At Levic Plastics, we know quite a bit about insert molding services but realize many of our customers probably do not. That’s why we took the time to write this article to help inform our clients a little bit more about the world of overmolding and insert molding services in Missouri.
Double Shot Overmolding Services in Missouri: What Are They?
The thermoplastic elastomer (TPE) is added to plastic substrates in these types of plastic overmolding services in Missouri. This process is also known as two-shot, multi-shot, or double-injection molding. Double shot overmolding enhances the appearance, handling properties, grip, impact resistance, or environmental resistance of injection molded parts.
The overmolding procedure, which adds additional material shortly after the substrate, is then formed to create strong bonds between materials. This process is typically carried out using multi-barrel injection molding machines. By using plastic overmolding services in Missouri, manufacturing steps can be cut out while still producing improved injection-molded goods.
Materials may be bonded chemically or mechanically depending on the substrate and overmold materials that are chosen (via undercuts, for example). In many cases, mechanical bonding is advised to strengthen any potential chemical bonding. Polycarbonate, ABS, HDPE, and nylon are frequently used substrate materials for overmolding.
Materials used as overmolds include thermoplastic elastomers like styrene-ethylene/butylene-styrene copolymer and thermoplastic elastomers like thermoplastic polyurethane (TPU), thermoplastic rubber (TPR), and thermoplastic vulcanite (TPV) (SEBS). Additionally, silicone overmolding is employed, particularly when a plastic component requires a softer rubber surface.
What Are Insert Molding Services in Missouri?
Insert molding is also commonly referred to as metal insert molding or plastic insert molding. This method is frequently used to add metal parts to injection molded parts while the parts are still being molded instead of after they have dried. By doing this, it reduces the need for post-molding manufacturing and assembly processes.
Mold cores that are cast into the actual molds are covered with inserts either manually or automatically. Following the sealing of the mold’s halves, plastic pellets are plasticized in the injector barrel and fired into the cavity, the flowing plastic material encasing the captured inserts. The inserts are now enclosed in the parts when they are ejected from the mold after the plastic has hardened.
Insert molding services in Missouri are often a one-time operation. Inserts are frequently threaded nuts that are used in subsequent part assembly, but they can also be bushings, sleeves, pins, blades, or even non-metallic components. A variety of manufacturers offer standard inserts. Knurled outer surfaces are common on inserts to improve their adhesion to plastic.
The term “insert molding” is also used to describe the overmolding process of covering an existing metal or plastic part with a layer of plastic or rubber material. A single-shot injection mold is used in this instance as well to place the metal or plastic part, and overmold material is then injected around it. Using a single-barrel injection molding machine and a preformed substrate, single-shot overmolding adds an extra layer of material to the product.
If you have any other questions or concerns regarding insert molding services in Missouri, one of our experts at LeVic Plastics will gladly assist you.
Overmolding Versus Insert Molding Services in Missouri
Both overmolding services in Missouri and insert molding involve fusing additional liquid plastic to solid metal or plastic components to produce an end product made of multiple materials. The use of pre-fabricated inserts in insert molding makes it one of two overmolding techniques. Contrarily, double shot molding entails producing an injection molded part and then placing it in a second injection mold where the same plastic, or the same plastic in a different color, will be applied while the product is still being manufactured.
Applications for Overmolding Services
In addition to its widespread use in producing parts that are assembled with threaded fasteners, insert molding services in Missouri are common when producing connectors, electronic sockets, etc. For soft grips on a variety of hand tools, including screwdrivers and surgical instruments, insert molding is used.
Multi-shot overmolding services in Missouri are not only helpful for many higher-value products like medical instruments, where it can provide enhanced grip, cleanability, moisture protection, and other properties, but it has many applications in high-volume personal products. Some of the most popular items are toothbrushes and disposable razors.
A two-step process that first encases the circuit in low-melt-temp resin and then adds a higher temperature protective shell can be used to overmold delicate electronic circuits. Overmolding is a technique used by automakers to eliminate the need for additional adhesive-based assembly steps. A plastic engine part with an overmolded elastomer seal is an example of a typical application.
Both insert molding services in Missouri and two-shot overmolding are common services offered by plastic injection molding companies in Missouri. Two-shot overmolding is typically used for high-volume production where the high capital costs are offset by lower labor costs due to the additional cost involved in special multi-shot machinery.
Multi-shot molding typically makes financial sense at part volumes of over 250,000 per year. Two-shot molding is also occasionally the only method for forging a reliable connection between dissimilar materials.
It’s a common misconception that the softness of the overmold material alone determines how the finished product feels when overmolding is used to create soft grips. The thickness of the layer that is applied also matters a lot because a thin layer will allow the softer top coat to feel through to the harder substrate.
Overmold Injection Molding Design
Given the many factors at play and the potential for errors to be repeated in countless injection-molded copies, overmolding is a difficult process. Early on in the part design process, overmolding service providers should be consulted in order to avoid the numerous pitfalls that are ready and able to prevent the realization of a successful part.
In designing for overmolded parts, the following general guidelines are applicable: Overmold edges must stop abruptly and at full thickness against a stop or into an indentation; they must not feather. The overmold’s surface texture can help the part release from the mold significantly. In addition, it masks any molding flaws by giving the impression that the part is softer than it actually is. Ample draft angles also aid in the release of mold. Gate and vent designs require careful consideration on the part of mold designers.
At LeVic Plastics, we have the staff, expertise, and equipment to assist with your next project. From large-scale orders to limited production runs in Missouri, our LeVic team will complete your order with the utmost service, quality, and efficiency. We are located just outside the Kansas City area in Grandview, MO, and would love the opportunity to assist with your next project.
We specialize in numerous production methods, including injection molding, EDM machining in Missouri, and CNC machining in Missouri. We’ll work closely with you to find the best option for your next production run.
To get started, call (800) 231-1232 or click here to get a free quote. We look forward to hearing from you soon!
