One of the difficulties often faced when printing high performance thermoplastics like PolyCarbonate is maintaining dimensional stability and minimising warping on large 3D prints. In the very early days of desktop 3D Printing, PolyCarbonate materials at the time required incredibly high printing temperatures (above 300°C), that is until recently with advanced PolyCarbonate materials like PC-Max which have been designed to print with easily obtainable and optimized temperatures (240-270°C). This improvement in usability along with excellent mechanical properties and heat resistance has boosted Polycarbonate into becoming one of the most popular thermoplastics for 3D Printing functional products and prototypes.
Getting started 3D Printing PC is easier than ever, requiring a heated bed capable of 90°C and a print enclosure for medium sized objects. However users will find printing large or solid objects in PC will produce 3D Printed parts with warping. So how can we achieve near-zero warping when printing materials like PolyCarbonate. We found the solution.
What causes PolyCarbonate parts to warp?
The simple answer is warping is caused by internal stress in the model. Think of the filament as a long ‘tangled’ polymer chain which is its ‘normal’ state. As the filament is extruded through the small nozzle, the chain is stretched and will want to return back to its ‘normal’ state, much like an elastic band will go back to its position when it is released.
This tendency to return to its ‘normal state’ causes internal stress in the 3D printed part. Warping or cracking will occur if the internal stress is stronger than the bed adhesion (for flex plates stress will cause the plate to flex) or interlayer adhesion.
The internal stress in the 3D Print will also compromise the mechanical performance of the part. this is why you will find suggestions to anneal some parts after 3D printing. Annealing will remove internal stress in the part thus improving mechanical strength, however will not reverse warping and will cause shrinkage and expansion in certain dimensions, less than ideal.
The key to printing PolyCarbonate parts with maximum mechanical performance and near-zero warping is by minimizing internal stress during the printing process
How do we minimize internal stress / warping during printing?
As the filament is deposited, heat will allow the Polymer chain to ‘move’ therefore return to its ‘normal’ state; eliminating internal stress. The closer the temperature is to the materials glass transition temperature, the better. Most high quality 3D Printers are equipped with a heated bed and a ‘heat retention chamber’ which can help prevent drafts and retain the heat produced from the bed. This ambient temperature will work effectively to minimize warping for small and medium prints however it is not controlled nor is it hot enough to print medium parts with high infil or large parts with near-zero warping.
To print these parts with near-zero warping, a 3D Printer with controlled chamber heating like the INTAMSYS FUNMAT HT is required. Two active heating components maintain a controlled internal chamber temperature (up to 90°C). As the electronics are also exposed to this ambient temperature, it is important high quality and industrial grade components are used, as is the case for the FUNMAT HT. Through maintaining a high chamber temperature we have been able to achieve completely solid medium sized PC prints with absolutely near-zero warping.
Warning: Adding active heating to any standard Desktop 3D Printer will likely result in permanent damage to the printer, all electronics and product materials must be tested and rated for performance in the chambers high temperatures. This is one of the reasons most 3D printers don't have active heating.
Comparison with and without active heating
When our FUNMAT HT was delivered one of the first things we wanted to test was how much the active heating would minimize warping. The best file to test was the base of our Car Jack design. We had previously printed Car Jack in PC-Max with relative ease and minimal warping on most parts, except for the base of the jack.
We decided to print the base of the jack again once on the FUNMAT HT with active heating and on another printer which has been considered one of the best ABS and PC desktop 3D printers. Both parts were printed with 100% infil, heated bed at 90°C and the ideal nozzle temperature for the printer. (250°C / 260°C). We expected the solid infil to cause some warping with the FUNMAT HT's active heating, but we were incredibly surprised at the difference. By printing at a lower infil, it would have been possible to minimize warping from the other 3D printer, however that would have also lowered mechanical performance.
While it is relatively easy to achieve excellent small to medium sized PolyCarbonate 3D Prints from many desktop 3D Printers, we have found for printing large or solid medium sized PolyCarbonate parts; nothing has compared to the out put of the FUNMAT HT. Printing PC with near-zero warping is here, thanks to the FUNMAT HT's advanced controlled chamber temp, insulation, safety cool down procedures and industrial grade components.