Stereolithography services proliferate.

Stereolithography Services Proliferate 

Being competitive in manufacturing today often depends on getting to market first. Part of the process often involves building prototypes for testing and analysis--as well as to see how a product will look "in the flesh." New rapid prototyping techniques such as stereolithography from 3D Systems, Inc., Valencia, Calif., have garnered lots of attention because of their ability to take concepts "from art to part" in a matter of hours (see PT, Feb. '89, p. 78). Stereolithography quickly and economically converts CAD designs into plastic prototypes.

Its dramatically new potential has spawned a fast-growing brood of so-called service bureaus, which will provide stereolithography prototypes to order, perhaps as part of an overall part or tool design and development project. 3D Systems, Inc. of Valencia, Calif., the first firm to bring the technology to market, has sold over 140 units of its stereolithography apparatus (SLA)--many of them to "Fortune-500" firms that plan to use them for proprietary purposes, and about 30-40 systems to new companies that have set up as service bureaus. Plastics resin suppliers are also starting to get into the act: Allied-Signal's Engineered Plastics unit has an SLA in its new design and development group, called Modulus, which provides assistance on applications using any type of plastic--not just Allied's own. And Dow Plastics is considering buying an SLA for its Materials Engineering Center in Midland, Mich.

CHOOSING A SERVICE BUREAU

Processors can benefit from using such service bureaus (see Processors' Page section), but there are some important points to consider beforehand.

The SLA accepts CAD data only in 3D format. A problem is that most CAD users are still working in 2D, so their systems can't interface with the SLA. This means work submitted to service bureaus either as blueprints or files from 2D programs must be converted into a 3D database. Customers bear the additional cost. The conversion process often takes more time than the SLA takes to build the physical model.

James Bednar, operations manager at Prototype Services, Inc., a Chicago service bureau, says the stereolithography process involves programming 30 to 40 variables. "No two service bureaus are likely to select exactly the same variables," says Bednar. "It's likely that if the same database is presented to 30 different service bureaus, they would come up with 30 different models." Many of these programming variables involve a trade-off between quality and cost. It's possible that these choices could be made for the user and not by the user, so close communication with the service bureau is important. Bednar says that proper selection of programming variables and proper handling of the "green" part immediately after processing depend on comprehensive knowledge and experience with stereolithography. Because of the variables involved, price and delivery time may be unreliable criteria for differentiating between service bureaus. Bednar also recommends that prospective users of a stereolithography service bureau (SB) consider the following when making their selections:

* What modeling software does the SB use?

* What are the qualifications of the SB's CAD operators? Are they degreed engineers? How long is their experience and on what systems?

* What design considerations are vital to producing a part within dimensional tolerances in the x, y and z directions?

* What issues are involved in part orientation?

* Can the SB provide design verification before making a part? If so, how?

* What is the range of software/design services provided?

* With 30-40 variables available, what are the most important issues the operator must be concerned with in programming the SLA computer control?

* How are parts cleaned to avoid damaging surfaces?

* How is part curing performed to avoid warpage?

* What range of overall part accuracy is promised? How is tolerance accuracy verified?

* What are the qualifications of the post-processing operator?

* What secondary processes can the SB provide, both directly and indirectly?

* Does the SB have a published quality-assurance program? Is it available for inspection?

* What are the SB's confidentiality procedures?

* Will the SB provide customer references or at least a customer list?

PHOTO : An auto company evaluated over 30 SLA service bureaus before selecting Prototype Services

PHOTO : to make this part for a dashboard instrument panel. Producing a part requires programming

PHOTO : 30-40 variables, involving trade-offs between quality and cost. Given the same database,

PHOTO : it's unlikely that two service bureaus will produce exactly the same part.