Metal Machining: Pros and Cons

Key Takeaways

• Metal machining provides superior strength, heat resistance, wear resistance, and dimensional stability for demanding applications.

• Metals enable precision manufacturing processes such as EDM but are generally heavier and more difficult to machine than plastics.

• Material selection should balance performance, cost, corrosion resistance, and machining requirements to achieve the best overall result.

Overview

When designing parts, one of the first decisions to make is whether to use metal or plastic. The right choice comes down to performance requirements and operating conditions. By understanding the strengths and limitations of each, you can lower costs without sacrificing functionality. This article explores the advantages and disadvantages of metal CNC machining.

Advantages of Metal Machining

High Mechanical Strength

Metals inherently have higher mechanical strength than plastics, making them ideal for applications requiring durability. Heat treatment can further improve strength and toughness.

High Wear Resistance and Heat Resistance

With the exception of super engineering plastics, most plastics have heat resistance below 100℃ (212°F). Metals, in contrast, have much higher melting points, making them suitable for high-temperature environments.

Common Metal Melting Points:

• Aluminum ∼600℃(∼1112°F)

• Iron ∼1200℃(∼2192°F)

• Stainless Steel ∼1400-1500℃(∼2552-2732°F)

Lower Cost Per Unit Volume of Steel

Metals, especially steels, are often less expensive on a per volume basis than general engineering plastics. Exceptions include copper, A7075 aluminum, and special steels. Machining costs, affected by material hardness and machinability, must also be considered. Comparing material prices alone can increase total costs, so considering part geometry is essential for cost control.

Conversely, the simpler the shape, the greater the proportion of material cost, making material based cost comparison more effective.

Stable Dimensional Accuracy

During machining, friction between the cutting tool and the material generates heat, which can cause distortion in the material. Plastic materials deform more easily under heat due to higher thermal expansion, while metals maintain dimensional stability during machining.

Electrical Discharge Machining (EDM) and Wire Cutting

Since metals are conductive, they can be machined using EDM or wire cutting. However, this conductivity can be a disadvantage in applications requiring electrical insulation.

Disadvantages of Metal Machining

More Challenging Machining Conditions

Metals are harder than plastics, which limits feed rates and increases tool wear. Depending on the material and type of machining, higher spindle speeds or more rigid machines may be necessary.

Prone to Corrosion without Surface Treatment

Unlike plastics, metals can corrode in their natural state. Even corrosion resistant materials like aluminum and stainless steel are not completely immune. Surface treatments such as plating, coating, sealing, or surface modification can help prevent corrosion. Metals are also generally less resistant to chemicals than plastics, which is one of the reasons why many household containers are made of plastic.

Higher Density

Metals are typically heavier than plastics. Aluminum is about twice as heavy as the average plastic, while iron is about six times heavier. Greater weight leads to higher transportation costs and energy requirements.

Higher Risk of Injury During Handling

Because metals are heavier and harder, it increases risks such as cuts during machining or handling. Sharp edges often require chamfering or deburring for safety purposes.

Metal CNC Machining at Yumoto Electric

Yumoto Electric delivers high-quality components fast, worldwide. We provide precision machining for a wide range of metals and engineering plastics. We have experience with over 200 materials including metals such as aluminum alloys, stainless steel, molybdenum, and titanium, and engineering plastics including PEEK, PPS, MC Nylon, and POM.

If you’re unsure about material selection or machining methods, we offer complimentary consultations to help optimize your design and production. For any questions, please feel free to contact us.