Continuous DLP 3D Printing : Working of CLIP and cDLM Technology

CDLP or Continuous Digital Light Processing is a technology that works on DLP technology principles curing photosensitive liquid resin with UV LED light focused from the DMD Projectors. The major difference between the CDLP and DLP technology is the elimination of peeling or vacuum effect or separation force in DLP technology after the curing of one layer.

We learned that in DLP technology DMD Projectors are used to cure the resin contained in a small VAT placed above the projector. The images of the slice get focused on the bottom of the VAT with a UV light source and get cured after focusing the image for 5 to 10 seconds. For separation of the base and the cured resin, a peeling step is performed. This type of 3D printing is called ‘Bottom-Up Printing’.

Schematic representation of Continuous DLP 3D Printing. Image Source: Carbon/Youtube 

The CDLP technology is newly developed by two major companies Carbon, Inc. and EnvisionTEC GmbH. The Carbon, Inc. introduced as the ‘CLIP Technology’ and the DLP pioneer EnvisionTEC GmbH named it ‘cDLM Technology’. We will learn both the technology step by step.

Working of CDLP Technology

The Continuous 3D Printing technology works on DLP technology by eliminating the peeling effect. The main process or heart of continuous 3D printing technology is the ‘Dead Zone’ which eliminates the separation or vacuum force produced while separating the printed part from the base of resin VAT.

GIF represents the working of  Dead Zone. Image Source: Carbon, Inc./Youtube.com

The ‘Dead Zone’ is the micro distance between the window (base of resin tank) and the printing part which allows the oxygen to move inside. The resin pass through this zone and the UV light from the projector cure the resin which is above the dead zone into a solid part. The resin below the dead zone progresses above the dead zone with the flow of oxygen and the next layer is projected. This entire process is done continuously with the help of oxygen which creates the Dead Zone maintaining ‘Continuous Liquid Interface’.

Once the printing is complete the part is then transferred to the thermal bath or oven to get baked as the part is partially cured. In a thermal bath or oven, the part will gain strength and other mechanical properties.

Carbon CLIP Technology

CLIP technology is a VAT Polymerization technique that uses UV Light to cure the liquid resin into solid parts. It projects the UV light from beneath the transparent resin tank like the DLP 3D printer, but here the resin tank has the ‘oxygen-permeable window’. The solid part is lifted upwards slowly layer by layer as the images of the slice are projected in sequence.

In the year 2015, a new technology of VAT Polymerization called the CLIP (Continuous Liquid Interface Production) technology which was a proprietary method of 3D printing was invented by Joseph DeSimone, Alexander and Nikita Ermoshkin, and Edward T. Samulski and was originally owned by EiPi Systems but is now being developed by Carbon, Inc.

Carbon, Inc. also claims that with CLIP technology the parts are 3D printed 100 times faster than the existing SLA and DLP 3D Printers.

EnvisionTEC cDLM Technology

The pioneer of DLP technology EnvisionTEC GmbH is the world leader in manufacturing high accuracy DLP 3D printers since 2002. They use high definition projectors to cure their customized resin materials which are made to serve different industries.

Image representing cDLM Technology. Image Source: EnvisionTEC GmbH

EnvisionTEC GmbH filed a patent on continuous 3D printing in the year 2006 describing the non-interruptive 3D printing on DLP machines powered by UV LED light projectors. They mentioned the use of an oxygen-permeable window under the VAT surface which eliminates the peeling effect. The patent was granted to EnvisionTEC in the year 2011.

Engineers and Technology Developer at EnvisionTEC recognized the challenges occurs while using continuous printing technology like inaccurate parts in the large platform. The use of oxygen below the resin tray is causing a slight tent due to pressure.

To overcome this challenge EnvisionTEC has manufactured 'Domeless Material Tray' which remains flat and parallel during continuous printing.

Conclusion

Both the Carbon CLIP technology and the EnvisionTEC cDLM technology works on the same principle of continuous 3D printing of liquid resin parts using DLP 3D printers. Both technologies face the same problem of inaccurate parts in largely built platforms.

Due to oxygen pressure below the VAT causes a slight tent on the material tray which results in making a dome type structure on the solid 3D printed part. This makes an impression on the printed part which creates inaccuracy in dimension.

EnvisionTEC GmbH has found a solution to eliminating the Dome-Effect by manufacturing flat and parallel built tray by using materials that do not get affected easily by the oxygen pressure used in the cDLM 3D Printer.