Recently, Carbon's 3D valuation exceeded 2.4 billion USD . I must admit that I personally think the process is a breakthrough, a real innovation.
This provided me with inspiration to again look at its intellectual property and create prior art to facilate circumventions of its patent.
Carbon has a technique which it denotes as Continuous Liquid Interface Processing (CLIP) . Carbon uses a Digital Micro-mirror Device (DMD) to illuminate a photopolymer through an oxygen-permeable window made of a fluorpolymer such as Teflon AF. Teflon AF can be sourced from Biogeneral . Nasa described how a teflon AF sheet can be made. A supplier of chemicals can be found here .
The permeation of oxygen through the window creates a persistent liquid interface, nicknamed "dead zone", where photopolymerization is inhibited between the window and the polymerizing part. Oxygen inhibition was an effect that was already shown to play a role by Denkari et al. in 2006 for silicon release coating invented by John Hendrik, see US7052263 (B2) . The "dead zone" in silicone release coating is so small that a peeling is needed to release the part from the transparent window. Hessel Maaldrink sped up the process by adding a force feedback sensor EP2043845B1 . Using Teflon AF and a polyuerethane Tumbleston et al. 2015 where able to extend the "dead zone" to approximately 30 micrometers. As such the part does not have to be peeled of from the optical window during the process and stair stepping is minimized. This allows for the production of flexible parts. Furthermore, the "dead zone" speeds up the viscous flow between two parallel plates, part and window, for the application of a new layer, see WO2014126837A2 , improving the print speed.
I will now try to create prior art and formulate a work around for the Carbon patent to extend the freedom of application of the transparent polygon scanner marketed as Hexastorm.
After studying the WO application of CLIP, I noticed that the European patent is different from the US patent. In the European patent EP2956823B1 claim one states ".. irradiating said build region through said optically transparent member to form a solid polymer from said polymerizable liquid while also concurrently advancing carrier away ..".
As such, I claim irradiating said build region with for example a transparent polygon scanner while not concurrently advancing away the part, but discretely. The part is exposed and moves after a full exposure. Moving during an exposure is also not possible as Hexastorm exposes a line and not a plane.
DMDs have a pattern/pixel rate of up to 20 kHz. Laser diodes can achieve a refresh rate up to 100 MHz. At 50.000 RPM and six sides, a transparent polygon scanner exposes at line rates of 5000 Hz. With a laser diode, the refresh rate is so much higher that it might be possible to alter the polymerization over much smaller distances. Stair stepping would be minimized even though the part is moved discretely.
If it is not possible, the procedure would still allow for the production of flexible parts.
The US patent, US 9216546B2, is wider in scope as claim one specifies "A method of forming a three-dimensional object, comprising the steps ...". The formulation using "steps" in US patent differs from "concurrently" in the European patent.
In the US the process is also under patent if the part is not moved during exposure. Carbon as a result markets its technology as "digital light synthesis technology", although Continuous Liquid Interface Processing (CLIP) seems more accurate in the European union.
Key in the US patent is that parts are produced upside down and moved away from a build surface which is not air. This is peculiar as the original patent by Hull in 1986 specifies both up and down projection in figure 3 and 4 respectively.
As such, I claim the use of oxygen-inhibition in down projection, where the top is up, using a transparent polygon scanner. Again, the fast exposure of a laser diode might minimize stair stepping and the "dead zone" will simplify coating. Additionally, using air instead of a teflon AF layer reduces costs.
After studying the following literature, dip and blade coating patent US5651934 of Charles Hull, flows in thin film coating by Christian Kushel, Zerphyr coating as described in US6159311, curtain coating as described in EP0928242 and the book Liquid Film coating by Kistler, I claim the following.
1. Firstly, the use of "dead zone" in 3D printing to facilitate the coating of liquids in down projection photo-polymerization where the top of the part is up. I will now explain this.
Boundary conditions during coating are important. A part solidified up to air provides a non-consistent liquid // solid boundary condition. During for example blade coating the coater can collide with the part. A dead-zone would prevent this and create a more consisting wetting of the substrate during for example Zephyr coating as it is entirely liquid.
2. Secondly, I claim that an array of transparent polygon scanners is integrated in the Zephyr blade. I claim that possibly in the Zephyr blade a Teflon AF film is partly applied between the liquid and air interface. I claim that in the Zephyr blade the pressure of the air is monitored. I claim that an opening is provided to actively supply liquid to the Zephyr blade using a pumping mechanism.
3. Thirdly, I claim that the teflon AF film or part moves parallel to the plane of illumination and not only orthogonal as in the CLIP patent. Transfer substrates are used by Admatec , Carima and TNO EP2272653. Especially, I look at the figure provided at the front page of US2012007287. I claim that the film in this figure denoted by 10 is teflon AF and the exposure module denoted by 9 is an array of transparent polygon scanners.
I label the process which fall under my claims and not under Carbon's claims as Hexaforming.