Machine Design

When to outsource rapid-prototyping work

And several tips for picking a vendor.

Jeff Hanson
Applications Engineer & Sales Manager
Eden Prairie, Minn.

The Web site lets users select rapid prototypes based on factors such as cost and geographic location. After users register (at no cost), they can upload an .stl file. The site offers all major rapid-prototyping technologies.

An .stl file of a machining fixture (upper left) was uploaded to Quotes from about 10 RP contract manufacturers using different technologies come back in seconds.

Price tags for rapid-prototyping equipment range from $25,000 to $1 million, so you'd think there are models for every company and application. Not exactly. Many companies have just not made rapid prototyping part of their design strategy. For these, outsourcing is the only option to gain what RP offers. Even for companies with RP equipment, outsourcing can play a role.

Companies often enlist the services of a qualified RP service bureau when:

Demand outstrips capacity. Demand for prototypes rises with the release of each new project. Instead of having excess machine capacity to handle peak loads, use outsourcing to meet department needs.

An application is best suited to a different technology. The first RP machines produced parts of brittle plastic. Modern equipment, however, can produce parts in real production plastics, metal, and tougher photopolymers. Others can produce telltale colors on a model, such as stress levels from some loading. But a different machine is needed for each.

The application needs several materials. Keeping multiple materials on hand can be costly, and switching a machine from one material to another can be time consuming — up to half a day in some cases. When you don't have the right material, let an RP vendor supply the needed parts.

The outsourced part serves as a test drive of equipment before a purchase. Demos and benchmarks don't tell the whole story. Learn what RP technologies can do by outsourcing prototype work to a shop using the same machine you're considering purchasing. The service bureau supplies the prototypes for product development while demonstrating turnaround time and capabilities.

Other considerations are that contract RP firms provide financial flexibility. In-house RP systems have fixed expenses for equipment, labor, and facilities. Outsourcing the occasional over-flow and its cost becomes a variable expense that can be managed within the budget.

To select a rapid-prototyping vendor, ask about:

  • The firm's capacity. Make sure the vendor has machine capacity to deliver quickly at all times. A vendor with one or two systems may not be able to handle large orders or may be backlogged with work from other customers.
  • Desktop estimating tools. Prototyping decisions hinge on answers to questions such as, "How much will it cost and how long will it take?" Few have the time to search for answers in the midst of a looming deadline. For quick "what-if" scenarios, look for a vendor that offers quick quotes right from a desktop PC.
  • Latest materials and a wide selection. Some vendors may not offer the latest in RP materials and may have a limited selection due to stocking costs. Vendors with a broad selection of the latest materials put fewer constraints on a design.
  • Multiple technologies. Because you expect a vendor to fill an RP technology gap, look for a company with multiple processes — machines from different vendors. Those with more than one RP technology are also more likely to recommend the best solution instead of just what they have available.
  • Equipment maintenance and service. In general, prototype prices have tumbled while repair and maintenance expenses have risen. As a result, some vendors have cut back on preventative maintenance and routine repairs, which may lead to inaccurate models. Most equipment manufacturers suggest preventive maintenance, so ask potential vendors about their maintenance schedules.
  • Offer advice and consultation. Will the vendor help you to pick the right RP process and material? Can they offer advice on finishing processes and secondary operations? The most useful vendor is one that is also a partner and advisor.
  • Well-run organization. Look for professional, established companies that are managed and run as real businesses, not garage-based operations.
  • Stand behind their work. Ask the vendor about their policy regarding prototypes with quality problems. These can arise when delivering one-off custom items in only a few days. The best companies offer a no-questionsasked policy for rebuilds or repairs.
  • Hours of operation. Crossing time zones and working longer than 8 hr/day calls for a vendor with extended hours of operation. Ask when the support staff is available to respond to inquiries. Also, ask if the RP equipment operates 24/7 and determine when orders must arrive to get into the day's queue.

A Few Properties For Rapid-Prototyping Materials

Tensile strength, Type 1 psi, ASTM D638
Tensile, elongation, Type 1 (%)
Flexural strength ASTM D790 (psi)
Specific gravity, ASTM D972
PC-ABS blend
Polycarbonate ISO
FurCure 700

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