A finished master pattern is enclosed in silicone to make a mold. Polyurethane resin is prepared and cast with vacuum assistance, then cured and removed from the mold. The casting is trimmed and checked against the drawing. The master finish and parting line need approval before mold making.

Urethane casting avoids the upfront cost of a machined metal injection mold for a short run. Injection molding is worth evaluating when quantities rise or the part must use the specified production thermoplastic. Compare the total cost of the master, silicone molds and castings against injection tooling and molded parts, using the planned order quantity.

The quote covers the master pattern, silicone tooling, polyurethane resin, casting labor, finishing and inspection. A second mold adds tooling cost; polished cosmetic faces, paint and inserts add handling. Send the quantity and drawing requirements together so the tooling and piece-price figures refer to the same scope.

Available PU families can approximate the feel or stiffness of ABS, PP and rubber-like materials. Transparent formulations are also used for appearance samples. A material described as ABS-like is not injection-molded ABS. Check the named resin data sheet before using cast parts for load, heat or chemical exposure tests.

Silicone tooling wears during repeated casting and demolding. Sharp features, undercuts, resin chemistry and cosmetic finish requirements affect usable mold life. More than one mold may be needed for a batch. The mold count should be shown in the quote, not inferred from a fixed number of shots.

Use 3D printing to check a single design or revise geometry without making a mold. Vacuum casting becomes useful when a small batch needs a repeated molded surface and specified polyurethane properties. Neither process automatically duplicates the mechanical behavior of the final injection-molded resin.

Mark mating faces, hole positions and other controlled features on a dimensioned drawing. Master accuracy, silicone movement and resin shrinkage affect the finished dimensions. Thick walls and difficult demolding can add distortion. Agree on inspection points and acceptance limits before the mold is made.

Send a STEP model, quantity, target material properties, finish and required delivery date. Add a PDF drawing for controlled dimensions, inserts, parting-line preferences and inspection notes. A clear surface or a functional test requirement should be called out with the relevant acceptance criteria.

About 1 mm is a starting point for some rigid polyurethane castings, while 1.5–3 mm is a more practical nominal range for many enclosure designs. Larger parts and unsupported walls may need added thickness or ribs. Keeping wall thickness reasonably uniform helps reduce sink marks and cure-related distortion; the final limit depends on geometry and resin grade.

Flexible silicone molds can release some undercuts and zero-draft features that would be difficult to demold from rigid metal tooling. Deep undercuts, tall ribs and textured faces still increase demolding force and the chance of mold damage. A revised parting line, local draft or removable mold insert may be needed after DFM review.

Yes. Threaded inserts, bushings and other metal components can be positioned in the silicone mold and cast into the polyurethane part. Post-installed inserts are another option. The insert location, surrounding wall thickness and expected screw loads should be reviewed before casting.

Drilling, trimming and light CNC finishing can be performed after polyurethane has cured. These operations are useful for precision holes, bearing seats and critical assembly interfaces. Allow material for finishing and provide suitable support during cutting, especially with thin or flexible parts.

Clear urethane casting can produce transparent covers, display windows and appearance prototypes, but long-term clarity is not automatic. Resin chemistry, master polishing, trapped bubbles, cure conditions and UV exposure all affect optical quality. Specify haze, transmittance and yellowing limits when the part will be evaluated under lighting or outdoor exposure.

Color can be mixed into the polyurethane resin or applied as paint after casting. Silicone tooling can reproduce the approved master’s matte, glossy or textured surface. Exact color matching should be checked against a physical sample because pigmented castings and painted parts can look different.

Bubbles and voids can result from trapped air, inadequate mold venting, moisture contamination, or resin mixing and curing conditions. Vacuum assistance reduces entrapped air but does not remove every possible defect. Mold dryness, resin handling, gate and vent design, and inspection are particularly important for clear parts and thin features.

Some parting-line and gate marks are expected because the silicone mold must open and resin needs an entry path. Their locations should be reviewed before the mold is made, especially on visible housing surfaces. Trimming, sanding, polishing or painting can reduce their appearance; an entirely invisible result should not be assumed.

Multi-stage polyurethane casting can create certain rigid-and-soft assemblies, including soft-touch details. A strong chemical bond between separately cast layers is not guaranteed. Mechanical interlocks, compatible materials and adhesion testing should be evaluated when the interface must resist peeling or repeated loading.

Flame-retardant polyurethane grades can be considered. For example, EPOC CRAFTER lists DPI 8263 with reported UL 94 V-0 testing on a 3 mm specimen. That result must not be applied automatically to every part thickness, color or finished assembly. Confirm the exact grade, test report and application-specific acceptance requirements before ordering.

First-article inspection can be specified for critical dimensions, assembly features, surface appearance or material requirements. Supply a dimensioned drawing with acceptance limits and identify the measurements or tests that need records. Agree on any approval hold point, sampling method and reporting scope before casting begins.

Changes to cast geometry normally require a revised master pattern and a new silicone mold. Minor adjustments may sometimes be possible through secondary machining or finishing. Confirm the CAD revision before mold fabrication and request a cost and schedule review whenever the design changes.

A CNC-machined master can be appropriate when accessible features and controlled dimensions are the priority. SLA is useful for complex contours or internal detail that would be difficult to machine, but support marks and layer-related defects must be removed before molding. Review the drawing, surface requirements and master inspection results before choosing the route.

The schedule depends on master-pattern approval, silicone mold preparation, resin availability, curing cycles, number of molds, finishing and inspection. A first-part date is not the same as the dispatch date for the complete order. Confirm both milestones, especially when multiple molds or cosmetic coatings are required.

Allow for the dimensional variation of each mating casting, not just its nominal CAD size. Specify critical interfaces and assembly gaps on the drawing, then check representative parts together. A deliberate reveal gap may be preferable to a perfectly flush joint that exposes minor mismatch; any fit requirement should be verified with the intended hardware.

A stored silicone mold may support repeat castings if the cavity remains clean, undamaged and dimensionally suitable. Storage conditions, mold chemistry, elapsed time and previous casting cycles affect that decision. Recheck the critical dimensions and finish before reuse; a new mold may be needed even if the original tool still exists.

Use a controlled CAD revision, identified resin grade and lot, approved color or finish sample, and documented mold and cure conditions. Inspect the first casting and monitor agreed critical features as each silicone mold is reused. If visible wear or dimensional drift appears, review whether the remaining parts can be accepted or the tool needs replacement.

Raised and recessed marks are possible, but shallow strokes, narrow gaps and sharp edges can lose definition when the mold is made or the part is finished. Supply the artwork as geometry in the 3D model and identify any controlled text details on the drawing. Confirm legibility on the master and first casting before approving the batch.

Specify the target hardness together with the part’s function, such as grip feel, compression, sealing or abrasion. Shore A is commonly used to describe softer elastomer grades, but hardness alone does not establish tear strength, compression set or service life. Compare named resin data sheets and test the proposed part under its intended loading conditions.

Transparent castings can help review the look of windows, light covers and displays. Define the viewing area, acceptable bubbles, haze, tint and inspection lighting before the master is polished. A visually clear prototype is not automatically an optical-grade or long-term UV-stable component; request samples and relevant test results when optical performance matters.

A casting must fit within the machine’s usable chamber volume with enough space for the silicone mold, gates, vents and supports. Long or thin geometries may also distort during curing or demolding even if they physically fit. For oversized parts, discuss sectioning and bonding, then define joint appearance and assembled dimensional acceptance before quoting.

An incorrect mix ratio, inadequate mixing, unsuitable temperature or interference from mold materials can prevent proper cure. Moisture can create other defects and must also be controlled according to the resin instructions. Segregate suspect castings, check the resin technical sheet and process records, and verify cure before machining, coating or releasing the parts.