Overview of 3D Printing Technologies
In this post I will attempt to offer a simple and concise overview of the most prominent 3D printing technologies.
Fused Deposition Modelling
We’ll start with what Plasticwright currently utilizes, Fused Deposition Modelling (FDM). FDM printers create objects by laying down successive layers of plastic by moving an extruding mechanism back and forth; after a layer is completed the build platform moves downward a single layer thickness. This is all controlled by a CNC controller driving stepper motors. As you can see in the photo gallery, objects created by this method have a grain. If you study the pictures you can see the tool paths on the top surface.
The most common materials for FDM printing are PLA and ABS; while Nylon, PET, PVA, and Carbon Fiber are seeing some use. Of the newer materials PET is the most exciting for everyday use as it offers the best of what ABS and PLA have to offer in one material.
Resin Based Printers
Resin based printing falls primarily into 2 different technologies: Stereolithography (SLA) and Polyjet. Both utilize a UV cured resin but differ in the deposition method. Respectively, these techniques are the main technologies that 3D Systems and Stratasys utilize in their printers.
Polyjet printers use a technique related to inkjet document printers. Each layer is laid down by a print head that moves back and forth just like a common inkjet printer would, after each layer is deposited the build platform moves downward to accommodate the next layer. As the print head lays down resin it also hardens it with a UV light. Parts printed by Polyjet have a smooth finish as the layers are in the tens of microns thick compared to the hundreds of microns FDM printers are capable of.
SLA printers utilize a UV laser and a vat of resin to create objects. The build platform is positioned above the vat and the laser is fired at it to build layers as the platform rises upward. As with Polyjet, SLA created models also have an ultrafine surface finish. SLA printers will soon become more common as critical patents held by 3D systems are set to expire in the next few years.
The early resins used in 3D printing were quite brittle and failed easily from fatigue at low loads. Resin technology has improved drastically since the early days; Stratasys has a resin that mimics the properties of ABS. However the ABS analogue resins are typically reserved for the high end printers leaving lesser materials for the low end printers.
Another type of 3D printer is called Laser Sintering. Laser Sintering creates part and models from powders and materials can range from wax to metals such as tool steel and cobalt. Each layer is created by powder being laid on a print bed and a laser melting the material.