Polycarbonate

PC - Polycarbonate

Polycarbonate is a thermoplastic, it's strong and impact resistant (It's used in the making of bullet proof glass and compact discs) temperature resistant and it can be extruded (at the right temperature). It can be bent and formed while cold without cracking or deform and it is also very optically 'crystal' clear to visible light (opaque to UV light), but it's actually not very easy to keep it clear during extrusion, see below -

Don't confuse Polycarbonate with Acrylic or Plexi-glass, they shatter and crack, Polycarbonate tends to just bend and deform and after much effort will eventually stretch like very hard rubber until it eventually breaks.

Polycarbonate has a glass transition temperature of about 150 °C (302 °F), so it softens gradually above this point and flows above about 300 °C -> Wikipedia

For more details, see the Wikipedia entry on Polycarbonate

Usage

Polycarbonate is an interesting material for 3D printing, it seems to have low warp, strong in filament form so is easily extruded using common extruder drive systems.

Heater Settings

Depending on the speed that you extrude and the size of the filament the hot-end may require settings of the following -

1.6mm filament tested - by RichRap

A heated bed was used at 85 Degrees C. The bed was covered in PET tape and then Kapton to top of that.

A RepRap Prusa Mendel was used along with a Wade Accessible Extruder (Greg Frost) and hobbed bolt designed for 1.75mm Filament.

@ 30mm/Sec print speed you can go down to as low as 255 Degrees C without the extruder jamming, but really 265 should be used as a minimum.

@ 60mm/Sec print speed you need around 285 Degrees C constant hot-end temperature

@ 80mm/Sec the temperature needs to be 295-300

@ 120mm/sec a temperature of 305 Degrees C was used (Maximum for the hot-end being used), but infill was sparse with breaks and solid layers had holes so higher temperature may be required.

The extruded filament behaves more like ABS than PLA and bonds very well together, strength seems to be similar at all the above temperatures and speeds.

It was observed that the faster and hotter an object was printed the more clear the end results, these were still closer to white than clear.

Moisture Issues

PC is very hygroscopic and will absorb moisture from the air, this can make some filaments have issues when being extruded, usually bubbles, oozing of filament when not desired and poor print quality. The uncovered PC filament was in free-air for many days while testing and other than a 'snow-white' effect to the finished parts moisture was not observed to cause significant issues - more testing on this needs to be done.

A test of drying the filament before is needed to see if the 'snow-white' effect can be minimised.

Other suggestions have included the transition of the filament from being amorphous (Clear) to semi-crystalline in structure, it would be nice to prove this in some way.

Availability

Filament produced for testing by RichRap was custom made at a cost of around £50/Kg UKP in a very small sample quantity (2KG).

Samples of this 1.6mm filament are out in the wild and should be tested on the Makerbot MK7 extruder shortly (October 2011) and also Bowden extruder configurations.

ProtoParadigm in the US has 1.75mm PC and 3mm PC available for sale at $23 per half-pound coil. This filament is custom extruded for 3D printing.

Ultimachine based in the U.S. has began selling it in both 1.75mm and 3mm diameters.

LulzBot sells reeled/spooled 3mm Polycarbonate filament

The only other identified source for PC in filament form is from Orbi-tech as 3mm plastic welding rod at a cost of around 120 Euro for 2.2KG

PC Plastic Blends

PC-ABS is also to be tested shortly, results will be added. The intention with most blends of PC is to lower the required extruding temperature. PC-ABS blends are common in the automotive industry and combine the strength and heat resistance of PC with the flexibility of ABS.

PC-Polyester could also be tested.

External Links

• Instructions for drying and printing with polycarbonate, with photos of clear PC prints: Printing with Polycarbonate
• Testing and pictures by RichRap can be found on the following Blog
• Video's of PC being Extruded and building objects can be found here
• A test of the 1.6mm PC filament being manipulated and bent can be seen here
• And the destruction of some printed Pyramids to demonstrate relative strength of PC, PLA and ABS materials can also be found here