The Engineering Impact of Material Choice
Material selection for manufacturability represents one of the most critical early-stage decisions in product development. The choice between aluminum and steel, silicone and EPDM, or standard versus specialty alloys cascades through every aspect of manufacturing — from initial prototyping through high-volume production.
Engineers often focus primarily on functional requirements when selecting materials. However, design for manufacturability principles deserve equal weight in the selection process, particularly when speed to market and cost optimization are priorities.
Manufacturing-driven material selection requires understanding how material properties interact with specific production processes. A material that machines beautifully may prove difficult to form or cut. This interplay between material characteristics and manufacturing capabilities determines both the success and cost-effectiveness of the final product.
The manufacturability perspective evaluates materials against specific criteria: machinability ratings, formability characteristics, thermal processing requirements, and compatibility with secondary operations. Materials that excel functionally but create manufacturing bottlenecks can significantly impact project timelines and budgets.
Machinability: The Foundation of Precision Manufacturing
Understanding Machinability Factors
Machinability encompasses multiple material characteristics that directly affect CNC machining operations. Hardness represents the most obvious factor, but chip formation, thermal conductivity, and work hardening tendencies prove equally important for manufacturing success.
Materials with hardness values exceeding 35 HRC typically require specialized tooling and extended cycle times. Softer materials may machine quickly but can create challenges with surface finish and dimensional accuracy due to material deflection during cutting operations.
Key machinability indicators include:
- Chip formation behavior: Materials that produce long, stringy chips can wrap around cutting tools and interfere with automated machining operations
- Work hardening characteristics: Some stainless steels and nickel alloys work harden rapidly during machining, requiring specific cutting parameters
- Thermal conductivity: Poor heat dissipation leads to tool wear and potential workpiece distortion
- Abrasiveness: Filled materials or hard particles accelerate tool wear and increase cycle times
Common Machinability Challenges
Complex geometries demand careful material selection to ensure manufacturability. Sharp internal corners represent a common design challenge — no cutting tool can produce a truly sharp corner.
All machined internal corners require some radius, with the minimum achievable radius depending on both material properties and cutting tool limitations. Tool accessibility becomes critical for deep pockets or narrow slots.
Material Category | Typical Hardness Range | Machinability Rating | Common Challenges |
Aluminum Alloys | 15-45 HRC | Excellent | Chip welding, built-up edge |
Carbon Steel | 20-50 HRC | Good | Work hardening in stainless grades |
Titanium Alloys | 30-40 HRC | Poor | High tool wear, heat generation |
Plastics (Engineering) | Shore D 70-90 | Variable | Melting, poor surface finish |
Copper Alloys | 20-35 HRC | Excellent | Gummy chip formation |
Critical design considerations for machined components:
- Radius requirements: Use the largest internal radius possible — typically 0.8mm (0.03") minimum for most applications
- Feature accessibility: Ensure adequate clearance for cutting tools, especially in deep pockets
- Surface finish expectations: Different materials achieve different finishes with standard machining operations
- Tolerance capabilities: Tighter tolerances require additional machining time and quality control measures
Read our Complete Guide to CNC Machining.
Formability and Converting Considerations
Material Behavior in Converting Operations
Converting processes — including die cutting, waterjet cutting, and digital cutting — each interact differently with various material properties. Thickness, durometer, and tear strength determine which cutting methods will produce acceptable results.
Very thin materials (under 0.5mm or 0.02 inches) present unique handling challenges regardless of the cutting method employed. These materials may require specialized fixturing or cutting parameters to prevent tearing or dimensional distortion.
Tolerance Capabilities by Manufacturing Process
Different materials achieve different tolerance ranges through converting operations. The American Rubber Converter Association provides standard tolerance guidelines that vary by material thickness and type.
Material Thickness | Die Cutting Tolerance | Waterjet Tolerance | Digital Cutting Tolerance |
0.5-3.0mm (0.02-0.12") | ±0.1mm (±0.004") | ±0.05mm (±0.002") | ±0.08mm (±0.003") |
3.0-6.0mm (0.12-0.24") | ±0.15mm (±0.006") | ±0.08mm (±0.003") | ±0.1mm (±0.004") |
6.0-12mm (0.24-0.47") | ±0.2mm (±0.008") | ±0.1mm (±0.004") | ±0.15mm (±0.006") |
Converting process selection guidelines:
- Die cutting: Best for high volumes of simple geometries in soft to medium durometer materials
- Waterjet cutting: Optimal for complex geometries and hard materials, limited by minimum feature sizes
- Digital cutting: Ideal for prototypes and small batches, good for intricate patterns
- Material compatibility: Consider tear resistance, compression set, and edge quality requirements
Read our Custom Gasket Production Guide.
Thermal Processing Requirements
Curing and Temperature Sensitivity
Many specialty materials require specific thermal processing conditions that directly impact manufacturing workflows. Form-in-place gasket materials may cure at room temperature over 24 hours or require elevated temperatures (150°C or 302°F) for 30-60 minutes.
Temperature-sensitive substrates limit the thermal processing options available for applied materials. A plastic housing that softens at 80°C (176°F) cannot accommodate gasket materials requiring cure temperatures above that threshold.
Critical thermal considerations:
- Cure temperature compatibility: Ensure substrate materials can withstand required processing temperatures
- Process sequence timing: Some materials must be applied and cured before other manufacturing operations
- Environmental controls: Maintain consistent temperature and humidity during processing
- Thermal expansion matching: Consider coefficient of thermal expansion differences between materials
Specialized Storage and Handling
Certain advanced materials require specialized storage conditions that affect manufacturing logistics. Materials requiring frozen storage (−25°C or −13°F) create additional complexity in material handling and work-in-process management.
Room temperature vulcanizing (RTV) materials have limited working times once mixed. These timing constraints can impact production scheduling and batch sizes.
Surface Treatment and Coating Compatibility
Adhesion Considerations
Surface finish specifications significantly impact the success of secondary bonding operations. Counterintuitively, extremely smooth surface finishes can reduce adhesion performance for certain applications.
Form-in-place gasket adhesion benefits from slight surface texture that provides mechanical bonding sites. Surfaces that are too smooth may require additional surface preparation steps like scribing or texturing.
Surface preparation guidelines:
- Optimal surface finish: 1.6-3.2 μm Ra (63-125 μin Ra) typically provides good adhesion for most applications
- Cleaning requirements: Remove all machining oils, cutting fluids, and contamination before bonding
- Texture considerations: Light texturing improves mechanical adhesion for elastomeric materials
- Chemical compatibility: Verify coating systems are compatible with both substrate and applied materials
Read our Form-in-Place Gasket Guide.
Assembly and Integration Factors
Tolerance Stack-Up Management
Material selection affects tolerance accumulation in multi-component assemblies. Compliant materials can accommodate larger tolerance variations than rigid materials, potentially simplifying manufacturing requirements for mating components.
However, materials that are too compliant may create assembly challenges. Pressure-sensitive adhesive (PSA) backed pads that are very thin or delicate may be difficult to position accurately during assembly.
Assembly optimization strategies:
- Material compliance: Use compliant materials to absorb tolerance variations where functionally acceptable
- Adhesive selection: Match PSA aggressiveness to material handling requirements
- Fixture design: Consider specialized assembly fixtures for delicate or difficult-to-handle materials
- Process integration: Evaluate dispensing alternatives to eliminate assembly steps entirely
Industry-Specific Material Guidelines
Aerospace and Defense Applications
Aerospace and defense applications typically push material performance to extremes, requiring materials that maintain properties across wide temperature ranges while meeting strict weight requirements. Weight considerations frequently drive material selection toward exotic alloys or advanced composites.
Military and aerospace specifications often mandate specific coating systems for corrosion protection or environmental durability. These requirements can significantly impact material selection and processing capabilities. Understanding aerospace design considerations early in the material selection process proves critical for project success.
Medical Device Considerations
Medical device applications prioritize biocompatibility and cleanability over pure manufacturing optimization. USP Class VI silicones are available in durometer ranges from very soft to relatively firm, each presenting different converting and handling challenges.
Quality requirements in medical device manufacturing typically include enhanced inspection protocols. These requirements may favor materials with more predictable manufacturing characteristics, even if other materials might offer superior functional performance.
Common Material Selection Mistakes to Avoid
Over-Engineering Material Properties
Engineers frequently select materials that exceed functional requirements by significant margins, creating unnecessary manufacturing complexity. Materials with superior properties often require more sophisticated processing equipment or longer cycle times.
The most cost-effective approach involves selecting materials that meet — but do not significantly exceed — actual performance requirements. This strategy typically results in better manufacturability and manufacturing cost reduction.
Ignoring Manufacturing Process Limitations
Material selection decisions made without considering available manufacturing capabilities can create significant production bottlenecks. Some materials require specialized equipment or processing conditions that may not be readily available.
Early engagement with manufacturing partners provides valuable insights into material processing capabilities and limitations. This collaboration can prevent costly design changes later in the development process.
Read our guide to working with Custom Manufacturing Service Providers.
Making the Manufacturing-Optimized Choice
Balancing Performance and Manufacturability
Successful material selection requires systematic evaluation of both functional requirements and manufacturing implications. Performance requirements should be clearly separated into "must-have" versus "nice-to-have" categories.
Often, materials that exceed functional requirements by large margins create unnecessary manufacturing complexity without providing meaningful product advantages. Early supplier engagement provides valuable insights into processing implications that may not be obvious from material data sheets alone.
Decision-making best practices:
- Create decision matrices: Weight both functional and manufacturing criteria according to project priorities
- Involve manufacturing partners early: Leverage expertise from suppliers with comprehensive capabilities
- Consider lifecycle requirements: Evaluate materials for prototype through high-volume production scenarios
- Plan for scalability: Ensure material choices remain viable as production volumes change
Frequently Asked Questions About Material Selection for Manufacturability
How does material hardness affect CNC machining costs?
Material hardness directly impacts machining time and tool wear. Materials exceeding 35 HRC typically require 25-50% longer cycle times and specialized cutting tools, increasing overall production costs.
What surface finish is optimal for form-in-place gasket adhesion?
A surface finish of 1.6-3.2 μm Ra (63-125 μin Ra) provides the ideal balance of mechanical bonding sites without creating excessive roughness that could interfere with gasket performance.
Which materials offer the best balance of performance and manufacturability for aerospace applications?
Aluminum 6061 and 7075 alloys typically provide excellent strength-to-weight ratios with good machinability. For extreme performance requirements, titanium 6Al-4V offers superior properties but requires specialized machining expertise.
How do thermal processing requirements affect material selection?
Materials requiring elevated cure temperatures (above 150°C or 302°F) limit substrate options and may require specialized equipment. Room temperature curing materials offer more flexibility but typically have longer processing times.
Manufacturing partners with comprehensive capabilities like Modus Advanced — with AS9100, ISO 9001, and ITAR certifications — can provide flexibility as volume requirements change, supporting material choices that work across multiple production scenarios from prototyping through high-volume production. Our engineering team evaluates materials not just for functional performance, but for optimal manufacturability across our eight core manufacturing processes, ensuring your material selection delivers both performance and production efficiency.
