Manufacturing guide
Material Selection Guide
A structured method for comparing metals, engineering plastics, and elastomers against function, process, environment, appearance, and supply requirements.
Guide introduction
How to use this guide in a real RFQ.
Material selection is a system decision. Strength or price alone does not describe how a grade will machine, mold, form, finish, assemble, age, or perform in the actual environment. A useful selection process begins with the end use and then checks manufacturing compatibility.
This guide provides a practical screening method for engineering and sourcing teams. Final approval remains the customer's responsibility where performance, compliance, chemical exposure, temperature, electrical behavior, optical quality, or regulatory requirements are involved.
Chapter 01
Translate the application into material requirements
Start with measurable needs and failure risks before comparing named grades.
Mechanical and dimensional behavior
Consider load direction, stiffness, impact, fatigue, wear, creep, friction, weight, and the dimensional stability needed over time. A strong material may still be unsuitable if it moves with temperature, absorbs moisture, or cannot hold the required geometry economically.
- Separate stiffness requirements from ultimate strength.
- Identify wear, sliding, and repeated-load interfaces.
- State the operating temperature range and load duration.
Environment and exposure
Moisture, chemicals, UV, cleaning agents, galvanic contact, heat, and outdoor exposure can change material behavior or finish choices. Use the actual exposure condition rather than a general label such as corrosion resistant.
- List chemicals and cleaning methods where relevant.
- Identify direct metal-to-metal contact between dissimilar materials.
- Confirm whether appearance must remain stable outdoors or under UV.
Documentation and compliance boundaries
If a material specification, declaration, traceability record, or customer-approved source is required, include it in the RFQ. Do not assume that a commercial grade name automatically meets an application-specific standard.
Chapter 02
Compare material families before exact grades
Families help narrow the field; exact grades then need process and application approval.
Metals for structure, heat, wear, and conductivity
Aluminum is widely used for lightweight machined and formed parts. Stainless grades support corrosion-focused applications. Tool steels suit wear and tooling needs. Brass and copper add machinability, conductivity, or thermal behavior. Titanium can offer strength-to-weight and corrosion benefits but changes machining cost and planning.
Engineering plastics for weight and integrated function
ABS, PC, PP, POM, nylon, PMMA, PEEK, and related materials cover different balances of toughness, appearance, friction, chemical behavior, temperature, moisture response, and processability. A molded grade and a machined stock grade are not automatically interchangeable.
- Check moisture absorption for precision nylon geometry.
- Review stress-cracking risk for transparent or chemically exposed plastics.
- Confirm additives, reinforcement, flame behavior, and color by exact grade when relevant.
Elastomers for grip, sealing, and flexibility
TPU and TPE can provide flexible interfaces, overmolded grip, sealing, and impact protection. Hardness, compression behavior, adhesion, chemical exposure, color, and process route should be evaluated together.
Chapter 03
Validate process, finish, and supply compatibility
The material must be available in a suitable form and remain compatible with the intended operations.
Match the material to the manufacturing route
Machining needs appropriate stock, chip behavior, thermal stability, and workholding. Molding depends on flow, shrinkage, drying, tooling, and process conditions. Sheet metal requires suitable thickness, formability, weldability, and surface condition. Casting uses alloy systems designed for the selected route.
Check finish and assembly interactions
Anodizing is associated with aluminum, passivation with suitable stainless grades, and many coatings require preparation or masking. Adhesives, inserts, welding, heat staking, and overmolding also depend on the exact material condition.
Approve the exact grade and revision
Record the approved grade, condition, color, reinforcement, supplier restriction where required, and applicable documentation. Any proposed substitution should return to the same functional and manufacturing review.
Comparison table
Material family screening table
These are selection directions, not substitutes for grade-specific engineering data or application approval.
| Family | Common reasons to consider | Manufacturing routes | Review carefully |
|---|---|---|---|
| Aluminum alloys | Low weight, machinability, thermal behavior, anodizing | CNC machining, sheet metal, die casting by suitable alloy | Grade, temper, stiffness, coating dimensions |
| Stainless steels | Corrosion resistance, durability, appearance | Machining, turning, sheet metal | Grade, work hardening, welding, passivation |
| Copper and brass | Electrical or thermal behavior, machinability | Machining, turning, bending | Softness, oxidation, plating, material cost |
| Engineering plastics | Low weight, insulation, friction, integrated geometry | Machining, injection molding, additive or casting routes | Moisture, creep, chemicals, exact grade |
| TPU and TPE | Flexibility, grip, sealing, impact protection | Molding and overmolding | Hardness, adhesion, compression, environment |
Practical design guidance
Actions to take before requesting a quotation.
TIP 01
Write requirements before grade names
Define load, environment, temperature, wear, appearance, weight, and documentation needs first.
TIP 02
Compare the exact process form
Machined stock, molding resin, sheet, and casting alloy can behave differently even within a broad family.
TIP 03
Include finishing and assembly
Check coating, welding, inserts, adhesives, overmolding, and contact with other materials.
TIP 04
Control substitutions
Approve alternatives against function, process, documentation, and appearance instead of accepting a name-only match.
Guide FAQ
Questions about material selection.
Can Kewei select the final material for my application?
Kewei can support manufacturing comparisons, but the customer should approve the final grade against end-use, safety, regulatory, environmental, and performance requirements.
Is a molded plastic grade equivalent to a machined plastic stock?
Not automatically. Resin formulation, reinforcement, stress history, moisture, and production method can affect behavior and appearance.
Why must material substitutions be approved?
Different grades can change strength, dimensions, finish response, color, processing, documentation, and long-term performance even when their common names are similar.
When should material documentation be requested?
State it during quotation, including the required specification, traceability scope, document type, and whether it applies to each shipment.