Many factors come into play when comparing the material properties of thermoplastics found in injection moulding versus “thermoplastic-like” materials used in an industrial-grade 3D printing technology like stereolithlography (SL).
SL uses a thermoset liquid, not a thermoplastic, which is UV-cured in layers to form final parts. Because of this major difference in fabrication methods, material properties like tensile strength, heat deflection and flexure modulus may differ from SL’s more traditional counterpart. Furthermore, SL produces anisotropic properties where the values for X, Y and Z axis may differ depending on the orientation of the build — a consideration unique to 3D printing processes.
At Proto Labs, a thorough selection of thermoplastic-like materials are offered through SL, but what may surprise you is the versatility and range of potential applications for SL parts. We’ll take you through each material and its properties, and compare them with one another (as well as with moulded plastics) to help you decide how to best implement SL.
Somos NanoTool has an added ceramic filler that increases stiffness and brittleness over other SL materials. Along with stiffness, Nanotool touts the highest temperature resistance compared to most materials offered in SL. It’s regularly used in aerospace and automotive applications that often require greater strength and temperature resistances.
Chart 1: One PC-like material and moulded PC thermoplastic are compared across six material property categories. Notice how the heat deflection in the PC-like parts are be much lower or have a wider range than the moulded PC due to the anisotropic properties discussed earlier. *Heat deflection was measured at 66 psi.
Accura Black 7820 has high strength and good dimensional stability, even in high humidity. The material is black and commonly used in automotive parts, consumer packaging, electrical housings and toys due to its impact resistance and ease of secondary finishing that provides the appearance of production quality.
Accura ClearVue Free offers a humidity and moisture resistant material that also provides good rigidity and toughness. This material can be used for products such as headlamps, bottles and where transparent assemblies are required.
NeXt offers an SL material with material properties that consists of high durability, good water resistance and is white in colour, it is also less prone to breakage than some other SL materials. You would find this material useful in products such as impellers, connectors, electronic covers, automotive housings and sporting goods.
ProtoGen 18420 has a white colour and is great for general use applications where temperature and humidity resistance is important.
Chart 2: Four ABS-like materials and moulded ABS thermoplastic are compared across six material property categories.
Accura Xtreme White 200 is comparable to both a polypropylene (PP) and ABS thermoplastic in that it offers strength and durability, lending itself well to application that require snap-fit features. Note that Xtreme White 200 has the lowest heat deflection of the SL materials offered at Proto Labs.
Accura Extreme offers a PP-like material that provides good toughness and durability where snap fits are required. This material is grey in colour and you would find this in assemblies or in demanding applications.
Chart 3: Two PP-like materials and moulded PP thermoplastic are compared across six material property categories. Notice that properties are fairly similar between each.
Unlike thermoplastics, long-term exposure to UV light and moisture will alter the appearance and mechanical properties of SL materials if they are not protected by plating or painting. Over time, you may experience part warpage, yellowing and brittleness in some parts. SL parts are not intended for long-term use in many instances, but understanding the short-term benefits of having highly cosmetic and functional parts to use during early prototyping can greatly benefit you.
Remember to work closely with the 3D printing experts to ensure that build orientation, anisotropism and material properties are optimised. Adjusting the direction in which the part is built can often improve the material properties and clarity of the part.
Dive deeper into stereolithography at protolabs.co.uk. For questions on 3D printing or any of our services, please contact a customer service engineers at email@example.com or +44 (0) 1952 683047.
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