PC/ABS PC/ABS blend (polycarbonate + acrylonitrile butadiene styrene), flame-retardant grade

PC/ABS is a blend of two plastics: polycarbonate (PC), which brings toughness and heat resistance, and ABS, which makes the mix easier to process and better behaved on a print bed. The result sits between its parents. It is tougher and handles heat better than plain ABS, and it is less fussy than pure polycarbonate, which warps hard and needs very high temperatures. Injection molders have used PC/ABS for decades for laptop shells, power-tool housings and car interior trim, so it is a familiar material to many engineers.

The grade we print is QIDI PC/ABS-FR, where FR means flame retardant. QIDI's product page says the grade uses a non-halogen flame retardant, is self-extinguishing, and can reach UL94 V-0 at 2 mm. UL94 is a standard flammability test: a small molded or printed specimen of a set thickness is held in a flame, and V-0 means it stopped burning quickly without dripping flaming particles. That is a statement about the filament's test specimen at that thickness, as reported by QIDI, not a certification of your printed part.

This matters because a printed part is not the specimen. Wall thickness, infill, gaps between extrusions and the part's geometry all change how it burns, and thinner walls than the tested 2 mm generally perform worse. FORMYQ does not certify printed parts to UL94 or any other fire standard. If your product needs a listed enclosure, treat PC/ABS-FR prints as development parts and plan formal testing of the final part, or a molded part, with your certification lab.

Where PC/ABS earns its place is in housings, brackets and covers that need to take knocks and some heat. It prints with a smooth, slightly satin surface, sands reasonably well, and holds screws better than brittle materials. It needs an enclosed, heated chamber and dry filament, which is why it is not a hobby-printer material but suits our QIDI Max4 and Plus5.

QIDI's data puts PC/ABS-FR's impact strength at 19.90 kJ/m², roughly double the fiber-filled nylons in this guide, which is why it's good for parts that get dropped. Elongation at break is low at about 3%, so it is not a bendy material: it takes knocks by absorbing energy rather than flexing a long way. Bending modulus of about 2 GPa means it is moderately stiff, similar in feel to ABS.

Strength figures vary between QIDI's own pages. The product page lists tensile strength of 40.10 MPa and bending strength of 67.79 MPa, while QIDI's filament comparison guide lists bending strength of 85.95 MPa in the XY direction. Different test setups or batches are the likely cause; we treat the lower figure as the safer design number.

Like every FDM part, PC/ABS is weaker between layers (the Z direction) than along them. QIDI's guide lists Z tensile strength at 34.26 MPa, which is quite good layer bonding for an FDM material, but it still means a bracket loaded so that layers peel apart will fail first along a layer line. Tell us how the part is loaded and we will orient it so the main stresses run along the layers.

For screws, PC/ABS is better than PLA or PET-CF because it is less brittle, so self-tapping screws and heat-set inserts both work well. It does creep slowly under constant load, especially when warm, so a clamp or press-fit that stays tightened near its heat limit for months can relax. If a joint must keep a fixed preload, use metal inserts and design the load path through them.

HDT, the heat deflection temperature, is the temperature at which a test bar bends a set amount under a fixed load; it is the best single guide to when a part starts to sag. QIDI's product page gives 102 °C (load not stated), while its comparison guide gives 88 °C at 0.45 MPa. We plan around the lower value, which puts PC/ABS-FR comfortably above PETG and in ABS territory or a little better.

Treat these numbers as limits for lightly loaded parts, not working temperatures. A bracket carrying weight, or a snap-fit held under strain, will start to deform below the HDT, especially over hours or days. For parts that live hotter or carry load when warm, step up to PC or one of the annealed fiber-filled nylons.

QIDI's guide lists optional annealing at 90 °C for 4 hours. Annealing relieves stresses frozen in during printing, but it can also shrink or warp a part slightly, so we only do it by agreement and check a test piece first.

Both PC and ABS degrade under UV without stabilizers, and QIDI does not claim UV stabilization for this grade. In practice this means color shift, surface chalking and gradual loss of impact strength on sun-exposed faces. For indoor parts or parts under a cover this isn't a concern.

If the part must live outdoors, paint it with a UV-resistant coating or choose ASA, which is formulated for outdoor use. Moisture and rain on their own are not a big problem for PC/ABS once printed; QIDI's guide lists saturated water absorption of only 0.3%.

PC/ABS generally handles water, mild soaps, diluted cleaners and brief contact with oils. Both polymers in the blend are attacked by strong solvents: acetone, MEK, many paint thinners and gasoline will soften or craze the surface, and brake fluid is generally aggressive toward polycarbonate. Isopropyl alcohol wipes are usually fine for occasional cleaning but can cause stress-cracking on parts that are under strain.

Stressed parts are the risk area. A clip or press-fit held under strain is much more sensitive to chemical attack than a relaxed part, and some sunscreens, hand creams and lubricants can trigger cracks. If your part will see a specific chemical, tell us and test a sample before committing to a batch.

The filament is hygroscopic, meaning it absorbs moisture from the air, and wet filament prints with bubbles, stringing and weaker layers. QIDI asks for drying at 70–80 °C (product page) or 80 °C (guide) before printing and storage below 15% RH, which we follow.

Printed parts are a different story: QIDI's guide puts saturated water absorption at 0.3%, so finished parts are dimensionally stable in humid rooms. The product page lists 2.10%, which conflicts with the guide and looks like a copy error from another filament; we rely on the guide value, which also matches the low uptake typical of PC/ABS blends.

PC/ABS prints with a smooth, low-gloss to satin surface. Layer lines are visible on curved and sloped faces, as with any FDM material, and they are most noticeable on shallow slopes near horizontal.

Color choice is usually limited compared with PLA; flame-retardant grades are often supplied in black, white or gray. Ask us what's in stock. The surface takes primer and paint well after light sanding.

Because this is a high-temperature material printed in a hot chamber, very small details such as fine text below a millimeter tall soften slightly. For crisp cosmetic models, PLA is still sharper and cheaper.

Sanding, filling and painting all work well. PC/ABS sands more cleanly than PETG, which tends to gum, and it takes standard plastic primers. Heat-set threaded inserts install well because the material melts and reflows cleanly around the knurls.

Vapor smoothing is not something we offer for PC/ABS; the polycarbonate fraction doesn't respond well to it. Annealing is possible per QIDI's guide but is done only by agreement, as it can cause small dimensional changes.

Supports come away reasonably cleanly, but surfaces that were supported will be rougher than top surfaces. If a face is cosmetic, tell us and we'll orient the part so that face is not on supports.

Our printers print to the model well, but every FDM part carries some shrink and tolerance. PC/ABS shrinks a little as it cools, and long flat parts can curl at the corners if the chamber isn't hot enough. We print it in a heated, enclosed chamber at our printers' 65 °C maximum, which is the low end of QIDI's stated range, so very large flat parts remain the hardest case.

Holes generally print slightly undersized, and vertical holes are more accurate than horizontal ones. For precise bores, ask us to print them slightly undersized and ream or drill them to final size.

Expect press-fits and snap-fits to need one test iteration. Send us your mating parts or the dimensions of the hardware, and we'll suggest clearances based on our process.