Metals such as steel, aluminium and brass were the traditional choices for design engineers for mechanical components for decades. The materials offered a predictable strength and wear resistance. But today’s manufacturing requires lighter and less expensive options that won’t compromise performance.

When deciding between metal or plastic, sometimes the analysis of the operating environment of the component is undertaken. Chemical exposure, operating temperatures and mechanical loads are some of the factors that need to be taken into consideration. Next, check the pros and cons of using plastic versus other materials for your project and see if it makes sense for you to use plastic.

How Weight and Strength Dictate Material Selection

Making the switch from metal is one of the main reasons for weight loss. Engineering plastics such as nylon and acetal have significantly lower densities than steel or aluminium, so components weigh only a little more than their metal counterparts. It is a direct weight saving and a saving of energy efficiency in moving parts that helps to ease stress on motors.

Metals have a higher absolute tensile strength, but some plastics have an impressive strength to weight ratio. They bear high mechanical loads, particularly if they are self-lubricating and friction is therefore reduced. To test the performance of a plastic component in your machine, using cut-to-size engineering plastic sheets is a simple way to create prototypes. This allows you to evaluate the material without committing to expensive injection moulding tooling.

How to Handle Corrosion and Chemical Exposure

In a marine, food processing or chemical environment, corrosion will cause metal components to deteriorate with use, especially over time. Rust can cause failure of parts and must be maintained frequently or have costly protective coatings. Stainless steel will provide protection, but it will also raise materials’ costs and weight of the assembly.

Due to this property, engineering plastics are a great alternative since they are natural and resistant to moisture, acids and industrial solvents. Resistant to corrosion and deterioration in the presence of strong chemicals. Their suitability makes them good for gears, bearings and rollers in wet environments.

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Thermal Properties and Frictional Heat

The difference between these two material groups is one of their temperature limits. Metals are able to resist high temperatures while maintaining their structural integrity, while plastics are not. Continuous operating temperature of a plastic must be checked before switching.

Although this is a drawback, plastics are still good at controlling friction. Many engineering grades do not need to be lubricated externally as they include lubricating oil internally. This feature helps to reduce the need for routine maintenance, such as greasing, and reduces the ongoing maintenance requirement.

How to Evaluate the Financial Impact

However, most of the times, it is the production budget that determines whether the parts are replaced or not. The raw metal stock can be costly and making complex parts from solid metal will take a considerable amount of time and energy to cut. Plastics can be machine processed more easily and quickly, reducing labour costs in manufacturing.

It’s important to take a component’s entire life cycle into account when determining the total financial impact. Here are some areas to check to see where you can save money:

• Lower initial material costs for high-performance polymers.
• Reduced machining time due to the softer nature of the material.
• Zero expenses for painting, plating or anodising.
• Decreased replacement frequency in highly corrosive environments.

Concluding Notes

The substitution of metal parts with engineering plastics has obvious advantages in terms of weight, corrosion-proof, production speed. But, before you finalize designs you need to thoroughly understand the mechanical loads and thermal limits of your application.

There is always a risk to switching materials, so testing a physical prototype is the most secure way to switch materials. Using the raw sheets provides an inexpensive method of creating test pieces and testing performance in actual working conditions.