Plastics manufacturing Questions and Answers: What is 2k Moulding?

Editor: MA Alexander Stark

Ireland — 2k moulding is one of the most innovative processes in use in plastics manufacturing today. Although the concept has been around for many decades, as with all tech processes, there have been a lot of technological advances in the use of 2k moulding in recent times. With a wide set of applications, it has many practical uses.

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2k moulding technology blends two materials or two different colour materials into one ending plastic part by using a specific 2k injection moulding machine.
2k moulding technology blends two materials or two different colour materials into one ending plastic part by using a specific 2k injection moulding machine.
(Source: Key Plastics)

2k moulding — sometimes known as double injection or two shot moulding — is a very innovative way to produce complicated moulded parts from two different materials. It’s a highly meticulous, specialised and automated manufacturing process which controls the injection of multiple materials. It is specialised because it involves the combination of hard and soft thermoplastics or thermoplastic (TP) and thermoplastic elastomer (TPE). It’s applicable to a broad range of products; think medical devices, keys on a computer keyboard and even all the specific parts that go into a car’s headlights.

There are many other potential uses for it too. For example, it can be used to improve the grip on product handles — for items like power drills, toothbrush’s, walkie talkie’s etc. Plastics are integrated into the product grip and this can be done through the use of 2k moulding.

How does 2k moulding work?

Simply put, the plastic moulding technology blends two materials or two different colour materials into one ending plastic part by using a specific 2k injection moulding machine. This machine has the power to take two totally different polymers and transform them into a single, final product.

A chemical bonding process is required so that the two or more materials can be combined into one component. The strategic choice of materials are a fundamental factor for the project’s success or not when using 2k injection moulding. Also, throughout this process, it’s vital to use the appropriate classification of cleanroom, given the type of product you are creating.

What about the 2k moulding machine?

2k moulding is performed on one machine which is programmed to perform two injections in one cycle. In the first cycle, a nozzle injects plastic into a mould. The mould is then automatically rotated and a different type of plastic is injected into the mould from a second nozzle. The 2k moulding machine can create a highly effective end result from very different polymers.

What equipment and tools are required?

A 2k moulding machine needs to be kitted with multiple injection screws; either a rotating tool, a transfer tool and/or a moving core tool; and any other required supporting equipment.

What’s the difference between 2k moulding and overmoulding?

A common question. Let’s first define overmoulding. Overmoulding is also a type of injection moulding process that allows for the combination of two or more different materials into a single product. This usually includes a rigid, plastic-base component overlaid with a pliable, thin rubber-like thermoplastic elastomer (TPE) exterior layer or other materials using either a one shot (insert moulding) or two shot (2k) technique. The main differences between overmoulding and 2k moulding can be summarised as follows: Overmoulding can be both a single shot (insert moulding) or two-shot. 2k moulding is just a 2 shot process. 2k tends to be a lot bigger than overmoulding and is used for larger operations.

In the overmoulding process, the material used must be cold to be removed. However with 2k moulding, the polymer is typically still flexible and hot — therefore it allows for more greater functionality. 2k moulding allows for large number of materials that can act as the moulding substance or equally be moulded on. With overmoulding, you are more restricted with the usable materials.

What are the benefits of 2k moulding?

There are many advantages to 2k moulding including:

  • Versatility: Due to the nature of 2k moulding, this process can be used for a variety of product designs across different industries. This could be cameras, automotive parts, power switches, medical devices etc. (More on medical devices below.)
  • Improved quality: As the moulding uses clear plastics, coloured graphics and neat finishes, it has multi-material efficiency. Furthermore it can be more durable and more aesthetically pleasing as many colours can be blended in the manufacturing process.
  • Increased product value and marketability: This multi-material efficiency of course improves the utilitarian aspect of the product and thus its overall marketplace value.
  • Expense:2k moulding is a streamlined process which allows for a lower price per unit… as all manufacturing procedures are completed in the injection stage.
  • Time: With no secondary processing, there is a gain in cycle time with it being a constant process. The end results means less assembly time & greater efficiency.
  • Reduced handling and secondary assembly:For example it’s less likely that you will have to prime, paint or coat the product afterwards.
  • Reduces cost and waste associated with potential assembly defects.
  • Enhanced tactile and cosmetic product features.

These are the main benefits associated with 2k moulding. While the counter argument and potential drawback is that the mould for 2k moulding and running the 2k moulding machine is more expensive… where high volume is needed, the overall cost and time can be significantly lower, thanks to a greater reduction in overall assembly and labour costs.

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