Material Selection in Precision Engineering: Balancing Performance, Cost and Production Efficiency

In the world of advanced manufacturing, selecting the right material is just as critical as the precision of the machining itself. At Protec Group Ltd, we specialise in low-volume, high-accuracy components for sectors like automotive, motorsport, defence, and aerospace. Whether producing a prototype, structural component or end-use part, our engineering team places strong emphasis on choosing materials that optimise both function and cost-efficiency.

In this article, we explore how different alloys and polymers perform in CNC machining, which factors influence material choice, and how Protec supports engineers in selecting the best solution for their application.

Why Material Selection Matters in Advanced Machining

Material selection plays a central role in the success of any precision engineering project. The wrong choice can lead to underperforming components, premature wear, or excessive production costs. On the other hand, selecting the right alloy or polymer ensures:

• Long-term reliability under load and stress
• Resistance to corrosion, heat, or chemical exposure
• Efficient production with tight tolerances and smooth finishes
• Compatibility with surface treatments and assemblies
• Feasibility for both prototyping and small batch runs

At Protec, we advise clients from the initial concept stage through to production, ensuring that their chosen material suits the part’s mechanical, environmental, and commercial requirements.

Overview of Common Materials Used in CNC Machining

Our CNC specialists work with a broad range of metallics and polymers, each with their own advantages depending on the project’s objectives.

Aluminium Grades for Lightweight Strength

Aluminium is one of the most widely used materials in CNC machining due to its excellent strength-to-weight ratio, high machinability, and suitability for surface finishes.

Key Grades:

• 6082-T6 – Ideal for general engineering and structural parts; strong and corrosion-resistant.
• 7075-T6 – High-strength aerospace-grade aluminium with excellent fatigue performance.
• 2011 / 6026 – Free-machining aluminium used for complex, precision-turned parts.

Why choose aluminium?

• Reduced cycle times
• Ideal for components requiring anodising or powder coating
• Perfect for weight-sensitive sectors like motorsport or UAVs

Stainless Steel for Durability and Corrosion Resistance

Stainless steel is the go-to material for components operating in harsh environments. It is durable, non-reactive, and performs well under mechanical stress and elevated temperatures.

Commonly Used Grades:

• 303 – Free-machining stainless for general-purpose use
• 304 – Food-safe and highly corrosion-resistant; used in architectural and industrial parts
• 316 – Marine-grade stainless with high resistance to chlorides and chemicals

Advantages:

• Excellent longevity and strength
• Compatible with welding and passivation
• Suitable for medical, defence, and chemical processing industries

Mild and Carbon Steels for Structural Strength

Steel alloys offer a practical balance between strength, cost, and machinability. They are often used in tools, fixtures, and automotive components.

Popular Choices:

• EN3B (070M20) – Low-carbon mild steel for general fabrication
• EN8 (080M40) – Medium carbon steel with improved strength and wear resistance
• EN24T (817M40T) – High tensile strength steel ideal for heavy-duty, load-bearing applications

Considerations:

• Easily machinable and heat treatable
• Offers high impact resistance
• Requires coating or plating to prevent corrosion

Titanium for Extreme Environments

Titanium is an exceptional material for high-performance applications due to its low density, biocompatibility, and superior corrosion resistance.

Grade Focus:

• Grade 5 (Ti-6Al-4V) – The most used titanium alloy in motorsport, medical implants, and aerospace components

Benefits:

• Excellent fatigue resistance
• Withstands high temperatures and corrosive agents
• Ideal for load-critical or life-saving components

Challenges:

• Expensive raw material
• Requires specialised cutting tools and slower feed rates
• Longer lead times compared to aluminium or steel

When Engineering Polymers Are the Right Choice

While metals dominate precision manufacturing, there are many cases where technical plastics or engineering polymers are the superior option.

Situations where polymers excel:

• Electrical insulation – Ideal for housings and enclosures in electronic systems
• Weight reduction – Perfect for lightweight applications like robotics, automation, and wearables
• Chemical exposure – Plastics like PTFE and PVDF resist aggressive solvents and acids
• Noise and vibration reduction – Natural dampening properties reduce resonance and mechanical noise
• Rapid prototyping – Cost-effective for early-stage design testing and fast iterations

Common Plastics Used in Machined Components:

• Delrin (Acetal) – High dimensional stability, low friction
• PEEK – High-performance plastic used in aerospace, medical, and oil & gas
• Nylon (PA6/PA66) – Durable, wear-resistant and self-lubricating
• PTFE (Teflon) – Non-stick, chemically inert, ideal for sealing and fluid handling

Engineering polymers are often used in precision assemblies, especially where traditional metals may introduce issues such as galvanic corrosion or unnecessary weight.

Our Approach to Material Selection

Protec’s engineering support team works closely with customers to evaluate material suitability across several key dimensions:

• Functional requirements – Load capacity, wear resistance, impact strength
• Environmental exposure – Heat, humidity, chemicals, or vibration
• Manufacturability – Tolerance targets, machining speeds, tooling wear
• Post-processing needs – Coatings, heat treatments, or surface finishes
• Cost and availability – Material cost, supplier lead times, and scalability

We also help customers optimise designs through Design for Manufacture (DfM) principles, recommending minor geometry changes to reduce machining complexity and increase material yield.

Beyond the Material: Considerations That Impact Performance

In addition to the raw material properties, other elements can influence the success of a machined part:

• Surface finishing – Anodising, bead blasting, polishing, or powder coating
• Tolerancing and fits – Ensuring compatibility with mating parts or assemblies
• Heat treatments – Enhancing hardness, strength, or fatigue resistance
• Compliance – Industry-specific requirements such as REACH, RoHS, or full traceability documentation

Protec offers end-to-end support from prototype to production, ensuring each component is manufactured and finished to meet the application’s exact demands.

A More Scientific Approach

If you have an accurate idea of specific performance characteristics you require from a material for your job (such as young's modulus, density, temperature operating range etc.), you can use a material selection table. These can be found in multiple way. But a good centralised location for these can be The University of Cambridge's website. A link to this is below:

Material Selection Charts

Final Thoughts

Selecting the right material isn’t just a technical decision—it’s a strategic one. It impacts every aspect of your project from unit cost and production time to product reliability and lifecycle. At Protec, our experience in multi-sector precision engineering enables us to guide customers through smart, cost-effective material choices that deliver long-term performance and value.

Need Support Choosing the Right Material?

If you are in the initial stages of a new project and are considering material selection and production method, send an to nick.prtak@protecltd.co.uk who will be happy to help.