Tooling Metals for Injection Molding
We will discuss the options for tooling materials, even though your choice in injection molding material might influence your decision. However, it is important to start with the tooling material options. This is because molding occurs before tooling, when you make your parts.
It is important to remember that injection molding can be used to produce million pieces of custom parts. So the metal molds that are used in this process must be durable.
For injection molding, hard tool steels were traditionally used. However, aluminum is now a popular choice, too. You can also use metals such as nickel, but for now we will be focusing on aluminum and steel molds.
To choosing a right material for tooling, you should clarify several questions:
- How many parts are molded?
- What type of plastic is used to mold the parts?
- How complicated is the part design?
- What is your total project budget?
Although mild plastics can be used in either aluminum or steel molds, some plastics that are very abrasive may work better with harder molds. Steel molds might be more adept at handling large quantities of plastic parts.
However, aluminum molds are a cost-effective choice. Many aluminum grades can be easily fabricated using processes such as CNC machining. This also reduces lead times. For low volume orders, aluminum may be an ideal tooling material.
Advantages of steel:
- Longer lifespan
- Abrasion resistance
Advantages of aluminum:
- Lower cost
- Less time to market
Important Properties for Injection Molding Materials
When choosing an injection molding material, it is important to consider the intended purpose of the part. Is it required to be strong, tough or elastic? Is it to exhibit high or low friction Is it chemically or heat resistant? Only choose an injection molding material after the desired properties of the material have been identified.
Consider the following material properties:
|Strength||POM, Nylon, PEEK,|
|Rigidity||POM, PMMA, PET, HIPS|
|Flexibility||ABS, LDPE, PVC|
|Heat resistance||PET, PEI, PP, PPS|
|Fatigue resistance||POM, Nylon|
|Chemical resistance||LDPE, HDPE, PP|
|Affordability||LDPE, HDPE, PP, PVC|
Injection Molding Materials
There are three types of suitable injection molding materials: thermoplastics that can all be used, thermosets that can be used, and elastomers which can be used. You can also create composites from two or more materials.
Because they are suited for the molding process, thermoplastics are often used. These plastics will become soft and malleable when heated, but they will return to their solid state when the temperature drops.
The hopper can then be filled with thermoplastics in a solid or granular form. They are then heated in the chamber to melt and injected into the mold. The heated plastic begins to cool and solidify inside the mold. This forms the final part.
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Materials For Specific Molded Parts
It is possible to choose from several materials when injection molding is done. There are some conventions that can be used for commonly manufactured parts like housings, containers and valves.
Here are some of the most common parts that can be injection-molded and the materials used for their production.
|Toys||ABS, Polystyrene and PVC||Injection molding is used to make many toys for children. However, it requires plastic that can withstand impact and be tough. ABS is used to make LEGO bricks, one of the most well-known toys.|
|Valves||PET, POM||Valves are used for shutting off liquid or air supply. They are often made by injection molding. They are often made from chemically resistant materials such as PET and POM.|
|Automotive components||ABS, PC, PET||Although injection-molded automobile components are very common, the quality of some plastics will depend on the particular part.|
ABS can be used to make panels and consoles, while PET is more rigid and may be used to make parts such as filters and pumps. Polypropylene is often used to make bumpers.
|Electrical components||PET, PEI, TPE||Injection molding is a common process for making electrical components. These plastics are strong and durable with low water absorption.|
|Bearings||POM, Nylon, PET, PPS||Injection molding can be used to make bearings and other parts of machines, provided that a strong plastic is used with good fatigue resistance.|
|Containers||Polystyrene, LDPE and HDPE||Containers are one of the most commonly manufactured injection-molded parts. They can be used for food, commercial products or any other purpose. Plastics with chemical resistance or translucency might be preferable.|
Since injection molding is a common method of producing commercial products. Therefore, it is important for manufacturers to be able to create parts from injection molding in a variety of colors. For example, companies may choose to match their branding with colors.
The good news is coloring your injection-molded parts is easy.
Some raw materials are pre-colored and pigmented, so they don’t require any further coloration. These are called compounded colors. There are three ways to make uncolored plastic pellets more vibrant:
A pigmented oil and a solvent can be used to color the pellets. Spray the mixture just before the molding process begins.
Mixing dry pigments
Pellets can be colored with dry pigmented dust instead of oil or solvent. The colored powder is then mixed with the pellets in the hopper.