Validate material combinations
Hard/soft combinations and different engineering plastics are assessed for adhesion, shrinkage, temperature profile, media exposure and service conditions.
Multi-Component Moulding
Injection Moulding with Integrated Functions
When multi-component
moulding is appropriate
Multi-component moulding is appropriate when the function comes from the interaction of several materials: hard/soft combinations, sealing lips, grip surfaces, flexible elements, visual separation or integrated assembly functions.
The benefit does not come from the number of components alone. What matters is whether the integrated solution is technically more robust, cleaner or more economical than separate parts, bonding, assembly or separate seals. This needs to be assessed early in the project because mould design and shot sequence largely determine the final solution.
Our guide “Multi-component moulding: integrating functions instead of assembling them” provides a detailed decision aid covering material combinations, tooling concepts and cost considerations.
Assess material compatibility, adhesion and transitions
In multi-component parts, the material combination determines function. Adhesion, the surface condition of the first component, processing temperatures, shrinkage, media exposure and service temperature influence whether the bond remains durable. Where material adhesion cannot be achieved, mechanical anchoring is provided through undercuts, through-holes or suitable anchoring geometries.
Transition zones are particularly critical because different wall thicknesses, flow fronts, cooling conditions and material properties meet there. For sealing or grip functions, contour, position and surface must be reproduced consistently; visible areas also require clean material separation and uniform surfaces.
Tooling concept and shot sequence must work together
Multi-component moulding requires a tooling concept that holds the first component securely and joins the second component in a defined way. Depending on the part, suitable concepts include rotary-table, transfer or indexing systems, conventional overmoulding, or sequential pre-moulding and final moulding in separate moulds – an approach that can also make the technology viable for smaller volumes.
Parting lines, shut-off surfaces, gate position, mould temperature control and demoulding must suit the material sequence. Even small positional deviations of the first component can affect sealing surfaces, bonded areas or visible transitions.
Interfaces in multi-component moulding
Design repeatable transitions
Sealing lips, grip surfaces, parting lines and bond contours must be reproduced cleanly in the mould. Positional accuracy, effective shut-off and a stable process window are critical to consistent transitions.
Prevent unwanted overmoulding and flash
On two-component parts, critical areas are often where the second component has to seal against the first component or against mould surfaces. These zones must be designed in both the part and the mould to prevent unwanted material transfer and flash.
Assess the economics of part integration
Multi-component technology is worthwhile when the assembly, sealing, joining or handling steps it eliminates justify the greater tooling and process complexity.
Engineering robust multi-component parts
The focus is the function of the finished part. Material combination, transition geometry, tooling concept and process control are therefore assessed together from an early stage.
1
Clarify function and material combination
BERGER assesses the role of each component and whether the material combination suits the application, cleaning or service environment, and required service life.
2
Develop the tooling and process concept
Transitions, positional accuracy, gating, overmoulding, mould temperature control, mould movement and demoulding are planned so that the required function is reproduced consistently.
3
Control production through relevant characteristics
Bond quality, sealing contours, surface finish, position and functional areas are controlled using appropriate inspection characteristics and approval criteria.
The value of multi-component technology lies in the function
A two-shot part is well engineered when the integrated function remains reliable over time. What matters is not the technical complexity of the mould, but whether the bond, transition zones, sealing surfaces, grip areas and visual separations remain stable throughout production.
Questions about multi-component moulding
When different material properties must be combined permanently in one part and this reduces assembly, sealing or joining operations.
It depends on the material combination, surface condition, temperature profile, geometry, overmoulding, tooling concept and process stability. The components must remain reliably bonded not only in initial samples but throughout production.
No. The decisive factor is whether functional integration and the downstream processes eliminated justify the additional tooling and process effort economically.
Yes. For multi-component parts in particular, function, material, transition geometry, sealing and tooling concept need to be coordinated early.
Hard/soft combinations are common: an engineering plastic such as PA, PC, PC/ABS or POM as the substrate, combined with a TPE for sealing or grip functions – with POM typically requiring specially adhesion-modified TPE grades. Combinations of different engineering plastics or colours are also possible, while pairings with widely differing melt temperatures can be critical. BERGER assesses adhesion, shrinkage and temperature control at an early project stage.
