Multi Shot Molding

Two materials, one part: rigid core plus soft-touch grip, clear window over colored body, sealing lip on a rigid frame. Multi-shot molding combines materials in one tool cycle – no gluing, no assembly, no delamination.

Three Ways to Combine Materials

• Two-shot (2K) molding: the tool rotates or the part transfers between two stations; materials bond chemically as the second shot fills
• Overmolding: a pre-molded part is placed into a second tool and molded around
• Insert molding: metal inserts (threads, pins, contacts) are molded into plastic for strength and threads

Where It Pays Off

Power tool grips, toothbrush handles, scissor and knife handles, handheld device frames, sealed electronics housings and threaded metal-in-plastic fasteners. Multi-shot removes assembly steps and glue – cutting cost and a whole failure mode at once.

Engineering Matters Here Most

Material compatibility, shrinkage differences and shot sequencing decide whether a 2K part bonds or delaminates. Our engineers design the tool sequence and select material pairs from proven combinations – two-shot tools are designed, built and trialed entirely in our own workshop.

Two-shot vs overmolding: choosing the right process

Both processes combine a rigid substrate with a second material, but the economics differ. Two-shot molding runs both materials in one machine cycle – a rotary press with two barrels – so cycle time stays near single-shot levels and bonding is excellent, but the tooling investment is roughly 30-50 percent higher. Overmolding molds the rigid part first, then transfers it (manually or robotically) into a second tool; lower tooling cost, more handling, and bonds rely more on mechanical interlock and surface preparation.

As a rule of thumb: above roughly 100,000 annual parts, two-shot usually wins on total cost; below that, overmolding is the pragmatic choice. Bond compatibility is the third variable – TPE onto PP bonds chemically, TPE onto PC usually needs a primer or mechanical features. Our engineers state expected bond strength in the DFM report rather than leaving it to the trial.

• Typical builds: grips, seals, buttons, gasketed housings
• Substrates we run: PP, ABS, PC, PA66 – see materials
• Programs served: medical, electronics, appliances

Tooling for two-shot is where programs are won or lost: the two cavities must register to each other within a few hundredths of a millimeter, and the substrate must be stable enough to survive a second injection without shifting. We build both halves of a two-shot tool as one matched set, flow-analyzed together, and trial them on the same rotary press that will run production – so what you approve in T1 is what runs in series. Lead times run longer than single-shot tooling, typically 35-45 days; the lead time guide explains the milestones.