Advantages of Injection Moulding

Whether you’re considering an injection molded part for your next project or need to replace an existing one, there are a few factors you should consider. These include design, surface finishes, tooling costs, and material compatibility. Understanding these factors can help you make the right decision. Read on to learn more about the advantages of injection molding and how to get started.

Design factors

One of the most critical design factors for injection molded parts is the wall thickness. The wall thickness affects many key characteristics of the part, from its surface finish to its structural integrity. Proper consideration of this factor can prevent costly delays due to mold issues or mold modifications. To avoid this problem, product designers must carefully consider the functional requirements of the part to determine the minimum and nominal wall thickness. In addition, they must also consider acceptable stress levels, since parts with excessively thin walls may require excessive plastic pressure and may create air traps.
Another factor to consider when designing a part is its ejection and release capabilities. If the part is released from the mold, the tools should be able to slide the plastic out. Injection molds usually have two sides, one of which is ejectable, and another that remains in the mold. In some cases, special features are required to prevent part release, such as a ramp or a gusset. These design features can increase the design flexibility, but they can also increase the cost of the mold.
When designing injection molded parts, the engineering team first determines the key design elements. These elements will make sure the injection process goes as smoothly as possible. This includes factors like wall thickness, rib design, boss design, corner transition, and weld line, among others. The engineering team will then perform a design for manufacturability analysis and, if all is well, can start building and testing the mold.

Material compatibility

Several factors can affect material compatibility of injection molded parts. When molding plastic parts, it is important to choose a material that is compatible with the part’s intended purpose. Many injection molding processes require that the two main plastic materials used are compatible with each other. This is the case in overmolding and two-shot injection molding.
The material you use to make an injection molded part will significantly impact the tolerance of the finished product. This is why material selection is as important as the design of the part. Many types of plastic resins can be used for injection molding. In addition, many of these resins can be modified or strengthened by adding additives, fillers, and stabilizers. This flexibility allows product teams to tailor the material to achieve desired performance characteristics.
One of the most common thermoplastics is polypropylene. It is extremely durable and has good impact strength and moisture resistance. This material is also recyclable and does not react with food.

Tooling costs

One of the largest costs for manufacturing injection molded parts is tooling. For an OEM, tooling costs can range from $15K per part for a simple part to $500K for a mold with complex geometry. Tooling costs vary based on the type of steel used and the production volume of the part.
To get a reasonable estimate, companies should have a final design, preliminary design, and sample part to hand when requesting quotes. The dimensions and complexity of the cavity in a mold are crucial in determining the tooling cost, as are the part tolerances. Part tolerances are based on the area covered by the part and its functions within the mold.
The type of mold you need can also impact your tooling costs. Injection molding machines can accommodate many different kinds of molds. Some molds are made from a single mold, while others require multiple molds. Some molds can be complicated, making them unmanufacturable, which in turn drives up the cost of tooling.
The costs for tooling for injection molding are not well known, but they do add up quickly. Many product development teams tend to consider the cost of the injection molding process in terms of direct materials, machine time, and labor, but that cost model often fails to take into account additional components.

Surface finishes

Surface finishes on injection molded parts are often used to mask defects, hide wear and tear, or enhance a product’s appearance. These finishes can also be useful when the product will come in contact with people’s hands. The surface texture you choose will depend on your desired functionality as well as the way you want to use the product. Generally, rougher textures provide better grip while masking minor molding imperfections. However, they can also make a product more difficult to release from the mold. This means that you may have to increase the draft angle of the mold. In order to get the best surface finish, the toolmaker and product designer must collaborate closely early in the design process.
There are several different surface finishes that can be used for injection molded parts. One type is known as the B-grade finish, and is compatible with a wide variety of injection molding plastics. Another type of finish is called a stone polishing process, and is ideal for parts that have no aesthetic value.

Overhangs

The injection moulding industry refers to overhangs on injection molded parts as “undercuts,” and these can lead to design instability. To minimize undercuts, the design must be parallel to the part’s surface. If an undercut is present, a zigzag parting line can be used.
The overhang is typically a few millimeters shorter than the surface of the mold. It is generally made from a lower-cost plastic material than the part’s surface area. The material used for the overhang should have sufficient strength to fulfill its function. An overhang will also help to prevent the piece from deforming or cracking.
Injection molding can create overhangs around the perimeter of a part. Overhangs are not always necessary; they can be added to parts as desired. Adding an overhang, however, will add substantial tooling costs. As a result, it is better to minimize the overall thickness of a design. However, in some cases an overhang can be useful to make the part look more attractive.
For parts with complex geometries, there are a few options for overhangs. Some manufacturers use side-action molds to form more complex shapes.

CNC machining

CNC machining of injection molded parts is a process that helps manufacturers achieve precise surfaces and shapes for their products. This process typically begins with the milling of the tooling, which is typically made of aluminum or steel. This tooling is then placed in a CNC mill. This machine carves the negative of the final plastic part, making it possible to achieve specific surface finishes. The process can be adapted to create a part with a complex structure or special features.
CNC machining allows the manufacturer to produce high-performance parts. This is possible because MIM parts do not experience induced stresses or internal pressure during the manufacturing process. Furthermore, the parts produced by MIM are more durable than CNC parts. Despite their advantages, CNC machining has its limitations, especially when it comes to design freedom and intricacy. This factor is largely dependent on the software used by the manufacturer or designer.
One drawback of CNC machining is its higher cost. Compared to injection molding, CNC machining is more expensive per part. The reason is that the initial mold cost is relatively high and is spread over a large number of parts. Once the injection molding process has been completed, the cost of the parts produced by this process becomes more competitive with those produced by machined parts. However, the cost gap increases with the volume of parts produced. This cost crossover generally occurs in quantities of at least 100 parts and can reach a maximum of 5000 parts.

Production volume

The production volume of injection molded parts varies depending on the material being used. Large volumes of parts are expensive to produce, while small quantities can be produced for low cost. Injection molding requires a precise mold, which is CNC-machined from tool steel or aluminum. The mold has a negative of the part that is injected, a runner system, and internal water cooling channels to aid in cooling the part. Recent advances in 3D printing materials have made it possible to produce molds for low-volume injection molding. Previously, this was not financially viable due to the high cost of traditional mold making.
A mold is used to produce plastic parts. The molding process is very fast, with each cycle taking anywhere from 30 seconds to 90 seconds. After a part is molded, it is removed from the mold and placed on a holding container or conveyor belt. Injection molded parts are generally ready for use right away and require minimal post-processing. Injection molded parts have a similar design to a photograph, since the geometry is directly transferred to the part’s surface texture.
When selecting a plastic mold, it is important to determine the volume that the part will be produced at. If the volume is low, softer plastics may be used. However, as the part is molded over, its performance characteristics may degrade. In low-volume production, it is important to consider the overall complexity of the part. This includes the part’s draft, wall thickness, and surface finish.

editor by CX 2023-04-19