What is 3D Printing?
3D printing is a relatively new technology that actually builds up a shape from the layering and fusing of polymers. This adding of layers is referred to as Additive Manufacturing (AM) and can produce a diverse array of products and prototype forms.
Yes 3D printing does share some similarities with CNC manufacturing. Both use programmed machines to product a finished product and they are controlled by a machine language. The big difference is how the product is produced.
CNC (Computer Numerical Control) starts with a solid block of material. The machine used, either lathe or mill makes multiple passes removing material to trim the solid down to a finished product.
The 3D Printing Process
To start the process of making a part 3D printable, there has to be a computer file containing all the product design information. This is done by using any number of CAD programs that can export the final file in a 3D printed format. A CAD program allows the designer to make the product on a computer and can be worked on in 3 dimensions. Everything is looked at on an X, Y & Z axis.
The CAD file is then sent to a “Slicer” program. This program examines the file and exports the information to “G Code” that the print can understand. This code tells the printer all the information that is required to make the product. All the product dimensions and machine movement is programmed into this file.
The printer is warmed up and the printhead, that melts the plastic into soft, almost liquid texture, and heated print bed are allowed to come up to the required heat levels. Every different material has different heat requirements.
When a 3D print starts there is only a flat level bed for the product to be built on. The printer starts by laying down an outer ring called a brim to prime or fill the printhead with material. The printer then starts laying down layer over layer and slowly builds the product up as it goes. Any locations in the design that have an opening or overhang require material to create a support. This is done by using a support material that fills in the openings and is removed after the print is complete. When the print is done the product is removed from the heat bed.
When the print is removed, it is in a raw state. When you look at the produce (see pictures provided) the layers are visible. For many applications such as a test parts or mounts a quick clean up is all that is required. If the produce requires a smoother finish there are materials and processes the can smooth the plastic and give a more plastic injection look.