates current uses, 3D printing offers tremendous potential for retail consumer uses, especially because the cost of production is less than other methods, and the part build time is minimal. In the latest incarnations, 3D color printing is also available. This means that a part can be printed to represent the colors of the finished product, to show label concepts or requirements, or to indicate the results of stress analysis or other failure mode effects (FME) analysis.

For the most part, all rapid prototype systems require a 3D computer model to start the process. In most cases a significant amount of file preparation must be undertaken to get a file to generate a correct rapid prototype model.

As part of the innovation process, some companies may employ one or several rapid prototyping technologies in-house. However, being a new “cutting-edge” technology, many firms can make use of service bureaus to provide their rapid prototyping as the need becomes evident. Most service bureaus have detailed websites to market and serve their customers.

A handful of service bureaus are fairly large companies with numerous employees and locations. Many provide related services and technologies, such as tooling, industrial design, molding and production. However, service bureaus are typically small companies, and while they may be small, many of them are vertically integrated and can provide services from concept models to finished functional parts.

Service bureaus tend to specialize in one or more areas such injection molding, casting, etc. Examine a company’s portfolio or case histories on their web pages, or discuss previous projects with the company to try to better understand areas of particular expertise. Sculptors have also used the technology to produce complex shapes for fine arts exhibitions.

In the near future, rapid prototype technology will become more widespread and pervade even to the home. For now though, for timely and expert delivery, the use of a service bureau is the best way for most innovative companies, individuals and organizations.

About The Author

Geoffrey Brennan