Advanced Guide to printing Polycarbonate Filament

Author: Matt Tyson/Wednesday, 22 August 2018/Categories: How To

Advanced Guide to printing Polycarbonate Filament

One of the best engineering plastics available for 3D Printing, PC was previously considered a difficult material to print. With the rise of new grades of PC; today polycarbonate is an accessible and popular 3D printing filament for both desktop and industrial users. Polycarbonate (PC) offers excellent heat resistance and tensile strength for real world applications. 

Note: When it comes to 3D printing polycarbonate, set up and settings may vary depending on the grade of PC. Generic PC materials require more demanding printing temperatures (300°C) than the popular and widely adopted optimized PC filaments (250°C). Advice in this guide is tailored towards printing grades of PC specifically developed for 3D Printing like Optimized PC and Nano Reinforced PC.

Contents:

What is PC?
  Generic PC
  Optimized PC
  Nano-reinforced PC

Printer Setup
  Loading & Unloading Filament
  Bed Surface
  Bed Leveling & Nozzle Height
  Pre-heating
  Enclosure
  Filament Storage

Printer Settings
  Nozzle Temperature
  Bed Temperature
  Controlled Chamber Temperature
  Cooling
  Rafts
  Supports
  Dual Extrusion

Post Printing
  Removing a print after completion
  Annealing
  Removing Layer Lines
  Painting
  Joining

Trouble Shooting
  Blocked Nozzle / Filament Jam
  Warping
  Poor Layer Adhesion
  Nasty smell during printing

What is PolyCarbonate (PC)?

Generic PC

Polycarbonate (PC) is an amorphous plastic which is made up of carbonate groups in its chemical structure.

PC is a rigid material offering fantastic stiffness, strength and heat resistance. PC exhibits a moderate chemical resistance and excellent temperature resistance, softening between 100-110°C (Glass Transition and Vicat temperature).

Generic Polycarbonate filaments are rarely used when compared to more accessible grades of PC. Generic Polycarbonate filaments are widely regarded as difficult to print without printer modifications or an Industrial 3D Printer due to their demanding printing requirements (300°C nozzle temperature).

Optimized PC

Optimized grades of PC are polycarbonate materials specifically formulated for 3D Printing. Optimized PC filaments print with more accessible printing temperatures (250°C) than the previous generation of generic PC filaments (300°C), bringing the functionality of PC to the desktop user.

Like other grades of polycarbonate, Optimized PC offers moderate chemical resistance and excellent temperature resistance, softening between 100-110°C (Glass Transition and Vicat temperature).

Filament manufacturer Polymaker assisted with the rise of PC 3D printing by formulating the first optimized PC material for both desktop and industrial 3D printing.

Nano-reinforced PC

PolyMax™ PC is a nano-reinforced  and optimized polycarbonate material exhibiting vastly superior impact resistance when compared with other grades of polycarbonate. PolyMax™ PC also offers a further improved printing experience, printing with less warping and with easier to remove support material.

Like other grades of polycarbonate, Nano-reinforced PC offers moderate chemical resistance and excellent temperature resistance, softening at 113°C (Glass Transition and Vicat temperature).

Printer Setup

Loading and Unloading Filament

Changing between two polycarbonate materials:
If the printer is currently loaded with a different colour of polyCarbonate, unload that material at 240-270°C and extrude your polycarbonate filament at the same temperature. Stop extruding the polyCarbonate filament after the previous colour has been completely purged and cleaned out.

Changing from a higher temperature material:
If the printer is currently loaded with a higher temperature material, unload that material at its recommended printing temperature, and then load and extrude your polycarbonate filament at that same higher temperature. It is important to load the PC at this higher temperature so the previous material can be pushed out.  Stop extruding the PC filament after the previous material has been completely purged and cleaned out, lower the temperature to 240-260°C, and extrude the PC plastic for a few more seconds.

Changing from a lower temperature material:
If the printer is currently loaded with a different lower temperature material, unload that material at its recommended printing temperature, and then load and extrude your polycarbonate filament at 240-270°C. Stop extruding the PC filament after the previous material has been completely purged and cleaned out. 

Bed Surface

For PC printing there are a variety of optimal print surfaces

BuildTak™, FlashForge Sheets etc. (Recommended)

These surfaces are an adhesive backed sheet designed to stick onto your printers bed or removable platform. These sheets are our favourite printing surface when printing polycarbonate due to their compatibility with other 3D printing materials, minimizing the need to recalibrate the printers nozzle height when printing multiple materials. 
In our experience we have found the FlashForge sheets are better than BuildTak™ for PC printing as the sheets are more durable and the adhesive helps to prevent the sheets lifting at high bed temperatures.

It is possible to slice damage these sheets as bubbles can still form if the PC parts warp. However if you remove the parts gently and set your nozzle height correctly, these sheets can last longer than other surfaces. If your nozzle height is too close or bed temp is too high, the parts can fuse too these sheets.

Perforated Boards (Recommended)
Perforated Boards are an excellent build surface for PC printing. During printing, the extruded PC plastic sticks through the perforated holes gripping the plastic to the board. 3D Printing on perforated boards will require a raft to ensure the final part has a smooth bottom surface.

Heated Glass Bed with Glue Stick
Printing PC straight onto a heated glass bed with PVA Glue stick is an excellent option. Printing on glass gives the bottom of your prints an incredibly smooth and shiny finish. We recommend applying a layer of PVA glue stick which acts as a ‘release agent’ when removing the finished print however glue stick isn't always necessary.

Once the 3D Print is completed, it must be removed from the build plate when the temperature is high. Removing a print after the bed has cooled may cause the glass to break because the print may shrink more rapidly than the glass plate.

This print surface is best suited for enclosed printers and printers with a controlled chamber temperature and setting your nozzle height correctly is extremely important when printing on glass.

Other:
When printing PC you can also print with a variety of other printing surfaces such as Kapton Tape and even hairspray (hairspray is not recommended).

Bed Leveling & Nozzle Height

It is important when printing polycarbonate that your first layer adheres to the printing bed. To achieve this it is important to ensure your bed is perfectly levelled and your nozzle height is set correctly.

We recommend levelling the bed and setting the nozzle height with a pre-heated bed (90°C) to account for any expansion or shrinkage that may occur.

The ideal nozzle height when printing most materials (including PC) is a distance of 0.1mm, this is the thickness of two pieces of paper. When changing between bed surfaces, it is important to adjust the nozzle height again to compensate for the added thickness of the bed surface.

Pre-Heating

For optimal results, it is recommended that you pre-heat the buildplate to 90°C atleast 15 minutes before printing PC. A longer pre-heating time (30 minutes up to 2 hours) may be required with larger printers, in colder climates or with lower wattage heated beds to prevent warping.

In printers with actively controlled chamber heating, preheating the build plate to 90°C and chamber to 60°C for 5 minutes is recommended.

Enclosure

Without the right printing environment (high temperature printing environment) parts printed in polycarbonate will print with too much internal stress, causing the print to warp while compromising the mechanical strength of the part. 

While an enclosure is not required to print small parts in PC, an enclosure is important when printing medium to large sized parts.

Many enclosed printers have top lids / doors which can be opened or removed. When printing PC on these printers, we recommend closing the lid to maintain a high internal temperature.

Photo: The UP300 desktop 3D Printer by Tiertime (left) and FUNMAT HT by INTAMSYS (right) are enclosed, a benefit when 3D printing polycarbonate filaments.

Filament Storage

Like many other plastics, polycarbonate is a hygroscopic material, absorbing moisture from its surrounding environment. When the filament passes through the hot end the moisture rapidly expands creating bubbles in between layers, poor layer adhesion, inconsistent extrusion due to material expansion and thus poor surface quality.
polycarbonate will typically absorb moisture over a period of months however in environments with high humidity (evaporative air-conditioning) this process can take days.

Removing Moisture:
It is possible to remove this moisture by drying the filament. To dry a spool of PC, place it in a pre-heated convection oven at 80˚C for 8 hours.

The temperatures listed are for ovens with accurate temperature control. It is important to pre-heat the oven before drying to prevent temperature over shoots. Drying without pre-heating or with higher drying temperatures will cause the filament to fuse together.

Preventing Moisture Absorption:
It is important to store and print your polycarbonate materials in their optimum environment (below 20% humidity) to prevent moisture absorption. It is important to prevent moisture absorption as excessive drying will degrade the filament. We recommend storing filaments in a resealable bag with desiccant when not in use and in environments above 20% relative humidity we recommend using a filament dry box like the PolyBox™ when printing. The PolyBox™ is a spool holder / dry box in an environment below 20% relative humidity, preventing moisture absorption.

Printer Settings

Nozzle Temperature

polycarbonate is considered a high temperature material for most machines, typically printing between 240°C - 270°C. Of course the optimal printing temperature of a PC filament will vary depending on which printer and filament brand you use. Some filament manufacturers add additives to their polycarbonate to increase or lower the materials printing temperature.

To find the optimal nozzle temperature we recommend starting with a temperature right in the middle of the manufacturer’s suggested settings. If the manufacturer recommends 240°C - 260°C, printing at 250°C is a good starting point. If your extruder can not reach the highest recommended temperature, try printing at the lower temperature. Based on the quality of the print we suggest adjusting ± 5°C at a time.

Troubleshooting Nozzle Temperature
If the nozzle temperature is too hot, you may experience wisps / stringing on the surface of the print, difficult to remove and fused support material , sagging and poor surface quality on overhangs and a harsh smell during printing (this smell is more prominent with some PC brands).
If the nozzle temperature isn't hot enough, you may experience compromised mechanical properties due to the poor layer adhesion, under-extrusion (uneven / rough surface quality) and if the filament is not melting fast enough; nozzle blockages.  

Bed Temperature

Printing PC requires a heated bed at 90°C -100°C. It is important your heated bed isn’t set above the materials glass transition temperature, which for polycarbonate is 100-110°C.

Controlled Chamber Temperature

A controlled chamber is not required to successfully print parts in PC, however is important for users interested in printing medium, large or full-size parts in PC. A controlled actively heated chamber will minimize internal stress (resulting in improved mechanical performance) ensuring near-zero warping.

On printers equipped with an actively heated chamber or advanced thermal system (like the INTAMSYS 3D printers); a chamber temperature between 60-70°C is ideal to print PC with low residual stress and near-zero warping / cracking.

Photo: Advanced Thermal System on the INTAMSYS FUNMAT HT maintains a high internal chamber temperature to print polycarbonate with near-zero warping. 

Cooling

When printing PC it is important to print with the part cooling fan off to prevent curling and warping.

Rafts

A raft is not required when printing polycarbonate materials however if the printing bed is not perfectly leveled, a raft can be used to compensate and improve bed adhesion while minimizing warping.

A raft can be required when using certain printing surfaces such as perforated boards.

When printing both the raft and model in PC, the raft removal will be a little harder when compared to ABS materials.

Supports

When printing both the supports and model in polycarbonate, supports will be harder to remove than ABS but should still peel away cleanly. Additionally dedicated supports can be used with a dual extrusion printer.

If supports are fusing to the model, try decreasing the printing temperature by -5°C adjustments or increase the distance between the model and supports.

If your supports are failing / collapsing during the print, try increasing support density and printing with a raft , this will improve adhesion for the supports.

Dual Extrusion

Support & Raft:
PolySupport™ is currently the best candidate interested in a dedicated support material for PolyCarbonate. PolySupport is a break away support material which was originally designed to break way from PLA.

With PolySupport™ you can take advantage of the different softening temperatures to make PolySupport™ peel away with ease. Place the print with supports attached in an oven and heat to 70°C or simply keep the supports on when annealing to soften the PolySupport™.

Dual Colour / Material:
In most cases, polycarbonate filaments will stick to other PC based materials; ideal for dual colour printing.

Post 3D Printing

Removing a print after completion

Once your 3D Print has completed, it can be removed from the build plate. The best method to remove your PC 3D Prints will depend on your build platform with some of these methods specific to removing PC prints. 

Rigid Build Platform
On rigid build platforms like glass or aluminium, a sharp paint scraper can be used to easily remove the model.

When printing on glass, the PC print must be removed from the glass platform when the temperature is high. Removing a print after the bed has cooled may cause the glass to break because the print may shrink more rapidly than the glass plate.

Some printers are designed so the platform can be removed from the bed while other printers the build platform may be fixed in the printer. If the platform is fixed, we recommend supporting the platform with your second hand to prevent uneven pressure on the bed which could affect your bed leveling.

Flexible Build Platform
Some printers on the market print on flexible build plates. With these platforms users can flex the plate to remove prints.

Annealing

What is Annealing?

Annealing is a process commonly used in metallurgy to heat the material and remove internal stress and toughen parts. A similar annealing process can be applied with some 3D printing materials and in the case of polycarbonate, will release internal stress maximizing mechanical performance.

Tips & benefits of Annealing Polycarbonate (PC)
A part which isn’t annealed will slowly release any internal stress in the form of micro-cracking, which can compromise up to 50% of the parts strength. Annealing polycarbonate releases the internal stress properly, maintaining the materials true strength and toughness.

To anneal polycarbonate, place the part in a preheated oven for one to two hours at 100˚C.

Polycarbonate will also 3D print with less stress and thus better strength when printing with an enclosure and or a heated chamber.

Removing Layer Lines

Polycarbonate like other materials can be post-processed after printing to remove layer lines and achieve a smooth surface for professional applications. PC can post-processed with either manual or automatic methods. Before post-processing it is recommended to print with a fine layer resolution to minimize processing time.

Like ABS and PLA, Polycarbonate can be wet or dry sanded to achieve  a suitable and smooth matte finish or to prepare the surface for painting. 

The high impact resistance of polycarbonate also makes tumbling a suitable option for automatic post-processing. Vibrational tumbling removes layer lines from the printed part by vibrating grit particles which slowly fall and scratch the surface of the part.

Painting

Polycarbonate plastics can be easily painted with acrylic, hardened 2k paints and enamel based paints. We recommend removing layer lines before painting and using a plastic primer. 

Joining

Parts printed in Polycarbonate can be joined with a variety of different glues.

Glue
Gluing parts printed in polycarbonate is simple, we have used both Super Glue or Two Part Epoxies. We recommend sanding contact surfaces with a coarse sandpaper to increase the surface area for the glue, this will result in a stronger join.

Trouble Shooting

Blocked Nozzle / Filament Jam

When 3D Printing it is possible to encounter filament jams or nozzle blockages, these blockages can be caused due to a variety of reasons.

Causes and Steps to Prevent Nozzle Blockage and filament jams.
In all of these cases if the filament cannot pass through the extruder, the extruder gear will continue to try push the filament and will eventually 'chew out' the filament. If you hear a clicking or clunking sound coming from the extruder, this is a good sign that the filament is jammed or will be if ignored. 

  • If your extruder temperature is too low during printing, the PC filament will not flow and will have difficulty extruding. Printing with the correct nozzle temperature will solve this issue.
  • If there is too much friction on the filament, the extruder may have difficulties feeding the plastic. Try feeding the filament with a spool holder in different positions (above, beside, behind the printer).
  • If the nozzle height is set too close to the bed, the filament will have difficulty feeding through the nozzle eventually causing a filament jam. When printing at finer layer heights (0.1 and 0.05mm) the correct nozzle height is even more important. To prevent this issue it is important to print with the bed leveled and the correct nozzle height.
  • If the part is warping or lifting off the bed, the part will be pushing against the nozzle limiting extrusion and material flow, in this case it is important to prevent the part from warping.
  • Nozzle Blockages can occur more commonly with finer nozzles. The majority of 3D Printers are equipped with 0.4mm nozzles, it is important when printing or experimenting with a smaller nozzle (0.2mm) to adjust printing speed and extrusion settings 
  • If the filament is of poor quality is oval shaped or manufactured with an inconsistent diameter, this can cause the filament to jam in the extruder. The industry standard for filament tolerance is ± 0.05 mm. If the filament is 1.75mm an acceptable diameter variance would be between 1.70 - 1.80mm. Premium and higher quality brands can offer ± 0.02 mm tolerance. If you have difficulties printing PC with only specific brands of filament this could signify issue with their quality control or simply printer compatibility.

Cleaning a PC Nozzle Blockage
If the nozzle is blocked with PC one of the most successful solutions is to feed more polycarbonate through the extruder with assistance. As polycarbonate is a considerably tough material, with assistance and a high nozzle temperature you can generally purge and remove the clogged plastic.

Warping

When printing higher temperature amorphous materials like PC, some users can have difficulty preventing warping, firstly lets look at why polycarbonate materials can warp.

Warping is caused by internal stress in the 3D printed part; there is one cause for internal stress when printing amorphous materials.

1. As the filament is extruded through the small diameter of the nozzle, the polymer chain of the filament is stretched and will want to return back to its ‘normal’ state, much like a stretched elastic band will go back to its position when it is released. At temperatures moderately close to the materials glass transition temperature, the polymer chain will 'relax', releasing the internal stress and preventing warping. Due to the higher glass transition temperature of PC (100-110°C), PC requires a heated bed and will print with moderate minimal internal stress at room temperature.

So how can we prevent warping and achieve near-zero warping when printing polycarbonate.

Preventing PC warping.

  • If parts are warping early into the print, this may be due to insufficient bed adhesion or an incorrect nozzle height. If the first layer of extruded plastic is not sticking to the bed, the internal stress during printing will be enough to quickly lift the part off the bed. It is important to ensure your nozzle height and bed is leveled correctly and that you are using the correct printing surfaces for PC.
  • Drafts, cool air from air conditioners and low environmental temperatures in winter can cause the PC to print with more internal stress. An enclosure with a closed front door can help to contain heat from the heated bed, raising the internal temperature required to minimize warping.
  • In an enclosed build volume of 150 x 150 x 150mm, heat from the build plate will raise the internal chamber more efficiently and faster than with a larger 250 x 250 x 250mm build volume. Preheating for a longer time may be required on larger printers to reach the required internal temperatures. 
  • Printing with a lower infil will produce parts with less material and thus less internal stress in some cases minimizing warping. Parts printed at 100% will suffer from significant warping when compared to parts printed at 25-50%. Parts should still be printed with a moderate infil (above 20%) as parts printed with a low infil are more suseptible to cracking.
  • Typically warping will occur on the outer edges of a 3D Print. In some cases, a raft can be used to extend the length of the part. The outer edges of the raft will warp instead of the part.
  • Printing on a printer equipped with an actively heated chamber is one solution to printing PC with near-zero warping. Active heating is important to successfully print full size parts in polycarbonate (eg. 300 x 300 x 300mm)

Photo: Polycarbonate parts printed at 100% infil. An advanced thermal system like on the INTAMSYS 3D Printers can ensure 'near-zero' warping.

Poor Layer Adhesion

Causes and steps to improve poor layer adhesion.

  • If the filament is under-extruding during printing there will be inconsistencies and gaps between the layer, compromising  mechanical strength and layer adhesion. It is important to ensure you are printing the polycarbonate filament at the right nozzle temperature to ensure consistent flow and to minimize drag or tension which may prevent the filament from feeding.
  • Poor layer adhesion can also be caused when printing with a polycarbonate spoiled with moisture. When the filament passes through the hot end, the moisture erupts creating bubbles in the extruded plastic, compromising  the parts mechanical properties. If a spool of filament has absorbed moisture, it can be dried however it is important to store the PC correctly and prevent this issue from occurring.

Smell during printing

Compared to other 3D printing materials, Polycarbonate can sometimes print with a noticeable smell.

Causes and steps to minimize printing odors

  • Polycarbonate materials will release a noticeable smell during printing if printed too hot. Printing at lower nozzle temperatures can sometimes minimize noticeable odors when printing PC.
  • Placing the printer in a ventilated space can help to minimize odors when printing PC, odors will also be less noticeable when printing with enclosed printers.
  • Some 3D printers are equipped with HEPA / carbon filters which can help to minimize the smell when printing PC plastics.

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