Introduction
Short run CNC machining services have become essential for prototyping, low-volume production, and custom parts across industries. They offer the precision of CNC technology without the tooling investment required for high-volume processes like injection molding or casting. But the success of any short run project depends heavily on material selection. The right material determines not only the final part’s properties—strength, weight, corrosion resistance, thermal stability—but also the machinability, cost, and lead time. This guide explores the most common metals and plastics used in short run CNC machining, their properties, applications, and key selection factors to help you choose the right material for your project.
What Metal Materials Are Commonly Used?
Aluminum Alloys
Aluminum alloys are among the most widely used materials in short run CNC machining. They offer a combination of lightweight, good strength, corrosion resistance, and excellent machinability.
Key properties:
- Density: ~2.7 g/cm³ (one-third that of steel)
- Strength-to-weight ratio: Excellent
- Corrosion resistance: Good, especially with anodizing
- Machinability: Excellent—high-speed machining, low tool wear
| Alloy | Key Characteristics | Typical Applications |
|---|---|---|
| 6061 | Medium strength, good corrosion resistance, excellent weldability | Automotive parts, bicycle frames, general mechanical components |
| 7075 | Very high strength, excellent fatigue resistance | Aerospace components, high-performance sports equipment |
6061 aluminum: Contains magnesium and silicon. It is versatile, cost-effective, and widely available. Used in automotive engine parts, bicycle frames, and structural components where moderate strength and good machinability are required.
7075 aluminum: Contains zinc, magnesium, and copper. One of the strongest aluminum alloys, it offers exceptional strength-to-weight ratio. Used in aircraft wings, fuselage components, and professional cycling equipment. More expensive and harder to machine than 6061.
Stainless Steels
Stainless steels are prized for outstanding corrosion resistance, strength, and durability. They contain a minimum of 10.5% chromium, which forms a passive oxide layer protecting against oxidation and corrosion.
| Grade | Key Characteristics | Typical Applications |
|---|---|---|
| 304 | Good corrosion resistance, excellent formability, weldability | Food processing equipment, architectural elements, kitchen surfaces |
| 316 | Superior corrosion resistance (added molybdenum), “marine-grade” | Marine hardware, chemical processing, seawater desalination plants |
304 stainless steel: Known as 18/8 (18% chromium, 8% nickel). Versatile, cost-effective, suitable for most environments. Used in food processing equipment, kitchen countertops, handrails, and general industrial components.
316 stainless steel: Contains 2–3% molybdenum, significantly improving corrosion resistance in chloride-rich environments (saltwater, chemicals). Used in marine applications, offshore platforms, chemical processing, and medical devices. More expensive and slightly harder to machine than 304.
Copper and Its Alloys
Copper and its alloys offer unique properties: excellent electrical and thermal conductivity, corrosion resistance, and attractive appearance.
| Material | Key Characteristics | Typical Applications |
|---|---|---|
| Copper (C101, C110) | Highest electrical conductivity; good thermal conductivity | Electrical connectors, wires, heat sinks |
| Brass (copper-zinc) | Good machinability, corrosion resistance, attractive appearance | Decorative hardware, musical instruments, plumbing fittings |
| Bronze (copper-tin) | High strength, excellent wear resistance, good corrosion resistance | Bearings, bushings, gears, sculptures |
Copper: Second only to silver in electrical conductivity. Used for electrical connectors, bus bars, heat sinks, and components requiring maximum conductivity.
Brass: Combines copper’s corrosion resistance with improved strength and machinability. Golden-yellow appearance suits decorative applications—door handles, faucets, musical instruments. Machines easily with low cutting forces.
Bronze: Copper-tin alloy (sometimes with phosphorus, aluminum, or silicon). High strength, excellent wear resistance. Used for bearings, bushings, gears in high-performance engines. Also used in art and sculpture for its aesthetic appeal.
What Plastic Materials Are Commonly Used?
ABS (Acrylonitrile Butadiene Styrene)
ABS is a widely used thermoplastic polymer offering a balanced set of properties at low cost.
Key properties:
- Impact resistance: Excellent—withstands sudden impacts without breaking
- Dimensional stability: Good—holds shape accurately during machining
- Machinability: Easy—low melting point allows faster cutting speeds
- Coloring: Easily colored for aesthetic flexibility
Applications: Consumer electronics housings (phone cases, laptop covers), automotive interior components (dashboards, door panels), toys (detailed, intricate designs), prototyping.
Polycarbonate (PC)
Polycarbonate is a high-performance thermoplastic offering transparency, impact strength, and heat resistance.
Key properties:
- Transparency: 88–92% light transmittance—excellent optical clarity
- Impact strength: Outstanding—used for safety helmets, riot shields
- Heat resistance: Heat-deflection temperature 135–143°C under load
- Machinability: Good but requires sharp tools; more powerful equipment than ABS
Applications: Electronics (computer monitor frames, phone screens), lighting (lamp shades, lenses), automotive (headlamp lenses, instrument panels), safety equipment (helmets, shields).
Polyethylene (PE) and Polypropylene (PP)
These polyolefin plastics offer cost-effectiveness and chemical resistance.
| Material | Key Characteristics | Applications |
|---|---|---|
| LDPE (Low-density PE) | Flexible, low cost, excellent chemical resistance | Plastic bags, flexible tubing |
| HDPE (High-density PE) | More rigid than LDPE, good chemical resistance | Water pipes, storage tanks |
| PP (Polypropylene) | Higher melting point (160–170°C), stiffer than PE, good chemical resistance | Food packaging, automotive interior, plastic furniture |
Polyethylene: Excellent chemical resistance against acids, alkalis, and many solvents. LDPE is flexible; HDPE is rigid. Low melting point requires careful temperature control during machining to prevent softening or deformation.
Polypropylene: Higher melting point than PE (160–170°C), better heat resistance. Stiffer and stronger than LDPE. Used in food packaging that may undergo sterilization, automotive interior components, and kitchenware. Machining requires accounting for higher shrinkage rate during cooling.
How Do Metals and Plastics Compare?
| Property | Metals | Plastics |
|---|---|---|
| Density | Higher (Aluminum 2.7, Steel 7.9 g/cm³) | Lower (ABS 1.05, PC 1.2 g/cm³) |
| Strength | High; withstands significant mechanical stress | Varies; PC has high impact strength; generally lower tensile/compressive than metals |
| Cost | Higher, especially alloys (7075, 316) | Lower, especially common plastics (ABS, PE, PP) |
| Machining difficulty | Some metals challenging (hardness, work hardening); aluminum is relatively easy | Generally easier; lower melting points allow faster speeds; high-performance plastics require care |
| Heat resistance | Generally high (steel withstands high temperatures) | Lower; ABS softens at lower temperatures; PC has better heat resistance but still lower than metals |
| Chemical resistance | Good; stainless steel in corrosive environments | Varies; PE, PP have excellent chemical resistance; others may be sensitive |
| Electrical conductivity | Good (copper excellent) | Generally poor; suitable for insulating applications |
What Factors Should You Consider When Selecting Materials?
Mechanical Properties
Strength: For load-bearing components, high-strength materials like 7075 aluminum, high-grade stainless steel, or bronze are required. Plastics generally have lower tensile and compressive strength.
Hardness: Harder materials resist wear and maintain shape under friction. Used for cutting tools, bearings, parts with constant rubbing. However, harder materials are more challenging to machine—requiring specialized tools and slower speeds.
Toughness: Ability to absorb energy and deform before fracturing. Essential for parts subject to impact or sudden loads—automotive bumpers, industrial guards, safety components. Polycarbonate and certain steel alloys are tough materials.
Cost Constraints
Material cost: Varies widely. Titanium, high-alloy steels, and specialized plastics (PEEK) are expensive. Common aluminum alloys (6061) and plastics (ABS, PE, PP) are cost-effective.
Processing cost: Materials that are difficult to machine increase processing costs. Stainless steel causes more tool wear, requiring frequent replacements. Aluminum machines easily, enabling higher speeds and lower processing costs. For tight budgets, choose materials with good machinability.
Application Environment
Temperature: If the part will be exposed to high temperatures, select materials with high heat resistance. Stainless steel withstands industrial furnace temperatures; polycarbonate suits moderate heat exposure (electronics components). Avoid low-melting plastics in hot environments.
Humidity and chemicals: In wet or corrosive environments, corrosion-resistant materials are essential. Stainless steel (especially 316) is ideal for marine or chemical applications. Some plastics (PE, PP) offer excellent chemical resistance and may be suitable alternatives.
A Real-World Material Selection Success
A manufacturer needed short-run (500 units) components for a marine sensor housing. Requirements:
- Saltwater corrosion resistance
- Moderate strength
- Cost-effective for low volume
- Good machinability
Considered options:
- 316 stainless steel: Excellent corrosion resistance, high strength, but expensive and slower to machine
- Aluminum 6061 with anodizing: Good corrosion resistance, excellent machinability, lower cost
- Polycarbonate: Lower strength, but corrosion-resistant and easy to machine
Selection: Aluminum 6061 with hard anodizing. Provided adequate corrosion resistance, strength for application, excellent machinability (reduced processing cost), and significantly lower material cost than 316 stainless.
Result: Parts delivered within budget and timeline. Field performance exceeded requirements with no corrosion issues after 18 months in marine environment.
Conclusion
Short run CNC machining services offer access to a wide range of materials—metals and plastics—each with unique properties suited to different applications. Aluminum alloys (6061, 7075) provide lightweight strength and excellent machinability. Stainless steels (304, 316) offer outstanding corrosion resistance and durability. Copper, brass, and bronze deliver conductivity, wear resistance, and aesthetic appeal. Plastics like ABS, polycarbonate, PE, and PP provide cost-effectiveness, impact resistance, transparency, and chemical resistance at lower densities. Selecting the right material requires balancing mechanical properties (strength, hardness, toughness), cost constraints (material and processing cost), and application environment (temperature, humidity, chemical exposure). With the right material choice, short run CNC machining delivers precision parts that meet performance requirements without the tooling investment of high-volume production.
FAQs
What are the most common metals used in short run CNC machining?
Aluminum alloys (6061, 7075) are most common due to their excellent machinability, lightweight, and good strength. Stainless steels (304, 316) are widely used for corrosion-resistant applications. Brass, bronze, and copper are used for conductivity, wear resistance, and decorative applications. Each metal offers a different balance of properties, cost, and machinability.
What are the most common plastics used in short run CNC machining?
ABS is widely used for its impact resistance, dimensional stability, and ease of machining—ideal for consumer electronics housings and prototypes. Polycarbonate (PC) is chosen for transparency, high impact strength, and heat resistance—used in lenses, safety equipment, and automotive components. Polyethylene (PE) and polypropylene (PP) offer cost-effectiveness and excellent chemical resistance for storage containers, tubing, and food packaging.
How do I choose between metal and plastic for my short run project?
Consider mechanical requirements—if high strength, rigidity, or high-temperature resistance is needed, metals are preferred. If weight reduction, cost-effectiveness, electrical insulation, or chemical resistance is primary, plastics may be better. Consider also the application environment—metal for corrosive or high-temperature environments; plastic for non-structural, chemically resistant, or insulating applications.
What factors affect material cost in short run CNC machining?
Material cost depends on base material price (aluminum cheaper than titanium), alloy composition (7075 more expensive than 6061), and processing difficulty (316 stainless harder to machine than 304). Additional costs include material sourcing, setup time, and tool wear. For short runs, materials with good machinability (aluminum, ABS) often have lower total cost even if material price is moderate.
Can short run CNC machining handle high-strength materials like titanium or Inconel?
Yes, but with considerations. Titanium and Inconel are difficult to machine—requiring specialized tooling (carbide, ceramic), slower speeds, rigid setups, and high-pressure coolant. Short runs are feasible but will have higher cost per part and longer lead times than machining aluminum or plastics. These materials are used when application demands their unique properties—high strength-to-weight ratio (titanium) or extreme temperature resistance (Inconel).
Contact Yigu Technology for Custom Manufacturing
At Yigu Technology, we specialize in short run CNC machining services across a wide range of materials—aluminum, stainless steel, copper alloys, ABS, polycarbonate, polyethylene, and more. Our team helps you select the right material for your application, balancing mechanical requirements, cost, and machinability. We optimize tooling and parameters for each material to achieve tight tolerances and excellent surface finishes. Whether you need prototypes, low-volume production, or custom components, we deliver precision parts with fast turnaround. Contact us to discuss your short run CNC machining project.
