Comparing 3D Printing and Other Prototying Methods

I read an article in a recent issue of Machine Design.com magazine titled “Rapid prototyping the old-fashioned way” written by Lincoln Charles, an Application Engineer with Phoenix Non-Ferrous Technologies in Franklin, NH. The premise was that there are instances where new technology isn’t always the best suited for your prototyping needs. The method put forth in the article produced metal parts in just a few hours for as little as $35. If that sounds like a great process it actually is. There are many “old-fashioned” prototyping methods that still make a lot of sense. The question every designer needs to ask when looking to prototype a part is which process fits best with my schedule, budget and physical properties requirements? So, the article got me thinking about old-fashioned methods vs. new technology methods and where it’s all going.

I don’t know every prototyping method out there and even if I did there wouldn’t be enough space to print them all here. Old-fashioned methods include metal castings like the one used by Phoenix, Urethane casting, CNC machining, foam core, wood molds, and others. New technology methods include SLA, SLS, 3D printing , Rapid Tooling, and others. With a wide range of options how do you make the right choice for your prototype? It really depends on what is important for that particular prototype. If speed is the most important factor you might pick 3D printing. If material properties are important, e.g. you need a metal part, you might pick CNC machining or casting.

Every method has its limitations. For example, urethane casting and metal casting methods require an element of craftsmanship. The quality of the part you receive is somewhat dependent on the person making the part. SLS equipment is typically very expensive so the option to bring this capability in-house is limited to companies with big pockets and heavy prototyping needs. CNC machining has limitations in creating undercut features and sharp internal corners. The limitations today are pretty much the same as they were 20 years ago. The equipment might be better, faster, or cheaper but you still can’t cut that sharp internal corner. What I like about the new technology methods is the versatility they provide and the ever increasing capabilities. The first SLA parts were brittle and easy to break. Today the parts are much tougher and there is a wide range of materials to choose from. 3D printing methods have made similar strides. Today, 3D printed parts can be used as a mold for casting rubber, urethane, and even metal. The printed part can be the final prototype to be used for functional testing, concept approval, or even as a production part.

Patterns and molds for metal casting, RTV molding and urethane casting applications

Directly print molds, mold inserts and patterns for metal casting

3D printed parts are used for functional testing and production parts

3D printed presentation models are used for evaluating and refining designs, as well as sales and marketing applications

As materials and technology improve, only 3D printing methods seem to have the potential to eliminate many of its current limitations. Wouldn’t it be great if you could design your part without having to consider manufacturing methods, select the material properties you want (glass, metal, plastic, wood), press the print button and have your final part in just a few short hours? Is this capability way off in the distant future?

What I’m curious about this week is what old-fashioned prototyping methods did I miss and which ones do you still use? What is your favorite prototyping method and why?

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