The 10 Most Commonly Used Materials in Custom Machinery: A Complete Guide Source:

Introduction

Choosing the right material is one of the most critical decisions in custom machinery design. The material affects everything from structural integrity and weight to cost efficiency and longevity.

This comprehensive guide covers the 10 most frequently used materials in non-standard machinery, spanning metals, engineering plastics, and specialty materials. These materials cover approximately 90% of practical applications, making them essential knowledge for engineers, designers, and manufacturers.

1. 6061 Aluminum Alloy

Overview

6061-T651 is a high-quality aluminum alloy that undergoes heat treatment and pre-stretching. It offers excellent machinability, easy welding and plating, superior corrosion resistance, and minimal deformation after processing.

Key Properties

Property Value

Density 2.75 g/cm³

Elastic Modulus 68.9 GPa

Poisson's Ratio 0.330

Yield Strength 55.2 MPa

Surface Treatments

Natural anodizing (clear coat)

Colored anodizing (various colors available)

Sandblasting (80 or 120 grit recommended before anodizing for optimal finish)

Applications

Aerospace Industry:

Aircraft skin panels

Equipment components

Rocket parts

Transportation:

Automobile body panels

Metro railcar components

Wheel hubs

Why Choose 6061 Aluminum? It is the preferred material for lightweight applications where corrosion resistance is essential. Its excellent strength-to-weight ratio and formability make it ideal for components that must be both durable and light.

2. 45 Steel (Medium Carbon Steel)

Overview

45 Steel is a premium carbon structural steel with a carbon content of 0.42%-0.50%. It has good machinability and excellent comprehensive mechanical properties after heat treatment.

Key Properties

Property Value

Carbon Content 0.42% - 0.50%

Density 7.85 g/cm³

Elastic Modulus 210 GPa

Poisson's Ratio 0.31

Yield Strength 355 MPa

Hardness (After Quenching) HRC 55-58

Hardness (After Tempering) HRC 20-30

Surface Treatments

Chrome plating

Nickel plating

Black oxide (oxide blackening)

Heat Treatment

Quenching: Significantly improves hardness, wear resistance, and service life

Tempering: Achieves optimal balance of strength and toughness

Applications

45 Steel is widely used for critical structural components:

Connecting rods

Bolts and fasteners

Gears

Shafts

Crankshafts

Why Choose 45 Steel? It offers an excellent balance of machinability, strength, and cost-effectiveness. After proper heat treatment, it achieves the hardness and durability required for high-stress mechanical components.

3. Q235 Steel (Carbon Structural Steel)

Overview

Q235, also known as A3 steel plate, is a general-purpose carbon structural steel. The "Q" denotes yield limit, and "235" indicates a yield strength of approximately 235 MPa. It comes in four quality grades: A, B, C, and D.

Key Properties

Property Value

Alternative Name A3 Steel Plate

Quality Grades A, B, C, D

Density 7.85 g/cm³

Poisson's Ratio 0.25 - 0.33

Yield Strength 235 MPa

Surface Treatments

Powder coating (plastic coating)

Baking paint

Advantages

Low carbon content

Balanced strength, plasticity, and weldability

Excellent cost-performance ratio

Applications

Q235 is ideal for cost-sensitive structural applications:

Building and construction: steel reinforcement, factory buildings, steel frames

Infrastructure: bridge components, transmission towers

Industrial: boiler shells, containers, machine frames

Why Choose Q235 Steel? It provides reliable performance at an affordable price. Perfect for non-critical structural members where high strength is not required but cost efficiency is essential.

4. S304 Stainless Steel (304 Stainless Steel)

Overview

S304 stainless steel corresponds to the Japanese SUS304 standard and Chinese GB standard 0Cr18Ni9. It offers excellent heat resistance, corrosion resistance, low-temperature strength, and mechanical properties.

Key Properties

Property Value

Japanese Standard SUS304

Chinese Standard 0Cr18Ni9

Density 7.93 g/cm³

Poisson's Ratio 0.394

Yield Strength 205 MPa

Key Characteristics

Excellent corrosion and heat resistance

Superior formability for stamping and bending

No heat treatment hardening

Non-magnetic

Surface Treatments

Brushed finish

Mirror polishing

Applications

Industry Typical Applications

Food Processing Storage tanks, conveyor systems

Chemical Industry Reaction vessels, pipelines

Medical Surgical instruments, hospital equipment

Household Kitchen cabinets, water heaters, bathtubs

Automotive Trim components, exhaust systems

Construction Architectural panels, railings

Marine Ship decks, hull fittings

Why Choose S304 Stainless Steel? It is the go-to material when corrosion resistance and hygiene are paramount. Essential for food processing, medical devices, and any application requiring cleanliness and durability.

5. POM (Polyoxymethylene / Acetal)

Overview

Also known as "Delrin" or "Acetal", POM is an engineering plastic with a density of 1.39 g/cm³. Its performance closely approaches that of metals, earning it the nickname "steel substitute."

Key Advantages

High hardness, strength, and stiffness

Excellent self-lubricating properties

Outstanding wear and fatigue resistance

Good chemical resistance

Cost-effective alternative to metals

Applications

POM is ideal for components requiring wear resistance and self-lubrication:

Gears and pinions

Bearings and bushings

Slides and guide rails

Cam followers

Food processing machinery (FDA compliant grades available)

Why Choose POM? It can replace brass, aluminum, bronze, and steel in many applications, significantly reducing weight and cost while maintaining excellent mechanical performance.

6. Polyurethane (PU)

Overview

Polyurethane is one of the most versatile polymer materials, with applications spanning virtually every industry.

Industry Applications

Industry Applications

Mining & Metallurgy Screen plates, shaking tables

Mechanical Engineering Rollers, conveyor belts, seals

Automotive Tires, O-rings, gaskets, suspension bushings

Light Industry Shoe soles, synthetic leather, fibers

Construction Waterproofing materials, flooring, sealants

Medical Implants, medical tubing

Aerospace Sealants, composite materials

Electronics Encapsulation, insulation

Key Advantages

Extremely versatile formulation options

Excellent abrasion resistance

Good oil and chemical resistance

Wide hardness range (from soft elastomers to rigid plastics)

Outstanding fatigue resistance

Why Choose Polyurethane? Its formulation flexibility allows engineers to customize properties for specific applications, making it suitable for everything from soft cushioning to heavy-duty industrial components.

7. Acrylic (PMMA / Plexiglass)

Overview

Acrylic, also known as PMMA (Polymethyl Methacrylate) or Plexiglass, is a transparent thermoplastic with over 92% light transmittance—surpassing even glass.

Key Properties

Property Value

Light Transmittance > 92%

Density ~1.18 g/cm³ (half the weight of glass)

Alternative Names PMMA, Plexiglass, Acrylic Sheet

Advantages

Superior transparency — clearer than glass

Soft, diffused light quality

Excellent weather resistance

High surface hardness and gloss

Good high-temperature resistance (compared to other plastics)

Easy to fabricate (thermoform or machine)

Safe — does not shatter into sharp fragments

Good chemical resistance

Printable and paintable for decorative effects

Limitations

Lower heat resistance compared to other materials

Flammable — requires careful handling in high-heat applications

Applications

Perfect for applications requiring transparency, aesthetics, and durability:

Architecture: skylights, partitions, display cases

Advertising: light boxes, sign boards, point-of-purchase displays

Protection: safety shields, machine guards, protective barriers

Displays: product showcases, museum exhibits, retail fixtures

Why Choose Acrylic? It offers the clarity of glass with half the weight, none of the shattering risk, and far greater design flexibility through thermoforming and fabrication.

8. Alumina Ceramic (Aluminum Oxide)

Overview

Alumina ceramic, with aluminum oxide (Al₂O₃) as its main component, is widely used in thick-film integrated circuits and high-performance industrial applications.

Key Properties

Property Value

Rockwell Hardness HRA 80-90

Density 3.5 g/cm³ (half that of steel)

Wear Resistance 266× that of manganese steel

Wear Resistance 171.5× that of high-chromium cast iron

Advantages

Extremely high hardness — second only to diamond

Exceptional wear resistance

Lightweight — only half the weight of steel

Excellent electrical insulation

High mechanical strength

Outstanding high-temperature resistance

Applications

Alumina ceramic excels in demanding environments:

Electronic components: circuit substrates, insulators

Industrial wear parts: liners, nozzles, chutes

High-temperature equipment: furnace components, crucibles

Precision components: bearings, seal faces, cutting tools

Why Choose Alumina Ceramic? When your application demands extreme hardness, wear resistance, and thermal stability, alumina ceramic provides performance that no metal can match—while being significantly lighter.

9. PVC (Polyvinyl Chloride)

Overview

PVC is the most produced plastic globally and offers the lowest cost among common engineering plastics.

Cost Comparison

PVC < Acrylic < PC (Polycarbonate)

Key Characteristics

Lowest cost among structural plastics

Excellent chemical resistance

Good weatherability

Versatile processing (extrusion, injection molding, calendering)

Good electrical insulation

Applications

Category Examples

Piping Systems Water pipes, drainage, conduit

Profiles Window frames, door frames, railings

Sheets Wall panels, signage substrates

Packaging Blister packs, cling film, bottles

Construction Flooring, roofing membranes, waterproofing

Consumer Products Rain boots, hose, toys

Why Choose PVC? It is the budget-friendly choice for applications where extreme performance is not required but cost efficiency is critical.

10. Nylon (PA / Polyamide)

Overview

Also known as polyamide (PA) or nylon, this engineering plastic is widely used across mechanical industries for its excellent wear resistance and self-lubricating properties.

Alternative Names

Nylon

Polyamide (PA)

Perlon (regional name)

Key Advantages

Excellent toughness and impact resistance

Self-lubricating properties

Outstanding wear resistance

Good chemical resistance

High fatigue resistance

Accepts reinforcement (glass fiber, carbon fiber)

FDA-compliant grades available

Applications

Nylon is the workhorse of mechanical engineering plastics:

Gears and worm gears

Bearings and bearing cages

Bushings and wear pads

Seals and O-rings

Cable ties and fasteners

Structural components (glass-filled grades)

Why Choose Nylon? It offers the best combination of toughness, wear resistance, and self-lubrication among engineering plastics, making it ideal for dynamic mechanical applications.

Comprehensive Material Comparison

# Material Category Density (g/cm³) Yield Strength (MPa) Key Characteristics Typical Applications

1 6061 Aluminum Metal 2.75 55.2 Lightweight, corrosion-resistant, easily machined Aircraft skin, auto body, hubs

2 45 Steel Metal 7.85 355 Good machinability, excellent heat treatment response Connecting rods, bolts, gears, shafts

3 Q235 (A3 Steel) Metal 7.85 235 Cost-effective, good weldability, balanced properties Buildings, frames, bridges, machine beds

4 S304 Stainless Metal 7.93 205 Corrosion-resistant, hygienic, non-magnetic Medical devices, food equipment, chemical tanks

5 POM (Acetal) Engineering Plastic 1.39 — Self-lubricating, wear-resistant, metal substitute Gears, bearings, slides, bushings

6 Polyurethane (PU) Polymer — — Extremely versatile, abrasion-resistant, wide hardness range Tires, seals, rollers, industrial parts

7 Acrylic (PMMA) Polymer ~1.18 — 92%+ transparency, lightweight, shatter-resistant Light boxes, displays, protective shields

8 Alumina Ceramic Ceramic 3.5 — Ultra-hard, wear-resistant, high-temp stable Wear liners, electronic substrates, insulators

9 PVC Commodity Plastic — — Lowest cost, high volume production Pipes, profiles, packaging, construction

10 Nylon (PA) Engineering Plastic — — Tough, self-lubricating, fatigue-resistant Gears, bearings, seals, structural parts

Material Selection Quick Reference

By Application Type

Need Recommended Materials

Lightweight 6061 Aluminum, POM, Acrylic

High Strength 45 Steel, Q235, S304 Stainless

Corrosion Resistance S304 Stainless, PVC, POM

Wear Resistance POM, Nylon, Alumina Ceramic, Polyurethane

Transparency Acrylic (PMMA)

High Temperature Alumina Ceramic, S304 Stainless, 45 Steel

Cost Efficiency Q235, PVC

Self-Lubrication POM, Nylon, Polyurethane

Conclusion

These 10 materials represent the foundation of custom machinery design. By understanding their properties, advantages, and ideal applications, you can make informed decisions that optimize performance, cost, and manufacturability.

Key Takeaways:

Metals (6061, 45 Steel, Q235, S304) — your structural backbone

Engineering Plastics (POM, Nylon, PU) — wear and motion components

Specialty Materials (Acrylic, Ceramic, PVC) — specific performance requirements

Bookmark this guide for quick reference during material selection, and share it with colleagues who design or specify materials for custom machinery.