We’ve received a couple of interesting videos on the new Form 3 technology from Formlabs, and they show a very unusual SLA process.
One of the great new features of the Form 3 line of 3D printers is that the laser illumination is said to be “uniform”. For those unfamiliar with this issue, let me explain.
SLA 3D printing involves flashing a vat of liquid photopolymer resin with a laser to cause that spot to solidify, or “polymerize”. Most SLA systems use a laser that’s mounted in a fixed position within the device, and a galvanometric mirror to direct the beam toward the target resin surface. Yes, it’s simply a tilting mirror.
But there’s a problem: when the mirror tilts excessively, as we described in a post last year about metal 3D printers, the spot illuminated by the laser gets distorted. Here we see how this problem occurs on a metal 3D printer, but it is exactly the same on an SLA 3D printer, except it’s upside down as SLA 3D printers tend to fire the laser through the bottom of a transparent resin vat:
The solution most often pursued by metal 3D printers is to lengthen the distance between the laser mirror and target, thus causing some metal 3D printers to be overly tall. But in a desktop 3D printer, that really isn’t a good option.
This can cause quality issues on the further edges of a 3D print, particularly if the 3D model includes finer details, which would be distorted by this effect.
This is what Formlabs is talking about when they say the laser is “uniform”. I wondered exactly how they were doing this, but the answer appeared in a couple of “deep dive” videos they just released:
Let’s take a look at how they are firing their laser with a screenshot from the video:
It seems that rather than aiming the laser upwards towards the resin vat, they instead fire it downwards to hit the usual galvanometric mirror. But instead of impacting the resin tank, it hits a secondary mirror at the top to reflect it downwards.
At the bottom there is a precision shaped mirror that reflects the beam in a perfectly vertical straight path, allowing the illuminated spot to be entirely “uniform”.
This is a very interesting approach that I have not seen previously in desktop SLA devices. I’m wondering if Formlabs has patented this. Well, no, I am certain they must have applied for a patent on this approach.
This unusual mirror approach to uniform SLA illumination could be a significant advantage to Formlabs, as I suspect it may be challenging for smaller companies to devise and fund the development of such a complex optical system.
When Formlabs said the Form 3 machines will provide “incredible detail and surface finish”, they weren’t kidding. This new laser engine is how they make that happen.