Plastics parts can meet a product’s functional requirements and have various advantages compared to metal parts. Therefore engineers are replacing metal parts with plastic parts for different applications.
For example, the latest model automobile vehicles are low in weight compared to old ones because plastic parts are replacing metal parts in new vehicle designs. This article covers the various advantages and disadvantages of plastic over metal parts.
Advantages of Plastic over Metal
One obvious advantage of replacing metal parts with plastics is lower weight and manufacturing costs. Cost and weight are not the only factors that industries are using more plastic parts in their products.
Apart from weight and cost, plastic parts have the following advantages compared to metal parts.
- High strength and toughness
- Superior design flexibility (Integrating multiple parts into one part)
- Lower weight and material cost
- Low manufacturing cost
- No need for secondary finish operation.
- You can eliminate the fasteners.
- Corrosion resistant.
- Reduced waste.
Here is a detailed discussion on the advantages of plastic parts over metal parts:
High Strength and Toughness
Plastic has the advantage of higher strength to weight ratio and toughness. Therefore, designed plastic parts are lighter in weight compared to metal parts.
Superior Design Flexibility
Plastic parts are manufactured by flowing molten plastic in the injection mold. This process has the advantage of manufacturing complex features, geometries and integrating multiple metal parts in one plastic part. Therefore it helps in reducing product costs.
Lower Weight and Material Cost
Thermoplastics parts are lighter in weight. Therefore plastic part weight and cost are less compared to metal parts.
Low Manufacturing Cost
The plastic parts manufacturing process (injection molding) has a relatively lower cycle time. As a result, plastic part manufacturing costs reduce compared to metal parts.
No need for Secondary finish Operation
Metal parts require secondary finishing operations to achieve required aesthetics and corrosion resistance. Whereas plastics have inherent corrosion resistance properties. And plastic part aesthetic finish depends on the injection mold finish. Therefore plastics offer advantages of eliminating secondary finish operation.
Eliminate Fasteners
The plastics manufacturing process has the advantage of integrating assembly features such as cantilever snap in the plastic parts. As a result, product assembly time and cost reduces.
Corrosion Resistance
Plastics are corrosion-resistant and non-conductive.
Reduced Waste
Plastic parts are manufactured by flowing molten plastic in the mold, whereas the material removes during the machining of metal parts. Therefore plastic has the advantage of manufacturing parts with low material wastage compared to metal parts. For high production volumes, we can use hot runner injection mold because of negligible Plastic wastage.
Disadvantages of Plastics over Metal
Along with so many advantages, using plastic parts instead of metal can have the following limitations.
- Higher initial tooling cost
- Higher lead time for tool development.
- Lower electrical and thermal conductivity.
- Limited working temperature range.
- The manufacturing process is difficult to control.
Let’s discuss the above disadvantages of plastic parts over metal in detail:
Higher Initial Tooling Cost
Plastics have a disadvantage of the high cost of injection molding tool development. Different parts require different injection molds, whereas machined metal parts do not require special tooling.
Higher Lead Time for Tool Development
Injection molding tool development has a longer lead time. But For smaller volumes, Plastic Prototyping techniques are used to get samples quicker. Therefore plastic parts have a disadvantage of higher lead time compared to metal parts.
Electrical and Thermal Conductivity
Plastics are not good conductors of heat. Therefore plastic parts can not be used where high heat and thermal conductivity are required. To solve this problem, we can use plastic parts in conjunction with metal parts.
Lower working Temperature Range
Plastics material is not recommended for very high and low temperature applications.
Manufacturing Process
It is difficult to control the injection molding process. Various Plastic injection molding defects will come up if the plastic parts design is not as per guidelines or the injection molding process is not in control.
To sum up, product designers across various industries are reducing product costs by incorporating plastics parts. You can expect 25 to 30% cost saving with metal-to-plastic conversion.
We will keep updating this article on the advantages and disadvantages of plastic over metal. Add your comments, questions, or suggestions on the advantages and limitations of injection-molded plastic parts in the comment box.
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