Materials evolution extends versatility of SL technology
Since its inception in the 1980s, stereolithography (SL) had been recognised as one of the most cost effective and flexible rapid technologies available, especially for the production of complex models.
As one of the pioneers in this field with the RenShape range of SL materials, Huntsman Advanced Materials has continued to research and develop innovative stereolithography materials specifically designed to meet the changing needs of an increasingly competitive global market with ever tighter time-to-market schedules.
Curing by laser
Stereolithography produces physical models directly from CAD data. These are produced by curing many successive layers of photopolymer with an ultraviolet laser beam in an SL apparatus. This is done without cutting, machining or tooling the model so they are produced very quickly – around 50 times faster than conventional modelling methods and around 25percent more cost effectively.
SL technology is already widely used in the aerospace, automotive, home appliances and electronics industries, where complex, often highly detailed models and shapes are required.
Some of the key milestones in the history of stereolithography materials development at Huntsman have included:
- 1988 – first acrylate system commercialised.
- 1993 – first epoxy resins with high accuracy.
- 2000 – first PP-like epoxy system.
- 2002 – first white epoxy resins with ABS-like characteristics.
- 2006 – next generation tough and durable SL resins.
This continuous development programme has resulted in pushing SL materials into different applications including concept modelling and prototype testing; casting and moulding patterns; medical models; short run production parts and prototype tooling and functional prototypes for customer testing and field approval.
With the combination of toughness, durability and improved overall functionality the latest RenShape ABS-like SL materials are the first to be currently used in a limited manufacturing capacity for specialist parts and certified for use in medical devices.
Future generations of advanced hybrid photopolymers currently under development at Huntsman will take stereolithography further into true volume production of finished parts.
Opaque characteristics
The wide range of commercially accessible stereolithography materials has enabled the production of opaque or coloured models with ABS-like characteristics.
These materials offer high temperature and high humidity resistance as well as good durability and impact resistance.
Thanks to the wide diversity of materials available, designers and engineers are now able to select the photopolymer that most specifically fits their modelling requirements.
SL photopolymers
The new generation of SL photopolymers has been designed to create prototype models and parts with improved overall functionality.
These durable parts have high impact strength together with long term dimensional stability, even under conditions up to 40°C and with 90percent humidity.
Two of the most recent and advanced photopolymers, RenShapeSL7800 and RenShapeSL7810, have been certified as conforming to the rigorous conditions of the FDA approved USP23 class VI test.
And this means they can be used for medical modelling and can be taken into sterile environments such as operating theatres.
Medical applications have proved particularly well suited to SL modelling as complex, often highly detailed, colourable models are required.
RenShapeSL7800 offers outstanding general performance properties combined with high impact strength and elongation.
This high performance, clear, amber-coloured photopolymer is designed for use on solid state SLA platforms and is particularly suitable for Quickcast patterns. Its low viscosity makes SL7800 easy to process with an ash residue upon burning reduced by 97percent.
With its antimony-free composition, RenShapeSL7800 produces non-toxic durable models that can be used for medical applications.
In addition to its excellent properties, RenShapeSL7810 is a white, ABS-like low viscosity, highly stable SL resin that produces strong models and prototype parts with a good surface finish and fine detail.
Processing with SL7810 is also easier due to the materials’ low viscosity and high strength of the models.
Hybrid materials
Huntsman Advanced Materials is already planning to extend the current Family of stereolithography photopolymers with a wider range of advanced hybrid SL materials.
These will be able to produce faster than ever, highly accurate display models and functional parts with a good surface finish.
Laurence Messé is Group Leader, Rapid Prototyping, Huntsman Advanced Materials. www.huntsman.com/advanced_materials
