How Selective Deposition Lamination (SDL) 3D Paper Printing and Rapid Prototyping Technology Works, Part 2 of 3: Printing the Prototype
In last week’s blog, I described the first step in the SDL process, generating the digital file. This week, we’ll cover how SDL works to produce 3D printed models and prototypes. Next week’s blog will describe the last part of the process, weeding the prototype.
Printing the Prototype
First, you manually attach the first sheet of paper to the printer’s build plate. The placement of the first sheet is not important, as the first couple of pages are attached as a base layer before the actual part cutting begins. (Fig. 3.1)
Once you determine that the blade depth and the adhesive levels are correct, you close the printer doors and the machine is ready to accept data from the SliceIT software.
From the PC and within SliceIT, you select ‘print’ and the 3D printer begins to make the part.
The printer applies adhesive on top of the first manually-placed sheet of paper. The adhesive is applied selectively – hence the name SDL – “Selective.” This means that a much higher density of adhesive is deposited in the area that will become the part, and a much lower density of adhesive is applied in the surrounding area that will serve as the support. (Fig. 3.2)
A new sheet of paper is automatically fed into the printer from the printer’s paper feed mechanism and placed precisely on top of the freshly applied adhesive. The build plate is moved up to a heat plate and pressure is applied. This pressure ensures a positive bond between the two sheets of paper. (Fig. 3.3)
When the build plate returns to the build height, an adjustable Tungsten carbide blade cuts one sheet of paper at a time, tracing the object outline to create the edges of the part. (Fig. 3.4)
When this cutting sequence is complete, the printer deposits the next layer of adhesive, and the whole process repeats until all the sheets of paper are bonded together, cut and the model is finished. After the last layer is complete, you can remove the part from the build chamber. (Fig. 3.5)
If you’re using the Mcor IRIS full-colour 3D printer, there’s one more step. Before any cutting, the Mcor IRIS pre-prints the colour outline of the part on each page in the appropriate colour combinations using a modified 2D colour inkjet printer that sits in the IRIS stand. Mcor’s patented water-based ink permeates the paper, preventing any white edges on the part. A barcode is also printed on each page to ensure the pages are in the right sequence. The pre-printed stack is then inserted into the 3D printer, which initiates the process described above in “How SDL Works” diagram. If a page is missing, the IRIS will pause to let you print a replacement. This process also fully colours the undersides, overhangs and sidewalls of models, which means you could recreate the ceiling and roof of the Sistene Chapel (at scale) in a single build.
Be sure to check back next week for the last part of the process, weeding the prototype.