Key Takeaways
- Printed SLA patterns feed traditional investment casting.
- Castable resin burns out cleanly for metal casting.
- Skips hard tooling for low-volume metal parts.
- Ideal for jewellery, art, and complex castings.
Investment casting is the oldest precision metal forming process — a pattern is coated in ceramic, the pattern is burned out, and molten metal is poured into the resulting cavity. Traditionally, patterns are injected wax, requiring a metal injection die. The die costs ₹50,000–5 lakh and takes 4–6 weeks. For one-off or small-batch metal parts, that tooling cost is prohibitive. 3D printed SLA patterns eliminate the die entirely.
How SLA Replaces Wax in Investment Casting
Investment casting requires the pattern to burn out cleanly at temperatures below the ceramic shell sintering temperature (approximately 700–900 °C), leaving zero ash that could contaminate the cavity. Wax burns cleanly at 200–300 °C. Standard resins leave significant ash. Castable SLA resins (Formlabs Castable Wax V2, Sculpto Wax, and similar) are specifically formulated to match or exceed wax burnout characteristics — typically <0.01% ash at 750 °C.
The process: print the part in castable SLA resin at ±0.05 mm accuracy → attach sprues and gates → coat 6–8 times in ceramic slurry → dry between coats → dewax/burnout at 750 °C → pour molten metal → break out ceramic → cut sprues → finish.
What This Enables
Any metal castable by investment casting — bronze, brass, gold, silver, aluminium alloys, stainless steel, titanium alloys — can be cast from an SLA pattern. This includes alloys not available in DMLS (high-tin bronze for musical instruments, 18-karat gold for jewellery, ductile iron for engineering applications). The SLA surface quality (Ra ≤3 µm) directly transfers to the casting surface — producing as-cast surfaces finer than sand casting with no die required.
Dimensional Accuracy
SLA dimensional accuracy (±0.05–0.1 mm) sets the upper bound for casting accuracy. Casting shrinkage (1.5–2.5% linear for most alloys) must be compensated in the SLA design — Layer X includes this in the DFM review for all casting pattern orders. Final casting dimensional accuracy is typically ±0.3–0.5 mm for features under 50 mm; tighter tolerances require post-cast machining.
Comparison with DMLS for Small Metal Parts
For identical geometry in 316L stainless or titanium, DMLS and SLA-pattern investment casting produce similar results at different cost points. DMLS has better dimensional accuracy and shorter lead time (5–7 days vs 10–14 days for casting). Investment casting enables alloys not available in DMLS, can reach larger sizes (investment casting has no practical size limit), and is significantly cheaper for very small quantities in precious metals (gold, silver).
Layer X offers both processes. Upload your CAD and specify your alloy to receive a comparison quote for both routes.
Applications at Layer X
SLA investment casting at Layer X serves: jewellery brands requiring custom 22k gold pieces without wax injection dies, aerospace customers needing titanium castings in alloys not available in DMLS powder, industrial customers needing bronze and brass components for hydraulic and pump applications, and art foundries producing limited-edition sculptures from digital designs.