Patterns and Tooling
While stereolithography is most often associated with prototyping, patterns and tooling account for a substantially higher percentage of overall SL material usage. The accuracy and precision of SL printing coupled with excellent surface aesthetics is ideal for creating patterns for various casting and molding processes including:
• Urethane casting ( also known as RTV molding)
• Investment Casting
• Thermoforming Patterns
• Injection Molding
Urethane casting is often used to fill the gap between prototype and production when part volume requirements or overall performance requirements exceed prototyping capability. SL is used as an efficient method of acquiring an accurate master pattern that is used to create a flexible RTV tool for casting. A specially formulated silicone rubber is poured and cured around the master pattern. The pattern is removed forming a core and cavity mold. Urethane casting capability is often a core competence of many AM service providers with SL capability.
UnionTech™ SL equipment is available in a range of sizes that can accommodate most master pattern needs. Photopolymers from multiple suppliers are well established for master pattern use and can be used on UnionTech SL equipment without restriction.
Investment casting of wax patterns in a ceramic shell to create forms for casting metal to create near net shapes is a historical and well established process. It is used to produce intricate small objects , like jewelry, as well as very large industrial parts. Stereolithography is used when tooling for wax patterns is not warranted due to volume or complexity to create an accurate hollow pattern.
UnionTech™ SL equipment utilizes a special software to create hollow, reinforced patterns that can withstand the ceramic pattern production process and still be efficiently removed via incineration without damaging the shell.
Use of SL for injection molding tooling has been an active area of development since the mid-90’s. The introduction of filled composite SL formulations in 2002 re-energized development efforts with heat deflection temperatures over 250° C and major increases in strength and stiffness.As SL formulation advances have continued to improve ease of processing, interest in this approach continues to grow, especially when SL part manufacture and injection molding is an integrated operation. The exceptionally smooth sidewalls produced by UnionTech™ SL coupled with the improved ease of finishing available from current filled composite SL formulations further enable this type of application for prototype, functional testing and bridge tooling.
After nearly 20 years of application and market development, AM rapid tooling is finding utility at the intersection of stereolithography (SL) process technology, material performance evolution, and fresh business model thinking.
Stereolithography has always offered the ability to efficiently manufacture a matched die set for injection molding within days. SL offers many advantages for this application over direct CNC machining.