The Difference Between Double Shot Molding And Overmolding

There are a variety of manufacturing methods used to create plastic molded products. Two methods mentioned in this article, double shot molding and overmolding, are viable manufacturing processes that offer several advantages for many plastic manufacturers. Both processes can be difficult to master since they require adherence to the very tightest of tolerances. Below, we discuss the differences and advantages between double shot molding and overmolding.

 

Double Shot Molding

Double shot molding, sometimes referred to as two-shot molding, is a manufacturing process used to produce complicated molded parts from two different materials by molding plastic around a preformed metal or plastic insert. The process is relatively simple; one material is injected into a mold in order to make the initial piece of the product, followed by a second injection of another material that is compatible with the initial injection molded piece. The two plastic resins then form a molecular bond and the multi-resin molded part is cooled and ejected.

 

Double shot molding is an ideal process for complex, multi-material, and multi-colored plastic products; specifically in high-volume production scenarios. Other advantages include:

 

Lower unit cost.

Reduced cost and waste associated with assembly defects.

Enhanced product quality.

 

Overmolding

Overmolding is a process of adding an additional layer of material over an already existing piece or part. This process is regularly used to manufacture parts, sub-sections of parts, and for prototype development. Typically, the substrate material (the first piece in what will be bonded and mechanically interlocked with other materials) is placed into an injection molding tool, at which point the overmold material is shot into or around the substrate. When the overmold materials solidify, the two materials become joined together as a single part.

 

If you are overmolding a metal part with plastic, you can really use any type of plastic. If you are overmolding a plastic part with another plastic, then there can be some compatibility issues. Your experienced molder will be able to recommend the best materials suitable for your project

 

Overmolding can be added to change the surface of a piece or product by adding texture, color, and incorporating necessary functionality components. Other advantages include:

 

Enhanced design flexibility and multi-material components.

Reduced secondary operations; assembly and labor costs.

Improved part strength and structure.

As mentioned above, these processes are relatively simple to understand. However, it is highly difficult to master. It requires high levels of technical expertise and attention to detail. When dealing with high-volume production scenarios, the smallest mistake can be costly. This is why it is critical to find a highly capable molding manufacturer. Once you find one, you need to involve them early on in the design phase of your part, as they can engineer value and quality into any problem areas. If you have questions or concerns regarding your part or the double shot or overmold processes, contact our experts at WIT MOLD today!

Multi-Shot Injection Molding and Two-Shot Injection Molding

Multi-shot plastic injection molding and two-shot plastic injection molding is an efficient and cost-effective method for molding custom plastic parts with two or more plastic resins or colors in one operation.

 

In multi-shot and two-shot custom plastic injection molding, plastic polymers from two or more injection units are applied through independent nozzles on one plastic injection molding machine to produce custom plastic parts such as soft-grip handle inserts, multi-colored parts, dashboard or instrumentation, or parts with molded seals, flexible hinges, or movable components.

 

The multi-shot and two-shot plastic injection molding technology enables:

 

Multi-color, multi-material and multi-component parts

New and wider range of designs

More complex parts and reduced cost

Production, handling and assembly efficiencies and savings

Reduction of multiple and secondary operations

Lower part cost

Enhanced product features and appeal, including tactile, ergonomic and aesthetics

Improved part and end use product integrity and quality

Elimination of secondary process for logos, graphics and text

With multi-shot and two-shot plastic injection molding, you get the integrated functionality, multiple colors and materials, molded graphics and soft touch layers over rigid components you want, while reducing productions steps, time and cost!

 

Applications

WIT MOLD has many years or experience with multi-shot and two-shot plastic injection molding, and designing and building high quality multi-shot and two-shot molds, for a wide range of applications, including:

 

Soft touch handle grips and components

Power tool handles

Electric toothbrush handles

Multi-color parts, switches, knobs, enclosures and assemblies

Movable parts and components

Parts with flexible hinges

Vibration, noise dampening and isolation

Caps and enclosures

Medical devices

Dental products

Two toned plastic lenses

 

Capabilities

WIT MOLD multi-shot and two-shot plastic injection molding capabilities include:

 

Two-shot material molding

High quality multi-shot tool design and building

Automated parts handling and packaging

Robotics and automated assembly

High volume production

Global systems and locations (United States, Mexico, China)

Tight tolerances

Material/product traceability

Class 100,000 (ISO Class 8) clean room molding

Full range of value-added and secondary finishing operations

Two-Shot Injection Molding Solutions

If you’re new to two-shot plastic injection molding, you might think it is more complex, more expensive, or more time consuming than other plastic molding processes. Taken alone, those may be true, but two-shot also creates considerable functionality and savings. Maybe you’ve been turned off by a manufacturer’s quality or delivery issues. We’re here to tell you that you deserve better.

 

When tolerances and on-time-delivery are important, OEMs choose Thumb Plastics for two-shot injection molded parts. We’re more than a manufacturer. We’re problem-solvers, working both with customers and vendors to build functionality, safety, and efficiency into everything we produce. You can rest assured you’re getting the quality you need at a competitive market price when you choose Thumb Plastics for your two-shot molding solutions.

 

Two-Shot Molding Process

There are two phases of the two-shot molding process. The first is similar to traditional injection molding: A shot of resin is injected into a mold and cooled to form a solid part. In the second phase, the just-molded part is transferred to a second mold via a rotating platen or a robotic arm, and receives the second shot of resin – in, through or around certain parts of the first molded part, depending on the design. The two plastic resins then form a molecular bond and the multi-resin molded part is cooled and ejected.

 

The process isn’t difficult to understand, but it’s highly difficult to master. It requires high levels of technical expertise and attention to detail, and even the smallest mistakes can cost big money, especially in high-volume production scenarios.

 

That’s why it’s critical to find a highly capable supplier. Look for excellent supplier quality scorecards, defined processes to mitigate against flash, flow lines, and short-shots, and contingency plans to expand capacity as your business and your two-shot molding needs grow.

 

Once you find a supplier, involve them early on in the design phase of your part. They can identify potential problem areas and engineer value into your product.

 

Two-Shot Injection Molding Applications

Two-shot injection molding is the ideal plastic molding process for complex, multi-color, and multi-material plastic products, especially in high-volume production scenarios. WIT MOLD services a variety of industries including lawn and garden, agriculture, and consumer, with significant experience in automotive.

 

From consumer goods to construction, two-shot molded components are used in nearly every industry, but are most commonly found in applications requiring the following:

 

Movable segments or components

Rigid substrates with soft grips

Vibration or acoustic dampening

Surface descriptions or identifications

Multi-color or multi-material components

Benefits of Two-Shot Molding

Compared to other methods of plastic molding, two-shot is ultimately a more cost-efficient way of producing an assembly with multiple components. Here’s why:

 

Part Consolidation | Two-shot injection molding reduces the number of components in a finished assembly, eliminating an average of $40K in development, engineering, and validation costs associated with each additional part number.

 

Improved Efficiency │ Two-shot molding allows multiple components to be molded with a single tool, reducing the amount of labor needed to run your parts and eliminating the need to weld or join components after the molding process.

 

Improved Quality │ Two-shot is carried out within a single tool, allowing for lower tolerances than other molding processes, a high level of accuracy and repeat-ability, and reduced scrap rates.

 

Complex Moldings │ Two-shot injection molding allows for the creation of complex mold designs that incorporate multiple materials for functionality that cannot be achieved through other molding processes.

DOUBLE INJECTION MOLDING / TWO SHOT INJECTION (2K)

Overmolding is an injection molding process where two materials are molded together. Types of overmolding include two-shot sequential overmolding, multi-shot injection molding or insert overmolding.  Unique part designs using different materials, sections, and colors can be a time-consuming and expensive proposition. Before beginning this delicate process, a 2-shot overmolding simulation and analysis will help determine how best to design the part and specifically where the best gate location would be and how the materials will function throughout the first or second shot as well as during a multiple shot molding cycle.

 

CAE 2-shot Overmolding Analysis helps determine:

The best gate location

Optimal material flow for multiple shots

How an insert can be place for efficient molding

Two-shot sequential overmolding is where the molding machine injects the first material into a closed cavity, and then moves the mold or cores to create a second cavity, using the first component as an insert for the second shot using a different material.

Multi-shot injection molding injects multiple materials into the cavity during the same molding cycle.

Insert overmolding uses a pre-molded insert placed into the mold before injecting the second material.

 

Double Injection, sometimes known as 2 material 2 shot molding or 2K molding, is an innovative manufacturing process used to produce complicated molded parts from two different materials. Through a highly specialized and automated process we carefully control the injection of multiple materials, including two different kinds of resin, into a single, multi-chambered mold.

 

Double Injection in performed on one machine that is programmed to perform two injections in one cycle. In the first cycle, a nozzle injects plastic into a mold. The mold is then automatically rotated and a different type of plastic is injected into the mold from a second nozzle.

 

Double Injection Molding optimizes co-polymerization of hard and soft materials to create powerful molecular bond. The result is a single part with production and feature advantages. It can be used for a variety of product designs across all industries. It also allows for molding using clear plastics, colored graphics and stylish finishes which improves your product functionality and marketplace value.

 

Double Injection advantages include:

 

Lower unit cost

Improved part integrity

Multi-material efficiency

Higher-quality plastic part fabrication

Reduced handling and secondary assembly

Reduces cost and waste associated with assembly defects

Enhanced tactile and cosmetic product features