Injection Molded Parts – Design Considerations

If you want to produce high-quality Injection molded parts, there are several factors to consider before the design process. These factors include the Surface finish, Material compatibility, and Tooling fabrication. This article will focus on some of these factors. Ultimately, you can save time and money by designing the parts in-house.

Design considerations

When creating a new part, or updating an existing part, design considerations for injection molded parts are critical. The decisions you make in these early stages of development can have a profound effect on the final product, and they can also have substantial cost and timing implications. In this guide, we’ll explore key design considerations, including how to maximize the efficiency of the injection molding process. We’ll also touch on how to optimize gate placement and parting lines.
To ensure a successful injection molding process, part design must balance structural integrity and plastic fill volume. This means creating parts with relatively thin walls that have adequate support and avoid warping or sinking. To do this, injection molded parts often feature ribs or projections to strengthen the walls. However, too thin of a wall can result in excessive plastic pressure and air traps.
One of the most important design considerations for injection molded parts is the direction of the parting line. For many applications, a parting line is obvious, but for others it’s a little less obvious. The first step in designing an injection mold is to determine which direction it should open.
Another critical design consideration is the part’s ejection. If a part isn’t ejected properly, it will stick to the mold. A part that has too many undercuts or ribs will end up stuck on the mold’s side, making it difficult to eject it from the mold. A part that has a draft angle of at least five degrees is much easier to eject.
Another important design consideration for an injection molded part is the type of plastic used. Some plastics do not tolerate undercuts. However, some materials are able to tolerate undercuts of up to five percent. Undercuts are not ideal and can increase the complexity and cost of the injection mold.
Another design consideration for injection molded parts is the radius of edges. Sharp corners can create high molded-in stresses and can lead to failure points. A radius eliminates this stress by redistributing the stress more evenly throughout the part. This also facilitates flow of the material through the mold.

Surface finish

Injection molded parts are often finished with additional processing in order to improve their aesthetic quality. There are a variety of finishing processes, including machining and sanding, which give injected molded parts a particular look, feel, or texture. The surface finish of a plastic part affects both its aesthetics and its functionality. According to the Society of Plastics Industry, certain standards for surface finish are essential to the aesthetics and durability of plastic parts.
Surface finish of injection molded parts depends on the primary design goal. For instance, some designs may need a part to be aesthetically pleasing while others may want to enhance its functionality. Surface texture is often used by designers and engineers to achieve different aesthetic goals, such as improving the product’s perceived value. A textured surface may also help hide imperfections and improve the part’s non-slip qualities.
Surface finish is a critical aspect of plastic injection molding. It can affect material selection, tooling, and other process decisions. It is important to determine the desired surface finish early in the design phase. A skilled plastic injection molder can assist you in making this decision. In addition to determining the finish you need, a skilled molder can help you decide the best material for the job.
The PIA classification system defines four basic grades for surface finish. There are subcategories for each grade. Group A surface finish is smooth, and grade B and C finishes are textured. The former is the most common and economical finish and is most suitable for industrial parts. It can hide deformations and tooling marks, and is the least expensive finish type.
Surface finish of injection molded parts can vary greatly, and can be crucial to the performance and appearance of the part. Some companies prefer plastic parts with a glossy finish, while others prefer a textured surface for aesthetic reasons. While the former may be better for aesthetic purposes, rougher surfaces are often preferred for functional or mechanical parts.

Material compatibility

Material compatibility is important for the durability of your injection molded parts. You can use multiple materials in the same part by mixing resins. This is an ideal solution for parts that require adhesion, friction, or wear. Fast Radius can simplify the material selection process, optimize part design, and speed up production.
ABS is a thermoplastic polymer that can withstand a range of temperatures. Its low melting point means that it is easy to mold, and it has good chemical and moisture resistance. ABS also has good impact strength, and is highly durable. It is easy to recycle. Nylon is another versatile material for injection molding. It can be used for car tires, electrical components, and various apparel.
When choosing the material for your injection molded parts, keep in mind that the type of resin will determine their tolerance. Injection molding is compatible with a wide range of plastic resins. Some materials are more suitable than others for certain applications, and many plastics can be modified with stabilizers or additives to improve their properties. This flexibility allows the product development team to customize materials to achieve the performance characteristics they desire.
Polyamides are another great option for injection molding parts. Both natural and synthetic varieties of these plastics have excellent properties. However, they have some drawbacks. For instance, nylon injection molding is difficult and can result in inadequate filling. However, Nylon injection molding has many benefits, including high impact resistance and heat resistance.
Polybutylene terephthalate (PBT) is a high-molecular-weight polymer with excellent mechanical and chemical resistance. It is a good choice for components in the medical, automotive, and lighting industries. Its low water absorption and low flammability make it suitable for many applications.
Polyurethane (TPU) is another polymer option. It has excellent resistance to abrasion, chemicals, greases, and oils. It also has high temperature resistance, and is suitable for ozone environments. However, TPU is more expensive than TPE and requires drying before processing. Moreover, it has a short shelf life.

Tooling fabrication

Tooling fabrication for injection-molded parts is an important component of the manufacturing process. The right design of the mold can reduce the cost and time required for a finished product. For instance, choosing the right type of core for the mold can reduce the amount of material used in the part, which is necessary to produce a high-quality product. It is also important to choose a design that is easy to mill into a mold.
Injection molding requires a mold with precise geometries. The mold tool must be constructed accurately and carefully to achieve the desired precision. It can be the biggest investment in the manufacturing process, but it is also critical to the success of a project. Large volume and high-precision parts often require more complex tooling, as they require the highest level of precision.
Tool steels typically used for injection moulding include H-13 and 420 stainless steel. Both of these materials are strong enough to produce parts of comparable hardness to wrought parts. These materials have low elongation values, so they are ideal for constructing injection moulding tools. Some of these steels also have excellent dimensional accuracy and are ideally suited for high-precision tool fabrication.
The process of plastic injection molding requires precise measuring and tooling fabrication. The mold must have the proper lead angle and space for the material to deform. Undercuts must be no larger than 5% of the diameter. Moreover, the injection molded part should be free of stripping or undercuts. Ideally, it should have a lead angle of 30o to 45o.
Various plastics can be used in the process of injection molding. The process can be used to produce cosmetic and end-use parts. Materials used in the molding process include silicone rubber and thermoplastics. If the part requires additional reinforcement, it can be reinforced with fibers, mineral particles, or flame retardant agents.
Increasingly advanced technologies have streamlined the process of tooling fabrication for injection moulded parts. The process has improved with the use of computer aided design, additive manufacturing, and CNC lathes. Approximately 15% of the cost of a finished injection molded part is spent on tooling fabrication.

editor by CX 2023-05-06