![\"acrylic](\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/09\/acrylic-CNC-machined-part-jpg.webp\")
<\/figure>\n\n\n\nWhat Is Acrylic?<\/h2>\n\n\n\n
Acrylic<\/a>, or PMMA (Polymethyl methacrylate), is a transparent thermoplastic often used as an alternative to glass, which is heavy and brittle and is not as UV resistant as acrylic. Acrylic\u2019s optical clarity makes it an ideal choice for lenses, display cases, and aquariums. <\/p>\n\n\n\n Acrylic is produced in a cast form or an extruded form, with the cast form being preferred for machining due to its higher melting point and rigidity, despite its higher cost \u2014 its rigidity makes it more stable during machining, so it can meet tighter tolerances. Extruded acrylic is more flexible and is better suited for bending or shaping operations. <\/p>\n\n\n\n Acrylic is sold under various trade names, with Plexiglas\u00ae<\/sup> and Perspex\u00ae<\/sup> being the most popular cast brands of acrylic.\u00a0<\/p>\n\n\n\n Listed below are some key characteristics of acrylic:<\/p>\n\n\n\n Polycarbonate is a transparent, high-strength engineering thermoplastic that is often used in applications in which transparency and toughness are required. Unlike acrylic, polycarbonate can be exposed to high levels of deflection without cracking. Polycarbonate is sold under various trade names such as Lexan\u00ae<\/sup> and Cyrolon\u00ae<\/sup>. CNC-machined polycarbonate parts, such as eyeglass lenses and diagnostic lab equipment, are used for various applications that rely on their clarity and toughness. If you have glasses, the lenses are likely made of polycarbonate instead of \u2018glass,\u2019 and have been since the 1980s.\u00a0<\/p>\n\n\n\n Polycarbonate stands out due to its toughness, machinability, and thermal resistance. However, it\u2019s affected by UV radiation and has poor scratch resistance. Listed below are some key characteristics of polycarbonate:<\/p>\n\n\n\n When machining acrylic and polycarbonate, it\u2019s important to use sharp cutting bits to limit friction between the tool and the part. Blunt tools will cause the plastic to melt due to heat build-up from the rubbing action and cause smearing. <\/p>\n\n\n\n Carbide tools are often preferred for thermoplastics, but polycrystalline diamond (PCD) cutters achieve the best results. Up-spiral end mills with one or two flutes are often the best tool for milling acrylic and polycarbonate, as the tool has a high material removal rate, is very sharp, and doesn\u2019t leave burrs on the machined part. Multi-flute tools can result in chips packing into holes and slots and fusing the material to the cutting tool. For drilling operations, a sharp drill angle of 135 degrees is preferred. <\/p>\n\n\n\n Both polycarbonate and acrylic will warp if fixtures are over-tightened because it causes the parts to bulge during machining. The material will spring back once removed from the machine, resulting in out-of-tolerance features. However, vacuum tables can hold the material in place when mechanical fixturing is not ideal. Alternatively, double-sided tape can also secure thinner sheets to the machine bed, although the adhesive residue can be difficult to remove.\u00a0<\/p>\n\n\n\n The exact speeds and feeds for machining polycarbonate and acrylic depend on many factors, including the machine type, part type, and fixturing. However, acrylic and polycarbonate must be cut at a high spindle speed (up to 18,000 RPM), and high feed rates are also preferred, as a slow feed rate can melt the material. <\/p>\n\n\n\n Polycarbonate has a higher melting temperature than acrylic, so it is not as prone to melting at lower speeds and feeds, and in some cases, slower feed rates are preferred for polycarbonate. Acrylic tends to chip more easily, whereas polycarbonate is tougher and does not chip as easily. <\/p>\n\n\n\n In most cases, compressed air is sufficient for cooling acrylic and polycarbonate parts during machining. However, this depends heavily on speeds, feeds, and the type of cutting operations. If flood or mist cooling is required, utilize water-based coolant because coolants that contain organic solvents can damage the part, especially acrylic.<\/p>\n\n\n\n Deciding between acrylic vs. polycarbonate CNC machining for a machined component is challenging as it depends on several factors. For example, applications that require increased toughness, higher thermal resistance, and good optical clarity are better suited with polycarbonate. <\/p>\n\n\n\n Acrylic has slightly better optical clarity and should be used in applications where clarity is the primary design factor. Both materials are easy to machine, provided speeds and feeds are relatively high. In some cases, post-machining polishing operations may be required for either material, especially if optical clarity is desired. <\/p>\n\n\n\n![\"Acrylic](\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/09\/Acrylic-CNC-machining-jpg.webp\")
<\/figure>\n\n\n\nCharacteristics of Acrylic<\/span><\/span><\/h3>\n\n\n\n
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What Is Polycarbonate?<\/h2>\n\n\n\n
<\/p>\n\n\n\n![\"polycarbonate](\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/09\/polycarbonate-CNC-machined-part-jpg.webp\")
<\/figure>\n\n\n\nCharacteristics of Polycarbonate<\/h3>\n\n\n\n
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![\"CNC](\"https:\/\/www.fictiv.com\/wp-content\/uploads\/2023\/09\/CNC-Machining-a-Plastic-jpg.webp\")
<\/figure>\n\n\n\nComparison Table of Acrylic vs. Polycarbonate<\/h2>\n\n\n\n
Property<\/strong><\/td> Acrylic<\/strong><\/td> Polycarbonate<\/strong><\/td><\/tr> Density<\/td> Approx. 0.42 lb\/in3<\/sup><\/td> Approx. 0.045 lb\/in3<\/sup><\/td><\/tr> Light Transmittance (Optical Clarity)<\/td> 92% for visible light and 72% for UV light<\/td> Up to 90% for visible light but as low as 0% for UV light<\/td><\/tr> Chemical Resistance (Alcohols)<\/td> No<\/td> Can be susceptible to attack with long-term exposure<\/td><\/tr> Chemical Resistance (Hydrocarbons)<\/td> Yes<\/td> Can be susceptible to attack by some hydrocarbons<\/td><\/tr> UV Resistance (Not Susceptible to Yellowing)<\/td> No<\/td> Yes<\/td><\/tr> Scratch Resistant<\/td> Yes<\/td> Only with special coatings<\/td><\/tr> Greatest Toughness<\/td> No<\/td> Yes<\/td><\/tr> BPA-Free<\/td> Yes (Coatings may contain BPA)<\/td> No (BPA-free compositions do exist)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Machining Acrylic vs. Polycarbonate<\/h2>\n\n\n\n
Tooling <\/h3>\n\n\n\n
Fixturing<\/h3>\n\n\n\n
Speeds & Feeds<\/h3>\n\n\n\n
Coolant<\/h3>\n\n\n\n
Choosing Between Acrylic vs. Polycarbonate CNC Machining<\/h2>\n\n\n\n