{"id":1833,"date":"2026-04-21T06:50:19","date_gmt":"2026-04-21T06:50:19","guid":{"rendered":"https:\/\/meitu-engelhardt.com\/?p=1833"},"modified":"2026-04-21T06:50:19","modified_gmt":"2026-04-21T06:50:19","slug":"silicone-compression-molding","status":"publish","type":"post","link":"https:\/\/meitu-engelhardt.com\/pt-br\/silicone-compression-molding\/","title":{"rendered":"Moldagem por compress\u00e3o de silicone: processo, aplica\u00e7\u00f5es e quando us\u00e1-lo"},"content":{"rendered":"
Silicone compression molding shapes pre-measured high-consistency rubber into cured parts inside a heated, closed mold \u2014 at a fraction of the tooling spend that liquid silicone rubber (LSR) injection demands. Silicone rubber compression molding is a manufacturing process that begins with a raw material slab, a machined mold cavity, and a press that compresses the polymer under heat and pressure. If your annual run sits between 500 and 50,000 parts with simple to moderate geometry, this cost-effective route is usually the quieter, cheaper answer than chasing an LSR injection tool. This guide covers the process, the HCR \/ LSR \/ RTV material families, mold design tradeoffs, the ISO 3302-1 tolerance classes you should quote on drawings, cost bands drawn from real sourcing data, and a volume rule for when to switch to LSR injection.<\/p>\n
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Quick Specs<\/h3>\n\n\n\n\n\n\n\n\n\n\n
Cure temperature<\/td>\n150\u2013200 \u00b0C (HCR \/ HTV) <\/td>\n<\/tr>\n
Cure time<\/td>\n~10 s per 1 mm wall thickness at 150 \u00b0C (cycle 60\u2013600 s) <\/td>\n<\/tr>\n
Clamp pressure<\/td>\n5\u201315 MPa (10\u201380 bar typical press range)<\/td>\n<\/tr>\n
Tolerance standard<\/td>\nISO 3302-1:2014<\/a> \u2014 M1 (fine) to M4 (coarse) <\/td>\n<\/tr>\n
Typical M2 tolerance<\/td>\n\u00b10.10 mm at 0\u20134 mm nominal features<\/td>\n<\/tr>\n
Shrinkage allowance<\/td>\n1.5 %\u20133 % (compound-dependent)<\/td>\n<\/tr>\n
Tooling cost (typical)<\/td>\nUS $800 \u2013 $4,000 per set, 4\u20136 week lead time<\/td>\n<\/tr>\n
Economic volume band<\/td>\n100 \u2013 50,000 parts\/year (above this \u2192 evaluate LSR injection)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

<\/p>\n

What Is Silicone Compression Molding?<\/h2>\n

\"What<\/p>\n

Silicone compression molding is a vulcanization process that shapes pre-measured high-consistency silicone rubber (HCR) inside a heated, closed two-part mold. Clamp pressure and heat cross-link the polymer into a solid elastomer, and the cured part is ejected for trimming. It is the oldest and simplest of the three dominant silicone manufacturing methods \u2014 the others are transfer molding and LSR injection molding.<\/p>\n

What is silicone compression molding, in one sentence?<\/h3>\n

Silicone rubber compression molding is a process that involves placing relatively solid and uncured high-consistency silicone rubber (HCR) into a mold, then cross-linking it with heat to produce a solid elastomer rubber component. It is the simplest of three dominant manufacturing approaches, in terms of number of necessary parts and budget.<\/p>\n

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\ud83d\udca1<\/span> Pro Tip<\/strong><\/div>\n

In the process, a weighed slug of uncured resin (recipe- and compound-dependent but typically 300-400 g\/m2) is placed into the lower cavity of a steel mold. The mold is then closed, with a dwell window.<\/p>\n<\/div>\n

<\/p>\n

How the Silicone Compression Molding Process Works (Step-by-Step)<\/h2>\n

\"How<\/p>\n

On paper the process looks simple. In practice every parameter \u2014 mold temperature, cure dwell, preform mass, clamp profile \u2014 is tuned to the compound and geometry. Here is the sequence most molders follow.<\/p>\n

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  1. Preform preparation. Uncured HCR is pre-weighed and pre-cut into slabs, strips, or discs sized to the cavity volume plus a small overfill (1\u20133 %) to force flash and prevent voids.<\/li>\n
  2. Mold preheating \u2014 steel mold is brought to cure temperature, 150 \u00b0C for platinum-cured HCR, or 170\u2013200 \u00b0C for peroxide-cured grades.<\/li>\n
  3. Loading \u2014 operator places the preform into the lower cavity in a single step. Multi-cavity tools may load 4, 8, or 16 positions.<\/li>\n
  4. Mold closure and bumping \u2014 press closes, then briefly re-opens once or twice (a “bump” or degassing cycle) to vent trapped air before final clamp-down.<\/li>\n
  5. Compression and cure. Full clamp pressure (typically 5-15 MPa) holds the material against cavity walls while heat vulcanizes the rubber. At 150 \u00b0C, cure time runs under 10 seconds per 1 mm of wall thickness (per Shin-Etsu Silicones’ molding literature<\/a> ), so cycle times are in the 60-600 s band for most parts.<\/li>\n
  6. Ejection \u2014 mold opens and the operator grabs the part, often by hand or via ejector pins.<\/li>\n
  7. Deflashing and post-cure. Excess material at the parting line gets torn, tumbled, ground (precision grinding) or cryogenically deflashed. Certain medical- and food-grade parts are then post-cured for 2-4 hours at 200 \u00b0C to drive off residual volatiles.<\/li>\n<\/ol>\n

    How long does the compression molding process take?<\/h3>\n

    A typical 3-mm-thick silicone gasket cured at 150 \u00b0C has an in-mold dwell of roughly 30 seconds; add mold-close, bump, and ejection and the full cycle lands between 60 and 180 seconds per press. Thicker cross-sections (10 mm+) push dwell time well above 5 minutes \u2014 which is why compression molding favors simpler, thicker parts; the cure-time penalty scales linearly with thickness. Shin-Etsu’s datasheet formalizes this as the “10 sec per mm at 150 \u00b0C” rule of thumb.<\/p>\n

    \n

    \ud83d\udcd0 Engineering Note<\/strong><\/p>\n

    Platinum-cured systems cures faster and cleaner than peroxide-cured HCR, but peroxide is still common for thick-section parts where a slower crosslink front can aid even cure. If your part must meet USP Class VI or food-contact FDA 21 CFR 177.2600, specify a platinum-cured compound from the get-go – later changes often mean re validatng tooling.<\/p>\n<\/div>\n

    <\/p>\n

    Silicone Materials \u2014 HCR, LSR, and RTV<\/h2>\n

    \"Silicone<\/p>\n

    “Silicone” is not a single material. There are three families of a generic name and they each behave differently in a compression-molding context in viscosity, process window and properties, The “default” for compression is HCR, LSR is primarily an injection molding material, and RTV offers limited series production application.<\/p>\n

    \n\n\n\n\n\n\n\n\n\n\n
    Property<\/th>\nHCR (HTV)<\/th>\nLSR<\/th>\nRTV-2<\/th>\n<\/tr>\n<\/thead>\n
    Form at room temp<\/td>\nGum \/ dough (solid)<\/td>\nTwo-part liquid<\/td>\nPourable liquid<\/td>\n<\/tr>\n
    Primary process<\/td>\nCompression, transfer<\/td>\nInjection<\/td>\nCasting, potting<\/td>\n<\/tr>\n
    Shore A range<\/td>\n20\u201380 (ASTM D2240<\/a>)<\/td>\n5\u201380 (ASTM D2240)<\/td>\n10\u201370<\/td>\n<\/tr>\n
    Continuous service temp<\/td>\n\u221260 \u00b0C to +230 \u00b0C <\/td>\n\u221250 \u00b0C to +200 \u00b0C<\/td>\n\u221255 \u00b0C to +180 \u00b0C<\/td>\n<\/tr>\n
    Tensile strength<\/td>\n6\u201311 MPa<\/td>\n7\u201310 MPa<\/td>\n2\u20135 MPa<\/td>\n<\/tr>\n
    Best-fit applications<\/td>\nGaskets, seals, kitchenware, thick-section parts<\/td>\nMedical, micro-optics, high-volume precision<\/td>\nPrototypes, encapsulation<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    HCR is what most engineers mean by “compression-molded silicone.” It generally arrives as a bulk gum that is catalyzed, pigmented then milled – produced into slabs and cut to preform weight. LSR is always pumped-meet-mix at the press, which is why almost all LSR lives in injection molds. Shore hardness (Shore A) is measured as per ASTM D2240 ; this standard has an international equivalent, ISO 48-4.<\/p>\n

    To dig into when silicone outperforms other elastomers on chemistry and temperature, see our silicone vs rubber selection guide<\/a>.<\/p>\n

    <\/p>\n

    Compression vs Transfer vs LSR Injection Molding<\/h2>\n

    \"Compression<\/p>\n

    Three primary processing methods can produce silicone parts. They are not interchangeable – they each target different parts of the volume and complexity spectrum. Before picking each, you should compare tooling, cycle, accuracy and what each excels at.<\/p>\n

    \n\n\n\n\n\n\n\n\n\n\n\n
    Dimension<\/th>\nCompression<\/th>\nTransfer<\/th>\nLSR Injection<\/th>\n<\/tr>\n<\/thead>\n
    Tooling cost (typical)<\/td>\n$800 \u2013 $4,000<\/td>\n$2,500 \u2013 $8,000<\/td>\n$10,000 \u2013 $50,000+<\/td>\n<\/tr>\n
    Cycle time (3 mm part)<\/td>\n60\u2013180 s<\/td>\n45\u2013120 s<\/td>\n20\u201360 s<\/td>\n<\/tr>\n
    Achievable tolerance<\/td>\nISO 3302-1 M2 \u2013 M3 (\u00b10.10 \u2013 \u00b10.25 mm)<\/td>\nISO 3302-1 M1 \u2013 M2 (\u00b10.08 \u2013 \u00b10.10 mm)<\/td>\nISO 3302-1 M1 and tighter (\u00b10.05 \u2013 \u00b10.08 mm)<\/td>\n<\/tr>\n
    Geometry complexity<\/td>\nSimple to moderate; undercuts difficult<\/td>\nModerate; some undercuts via inserts<\/td>\nComplex; sliders, lifters, micro-features<\/td>\n<\/tr>\n
    Labor per piece<\/td>\nHigh (load, unload, deflash manually)<\/td>\nModerate<\/td>\nLow (fully automated)<\/td>\n<\/tr>\n
    Flash \/ scrap<\/td>\nSignificant \u2014 usually hand-trimmed<\/td>\nModerate<\/td>\nMinimal \u2014 near net-shape<\/td>\n<\/tr>\n
    Economic volume band<\/td>\n100 \u2013 50,000 parts\/year<\/td>\n5,000 \u2013 200,000 parts\/year<\/td>\n50,000+ parts\/year<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    “Compression molding is more labor-intensive, has longer curing times and increased cycle times compared to plastic injection molding. For small parts, typical tolerance lands around plus or minus 0.1 mm if strict, referencing ISO 3302-1.”<\/p>\n