REVIEWING THE DIMENSION FDM 1200WS by Kevin Dahlquist and Matt Spangard
Good, fast, or cheap. Pick two. Until recently, that was your choice when it came to creating a prototype of a new product. That's all changing thanks to the Fused Deposition Modeler (FDM) machine - professional and weekend inventors alike are all starting to benefit.
Recent advances in rapid prototyping have caused a paradigm shift in the way individual inventors and product design firms design, develop, and deliver new products to market. In the past, we relied on old-school methods in messy media such as foams, wood, plaster, and whatever else it took to represent and test a particular item. This process played a leading role in the slow pace of product development.
Today, product design has shifted into high gear with rapid prototyping machines cranking out actual-size parts that look and feel like the real thing in hours rather than days, weeks or months.
While various methods and media are used to provide a wide variety of results, the fundamental premise of rapid prototyping is generally the same. Based on a Computer-Aided Design (CAD) file, a computer virtually slices a model into layers and then builds each layer one on top of the other until a complete model has been created.
Some of the earliest rapid prototyping machines used layers of paper laminated together to produce parts. Later, the additive technology of thermal wax printing produced more accurate visual models. Unfortunately, these models were as delicate as they were accurate. Stereolithography (SLA) technology, in which a laser solidifies a photosensitive liquid resin, was pioneered years ago and continues to be popular today.
FDM technology uses the traditional layer building approach, but extrudes melted Acrylonitrile Butadiene Styrene - ABS plastic to you and me - onto a platform like squeezing out a tube of toothpaste. Since gravity dictates that any extruded media will fall as far as it is allowed, the ABS plastic requires a support structure to hold it in place while it cures. Recently, FDM manufacturer Stratasys (www.stratasys.com) has developed a type of support structure that dissolves when exposed to a high temperature chemical bath, while leaving the native ABS plastic intact. This makes it easy to clean the finished parts completely and without the risk of damaging detailed features.
ABS plastic is one of the most common plastics used in everyday consumer products. Prototyping using ABS media allows for a more precise and durable part that accurately represents both the look and feel of a finished product. As with most methods that produce models layer-by-layer, the end result has a visible layer texture on the surface that may require a little sanding or filing to smooth out. Traditional ABS models are not as dense as injection molded parts, but recently Stratasys has developed a hybrid material they call ABS+ which combines traditional ABS with polycarbonate material. According to Rob Alge of Prototyping Solutions (www.ttaweb.com), the end-result of using ABS+ is that the models are 40 percent stronger than previous versions, further closing the gap with injection molded parts. Some higher-end FDM machines can use 100 percent polycarbonate plastic - also known as "Lexan" - for very high-strength parts.
So how much does all this cost?
"Entry-level ABS Dimension machines start right around $20k," said Alge. "That is a fraction of what these machines have cost historically. More advanced machines, which have improved resolution, capacity, and material options can get into the six-figure range."
The mid-level demo FDM machine that Prototyping Solutions provided to us for this article runs approximately $25K. For basic ABS parts that fit within an 8"x8"x12" build envelope, our Dimension is a steal. The Dimension Elite series, which boasts improved resolution (.007" build layer), and Dimension's ABS+ material costs $32,000, proving you don't need to spend six figures to get a machine that can handle almost anything you throw at it.
The new "bargain" FDM machines sound like a great deal for small product design firms, but what about the independent or weekend inventor? If you'd rather buy a new Cadillac than a new FDM machine, you're still in luck. The decreased operating costs of FDM machines have allowed many service bureaus to offer their services to independent inventors. All you'll need to supply is a CAD file, typically in SLA format (originally developed for a different process - Stereolithography - but almost universally accepted for all rapid prototypes), and you can have your parts within days.
Two of the bureaus that we use regularly are Quickparts (www.quickparts.com) and Xpress3d (www.xpress3d.com). Both have the resources to build parts quickly, conveniently, and from a wide variety of materials.
The industry has come a long way in the world of rapid prototyping. Upgraded materials and methods are being implemented at an unprecedented rate - bringing this technology into the reach of the independent inventor for the first time. Finally, you can obtain "good, fast, and cheap" prototypes just like the big guys.
4 STEPS TO FDM PARTS:
STEP ONE
Create a CAD model of the part. Part files are exported from CAD software in the popular .STL format, for use with rapid prototyping machines. This file is then transferred to a computer or delivered to a service bureau to build.
STEP TWO
Software specific to the FDM machine process analyzes the part, references the specified options and build orientation, and then slices the part into thin sections along with a support structure which is generated as needed.
STEP THREE
The build file is sent to the FDM machine and layers of plastic and support structure are extruded one layer at a time. The build environment is kept at a nominal temperature to ensure optimal bonding of one layer to the next. Depending on part quantity, size, and density, build time can range from several minutes to several days.
STEP FOUR
Part is removed from the machine/platform. Many simple parts can simply be separated from the support material by hand. Delicate or detailed parts utilize a cleaning machine which is filled with a hot chemical solution specifically designed to break down the support structure while leaving the ABS part intact.
