Selecting the Right Rapid Prototyping System
In 1991 Dr. Thomas Pang invented the first epoxy based photopolymer that improved the SLA accuracy by an order of magnitude. Thus, mainstream rapid prototyping took off with form-fit models that actually verified CAD data. Design teams were delighted that they could quickly and reliably iterate and test designs. Soon, enterprising companies determined that these accurate SLA models could be used as master patterns for casting multiple copies of durable cast urethane prototypes.
Layer additive rapid prototyping companies emerged in the early 1990’s offering additional technology choices. DTM, along with the University of Texas, developed Selective Laser Sintering. Here a laser beam is used to precisely sinter (or melt) nylon powder one thin layer at a time. Stratasys soon offered Fused Deposition Modeling. A thermoplastic spool is melted at the nozzle and deposited with a XY plotter style motion.
Just after the year 2000 two more technologies emerged, digital light projection and PolyJet. EnvisionTec developed a photopolymer technology using digital light projection. Very small mirrors (like those used in LCD Projectors) are accurately positioned to selectively cure the free surface of a liquid photopolymer. PolyJet™ from Objet utilizes conventional print-head technology to deposit a photopolymer and quickly cure it one layer at a time with UV exposure. This is the first technology with the ability to deposit two separate materials—allowing users to dial in desired surface hardness and shades of grey.
Selecting the Right RP Technology from a Service Provider
The first step is to select a reputable service provider that offers a breadth of RP solutions. This protects the customer from getting a solution that is force fit, like a size 6 shoe on a size 10 foot. Each project has a separate set of important requirements. Skilled project engineers can quickly match the solution that best fits each unique project. Sometimes delivery is the driving factor, other times mechanical properties drive the decision. Often final product testing and early market trials are accomplished with CNC’d prototypes and/or QuantumCast enclosures. So, when considering RP options, it is best not to limit oneself to only layer additive methods.
For small quantities, when mechanical properties drive the decision, CNC is often a very good solution. Skilled CNC programmers can turn projects quickly and deliver prototypes fabricated with: Polycarbonate, Polycarbonate with 20% glass fill, ABS, Delrin, PEEK, Ultem 1000, and other popular materials suitable for electronic enclosures.
For intermediate quantities (i.e., 5 to 50) with stout mechanical performance requirements, a popular proven solution is QuantumCast™ (figure 1). This next generation cast urethane technology offers a variety of high performance characteristics like high heat deflection temperatures, high flex modulus, and at the same time high impact strength. Threaded insert strength is often an issue. QuantumCast™ offers a proprietary technique for securing threaded inserts (figure 2) with twice the strength of adhesive bonding.
Purchasing an RP System
Finally, a good question to ask is: Is the system sufficiently versatile enough to satisfy the majority of your in-house needs?
Note: Desktop Factory is now defunct and refunded deposits to everyone.