Silicone molds poured under vacuum, cast in polyurethane resin. One master pattern, 25 to 50 copies, and a color or texture that matches the final part. Send a 3D file and we will tell you if the part suits the process.
Most complaints trace back to the master pattern, not the resin.
Thin walls and sharp internal corners concentrate stress at the parting line. Each demold opens the tear a little more, so copy 20 looks worse than copy 5. Fillets of at least 0.5 mm and a draft of 1° to 2° on vertical faces keep a mold running to its expected 25 to 50 cycles.
Resin that degasses poorly or a mold filled too fast traps voids against the cavity wall. You see them after the part is painted, not before. Vacuum degassing of the resin and a slow, bottom-up fill move the bubbles to the overflow, away from visible faces.
Polyurethane shrinks as it cures, typically a few tenths of a percent. On a 200 mm housing that is enough to break a snap fit. We compensate the master pattern for the shrink rate of the specific resin before the silicone is poured, so cast dimensions land where the drawing says.
Casting a soft durometer over a metal or rigid plastic insert only works if the insert is clean, warm, and mechanically keyed. A smooth bore and room-temperature insert give a bond that peels by hand. Undercuts, a light bead blast, and preheating fix most of it.
The process has three moving parts: the master, the mold, and the resin. Control all three and the copies match.
We machine or print the master to ±0.005 mm, then polish it to the surface finish you want to see on the copies. Silicone picks up every scratch on the master, so the master is finished before the mold is poured, not after.
Shrink compensation happens here. Each resin grade has its own cure shrinkage, and we scale the master by that number. Wall thickness, draft, and corner radii are checked at the same time. If a feature will not release from a flexible mold, we say so before cutting metal.
The master is suspended in a frame, silicone is poured around it, and the whole frame goes into a vacuum chamber. Pulling the air out before the silicone cures stops bubbles from forming against the pattern. That is where the process gets its name.
Cured molds are cut open along a planned parting line, the master comes out, and the cavity is filled with polyurethane under vacuum. A single mold yields 25 to 50 parts depending on geometry and resin. Soft durometers and deep undercuts shorten that count; simple blocks extend it.
Pick the process by copy count, geometry, and what the part has to prove.
| Situation | Better fit | Why |
|---|---|---|
| 1 to 5 copies, simple shape | CNC machining | No mold cost, tighter tolerance |
| 5 to 50 copies, same shape | Urethane vacuum casting | Mold cost spread across copies |
| 50 to 200 copies | Vacuum casting or bridge tooling | Depends on tolerance and resin |
| Deep undercuts, one-piece part | Vacuum casting | Flexible silicone releases the feature |
| Living hinge, thin flexure | Vacuum casting | Soft resin flexes without cracking |
| Optically clear, no seams | CNC or polishing | Casting leaves a parting line |
| Overmold on metal insert | Vacuum casting | Insert placed in cavity before pour |
| 200+ copies, tight tolerance | Injection molding | Steel tool holds size over long runs |
Casting rarely stands alone. These are the steps we run in-house so the master, the mold, and the finish stay in one schedule.
Silicone molds from one master, 25 to 50 copies per mold, rigid or soft durometer resin, color matched to a Pantone or RAL reference.
SLA, DLP, and FDM masters when the geometry is organic. We print the pattern, finish it, and cast from it in the same building.
16 simultaneous 5-axis centers for masters that need tight tolerance, sharp corners, or a machined surface straight off the tool.
Mill-turn work for inserts, threaded bosses, and metal cores that get cast into the polyurethane part.
Paint, texture, bead blast, and laser marking. Cast parts can carry the same cosmetic finish as the production version.
Bridge quantities from 50 to a few hundred parts before steel tooling is committed, using the same drawings and inspection plan.
Numbers to check before you send a file.
| Parameter | Range | Note |
|---|---|---|
| Copies per silicone mold | 25 to 50 | Fewer with deep undercuts |
| Minimum wall thickness | 0.8 mm | 1.5 mm for structural ribs |
| Draft on vertical faces | 1° to 2° | Below 1° risks tearing |
| Internal corner radius | 0.5 mm minimum | Larger radius, longer mold life |
| Maximum part size | 600 × 600 × 600 mm | Larger sizes quoted case by case |
| Cast tolerance | ±0.15 mm per 100 mm | Tighter on the machined master |
| Surface finish | Ra 0.8–1.6 μm | Matched to master polish |
| Insert placement | Metal, PCB, threaded boss | Cast in during the pour |
We are a CNC shop first, which is why the masters hold tolerance.
15 years of cutting metal and building patterns. Casting sits next to the machine shop, not in a separate supply chain.
Masters, inserts, and fixtures are machined on the same floor that runs the casting cell. No waiting on an outside pattern shop.
The master pattern is machined to ±0.005 mm. Cast copies inherit that geometry minus the resin shrink we compensate for.
7,600 m² across 3 wholly-owned plants, with 150 technicians covering machining, casting, finishing, and inspection.
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022. Your drawings stay confidential under NDA on request.
Raw material check, in-process monitoring, and final inspection on every run. Reports on request, including dimensional data.
Interior trim, connector housings, and gaskets cast in soft durometer resin for fit checks on a real vehicle.
Gripper pads, cable boots, and joint covers where a flexible resin has to survive repeated deflection.
Housings and seals for design verification before a validated tool is cut. Smooth surfaces, no visible voids.
Dust covers, bellows, and control panel seals in small runs where injection tooling cannot be justified.
Expect 25 to 50 parts from one mold. Simple blocks with generous draft sit at the top of that range. Deep undercuts, thin walls, and very soft resin sit at the bottom because the silicone stretches further on every demold.
If you need more than 50 copies, we pour a second mold from the same master. The master is kept, so the second mold matches the first.
The machined master is held to ±0.005 mm. The cast copy adds resin shrinkage and silicone flex, so we quote cast tolerance around ±0.15 mm per 100 mm.
When a feature has to be exact, such as a bearing bore or a thread, we machine that feature after casting or cast in a metal insert.
0.8 mm is the practical minimum for a flat wall. Thin walls fill poorly and tear the mold on release. Structural ribs should be 1.5 mm or thicker.
Thick sections above 6 mm can shrink and sink. We core them out or split the part into two castings.
Yes, but expect a visible parting line and some internal haze. Clear resin also yellows faster than opaque grades.
For an optically clear lens or light pipe, CNC machining and polishing gives a better result than casting.
Yes. Threaded bosses, metal sleeves, and small boards are placed in the cavity before the pour, and the resin encapsulates them.
The insert needs a mechanical key. A smooth bore will pull out. We usually add knurling, a groove, or a light bead blast to the insert.
Quotation and free DFM analysis come back within 12 hours. Once you approve the master, production can start within 24 hours.
A typical run of 25 cast parts with finishing ships in 3 to 5 days after mold approval. Paint and texture add time.
No. We run from a single prototype to 10,000+ part runs across the shop, and casting handles the low end where tooling cost would dominate.
One casting is often enough to check fit and feel before committing to more copies.
Yes. Uploads are secure and confidential, and we sign an NDA on request before you share drawings.
Our ISO 27001:2022 certification covers how we handle your data inside the plant.
We review your 3D model, flag any feature that will not release from a silicone mold, and come back with a quote, a copy count, and a lead time.
12-hour quote100% inspectionNo minimum order quantityNDA on request
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Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
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