Printing Polycarbonate: Avoiding Warping and Delamination

Polycarbonate is used in riot shields and aircraft canopies. Its real-world toughness and heat resistance are exceptional. It is also the most demanding common FDM material to print correctly. Every requirement — temperature, enclosure, drying, bed preparation — must be met simultaneously, or the print will fail.

Hardware Requirements

All-metal hotend: PTFE-lined hotends are not suitable for PC. PTFE begins to off-gas at temperatures above 240°C and degrades around 260°C, producing toxic fumes and contaminating the melt. PC prints at 260–300°C, so an all-metal hotend is mandatory. This is non-negotiable.

Heated bed above 100°C: PC warps severely on a cold bed. The bed must maintain 100–120°C throughout the print. Most Bambu Lab printers achieve this; many open-frame printers do not.

Enclosed chamber: An enclosed chamber is not optional for PC. Even with correct temperatures, printing in an open environment causes the deposited material to cool too rapidly, resulting in layer delamination. The enclosure maintains ambient temperature at 40–60°C, which is sufficient to keep the previously deposited layers warm enough for proper interlayer bonding.

Moisture Management

PC is highly hygroscopic. Dry at 80°C for 8 hours before printing — including freshly opened factory-sealed spools. Wet PC produces severe stringing and poor surface quality — the defects from wet PC are among the worst of any material. Users with paper spools can go to 100°C for more thorough drying.

Print Settings

Bed Adhesion

PC is infamous for both failing to adhere and adhering so strongly that it pulls chunks from the bed. The solution is a PEI sheet with a thin glue stick application. The glue stick improves initial adhesion on the first layer and then acts as a controlled release agent as the print cools.

Without glue stick on PEI, PC may adhere so strongly that removing it without damage is impossible. Too much glue reduces adhesion and the print may lift mid-print.

Common Failure Modes

Warping corners: Usually caused by insufficient enclosure temperature, bed temp below 100°C, or any cooling fan. Check all three.

Layer delamination mid-print: The most common PC failure. Usually caused by ambient temperature fluctuations — a door opening, a fan running nearby, or an enclosure that is not fully sealed. Also caused by any cooling fan above 0%.

Stringing and rough surface: Almost always moisture. Dry the filament.

Poor bed adhesion on first layer: Either the bed is below 100°C, insufficient glue stick, or the Z offset is too high. Check bed temperature with an IR thermometer at the build plate surface, not the sensor reading.

Transparency

Natural PC filament prints with functional translucency. It will not be optically clear — FDM layer lines scatter light — but it transmits light usefully for applications like indicator windows and light diffusers. Sanding through to 2000 grit and polishing significantly improves clarity for display applications.