Resin casting beats 3D printing when you need a small batch of identical parts with a production-like finish, while 3D printing wins for one-offs, early prototypes, and designs that are still changing. The resin casting vs 3D printing choice comes down to quantity, surface requirements, and how much the design will change. Resin casting here means pouring liquid polyurethane resin into a flexible silicone mold made from a master pattern, the physical original that the mold copies.
Both processes skip the machined metal tooling that injection molding requires, which is why they compete for the same short runs. Two of our projects, handles recast for Barcade’s arcade cabinets and ornamental plaster elements for a West Village brownstone, show where each one fits.
Resin Casting vs 3D Printing: How Do the Costs Compare?
3D printing needs no mold or tooling, so there is no up-front investment to recover. Resin casting puts its cost into the master pattern and the silicone mold, then makes each added part for the price of resin and a cure. In its vacuum casting guide, Formlabs puts a silicone mold at $200 to $1,000, against $5,000 to $100,000 for a steel injection mold.
The balance tips toward casting as parts get bigger. Formlabs notes that vacuum casting can make larger parts much faster and cheaper than 3D printing, with molds up to about 20 inches on the longest side and cast weights up to 3.3 pounds. A cast part also copies the finish of its master, so the surface work happens once on the pattern instead of on every piece.
Silicone molds wear out. Formlabs puts one mold at roughly 50 casts, Mack Prototype cites 20 to 25 depending on size, part geometry, and material, and a larger run means making more molds from the same master. Our guide to mold making and casting covers how those molds are built.
When Is Resin Casting the Better Choice?
Casting wins when you need repeatable parts that look and feel like finished production pieces. Cast urethanes come in rigid and flexible grades, clear and colored, and Mack Prototype lists their strength at about 80 to 90 percent of comparable thermoplastics. Every part comes from the same mold, so every cast copies the same master.
Our work for Barcade shows how this plays out. Barcade needed replacements for the handles on its Quick & Crash arcade controllers, which were thin-walled, injection-molded ABS (acrylonitrile butadiene styrene) and no longer available from the manufacturer. We 3D scanned the samples Barcade supplied and rebuilt them in CAD (computer-aided design) with redesigned internal ribs. We then cast new Quick & Crash controller handles in a urethane resin chosen for impact resistance, at Shore 85D hardness, from rigid, high-tear-strength silicone molds.
Degassing the resin under vacuum before pouring pulled trapped air out of the liquid, and the redesigned ribs helped it flow evenly into the mold. The handles drop into the original electronics without modifying the cabinet, wear far better than the originals, and look like them. Development took three months.
When Should You Stick With 3D Printing?
Printing is the right call for one-off parts, for prototypes you plan to test and revise, and for geometry a two-part mold can’t release, such as enclosed internal channels. A design change on a printed part is a file edit, while a change after casting means a new master and new molds.
Printing also wins on speed to the first part, since casting needs the master, the mold, and cure time before the first part exists. For a single display piece or a fit check, that head start settles the question. Quantity alone doesn’t rule printing out either: Formlabs points out that a print farm can handle batches of hundreds or even thousands of parts.
The Barcade job also shows why we print before we cast. Before we committed to the molds, we printed prototype handles and test-fit them on one of Barcade’s deployed cabinets, to check how they felt in the hand and whether the internal parts fit. We would test-fit a printed prototype before committing to molds on any part that has to mate with existing hardware.
How Is a Casting Mold Made From a 3D Printed Master Pattern?
A silicone mold reproduces whatever the pattern’s surface holds, flaws included, so the pattern has to be as clean as the finished part. That is why SLA (stereolithography) is the only process we use for master patterns. The highest-quality pattern gives the highest-quality cast. Formlabs likewise notes that SLA gives a smoother surface than SLS (selective laser sintering), the other process commonly used for casting patterns.
To make the mold, the pattern is held in a mold box and silicone is poured around it. After the silicone cures, the mold is opened and the pattern is removed, and Mack Prototype notes the master can be kept to make additional molds when a run needs them.
The same sequence works for other cast materials. For a West Village brownstone, we modeled nine types of custom ornamental plaster elements in CAD from 2D drawings, printed one SLA master pattern for each piece, and built a single urethane rubber mold for every master. Casting in plaster and installation followed.
Going from drawing to printed master took one to two days for most elements and about a week each for the corbel and the half dome. Because the masters were printed and then molded with no test piece in between, we would settle each model completely in CAD before printing, since a flaw in the print is a flaw in every cast.
What Happens When You Outgrow Silicone Molds?
A silicone mold gives out after a few dozen casts, so a bigger run means more molds from the same master, or tougher tooling. Molds in HTV (high-temperature vulcanization) rubber can last 300 to 500 casts, Formlabs notes, and one master can feed several molds or a multi-cavity mold. Past a few hundred parts, injection molding is the sensible next step. Formlabs puts a steel mold at $5,000 to $100,000, good for millions of parts.
Casting also has material limits. Formlabs notes that casting resins mimic production polymers but cannot reproduce the final injection-molded material, and cast parts still post-cure for up to a week and stay vulnerable to UV light and high temperatures. If the part needs a specific production thermoplastic or real heat resistance, that points toward molding. We break down that next step in our comparison of 3D printing vs injection molding for small production runs.
Before choosing, answer four questions: how many parts you need over the next year, whether the design will change after the first batch, whether the surface has to match from part to part, and whether the part carries real loads or heat. Those answers point to printing, to casting, or to a printed master followed by casting.
Weighing printing against casting for a specific part? Send the CAD model and the quantity you expect through the contact form and we will say which route fits. Prefer to talk first? Call 718-557-9578.
