Additive Manufacturing Pt 1: What is Stereolithography?
With all the buzz about Additive Manufacturing, or 3D Printing, in the manufacturing world today, there is a lot of mystery and confusion surrounding the common practices and techniques. So, this week’s blog post will address a common type of 3D printing known as Stereolithography.
But first, What is Additive Manufacturing?
Additive manufacturing is the process of creating a part by laying down a series of successive cross-sections (a 2D “sliced” section of a part). This technology came into the manufacturing world about 35 years ago in the early 1980s, and was adapted more widely later in the decade. A more common term used to describe additive manufacturing is 3D Printing – a term which originally referred to a specific process, but is now used to describe all similar technologies.
Now that we’ve covered the basics of 3D Printing, What is Stereolithography?
Stereolithography is the process of building an object by curing layers of a photopolymer, which is a polymer that changes properties when exposed to light (usually ultraviolet light). Typically this causes the material to solidify, or cure.
This technique uses a bath or vat of material. An Ultraviolet Laser will cure a layer of photopolymer on a platform. The platform is then lowered into the bath, and another layer of material is cured over the top of it.
A variation on this technique, referred to as Poly or Multi-Jet printing, has a slight modification to the process. Instead of using a bath of material, Jet printing uses separate reservoirs of material, which are fed through a UV laser. The material reservoirs in this process are quite similar to inkjet printer cartridges, and function similarly to an inkjet printer. This technique was developed by Objet Technologies, which was acquired by Stratasys in 2012.
What Are the Advantages of this Process?
Stereolithography is fast. Working prototypes can easily be manufactured within a short period of time. This, however, is greatly dependent on the overall size of the part.
SLA is one of the most common rapid prototyping techniques used today. It has been widely adopted by a large variety of industries, from medical, to automotive, to consumer products.
The SLA process allows for multiple materials to be used on one part. This means that a single part can have many several different structural characteristics and colors, depending on where material is deposited. In addition, all of the materials used in SLA are cured through the same process. This allows for materials to be blended during manufacturing, which can be used to create custom structural characteristics. It should be noted, however, that this is only available with either the MultiJet or PolyJet SLA machines.
Of the all the technologies available, SLA is considered to be the most accurate. Capable of holding tolerances under 20 microns, accuracy is one of the largest benefits to this technique.
What Are the Disadvantages of this Process?
Historically, due to the specialized nature of the photopolymers used in this process, material costs were very high compared to other prototyping processes. They could be anywhere from $80 to over $200 per pound. The cost of a machine is considerably large as well, ranging anywhere from $10k to well over $100k. Though recently, a renewed interest in the technology has introduced more consumer grade SLA machines, which has helped to drive down prices. New material manufacturers have also appeared in recent years (spot-A Materials and MakerJuice Labs), which has cut prices drastically.
Stereolithography is a process that requires the use of a support structure. This means that any part produced with this technique will require a secondary operation post-fabrication.
There are quite a few different ways to 3D print a part, with unique advantages and disadvantages of each process. This post is the first part of a series, discussing the different techniques. Thanks for reading!