Compression vs Injection vs Transfer Molding

Author: Site Editor Publish Time: 2026-10-22 Origin: Site

When a standard seal won’t fit, you need a custom molded part. The three processes – compression, transfer, and injection molding – differ in tooling cost, cycle time, and part complexity. This guide helps you choose the right one.

Compression Molding

Rubber is placed in a heated, open mold and compressed. Lowest tooling cost, slowest cycle, good for large or simple parts and low volumes.

Best for: low volume, large parts, simple shapes, prototypes.
Trade-offs: flash to trim, looser tolerances, longer cycle.

Transfer Molding

Rubber is forced through a gate into a closed cavity. Better dimensional control than compression, moderate tooling cost, good for inserts and moderate volumes.

Best for: parts with inserts, moderate volume, better repeatability.
Trade-offs: some material waste at the sprue.

Injection Molding

Rubber is injected into a closed, heated mold at high speed. Highest tooling cost, fastest cycle, tightest tolerances, best for high volume.

Best for: high volume, complex geometry, tight tolerances.
Trade-offs: high upfront tool cost.

Comparison Table

Factor	Compression	Transfer	Injection
Tooling cost	Low	Medium	High
Cycle time	Slow	Medium	Fast
Tolerances	Loosest	Good	Tightest
Volume fit	Prototype / low	Medium	High

How to Choose

Prototype or <1,000 parts – compression.
Inserts or 1k-50k – transfer.
>50k or tight tolerance – injection.

FAQ

Which is cheapest?

Compression has the lowest tooling and is cheapest at low volume. Injection wins per-part cost only at high volume.

Can you mold to my drawing?

Yes. Anlintech molds FKM, silicone, EPDM, NBR, HNBR, and FFKM to print, with material certification and dimensional reports.

What about tolerances?

Molded rubber follows ISO 3302-1 classes; we confirm the achievable class for your geometry before tooling.