What is 2k injection molding?

What is 2k injection molding?

In 2k injection molding, or 2 shot molding, two materials (colors) are processed into a single plastic item. Using a 2K injection molding machine, this plastic molding technique mixes two materials or two distinct colors of materials into one final plastic product, combining the benefits of 2 materials with differing qualities into a high-quality link. 

What is the 2k injection molding process?

Both materials are simultaneously injected into the mold cavity during the 2K molding process. Typically, there are two types of materials: an elastic substance like TPE or TPV and a stiff material like polypropylene. Compared to conventional single-material injection molding, the combination of two materials enables more intricate designs and improved functioning.

Step 1: The two injection canisters are filled with raw ingredients, which are then heated and under pressure to preserve the viscous condition required for injection to take place. While the other moulding box stays closed, the first crate is opened and shot with the first injection.

Step 2: The part that was just formed from the first injection is robotically moved to the second mould as soon as the press on the first crate is opened. Thus, the first chamber is once more open and prepared for the second injection.

Step 3: After closing the second chamber’s press, the second injection is fired into the first chamber, which is now open, until it fills up just like the first one did, guaranteeing that the final items are uniform.

Step 4: Robotic arms are used to open the second chamber once more and move the second portion inside. This procedure is carried out as quickly as possible until the necessary quantity of goods is reached.

2k injection molding

What are 2k injection molding advantages?

  • Improved aesthetics: The 2k injection molding technique may be more appealing as it allows for the manufacture of two colors (2K) of the product in a single production process. Modification is hence easier to be added, for extra features like logos, patterns, colours, etc. 
  • Improved efficiency: Since the majority of it is automated, manufacturers can save a significant amount of time and money that would have been spent on labor expenditures. 
  • Design range: 2k molding offers a lot of alternatives and is a good way to manufacture metallic mold items and transparent plastic at a reasonable price, and designers can be more flexible with their design choices. 
  • Reduced post-processing: The all-inclusive nature of the two-shot injection method eliminates the need for additional steps like post-processing, which typically result in needless increases in expense, time, and energy use, at the same time, increasing the precision of the final product. 
  • Part perfection: Using conventional manufacturing techniques, distinct components are typically produced in separate batches and then assembled to form a single unit, which is a resource waste. By ensuring a considerable reduction in the number of parts required, two-shot injection molding helps save money, time, and energy, and avoid any potential mistakes between the 2 materials.
  • Reduced time: The secondary processing time is not necessary during the 2k molding process.

What are 2k injection molding applications?

Two shot molding design injection, or 2k injection molding, is a highly adaptable process that may be used to make complicated and complex components with a variety of design elements. The medical sector is the most frequent user of this molding technique. For example:

  • Medical instruments: 2k molding is useful in the medical profession for applications such as ergonomic handles with soft-touch grips, multi-material housings for medical instruments, and over-molded grips for surgical tools. 
  • Automobile industry: 2k injection molding is widely used in the automobile industry to produce parts like multi-material gaskets, instrument panels, and gear shift knobs. In this business, combining flexible and stiff materials is crucial. 
  • Consumer Electronics: Both soft-and hard-touch surfaces are needed for many electrical components. Products like smartphone covers, remote control buttons, and electrical enclosures with integrated seals are made with 2k injection molding.

What are the mould requirements for 2k injection molding?

In order to guarantee that the two materials are injected correctly and that the final product satisfies the required criteria, the mould design and manufacture for 2k molding is an essential part of the process. To accommodate each material, the two shot mould has to be constructed with two distinct chambers that are meant to keep material from leaking between them. In addition, in order to guarantee that the ingredients cool and solidify properly throughout the molding process, the mold must also be built with enough cooling channels. The mould also needs to be rotatable through 180 degrees, with symmetrical inserts. 

2k injection molding vs over molding

Another kind of injection molding technique that enables the blending of two or more distinct materials into a single product is over molding. A stiff plastic foundation component is often covered with a thin, malleable layer of thermoplastic elastomer (TPE) or other material utilizing a 1 shot (insert molding) or 2 shot (2k) process.

While sounded similar, 2k molding and over molding share certain key differences: 

  • Number of shots: Over molding can be done in two steps or in one shot (insert molding). Two-shot molding is all that 2k molding is.
  • Amount of production: When it comes to larger operations, 2k is typically much larger than over molding.
  • Material: The material used in the over molding process needs to be cool in order to be removed. However, as the polymer is usually still heated and flexible after 2k molding, it offers additional utility. A wide range of materials may be moulded on or used as the molding substance thanks to 2k molding, however, there are limitations on the materials that may be used for over molding.

medical molding


At Micro Systems, our team of experts in injection molding can provide turnkey solutions for your 2k injection molding projects, for a variety of applications in the medical and pharmaceutical, diagnostics, drug delivery and other applications. We are ISO 9001 and ISO 13485 accredited, with ISO Class 7 cleanrooms and more than 20 years of experience supplying precision molds and injection molding solutions to major life sciences companies all over the world. 

Contact us today to discuss your 2k injection molding project!