Stereolithography or SLA is the veteran of 3D print technologies having been around since the late 1980’s. Despite its age it still continues to be one of the most widely-used rapid protoyping technologies for plastic models. It has been widely used in the medical and automotive industry due to the accuracy of the prototypes produced.
What is SLA?
Graphite AM use three different types of SLA from DSM: Watershed XC 11122, PerFORM and DMX SL 100.
Watershed XC 11122 is used for general purpose plastic due to his elongation to break, water resistance and optical clarity. The material is clear but is available in a number of finishes. This material is best used for concept models, master patterns or lenses.
The second SLA material is PerFORM, which is a ceramic material but also available in a number of different finishes. The ceramic material used gives high-accuracy, low shrinkage and can offer an exceptionally smooth surface finish. PerFORM is used on tooling for composites, tooling for injection moulding, parts that will be metal plated or subject to high temperatures or high voltage.
The last material using the SLA process is DMX SL100. A tough and durable material with an impact resistance similar to thermoplastics. Used for prototypes with snap fit features, living hinges and composite tooling applications.”
How it works
The SLA process uses a vat of UV-curable liquid resin, which is cured by a laser to build parts one thin layer at a time. The laser ‘draws’ a single layer cross-section of the part on the top surface of the liquid resin, curing and solidifying it whilst joining it to the layer below.
Once a layer has been drawn and cured, the SLA machine’s platform is lowered by an amount equal to the depth of one layer. This then allows the re-coater blade to sweep across the vat, spreading another layer of fresh resin, ready for the laser to draw on. In this way a whole three-dimensional part is built up. Once completed, the build is drained, washed in a chemical bath to remove the excess resin, and then finished to your specifications.
What are the benefits of SLA?
- Accuracy
- Speed
- Good surface finish
- Tear resistant
- Water resistant
- Stiffness
- High temperature resistant
What can SLA be used for?
- Concept models
- Prototypes
- Lenses
- Jigs and dies
Examples of where SLA has been used
Toolcraft Plastics & Graphite develop rapid injection moulding tools
Toolcraft Plastics (Swindon) Ltd is a long established, plastic product mould toolmaking, injection moulding and vacuum forming firm. The company offers a complete design to production service, including design, printing and product assembly. Toolcraft came to Graphite Additive Manufacturing when they were looking to create a quick turnaround injection moulding tool.
The challenge was to create a cost-effective and fast way to produce a very small amount of mouldings. Toolcraft wanted a tool that could be mounted in their standard machines to handle short runs of plastic injection moulding and produce good results in a range of different materials: ABS, polypropylene, TPE (Thermoplastic Elastomer) and PA (polyamide).
A mould tool for Toolcraft’s supermarket trolley coin was 3D printed by Graphite, utilising a ceramic filled plastic. The two part mould was built on a stereolithography (SLA) machine at Graphite’s base in Aylesbury, within one day. Complicated metal tooling can take weeks to produce and at a much greater cost.
Toolcraft mounted the new 3D printed tool in their standard tool bolster and ran it in one of their automatic injection moulding machines. The results, for the short production runs in each of the chosen materials were excellent.
The ceramic filled plastic tool does not have such a long life as a steel or aluminium one – but as a cost and time effective technique the process is ideal. The 3D printed tool option is now offered by Toolcraft to customers with either very small run projects or those with a requirement for an urgent turnaround, especially as the printed plastic tool can supply a batch of mouldings in a matter of days, perhaps while the customer is waiting for a standard metal tool to be produced.
