Fyous could reduce 3D printing resin material used in dental aligners by 10 times with PolyMorphic moulding and reconfigurable pin tooling technology
Transparent teeth aligners have become very popular in the last decade. The process involves 3D scanning of the teeth, correcting them in software, and 3D printing the altered teeth to use as a mould in a vacuum/thermal forming process, where an optically clear and tough material is used for the aligners.
The Problem
Currently, the teeth molds are 3D printed using the SLA method because of the high-resolution surface finish. SLA resins are very expensive and not usually environmentally friendly or degradable. Additionally, with one customer for Invisalign or equivalent needing 10-40 aligners over the course of treatment, there is a significant amount of one-time-use wastage.
There is also the financial cost of 3D printing solid moulds when they are not actually necessary. The important part of the mould is the outer surface. So, what if you could print the mould hollow/shelled out?
Fyous ran a trial with their PolyMorphic moulding machine (which creates reusable moulds out of thousands of tiny pins) assisting in the production of Dental teeth aligners. The objective is to try and reduce the amount of print time and material consumption.
Methodology
Fyous started with a typical solid 3D model of some scanned teeth, as seen below. The teeth were then modified in CAD to allow them to be shelled to a thin-walled version. Once processed, the walls of the model were 0.3mm thick.
The 3D model was then converted to an STL file and 3D printed on a Formlabs Form 3 printer with grey V4 resin, and at the same time put through Fyous's Object surface point mapper software (OSPM) for use with Polymorphic moulding. Think of this like a slicer for a 3D printer.
OSPM software application result
Once this is done, the PolyMorphic moulding machine can start working its magic, shapeshifting the pin tooling into the correct geometry. This takes about 5 minutes. Once complete, this is what it looks like.
The 3D print of the very thin-walled teeth mould is then positioned over the top of the pins, which provides support for the very weak but detailed 3D printed surface.
This is a cross-section of the 3D printed shelled/hollow surface position over the supporting reconfigurable pins. The 3D printed part is only 0.3mm thick.
CAD Illustration of the pins in position to support the 3D printed outer skin.
The image below compares a hollow/shelled part vs a solid part. The grey area is the material that is removed equating to a 7997mm³ reduction in volume. The new hollowed-out part has a new volume of 1131mm³ from 9129 mm³ which is a 707.8% decrease.
This is the vacuum / thermo forming process in action. The material being formed is a PET sheet.
To compare results. We then tried to vacuum form the 3D printed teeth mould removed from the reconfigurable pin tooling support structure to see the results. And unsurprisingly, it collapsed under the pressure. SQUISH!
Results
Comparing the 3D printed resin material usage of the shelled thin wall and solid teeth showed a 10x reduction.
So, what does this mean?
Well, imagine how many people worldwide are using clear teeth aligners and how many teeth moulds are being produced daily. Let us say it is a million per day. The table below demonstrates the environmental and economic benefits of PolyMorphic moulding, which, if used to assist in the production of Dental Aligners, could be a game changer.
|
Shelled |
Solid |
Saving |
Time |
42 min |
54 min |
22% |
Material |
1.24 ml |
12.85 ml |
1/10th of material |
1 million units |
1,240 L |
12,850 L |
11,610 L |
Cost per 1mn (£150/L) |
£186,000 |
£1,927,500 |
£1,741,500 |
