PC Polycarbonate (PC) and PC blends

Polycarbonate is the clear, tough plastic used for safety glasses, machine guards, headlight lenses and electrical housings. It combines high strength and stiffness with a heat resistance well above ABS and ASA, which makes it one of the most capable materials you can print without moving into fiber-filled nylons or PPS. QIDI lists PC as a supported material on both the Max4 and Plus5 spec sheets.

It is also one of the most demanding materials to print. PC has a high glass transition temperature (Tg, the point where a rigid plastic starts turning rubbery); Polymaker lists 113 °C. As a hot PC part cools toward room temperature it shrinks and builds internal stress, so it wants a very warm chamber. Polymaker's PolyLite PC datasheet asks for an enclosure at 70–100 °C. Our printers have an active chamber that reaches 65 °C, which is enough for small and medium parts but not ideal for large, tall or flat pure-PC parts.

That is why PC blends matter. Many manufacturers sell PC modified to print at lower temperatures with less warping, such as Prusament PC Blend, and PC/ABS blends trade a little heat resistance for much easier printing. When a buyer asks for PC, we decide with you between pure PC, a PC blend or PC/ABS based on part size, heat and impact needs. QIDI does not currently sell a pure PC filament, so the values on this page come from other manufacturers' datasheets.

On paper, PC is one of the strongest unfilled filaments. Polymaker's PolyLite PC datasheet lists 69.1 MPa tensile strength along the layers and 106.1 MPa bending strength, both well above ABS and ASA from the same manufacturer. It is also stiff, so brackets and housings flex less under load.

PC is famous for impact toughness in molded form, but printed PC behaves differently. Layer lines act like tiny notches, and Polymaker's notched Charpy impact result for PolyLite PC is 4.1 kJ/m², lower than its ABS. In practice, a printed PC part with rounded corners and solid walls is very tough, while one with sharp internal corners can crack from a hard knock. Design detail matters as much as material choice.

Between layers, PolyLite PC tests at 52.8 MPa in Z against 69.1 MPa in XY, a relatively strong layer bond for FDM. This anisotropy, the difference in strength by direction, still means we orient parts so the main load runs along the layers. PC also creeps less than ABS or PETG under a steady load, which helps for clamps and brackets that hold tension at warm temperatures.

Heat deflection temperature (HDT) is the temperature where a standard bar bends a set amount under load. Polymaker lists 111 °C at 0.45 MPa and 107 °C at 1.80 MPa for PolyLite PC. Prusa states that Prusament PC Blend resists temperatures up to 113 °C, load not stated. These figures put PC clearly above ABS and ASA and below high-temperature composites such as PAHT-CF or PPS-CF.

Polymaker recommends annealing PolyLite PC at 90 °C for 2 hours soon after printing to relieve internal stress. Annealing can cause small dimensional changes and some warping, so we only do it by agreement and usually on a test part first. PC blends generally sit a little lower in heat resistance than pure PC; check the specific grade on your quote.

Polycarbonate is moderately resistant to weather but tends to yellow and lose surface quality with prolonged UV exposure unless it is UV-stabilized or coated. Datasheets for 3D printing PC generally do not publish UV aging results, so treat PC as an indoor or shaded material by default.

For outdoor use where you also need heat resistance, a UV-resistant paint or clear coat on a PC part, or ASA-CF, is often a better answer than bare PC. Tell us the location and exposure and we will suggest the right combination.

Polymaker rates PolyLite PC as good against weak acids and oils and greases, fair against weak alkalis, and poor against strong acids and strong alkalis. Polycarbonate is generally attacked by acetone and many solvents, and is known to stress-crack in contact with some aggressive cleaners, ammonia-based products and certain fuels, especially when the part is under load.

Isopropyl alcohol for a quick wipe is generally fine, but repeated soaking is not recommended. Brake fluid, gasoline and strong alkaline degreasers are generally poor matches for PC. If your part must survive a specific chemical, tell us and plan to test a sample.

PC is hygroscopic, which means it absorbs moisture from the air, and printing damp PC causes bubbles, rough surfaces and weak layers. QIDI's wiki marks drying as required for PC at 75–85 °C for 8 hours, and Polymaker recommends 75 °C for 6 hours. We dry PC before every job and print from dry storage.

Once printed, PC parts are dimensionally stable in ordinary humidity and do not swell like nylon. Hot, humid environments over long periods can slowly reduce PC's toughness, so continuous use in hot water or steam is not a good fit.

Printed PC has a smooth, slightly glossy surface with visible layer lines. Natural or transparent PC prints as translucent rather than clear: Polymaker quotes 89% light transmission for the raw material, but layer interfaces scatter light in a printed part.

PC can be sanded, though it is harder work than ABS, and it takes primers and paints suited to polycarbonate. For translucent parts, sanding and a clear coat can improve clarity somewhat; it will never look like molded glass.

Annealing: Polymaker recommends 90 °C for 2 hours shortly after printing to relieve internal stress. We do this only by agreement, because it can cause slight shrinkage or warping and may need a test part first.

Sanding and painting: wet sanding with progressively finer grits removes layer lines, and paints rated for polycarbonate stick well after a light scuff. Avoid solvent-heavy paints that can craze PC.

Threads and inserts: PC holds brass heat-set inserts very well thanks to its heat resistance and stiffness. Tapped threads also work in solid sections. Self-tapping screws can crack PC if the pilot hole is too small.

Smoothing: vapor smoothing isn't something we offer for PC. Ask us about sanding and clear coating if surface appearance matters.

PC shrinks more than PLA or PETG as it cools from a high printing temperature. Small and medium parts hold dimensions well in our heated chamber, while large parts are more likely to bow or lift at the corners. Prusa warns that large models in Prusament PC Blend tend to warp.

Holes usually print slightly undersized. For bearing fits and dowel pins, design a little clearance or let us drill or ream holes to size. For tight tolerances, mark critical dimensions so we can orient the part and, if needed, finish those features after printing.