Custom Urethane Casting Service for Low-Volume Parts

YS Precision provides custom urethane casting services for functional prototypes, appearance models, pilot builds, bridge production and low-volume plastic parts. The process uses polyurethane resin and reusable silicone molds to produce production-like parts without injection mold tooling. It is also known as polyurethane casting or vacuum casting.

This service is intended for teams that need more than a few prototypes but whose quantities do not yet justify injection molding. Before production, we review geometry, quantity, material behavior, critical dimensions, appearance, inserts and assembly conditions. This establishes whether the process is appropriate and how production should be planned.

How the Urethane Casting Process Works

Production begins with a master pattern made by SLA 3D printing or CNC machining. SLA works well for intricate shapes, while CNC machining may be selected for controlled reference surfaces or specific machined features. The master is sanded, polished or textured to the required standard, as the mold will reproduce its surface.

Liquid silicone is poured around the prepared master and cured to form a flexible RTV silicone mold. Once the master has been removed, a two-part polyurethane resin is mixed, degassed and poured into the mold under vacuum. This reduces trapped air and helps the resin fill ribs, bosses, undercuts and fine surface details.

After curing, each part is demolded, trimmed and finished. The soft tooling can be reused for a limited production run, making the process practical for small batches where direct 3D printing or machining every unit would be inefficient.

Cast Urethane Material Options

Urethane casting materials are formulated to simulate selected characteristics of common thermoplastics and elastomers. Because they are polyurethane (PU) casting resins rather than the final injection-molding materials, selection is based on what the parts need to demonstrate during testing or use.

These materials can approximate particular properties of ABS, PC, PMMA, PP, nylon or rubber, but they are not certified substitutes for production thermoplastics. Applications requiring a UL rating, medical-grade certification, defined chemical resistance or long-term environmental performance must be checked against the selected resin data.

Design Review and Silicone Tooling Planning

Flexible silicone molds can release moderate undercuts and reproduce contours that would be difficult to machine repeatedly. Even so, the design affects resin flow, dimensional consistency, surface quality and mold life. Our review may cover:

• Wall-thickness transitions and possible sink or distortion​
• Deep ribs, narrow slots and difficult-to-fill features
• Undercuts and stress during demolding​
• Parting-line, gate and vent positions​
• Visible cosmetic surfaces​
• Threaded inserts and embedded hardware​
• Mating features and enclosure fit​
• Areas requiring secondary CNC machining

A typical RTV silicone mold may produce approximately 10–25 castings. Actual yield depends on geometry, resin, finish requirements and demolding stress. Larger batches may require more than one mold to support the schedule and maintain consistency.

Finishing, Inserts and Assembly Support

Color can be added to the resin before casting or applied later by painting. Available secondary operations include sanding, polishing, surface texturing, screen printing, laser marking and clear coating. We can match specified RAL or Pantone references, subject to sample approval.

Threaded inserts, bushings and other hardware can be cast in place or installed afterward. For multi-part products, YS Precision can coordinate cast parts with CNC-machined parts, sheet metal parts, silicone components and hardware. Trial fitting and simple assembly help identify interference, uneven gaps, fastening issues or appearance mismatches before shipment.

When to Choose Urethane Casting

Urethane casting is often considered for approximately 10–100 parts, although the economical range depends on part size, complexity, finish and mold life. Suitable applications include:

• Functional prototypes and engineering validation parts
• Low-volume enclosures and housings​
• Marketing samples and exhibition models
• User-testing and pre-production units​
• Pilot builds and small-batch plastic parts​
• Bridge production before injection mold tooling is ready

This approach is used in medical-device development, automotive projects, consumer electronics and industrial equipment when production-like parts are needed before volume manufacturing.

It is a useful option when 3D printing cannot provide the required surface quality or consistency, machining every unit would be inefficient, and the projected demand does not yet support injection mold tooling.

The process is not suitable for every short run. Parts requiring very tight tolerances, certified production materials, sustained high temperatures or long-term high-volume supply may be better suited to CNC machining or injection molding. We compare the options according to geometry, quantity, material performance, tolerance and design maturity.

Inspection and the Transition to Production

Quality control begins with the master pattern. We check its key dimensions and surface condition before mold making, then monitor casting, curing, trimming and finishing. Final inspection may include critical dimensions, surface quality, color, insert position and fit with mating components.

For many projects, urethane casting provides a controlled step between an initial prototype and stable volume production. It supplies enough parts for assembly checks, functional validation, customer evaluation or pilot use while the manufacturing plan is still developing.

When the design stabilizes and demand increases, we can support the transition to prototype or production injection molding. Information from material trials, fit checks and pilot builds can inform the tooling review and reduce avoidable changes later.