The term “back to the drawing board” is more than a cliché. Planning for and producing multiple iterations of any product is the most effective way to reduce overall project costs. And this is no different than when designing a part made from plastic. It also helps avoid long-term risk and delivers the most optimized part design possible. And no matter how skilled the engineer or powerful the design software they use, that means prototyping.
For example, medical device manufacturers must assess the ergonomics and functionality of a surgical instrument before offering it to physicians. Commercial drone designers might make dozens of test flights in wind tunnels to determine their craft’s airworthiness, robot builders want to see how efficiently their latest droid design performs its assigned tasks, and smart automakers perform numerous form, fit, and function checks on countless components with every new model. Each of these activities requires a prototype (or more likely, multiple prototypes).
This is especially true for plastic parts, where demand for the winning design hopefully skyrockets and requires subsequent investment in high-volume production tooling, aka plastic injection molds. What better way to avoid a costly design mistake than to prototype until it is perfected? On the flip side, manufacturers from all industries often evaluate their newest metal brainchildren by first 3D printing, machining, or molding plastic versions of them. Again, it’s about reaching the finish line in the most effective manner.
Within the product development process, plastic prototypes have different use cases:
Fortunately, there are several options available for prototyping plastic parts. Each provides its own distinct advantages (and limitations) that might determine which is most suitable for your application.
Part size, surface finish quality and feature size/resolution requirements should also be considered when choosing a service for prototyping.
Whatever manufacturing technology you choose for a plastic prototype, ensuring that your part is manufacturable via the intended production method is crucial. In other words, don’t paint yourself into a corner by 3D printing prototypes, only to discover when quantities ramp up that the parts can’t be injection molded.
Let’s start the discussion with a brief overview of the technology that quite literally launched the rapid prototyping industry more than three decades ago: 3D printing. In those early days, the only option was stereolithography (SLA). Today, however, manufacturers can choose from a range of technologies, including selective laser sintering (SLS), jetting processes like PolyJet and Multi Jet Fusion (MJF), and SLA’s faster though slightly less accurate cousin, Carbon DLS.
We’ve published numerous design tips covering these technologies, so refer to those for the technical details behind accuracy, raw material selection, and surface finish capabilities. Suffice it to say that all are excellent for making prototypes; several are also fast enough and their feedstocks robust enough to support low-volume, end-use part production. Here are some additional benefits and challenges with 3D printing.
The terms “plastic injection mold” and “prototyping” have long been exclusive of one another. That’s because the high-volume production tooling needed to manufacture the lion's share of plastic parts is both expensive and requires months to develop. We changed this paradigm at Protolabs with quick-turn aluminum tooling, which can mold hundreds of prototype parts and is typically delivered within a week or so.
There's no need for a lengthy list of pros and cons here, as this decision tree has but one or two branches. If you need a hundred or more injection molded prototypes for functional testing, quick-turn tools give customers parts made of real material, really fast, and boasting tolerances and surface finishes nearly identical to those made with production tooling. Quick-turn molds can also serve as a bridge tool until that production mold is complete, or for pilot runs to test the molded part design.
The caveat is that it takes time. Time to design the mold, time to machine it, time for testing and final approval. It's still much faster and far less costly than the "hard tool" alternative just described, but could be prohibitively expensive in situations where 3D printing or machining will solve the immediate problem. As suggested earlier, it's a lot to think about, so give us a call or upload your part design to our digital quoting platform to evaluate the options and receive automated design for manufacturability (DFM) feedback. Happy plastic prototyping.
Selecting the appropriate materials for prototyping is crucial to represent the final product accurately. Prototyping enables designers and engineers to test concepts, refine designs, and validate functionality before moving to full-scale production. It’s essential to use materials that can endure prototyping demands while closely simulating the end product’s mechanical properties.
With various materials available for injection molding, choosing the right one is critical to creating effective prototypes. Acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) are commonly used plastics in injection molding prototypes. Each has unique advantages and disadvantages, making it important to consider the specific needs of your prototype.
Prototyping materials encompass plastics, metals, and other substances used for creating preliminary models. These models allow for refining functionality, conducting user tests, and making adjustments without the high manufacturing costs. Injection molding, a process that heats and injects plastic into a mold, is a popular method for prototyping and mass production due to its efficiency in creating detailed parts.
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Choosing the right plastics is essential for successful injection molding. Materials need to fill molds without defects and accurately withstand any post-processing. Prototyping materials must be similar to final production materials in attributes like heat or chemical resistance, elasticity, and moldability. If there’s a significant difference, the prototype may not accurately represent the final product, leading to costly and time-consuming revisions.
ABS is an extremely versatile thermoplastic made from three distinct monomers: acrylonitrile provides thermal stability, butadiene improves impact resistance, and styrene gives rigidity and ease of processing. The combination creates a durable plastic with high strength and flexibility compared to rivals.
ABS is also dimensionally stable across a wide temperature range, resisting warping or deformation up to approximately 221°F. It can be easily machined and finished with coatings or metallic platings for functional or aesthetic requirements. These properties make ABS a go-to choice for consumer products, automotive parts, protective equipment, toys, and prototypes.
PLA (Polylactic acid) is a biodegradable, plant-based alternative created from renewable ingredients like corn starch, cassava, or sugarcane. Because it is biodegradable, it is commonly used for medical implants like stents and implantable drug dispensers designed to biodegrade over time. While PLA is easy to process and more environmentally friendly than oil-based plastics, its mechanical performance limits use cases compared to plastics like ABS.
PLA’s tensile strength and heat resistance are inferior to ABS in injection molding applications. PLA begins softening at temperatures above 140°F, making it more prone to warping. The material also becomes brittle when subjected to basic solutions or weathering effects over time. These drawbacks necessitate more careful design considerations compared to durable ABS.
The underlying compositional differences between oil-based ABS and plant-sourced PLA dictate divergent material characteristics that significantly impact injection molding suitability. Where ABS offers strength, flexibility, and is easy to manipulate into detailed molds, PLA suffers fundamental limitations like brittleness, poor stability, and lower heat thresholds that rule out intricate applications.
ABS has inherently superior durability than brittle PLA due to its elastomeric properties. The butadiene segments allow ABS resins to flex and stretch, while acrylonitrile and styrene provide strength, making ABS an ideal choice for functional prototypes undergoing rigorous testing. PLA is prone to fracturing when dropped or impacted and is unable to emulate the resilience of final ABS production plastics.
With a glass transition temperature of 221°F compared to PLA’s 140°F, ABS remains dimensionally stable across the high temperatures involved in injection molding processes. This prevents warping while allowing very precise mold flows to fill intricate cavities. PLA risks deformation, shrinking, and sinking at the temperatures required for fast, high-volume injection cycles.
ABS strikes an excellent balance between rigidity for precision and flexibility for releasing injection molded parts without distortion or cracking. The material can flex slightly to fill complex curves and negative spaces without collapsing or sacrificing surface quality. PLA’s comparative rigidity limits possible prototyping geometries due to the increased likelihood of cracking upon demolding.
With suitable viscosity and flow properties, ABS easily achieves glossy, glass-smooth finishes out of the mold. The symmetry and strength also make ABS the preferred plastic for bonding, painting, smoothing, and other secondary finishing processes often required for prototypes. PLA’s susceptibility to moisture absorption and crystallization makes achieving the surface qualities or post-processing seen in ABS challenging.
While extremely useful for prototyping, ABS does come with environmental considerations regarding its oil-based composition and difficulties recycling certain grades. The non-biodegradability and presence of hazardous Bisphenol-A in some variants make responsible disposal important. However, the durability of ABS leading to long lifecycles offers a form of efficiency. Overall, designers should account for environmental impact along with performance needs when selecting ABS.
ABS remains highly cost-effective for low- to mid-volume injection molding orders compared to alternatives like PLA or nylon. Less defective parts, quicker cycle times, and better versatility to adapt prototypes across the testing process also boost value. If design requirements align with ABS properties, it offers outstanding “bang for your buck” even with added finish work.
Despite being petroleum-based, ABS’s long lifespan and recyclability offer a form of sustainability. Its durability means less frequent replacements, and its recycling ability reduces the environmental footprint by minimizing the need for new resources. This aligns with the principles of a circular economy. PLA, celebrated for its biodegradability and renewable origins, faces scrutiny over its decomposition rate and resource use. While industrially compostable, PLA can decompose in non-optimal conditions for up to 80 years. Additionally, the production of PLA is resource-intensive, requiring 2.7 grams of corn to produce 1 gram of PLA, raising concerns about the ethical use of agricultural resources.
The most crucial factor when weighing ABS against other plastics is properly matching material performance to application requirements. Considerations like temperature or chemical resistance needs, lifetime and aging properties, post-processing needs, expected user conditions, and performance validation targets should dictate material selection. ABS balances superior mechanical properties and processability to a wide spectrum of prototypes. However, unique electrical or medical devices may consider finding a material specialty suited to their niche.
If you are still unsure whether PLA or ABS makes the most sense for achieving your next prototype milestones, the experts at Protoshop can help review application details and provide straightforward plastic resin recommendations. By precisely aligning prototype requirements to material characteristics, together, we can enable your prototypes to effectively inform downstream decisions, uncover insights, and hit development targets right on schedule.
Want more information on plastic prototype manufacturing? Feel free to contact us.