![]() ABS has good dimensional stability and surface finish, and can be painted or coated for aesthetic purposes. It is one of the most widely used plastics for CNC machining, as it is easy to cut, drill, tap, and glue. Acrylonitrile butadiene styrene (ABS)Īcrylonitrile butadiene styrene (ABS) is a thermoplastic polymer that combines the strength and toughness of acrylonitrile and styrene with the flexibility and impact resistance of butadiene rubber. Acrylic is not resistant to solvents or chemicals, and can degrade under UV exposure over time. It also has a low heat resistance and can deform or melt at high temperatures. Acrylic is often used for signage, displays, lenses, lighting fixtures, and decorative items.Īcrylic has a high tensile strength and modulus of elasticity, but it is brittle and prone to cracking or chipping under impact or stress. It is easy to machine and polish, and can be colored or tinted for various effects. Acrylic (PMMA)Īcrylic, also known as polymethyl methacrylate (PMMA), is a transparent thermoplastic that offers excellent optical clarity, light transmission, and weather resistance. ![]() We hope this guide has helped you to understand the basics of plastic CNC machining and to make an informed decision for your project. In this guide, we have introduced some of the most common plastics used for CNC machining, their properties, advantages, and disadvantages, and how to select the best plastic for your needs. However, choosing the right plastic for your project can be challenging, as you need to consider various factors such as mechanical strength, stiffness, toughness, heat resistance, chemical resistance, optical clarity, biodegradability, cost, and processing difficulty. Avoidance of this type of coolant is generally a good practice if any amorphous materials are being machined as it can be difficult to determine compatibility until it is too late.Plastic is a great material for CNC machining, as it offers a wide range of options for different applications and requirements. Petroleum based fluids can be used for many semi-crystalline plastics such as nylon, acetal, polyesters, PTFE and most thermosets. Two flood coolants suitable for most plastics are Trim 9106CS (Master Chemical Corp.-Perrysburg, OH) and Polycut (Tullco-Savannna, GA.) A mist coolant generally suitable for plastics is Astro-Mist 2001A (Monroe Fluid Technology-Hilton, NY.) Misting and flood coolants should always be non-aromatic and water-soluble solutions as many amorphous materials such as acrylic, polycarbonate, Noryl PPO, polysulfone and Ultem PEI are prone to stress cracking, a form of chemical attack from incompatible coolants. In addition to using the pressurized air to keep frictional heat down, the air can be used to direct the swarf away from the rotating part to avoid chip wrap. Pressurized air can be used on most turning and boring operations. Experimentation as to which is more appropriate for a give part is often recommended. The coolants acceptable for plastics include air, misting systems and flood coolants. The reduction of frictional heat via the use of coolants improves the surface finish of machined parts as well as part tolerances and leads to longer tool life, thus saving money. The amount of heat being generated depends on the depth of cut, feed rate and tooling geometry (neutral to slightly positive geometries are always suggested.) Deep holes and cuts involving tool-to-part rubbing generate frictional heat that generally has to be minimized through the use of coolants. However plastics being thermal insulators cause the generated heat to be held at the cutting interface. The low friction and lower hardness of plastics (compared with metals) reduces the frictional heat build-up at the tool tip during machining operations. Examples of high performance materials that almost always require the use of coolants are Torlon PAI and Celazole PBI. Some highly filled, high performance materials, which are very hard by their nature benefit from the use of coolants, but most general purpose materials such as UHMW, nylon, acetal and PTFE (Teflon) can be machined dry, making part clean-up and handling easier. Both involve more tool-part friction than milling and turning operations. The two most common exceptions are drilling and part-off operations. Coolants are not generally required for most machining operations involving engineering thermoplastics.
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