Begin with the working environment
Material selection starts with the job of the component. Describe the load, contact surfaces, temperature exposure, moisture, chemicals and expected service life. Add electrical, optical or appearance requirements when they matter. A material name alone does not establish performance in the finished part.
Compare a grade and a process together
A stock material for CNC machining, a resin for injection molding and a powder or liquid resin for 3D printing are different product forms. Even when their names sound similar, they can require different processing conditions and give different results. Compare the supplier's grade data and the condition of the material after manufacturing.
Read property values with their conditions
Density helps estimate mass from part volume. Tensile strength and elongation describe different aspects of a tensile test. Heat deflection temperature describes deformation under a stated load and test method; it should not be treated as an unrestricted operating-temperature guarantee. Use matching test conditions when comparing values, and keep the material grade attached to the data.
Include the surface and assembly
Check whether the chosen surface finish suits the base material and whether coating thickness affects a fit. Consider threads, press fits, wear pairs and dissimilar materials in the assembly. For a visible part, define color and cosmetic acceptance as well as mechanical requirements.
Close the remaining choices
Provide the required grade when it is fixed. Otherwise describe the application, process preference and priorities, then review proposed alternatives before production. A sample or prototype can answer a specific question, but the test should reflect the loads and environment of the intended use.
Metal stock selection
Select a metal grade for the part’s loads, corrosion exposure and subsequent finishing. Stock form and heat-treatment condition also affect machining and dimensional stability.