Castable Resin (Investment Casting Patterns)

Castable resins are photopolymers formulated to burn out of an investment mold with almost no residue, so a printed part can replace the wax pattern in investment casting, the lost-wax process. The pattern is attached to a sprue tree, embedded in investment, burned out in a kiln and replaced by molten metal. Two families are common: wax-filled resins, which contain a significant share of wax and behave more like wax during burnout, and unfilled clean-burning resins, which are stiffer but need a more careful burnout schedule.

Choose castable resin for small, detailed metal parts made as one-offs or in low volumes, where a wax injection tool would not pay off: rings and jewelry, dental crowns, bridges and partial denture frameworks, and small precision castings. The printed pattern is not the product; the final quality depends just as much on investment, burnout and casting. Patterns are fragile and heat-sensitive, and resin expands before it burns away, which can crack the investment if the schedule is wrong.

Mechanical and physical properties

Printing castable patterns

Castable patterns are printed on SLA, DLP or MSLA machines with fine layers, then washed and, depending on the grade, post-cured as the resin manufacturer specifies; both steps affect pattern strength and burnout. DLP and MSLA print many small patterns in one build, which is why they are common in jewelry and dental labs. Design and ordering points:

• Orientation and supports: place supports on faces that will be sprued or are easy to finish in metal, and keep them off stone seats, prongs, engraved areas and the fitting surfaces of dental work.
• Fine features: thin prongs, filigree and openwork are fragile in the pattern and must also survive investing; allow some extra thickness on features that will be polished in metal.
• Shrinkage allowance: metals shrink as they solidify, and investments expand to compensate. Agree with the caster whether patterns should be scaled, and by how much.
• Hollow and thin-walled designs: less resin in the pattern means less expansion during burnout and less metal in the casting; hollow patterns need openings so the investment can fill them and resin can drain.
• Sprues: patterns can be printed with sprue stubs if the caster specifies their position and size; otherwise the caster adds sprues in wax.
• Handling: wax-filled patterns bend and scratch easily; pack them individually so they do not touch, and keep them cool until investing.

Burnout and investment casting

A resin pattern behaves differently from wax in the flask. Wax melts and drains early, while resin softens, expands and only then decomposes, so the burnout schedule and the investment must suit resin. Notes for casters and buyers:

• Schedule: a typical resin schedule heats in stages, with a low hold to dry the investment and melt out any wax content, an intermediate hold while the resin decomposes, and a long hold at about 730 °C for gypsum-bonded investment to burn off remaining carbon, before the flask is brought to casting temperature.
• Air flow: resin needs oxygen to burn out completely; a well-ventilated kiln and flasks placed sprue-down on a raised grid help prevent residue.
• Investment: resin-compatible or high-strength investments resist cracking better; follow the investment manufacturer's mixing ratio and setting time.
• Alloys: gypsum-bonded investments suit gold, silver, bronze and brass; cobalt-chrome, palladium and platinum alloys need phosphate-bonded investment and higher burnout temperatures.
• Order scope: state whether you need printed patterns for your own caster or finished metal parts; feasibility of the casting route, the alloy and the lead time are confirmed during quote and order review.

Tolerances and surface

Without a tolerance on the drawing, Uretyco's default for SLA parts is ±0.2 mm or ±0.2%, whichever is greater, and it applies to the printed pattern. The cast metal part adds shrinkage, investment expansion and finishing loss, so its accuracy is agreed separately for each casting job. Pattern surfaces are very smooth, but every support mark, layer step or fingerprint transfers to the metal; finished pieces are usually polished, which removes a thin layer of metal.

Finishing options

Finishing happens at two stages: on the pattern before investing and on the metal after casting. Pattern finishing stays light, because wax-filled resins are soft.

Cost and lead-time drivers

Castable resins are among the more expensive photopolymers, but patterns are small, so print time, batching and manual work usually dominate the cost:

• Batching: many rings or dental units fit in one build, especially on DLP and MSLA, which lowers the cost per pattern.
• Build height: tall patterns and upright orientations take longer to print.
• Supports and cleanup: delicate patterns are freed from supports carefully by hand.
• Casting scope: when metal parts are ordered, metal and finishing usually outweigh the pattern cost, especially with precious alloys.
• Remakes: a failed casting needs a new pattern, so sound sprue planning and a controlled burnout matter for the overall lead time.

Castable resin vs. other pattern routes

For one-off and custom pieces, castable resin and jetted wax avoid tooling entirely. Once a design repeats in volume, a wax injection tool lowers the cost per pattern, and for complex cobalt-chrome parts, direct metal printing can replace the casting step altogether.

When not to choose castable resin

Typical applications

• Rings, pendants, earrings and custom jewelry in gold, silver and platinum.
• Dental crowns, bridges and partial denture frameworks for casting in precious or cobalt-chrome alloys.
• Patterns for pressed dental ceramics.
• Small precision castings such as watch components, miniatures and small mechanical parts.
• Art and sculpture castings in bronze and brass.
• Prototype castings before a wax injection tool is made.

Specifying castable resin on Uretyco

1. 1
   Upload STL or 3MF

   Export in millimeters with a fine mesh; organic jewelry and dental surfaces need a high mesh resolution to stay smooth.

2. 2
   Choose castable resin and the grade family

   State whether you prefer a wax-filled or an unfilled grade, or leave the choice open; name a specific resin only if your casting process is validated for it.

3. 3
   Describe the casting process

   Give the alloy, the investment type and whether your caster has a resin burnout schedule, so a suitable grade and pattern layout can be proposed.

4. 4
   Mark critical areas

   Mark stone seats, fitting surfaces and decorative faces that must stay free of supports, and note any scaling for metal shrinkage.

5. 5
   State the scope

   Say whether you need printed patterns only or finished metal parts; casting routes, alloys and lead times are confirmed during quote and order review.

FAQ

Wax-filled or unfilled castable resin?

Wax-filled grades burn out more like wax, expand less and tolerate a standard schedule better, which reduces investment cracks; their patterns are softer and need careful handling. Unfilled grades hold thin prongs and sharp details better and are easier to handle, but they need a slower, well-ventilated burnout. The right choice depends on the design and the caster's equipment, so agree on it before printing.

Can a standard wax burnout schedule be used?

Usually not without changes. Resin needs longer holds and good air flow to burn out completely, and a fast wax schedule can leave residue or crack the investment. Use the schedule published for the specific resin and investment, adjusted to the flask size.

Can standard resin be used for casting?

Standard resin is not formulated to burn out cleanly; it usually leaves more ash and expands more, which causes casting defects. For investment casting, use a castable grade. For larger industrial castings, foundries sometimes use hollow patterns printed in standard SLA resin with ceramic shells, which is a separate process.

Does castable resin end up in the mouth?

No. The pattern is burned out completely, and the patient receives the cast metal or pressed ceramic restoration. Compliance therefore depends on the alloy or ceramic, the validated casting workflow and the regulatory responsibility of the dental laboratory or practice that makes the device.

Related resources

• Standard SLA ResinSmooth resin for models and silicone mold masters.
• Dental ResinResins for dental models, surgical guides and splints.
• Cobalt ChromeCast or printed alloy for dental frameworks.
• Aluminum A356 (Cast)Aluminum alloy for sand, investment and permanent-mold casting.
• Molding & Casting OverviewTooling-based molding and casting routes compared.
• 3D PrintingTechnologies, tolerances and cost drivers.