What is two-shot injection moulding?

Two-shot moulding, also referred to as multi-shot, double-shot, or dual-shot moulding, is an injection moulding process in which two distinct plastic resins are moulded together within a single cycle. The resins are introduced sequentially, rather than simultaneously, and the product remains within the mould throughout both stages, resulting in a single, continuous production step.

What is the two-shot injection moulding process?

Since the procedure is completed in a single step, just one mould tool is needed for two-shot moulding.

The initial shape of the product is formed when the first polymer (the substrate) is injected into the chamber of the first-shot tool. Following this, the tool rotates 180 degrees and separates while retaining the first shot. The mould tool then closes, aligning the first shot with the second cavity. The second polymer is subsequently injected into the second-shot cavity over the substrate. Once the mould tool rotates back 180 degrees to its original position, the finished moulding is ejected from the tool.

What are two-shot injection moulding applications?

Two-shot injection moulding is the preferred method for producing complex, multi-coloured, and multi-material plastic components, particularly in high-volume manufacturing environments. This technique is widely used across various industries, including consumer products, automotive, medical devices, packaging, and personal care items. Two-shot moulding is commonly employed in the production of:

• Toys
• Containers
• Toiletries
• Gardening tools
• Movable  parts
• Surgery and medical equipment
• Kitchen utensils
• Other multi-colour, multi-material parts

What are the benefits of two-shot injection moulding?

Two-shot injection moulding eliminates the need for multiple production phases, offering several advantages to moulding manufacturers. These include reduced manufacturing costs, enhanced ergonomics and aesthetics, superior mechanical bonding, faster production cycles, and more efficient material utilisation. As a result, engineers can easily produce multi-material and multi-coloured components without the requirement for additional machining steps.

Reduced manufacturing costs:

As the number of parts in a final assembly is decreased with two-shot injection moulding, there could be a huge saving in research and development, engineering, and validation expenses for each increased part number.

Improved aesthetics and ergonomics:

Products manufactured using the two-shot method can retain essential structural properties while offering enhanced aesthetic and ergonomic appeal. The load-bearing component is moulded in the first phase of the process, with the second phase allowing for the application of a more aesthetically pleasing material. This technique also facilitates the addition of materials more suitable for human contact, such as soft, rubber-like materials, which provide improved grip and a more comfortable feel for handling.

Superior mechanical bonding:

Given excellent material selection, the product’s various levels join together molecularly throughout the moulding process, hence, the bond is frequently more durable than traditional moulding and assembly and even more durable than other cutting-edge techniques like over- and insert moulding.

Quicker production time:

As multiple layers of a product can be incorporated during the two-shot moulding process, the need for secondary assembly is often eliminated, enabling injection moulders to significantly reduce production time. Although the duration of a single cycle may be longer than that of traditional injection moulding, it remains more time-efficient than running two separate cycles to produce the same component.

More efficient material usage:

Two-shot moulding could help combine the greatest qualities of different materials, to create complex mould patterns with strong bonding to ensure durability and longevity.

Micro Systems is a UK based manufacturer of medical moulds, micro moulds and medical injection-moulded parts. We cater for our customers starting from mould design through mould manufacturing and development to validation within an ISO Class 7 cleanroom. We are ISO 13485 and ISO 9001 certified. Micro Systems products include moulds for medical or high-precision plastic manufacturers and injection-moulded medical parts produced on-site at our Optimold facility. Contact us today to get the best quote for your medical injection moulding project. 

(Photo: Micro Systems)