Services
Vacuum Casting
Silicone-mould casting for 10–50 piece runs of rigid, soft and transparent plastic parts — far cheaper than tooling, with near-moulded appearance.
You need twenty housings, and production tooling is three months away — that is the classic case for vacuum casting. A master pattern is built, a silicone mould is taken from it, and polyurethane resin is poured under vacuum. One silicone mould typically yields 15–25 parts.
What you gain is the time and cost of steel tooling skipped, with appearance and feel close to moulded parts. What you accept is short mould life, PU analogue materials rather than true engineering thermoplastics, and slight dimensional drift as the mould ages.
Capabilities
- Parts per mould
- Typically 15–25, depending on complexity and how easily the part releases
- Typical lead time
- 7–12 working days for master pattern, silicone mould and first parts
- Quantity
- 10–200 pieces; beyond that, rapid tooling is usually worth evaluating
- Achievable results
- Rigid, soft (Shore A20–A90), transparent, translucent and flame-retardant analogues
Solutions
Pilot runs before tooling
Cast parts for market testing, customer samples and pre-certification, so the design is settled before steel is cut.
Overmoulded and multi-material parts
Soft grips, seals and keypads cast separately from the rigid housing and assembled.
Clear parts and lenses
Cast clear PU, polished afterwards, for light guides, lenses and transparent covers.
Shows and sampling
When you need dozens of cosmetically identical units and tooling will not arrive in time.
Process Overview
A master pattern is machined or printed and finished to the exact surface you want — that finish is the ceiling for every cast part. Silicone is poured around it, cured, then cut along the parting line to release the pattern, leaving a cavity. Two-part PU resin is poured into that cavity inside a vacuum chamber, which draws out air before the resin cures.
Because silicone is elastic, moderate undercuts release without side actions — more forgiving than steel. But silicone ages with heat and pouring cycles, so later parts drift slightly in dimension and surface.
Materials
- ABS-like PU (general structural parts)
- PP-like PU (tough parts, snap fits)
- Clear PC-like PU (transparent parts, lenses)
- Soft PU, Shore A20–A90 (grips, seals)
- Heat-resistant analogues (short-term thermal exposure)
- Flame-retardant analogues (rating must be confirmed per project)
Surface Finishes
- Blasting and texture (applied to the master)
- Painting and clear coat
- Polishing of clear parts
- Screen printing and laser marking
- Insert moulding of nuts and metal parts
- Assembly
Tolerances & Size Limits
- General dimensions
- ±0.15 mm or ±0.3%, whichever is greater
- Shrinkage
- PU shrinks roughly 0.15–0.3%, more noticeably along long dimensions
- Minimum wall
- 1.5 mm recommended; thinner sections risk short fills
- Batch consistency
- Later parts from one mould drift slightly; tight-tolerance parts are managed per mould
Design Guide (DFM)
The master sets the cosmetic ceiling
Cast parts reproduce the master exactly. If you want high gloss, the master must be polished to high gloss — it cannot be recovered later.
Include draft
Silicone is elastic, but 1°–2° of draft still helps, particularly on deep cavities, and reduces drag marks.
Keep walls even
Sharp thickness changes trap bubbles and produce sink marks. Core out heavy sections.
Position inserts in advance
Nuts and brackets are placed in the cavity before pouring — mark their position and orientation on the drawing.
Avoid thick clear sections
Thick transparent sections retain micro-bubbles. Keep under about 8 mm or split and bond.
Quality Control
- Silicone mould made only after the master is approved for surface and dimension
- First-off approved for appearance and fit before the run
- Dimensional drift tracked by mould count; mould replaced when out of tolerance
- Every part inspected cosmetically before shipping
FAQ
How close are cast parts to moulded parts?
Cosmetically very close. Structurally there is a real gap — PU is a thermoset analogue and should not be used to draw long-term reliability conclusions about moulded ABS or PC.
How many parts come from one mould?
Usually 15–25, fewer where the part has deep cavities, slender features or undercuts. For larger runs we open several moulds in parallel to keep parts consistent.
Can cast parts be used for certification samples?
For appearance and structural submissions, yes. Where flammability rating or food contact is involved, tell us in advance — the material has to be confirmed against the specific standard.
Need vacuum casting? Send the drawing to an engineer.
First reply within 30 minutes during working hours (4 working hours at the latest); full quote and DFM feedback typically within 12 working hours.