Top 10 Considerations when Ordering Prototype Plastic Parts

Whether you're an experienced veteran or a first-time user of prototype plastic parts, it's a good idea to make sure you're up to speed on the latest tools and techniques.

1. Understand your technical requirements.

The first step in ordering prototype plastic parts is to fully understand the basic technical requirements for your part—form, fit and function. To understand form and fit requirements, you will need to consider geometric details such as size, required dimensional accuracy, desired level of cosmetic appeal and possibly even the prototype's color.

To understand functional requirements, you must know the environment in which the part will work. This typically involves operating temperatures and material strength properties (e.g. tensile strength, hardness, etc.) for a particular application. Also take into account the number of prototypes you require to determine which method best fits your needs.

2. Know your project's business constraints.

Budget and schedule limitations can drive the selection of a particular prototyping method or supplier. If you need a few prototypes overnight, several RP technologies and suppliers can provide that service. If you need fully functional prototype parts and your turnaround time is a week, rapid injection molding (RIM) may be your best option.

3. Match your requirements to key prototype development capabilities.

Understanding each processes' specific capabilities and limitations is important in achieving prototype parts that meet your requirements.

For example, RP is best used for obtaining complex shapes in low quantities and very short leadtimes, typically one to ten parts and one to five days, respectively. If you need ten to one hundred prototype parts and have five to ten days, an RP-based RT process may be appropriate. If functional testing is planned, rapid injection molding an accommodate twenty-five to one thousand production-quality parts in a timeframe of five to fifteen days.

"It's important that design engineers evaluate the different prototyping processes available and match the appropriate process to their specific requirements," says Henry Baum, manager, mechanical engineering at Sunnyvale, CA-based Harmonic, Inc. "For example, RP allows a designer to become comfortable with a part's design while RIM allows testing and validation of functionality."

4. Make sure your design fits your prototype-creation method.

Napkin sketches or 2-D drawings are fine for developing a general design concept, but these formats won't provide enough data to take advantage of the online quoting and advanced prototype-manufacturing processes available today. Instead, your part design needs to be in 3-D CAD format.

Jason Dickman, co-owner of Tulsa, OK-based American Precision Prototyping, a RP SB, says the advent of 3-D modeling is a boon to prototyping technologies. "One advantage of a service bureau is that it can take a 2-D representation of a product and make it a 3-D CAD model, which can be used for all prototyping processes."

The most commonly used 3-D file formats are STL files, IGES or STEP model data files. Most CAD programs are able to output one or all of these file formats.

5. Select the prototyping service provider with the best qualifications.

Research the provider's ability to meet your basic requirements and solve unpredicted technical problems. This may include obtaining references from past customers, asking about the level of customer service received and the technical expertise of the vendor. It's important to choose a vendor that is willing to educate customers and help make decisions; many customers don't have the advantage of being as close to the technologies as the service providers are.

You also may want to consider vendors with an online quoting system, a convenient tool that may help speed the quoting process. But don't neglect the importance of good service. Working solely electronically may not be the best fit for your project.

"This business is based on personal relationships," explains Terry Wohlers, founder and president of Wohlers Associates (Boulder, CO)—an independent consulting firm for prototyping and rapid product development. "Communicating and offering quotes exclusively online may not be the best answer for some customers, because there are so many variables to understand. A good service provider will understand the complexity of a customer's design, so Web tools should act as support, not a replacement for personal interaction."

6. Protect your design.

Although nondisclosure agreements are standard in the prototyping industry, make sure your service provider is protecting proprietary design information. Providers should never publish information about your project without prior approval. If a provider's terms don't encompass all items you feel are necessary, you will want to initiate your own nondisclosure agreement.

It's also a good idea to limit the distribution of your design information only to vendors that you've chosen to evaluate. This allows you to keep track of who has copies of your design. An alternative to this is to choose a service provider with an online quoting tool that doesn't require you to provide the actual design.

7. Weigh the pros and cons of how to buy your parts.

In the prototype-creation process, there are primarily two types of providers to choose from: brokers and service bureaus, and you should understand the intricacies of each option.

• Brokers generally represent several prototyping services with access to a variety of technologies to meet a wide range of customer requirements. Working essentially as a manufacturer's representative in exchange for a commission or fee, they generally do not own the equipment used to generate parts.
• Service bureaus have the in-house ability to take your 3-D CAD model, manufacture the prototype parts and ship them to you within a few days. Throughout the process, you can communicate directly with the engineers responsible for the quality of your parts.

One thing you shouldn't have to worry about when ordering your prototype parts is the geographical location of the manufacturer.

"With e-mail and online quoting tools, design engineers are no longer constrained by location for fulfilling prototyping needs," said Mike Thursby, senior project engineer, Printek (Benton Harbor, MI), a provider of printer solutions for mobile computers. "Working with a provider five states away is not a complicated process. Although shipping costs may be a bit more, that's a trivial point when considering the project value and importance of turnaround time in our industry. In the end, it's all about finding the right fit for your needs, so you shouldn't be afraid to shop around."

8. Expect the unexpected.

Even if you're clear about expectations from the start, you'll want to be prepared for unexpected hiccups during the prototyping process. Common obstacles include unplanned design changes, technical problems in the prototyping process, or issues involving a part's design or file representation. Most service providers will assist customers through these complications, even if a design change is requested and the part is already being made.

"It's not unusual for customers to call and ask the status of their part just hours after it was ordered because they want to make a design change," says Mike Rufo, president of Design Prototyping Technologies (DPT), an East Syracuse, N.Y.-based service bureau for rapid prototype parts. "If it's already being manufactured, we'll usually just charge for the build time and remake the part with the new design."

9. Don't limit yourself to a single prototype-creation method.

It's not uncommon to take a prototype through stages and use different prototyping methods to meet the requirements of each stage. Specific aspects to consider include planned design iterations, function testing volumes, production validation benefits and bridge-tooling opportunities.

"In some cases, a customer may think they should use one type of RP for all stages of product design and development. Savvy customers know that different technologies are better suited for different design stages," explains Rick Chin, president, Xpress3D (Shrewsbury, MA). "During design, prototyping should progress from fast and inexpensive Z models, to good, general purpose SLA and FDM models, to production-grade RIM."

10. Help is available.

A diverse range of resources can help you learn more about prototype-creation methods, from consultants to Internet help guides that provide in-depth information on the various methods. Similarly, consultants and other prototyping professionals are available to answer questions and lend advice on your prototyping situation.

Understanding your prototype-creation requirements and matching them with available technologies and service providers will pay dividends in the long run. Work with a provider who can assist you throughout the process, helping you overcome the inevitable surprises that pop up in almost any new product development process.

For more information contact Brad Cleveland, president and CEO of The Protomold Company, Inc. (Maple Plain, MN).