The custom silicone molds tooling required weeks of lead time and large minimum order quantities. They have the right tolerance to match most steel molds for thousands of cycles. The manufacturers can easily modify or adjust in hours.
The custom silicone molds also work with a far wider range of casting materials. They have become the best choice for runs between 1 and 10,000 parts. Most small to medium manufacturers use these for most of their projects.
Types of Custom Silicone Molds for Manufacturing
Most manufacturing processes rely on specific mold designs for consistent results.
Two part block molds
These are best for low detail parts with no undercuts. They require the least time and labour to manufacture correctly.
Insert molds
These hold metal or hard plastic reinforcement during casting. The insert becomes a permanent part of the final finished component. This style eliminates secondary assembly and adhesive bonding.
Compression molds
These are built for use under high and consistent production pressure. They produce extremely dense parts with almost zero internal voids. Most high volume industrial rubber products hold tolerance through many thousands of production cycles.
Injection molds
These are for very-low-viscosity liquid materials. They fill evenly at much lower pressure. A good silicone mold maker will recommend this for most medium runs.
Multi cavity molds
These produce multiple identical parts in every single production pour. They are the most efficient option for medium- and large-batch production.
Split molds
These are the best options for complex external geometries. They separate along multiple carefully planned parting lines to release the part. They require more skill to design and manufacture.
Flexible sleeve molds
These are used for parts with internal undercuts. The flexible core can stretch and deform to release from otherwise trapped geometry.
Main Design Features for Precision Results
Any minor errors here will create consistent defects across every part. Most mold failures trace back to one of these core design features. Even custom made silicone molds quebec use these same design rules.
Draft angles of 0.5 to 2 degrees are the minimum for clean demolding. Steeper angles are better for parts with rough or textured surface finishes. Most designers add slightly more draft than the stated minimum.
Wall thickness between 6 and 12 mm provides the best balance of properties. The thin walls will flex and deform under pressure during production. The thick walls waste material and cure unevenly.
Vent channels allow trapped air to escape as the material fills the mold. Any small trapped air bubbles will create visible defects on the part surface. Vents are usually less than half a millimetre thick to prevent leakage.
Registration pins ensure both halves of the mold align perfectly every time. Even one tenth of a millimeter misalignment will ruin part tolerance. The pins hold alignment for thousands of cycles without adjustment.
Parting line placement has a huge effect on final part finish and labour. A poorly placed parting line will add hours of secondary finishing. The best parting lines follow natural edges and breaks in the part geometry.
Gate location controls the way material flows and fills the mold cavity. A bad gate location will create flow lines, voids and internal stress. The best gate positions allow material to fill evenly from the lowest to the highest point. Most test pours are done to refine gate location.
Materials For Silicone Molds
custom silicone molds can be operated with a far wider range of materials than any rigid mold. Each material has specific requirements that change mold design slightly. The same mold can often be used for multiple materials.
Polyurethane resins and foams
These are the most common materials used for production casting today. They offer a very wide range of hardness and physical properties.
Epoxy compounds
These are used for high strength structural parts and industrial tooling. They have higher temperature resistance than most polyurethane formulations. Epoxy produces extremely hard, rigid parts with a very high surface finish.
Wax
Wax is used for master patterns and investment casting. It melts cleanly and leaves almost zero residue inside the mold cavity. Wax patterns can be finished to high surface roughness standards.
Concrete and plaster
These are used for construction and decorative structural components. These abrasive materials will wear out most rigid molds very quickly.
Food grade materials
These can be cast safely in correctly formulated food safe silicone. This is commonly used for product testing and small batch food production. All materials used must meet relevant food safety standards for contact.
Low melt alloys
Alloys under 300 degrees Fahrenheit can be cast reliably in silicone. This allows the production of small metal parts without expensive hard tooling. Most low run metal components are now produced this way for prototyping.
Rubber compounds
The rubber compounds and elastomers are cast for a wide range of end uses. The industrial rubber components can be manufactured in small runs. This method avoids the high tooling cost associated with compression molding.
Manufacturing Process Steps
- Step 1. Prepare a clean, accurate 3D scan or CAD file for the part. All adjustments and modifications must be completed before the pattern is made.
- Step 2. Create and finish the master pattern to the required standard. The finished mold will reproduce every single mark and defect on the pattern.
- Step 3. Build and seal the mold box and apply a thin, even release agent.
- Step 4. Mix the two-part silicone to exact and carefully measured ratios. Most good makers use digital scales accurate to one-tenth of a gram.
- Step 5. Place the mixed silicone in a vacuum chamber to remove air bubbles. This step removes almost all of the tiny air bubbles created during mixing.
- Step 6. Pour the silicone into the mold box at a slow and consistent rate. Pour speed has a very large effect on the number of remaining air bubbles.
- Step 7. Leave the mold to cure fully at a consistent room temperature. Cure time ranges between four and twenty-four hours depending on the silicone type.
- Step 8. Demold the master pattern and trim the mold to the final finished shape. This step requires slow, careful technique to avoid cutting or tearing the mold. A good demold will leave the mold ready for production.
Quality Control Methods
Good quality control will catch defects before they reach production. The dimensional checks are performed with calibrated callipers at multiple points. The tolerance should be checked across every critical feature of the mold. An experienced silicone mold maker will complete this check before delivery.
Surface roughness measurements confirm the mold matches the required finish. The consistent surface finish produces consistent parts every single cycle. The fill pattern analysis uses a test pour to confirm material flow behaviour. This test will show gate location issues and venting problems.
Cycle count tracking records the number of pours each mold completes. This allows scheduled replacement before the mold begins to degrade and fail. Most molds will produce consistent results up to a known cycle count. This method is ideal for small runs of industrial rubber products.
The temperature monitoring during use confirms consistent cure conditions. Any changes in temperature can have very large effects on final part quality.
The visual inspection checks for small cuts, tears and defects in the mold surface. Most small defects can be repaired easily if caught early enough. Unrepaired defects will grow larger with every production cycle. Many rubber extrusion manufacturers also follow this exact testing process.
Stress testing confirms the mold will hold up to extended production use. The mold is put through ten test cycles under full production conditions. This test catches almost all latent defects that would fail later in production. The right custom silicone molds will often far exceed their rated cycle count.
Conclusion
It has allowed small companies to compete with much larger operations fairly. The lead times have dropped from weeks to days for most new part development. The manufacturers can test and iterate on new designs. This has led to far faster innovation across almost every industrial sector.
We manufacture gaskets, seals, molds and custom formed rubber parts for every industry. All parts are tested and inspected before they leave our facility. Call us today at +1(647) 294-5240 to get started on your project. You can also send your drawings to [email protected] for an accurate quote.