3D Printing Polycarbonate – Why and how?

This is the first blog post series in which we discuss different classes of engineering FDM filaments. This particular post will focus on 3D Printing Polycarbonate filament, use cases, pros and cons and delve into some tips for a successful Polycarbonate print.

What is Polycarbonate?

Polycarbonate (PC) describes a group of thermoplastic polymers which tend to be stronger and tougher than commodity plastics such as PET and PLA.

Polycarbonate also exhibits good temperature resistance (up to around 135 ˚C) and impact resistance making it useful both as a commodity plastic and also as an engineering plastic. PC can also undergo large plastic deformation prior to cracking. The strength, toughness, optical clarity and  ease of fabrication of PC lends to a variety of uses including kitchen appliances, lenses, windows and is also used to make CDs.

Polycarbonate can also contain flame retard additives and is an inherently electrically insulating material. Thus it finds itself being routinely used in electrical and automotive applications. 

Polycarbonate in FDM printing

In its virgin (pure) state PC has a high glass transition temperature of around 147 ˚C which gives it its excellent thermal performance. However having such a high glass transition is also a drawback when it comes to FDM extrusion of this material. Typical consumer and pro-sumer 3D printers are usually not equipped to cater for the high printing temperatures required to print PC in its pure state. For successful printing of virgin PC FDM parts, nozzle temperatures above 320 ˚C, build-plate temperature in excess of 130 ˚C and an actively heated build chamber are typically required. Otherwise, printing this material at lower temperatures can potentially lead to warping and insufficient layer adhesion, resulting in unusable parts

Nevertheless, several polycarbonate filaments which can be printed on consumer and prosumer printers more easily have been introduced to the market. These include easy to print polycarbonate materials such as Polymaker PolyLite or PolyMax PC and Ultimaker PC. Alternatively, PC can also be alloyed with other thermoplastics such as ABS to improve print-ability whilst retaining most of the excellent material properties of PC.

Why print PC?

The most obvious reason to use PC in your prints is its mechanical strength combined with its excellent toughness which greatly surpasses that of PLA, ABS and PET-G. This enables one to print functional parts and prototypes which can withstand a tough beating! The high temperature resistance, and electrically insulating properties also make this material an ideal candidate for electrical components and enclosures for electronics which tend to get hot during use.

The excellent optical clarity of PC also makes it useful for transparent prints used for both aesthetic and functional uses! Polycarbonate can also undergo large amounts of plastic deformation before failing making it useful for load bearing parts.

*the values presented in this table were obtained from the manufacturers’ websites and data sheets. Since manufacturers can use different testing methods, some values cannot be directly compared and only serve to give an indication of the mechanical properties. Furthermore the mechanical properties of the printed part will depend greatly on the printing parameters and orientation of the printed part. 

The table above shows the mechanical properties of some FDM Polycarbonate materials compared to the typical properties of other FDM filaments. It is immediately evident that the ultimate tensile strength of PC materials is about 1.5 times that of PLA and double that of ABS and PET-G. Furthermore PC materials tend to have higher toughness (as indicated by impact strength) and tend to fail under higher rates of strain when compared to other materials. Moreover Polycarbonate materials tend to have a higher glass transition temperature which indicates better high temperature performance.

How to succeed when 3D printing Polycarbonate

Polycarbonate filament absorbs moisture from it surroundings and thus needs to be dried before printing. Most PC materials will be completely dry if heated to 80-100 ˚C for 4-8 hours in a oven. If you have left your polycarbonate filament outside of an airtight container for a few days or if you see small bubbles in the filament during extrusion or excessive stringing in printed parts it is recommended to dry your filament. Printing with wet filament can cause printed parts to exhibit diminished mechanical performance. Furthermore when printing with transparent filament, excessive moisture will cause the printed parts to become opaque.

As previously mentioned another consideration when printing PC are the high temperatures required. It is recommended to use a printer which can heat the build-plate to at least 100 ˚C and the nozzle to at least 250 ˚C. For this reason an all metal hot end is required when printing with PC. It is also recommended to print PC slowly (20-40 mm/s) especially if your printer cannot reach very high temperatures. In fact printing slowly can prevent layer splitting and can also help reduce warping!

Another requirement for successful printing with PC is a printer enclosure, especially for medium and larger sized prints. Using an enclosure retains some of the heat generated by the heated build-plate.This will reduce the tendency for poor layer adhesion and for warping.

Professional and engineering grade materials tend to have a narrow range in which they show optimum print-ability with polycarbonate being one of these materials. It is thus generally recommended to find the optimum printing setting for your material printer combination. This can be done by following this blog post which describes how to find the optimum build-plate temperature for least warping with Magigoo adhesives. We have also tested some materials with Magigoo PC, the printing settings for these materials and others can be found by following this link! It is also recommended to avoid using active part cooling when printing with PC and to use a brim for medium and larger sized prints.