With modern software, you can create a part in 3D CAD, perform digital analyses, and then send it directly to manufacturing for tooling and production. So why does anyone prototype anymore? It’s not that they’re old fashioned or just enjoy throwing away money. It’s that there are still things you can’t know just by looking at a model on a screen—like how it feels in your hands, how potential customers will respond, and whether it will do the job it was built to do in a world full of inexact measurements.
photo credit: pdnotebook
Every physical prototype costs money and adds time to the design cycle, but the good news is that internet, modern additive manufacturing methods, and rapid prototyping services can keep those losses at a minimum. And remember, a prototype that saves you from sending design errors to production or into the market is always a bargain.
If you haven’t started using rapid prototyping methods yet—or if you’re not sure whether the approach you’re using is bringing you value, consider the following:
- Be clear on your goals. Organizations and industries seek out rapid prototypes for different reasons. You should be clear on yours from the beginning because your goals are critical to the technology and vendors you choose. Typically, developers look to rapid prototypes for concept models, ergonomic studies, and visual analysis, but sometimes they can cross over into functional testing and even pattern creation. If you think your company needs “all of the above,” you’re going to need more than the one RepRap machine in Larry’s garage. Which leads us to the next best practice.
- Find out what’s out there. Not all rapid prototyping methods are equal. So it pays to understand your choices before buying a machine or contracting out a project. Consider the seven basic processes available from the additive manufacturing (3D printing) realm:
- Vat photopolymerization (such as stereolithography or SLA) is known for high resolution and accuracy and the ability to produce complex parts. But parts may not be as durable as those produced by other methods.
- Material jetting works with two materials simultaneously, so you can vary the properties – such as stiffness or color – in one object.
- Material extrusion (such as fused deposition modeling or FDM) lays down material much like a hot glue gun. It’s the method used by most hobbyists/makers because it’s inexpensive. But, depending on the model, it can take some time to print.
- Powder bed fusion (such as laser sintering or SLS) leaves an uneven surface that requires some machining to smooth out (and therefore impacts accuracy where tolerances are a concern). The good news is that it’s fast and produces almost no waste.
- Binder jetting can produce plastics and metals, in color. Best of all, it’s inexpensive. Unfortunately, objects are fragile and may need curing.
- Sheet lamination has the unique quality that it doesn’t require high temperatures. That means you can lay down electrical wires as part of the build up process. Typically, you see this method used in aesthetic and visual models, since it’s not structurally robust.
- Directed energy deposition is quick, inexpensive, and works with metals. Best of all, it can operate in an open air environment, which means it can build big items. Downside? It’s not always very accurate.
To learn more about these seven approaches, read this page from Loughborough Unversity or, better yet, get in on Mark Cotteleer’s excellent free online course 3D Opportunity: Additive Manufacturing for Business Leaders.
- Don’t abandon non-additive manufacturing methods yet. More and more developers send their 3D models to printers for prototyping because it’s cheap, fast, and convenient. But in some cases, better value or quality may come from a different, or even older approach. Eager to compete, machining companies now promise high-quality CNC-made prototypes with the same 1- to 3-day turnaround offered by 3D printing services. Urethane casting and quick turn tooled injection molding may provide a broader choice of plastics. And a role still exists for carved Styrofoam and cardboard when you just need a cheap, quick way to get an idea “out of your head and into your hands.”
Now that you have an overview of your choices for rapid prototyping, you can more confidently talk to sales reps and project managers about your next steps. But you’re not home free yet. In part two of this series, we’ll provide a couple reminders for creating robust geometry. We’ll also talk about how to get good results from service providers and what to expect if you’re thinking about buying your own system.
A Part Number Anthology 
Part numbering. For most engineers, this two-word phrase is all it takes to conjure up especially strong feelings about what it means to be “right”, and what it means to be very, very “wrong.” We've assembled a handful of our part number greatest hits in this eBook anthology.
