Choosing the right materials for your CNC machining project is crucial for its success. Whether you are a seasoned professional or new to the world of CNC machining, understanding material selection is essential. In this blog post, we will provide you with a comprehensive guide on how to choose the right materials for your CNC machining projects. From metals to plastics, we will explore the properties, advantages, and applications of various materials. By the end of this post, you will have a clear understanding of how to select the perfect material for your next CNC machining endeavor. Let’s dive in!
Common Metal Materials for CNC Machining
In addition to providing 3D printing services, we also offer laser cutting, silicone molding, and CNC machining services. Among these, CNC machining involves several primary metal materials:
- Aluminum Alloy 6061
Aluminum alloy 6061 is a high-quality product produced through heat treatment and pre-stretching processes. While its strength may not match that of the 2XXX or 7XXX series, it boasts various magnesium and silicon alloy characteristics.
Advantages:
- Excellent machinability
- Good welding characteristics and electroplating properties
- Excellent corrosion resistance
- High toughness and dimensional stability after processing
- Dense, defect-free material
- Easy to polish, apply color films, and achieve excellent oxidation effects
- 7075 Aluminum Alloy
7075 aluminum alloy is a cold-treated forging alloy known for its high strength, surpassing that of soft steel. It stands as one of the strongest commercially available alloys.
Advantages:
- Ordinary corrosion resistance
- Good mechanical properties and anodic reaction
- Fine grains for enhanced deep drilling performance and tool wear resistance
- Copper
Pure copper, also known as purple copper, is a ductile metal renowned for its excellent conductivity and rose-red surface. Although not entirely pure, it contains 99.9% copper, supplemented with other elements to improve surface and performance.

Advantages:
- Good conductivity, thermal conductivity, ductility, and deep drawing properties
- Excellent corrosion resistance, making it suitable for various applications in the chemical industry
- Good weldability and suitability for various processing methods
- Brass
Brass, a copper-zinc alloy, exhibits high strength, hardness, and chemical corrosion resistance. It also boasts prominent machining performance.

Advantages:
- High strength, large hardness, and strong chemical corrosion resistance
- Notable machining properties, including strong wear resistance
- 45# Steel
45# steel, also known as “oil steel” in GB, offers high strength and good machining properties.
- High strength and good machining properties
- Suitable for hydrogen welding and argon arc welding after proper heat treatment
- 40Cr Steel
40Cr steel, a standard steel grade in China, is widely used in the mechanical manufacturing industry.
Advantages:
- Good comprehensive mechanical properties
- Good low-temperature impact toughness and low notch sensitivity
- Good hardenability, suitable for various treatments including tempering, cyanidation, and high-frequency quenching
- Q235 Steel
Q235 steel, a carbon structural steel, is known for its yield strength (with “Q” representing yield strength). Typically, it is used without heat treatment.
Advantages:
- Widely applicable due to good coordination of strength, plasticity, and welding properties
- Decreased yield value with increasing material thickness
- SUS304 Steel
SUS304 refers to 304 stainless steel, characterized by good machinability and high toughness. Stainless steel 303 can also be machined.
Advantages:
- Good corrosion resistance, heat resistance, and mechanical properties
- Good hot working properties with no hardening phenomenon after heat treatment
- Non-magnetic properties

Common Plastic Materials for CNC Machining
01 ABS (Acrylonitrile Butadiene Styrene)
ABS is a ternary copolymer of three monomers: acrylonitrile, butadiene, and styrene, making it one of the most widely used polymers. It organically unifies the various properties of PS (polystyrene), SAN (styrene-acrylonitrile), and BS (butadiene-styrene), combining toughness, hardness, and balanced mechanical properties.

Colors: White, Black, Beige
Features: ABS exhibits common properties from its three components:
- The acrylonitrile component confers chemical corrosion resistance, heat resistance, and a certain surface hardness. It is unaffected by water, inorganic acids, or food acids, usable within -50°C to +70°C, with excellent impact resistance at low temperatures and good dimensional stability at elevated temperatures.
- The butadiene component provides high elasticity and toughness, with high mechanical strength and rigidity, scratch resistance, high tensile strength, abrasion resistance, and high surface strength.
- The styrene component imparts thermoplastic processing characteristics and improves electrical properties. It is easily colored, processed, electroplated, and exhibits excellent chemical and electrical insulation properties.
Drawbacks:
- Susceptible to weathering, limited acid resistance, soluble in ketones, softens in hydrocarbons, fats, aromatic compounds, and aldehydes.
Applications: Used in model materials such as architectural models, figurine models, food industry components, industrial electronic components, refrigeration industry, etc. In the electronics field, ABS can be used to manufacture antenna sockets, coil frames, circuit boards, converters, speakers, and connectors.
02 POM (Polyoxymethylene/ Acetal)
POM, also known as polyoxymethylene or acetal, is a high-melting-point, highly crystalline thermoplastic engineering plastic. It is one of the hardest plastics in thermoplastic materials and one of the varieties of plastics with mechanical properties closest to metal, commonly known as “acetal.”

Colors: Black, White
Features:
- Resistant to organic solvents, insoluble at room temperature, good low-temperature performance, similar thermal deformation temperature to PC/PTFE nylon, higher than PVC/PS/PE.
- High compressive strength, second only to fiberglass; excellent wear resistance and resistance to creep; high mechanical strength and hardness; high dimensional and shape stability; retains toughness at temperatures below -40°C.
- Good sliding properties, does not absorb water, good abrasion resistance, chemical resistance, and hydrolysis resistance; inert, suitable for contact with food; good machinability.
Drawbacks:
- Poor resistance to acids, especially mineral acids; poor UV resistance; not self-extinguishing; sensitive to impact.
Applications: Suitable for making sliding parts, precision mechanical parts, water-resistant parts, precision parts with stable dimensions, and widely used in mechanical equipment components such as bearings, gears, impellers, cams, washers, liners, guides, handles, grips, etc.
03 Phenolic Laminate (Bakelite)
Phenolic laminate, also known as bakelite or phenolic resin laminated paperboard, is made by impregnating bleached wood pulp paper with phenolic resin and hot pressing it into boards.
Colors: Orange, Black
Features:
- Excellent electrical performance at room temperature, good machinability, density of 1.45, curvature ≤3‰, excellent electrical, mechanical, and machining properties.
- Intermediate electrical insulation, non-absorbent, non-conductive, non-static, wear-resistant, and heat-resistant.
Drawbacks:
- During the molding of phenolic products, heating is required, resulting in longer processing times than ordinary plastics. Molds require higher demands on steel due to greater wear.
Applications: Used for insulation structural components in electrical motors and equipment with high mechanical performance requirements, can be used in transformer oil. Also suitable for PCB drilling, silicone rubber molds, fixtures, distribution panels, electrical appliances, mechanical parts, communication equipment, electrical insulation components, etc.
Economic Benefits: The raw material price of phenolic laminate products is nearly 50% of the price of ABS. Despite the longer processing time and higher mold wear requirements during molding, it remains the preferred alternative for many plastic parts due to its advantageous raw material prices.
04 PMMA (Polymethyl Methacrylate/ Acrylic)
PMMA, also known as acrylic or acrylic sheet, is an early-developed important thermoplastic polymer material.

Color: Clear
Features:
- High glossiness suitable for surface polishing, light transmittance of 92%, refractive index of 1.49 comparable to the best optical glass. Stable shape under heat, usable in the range of -40°C to 90°C, UV resistant, good weather resistance, resistant to inorganic acids, alkalis, hydrocarbons, and cleaning agents, tear resistance better than other plastics.
- Good electrical and dielectric properties, excellent mechanical strength.
Drawbacks:
- Sensitive to stress fractures, poor chemical and impact resistance, brittle, mechanical properties are effective in the short term, require low tensile strength below 1500psi to avoid brittleness in long-term use, low impact resistance, reduced toughness with temperature, susceptible to corrosion by chlorinated hydrocarbons, aromatics, and ketones.
Applications: Used in machine covers and parts, clock dials, electric fan blades, relay covers, windshields, electrical medical equipment, transparent models, specimens, decorations, dentures, advertising plaques, etc.
05 PP (Polypropylene)
PP, short for polypropylene, is a polymer synthesized by polymerizing propylene through addition reactions. It is a white waxy material, transparent, and lightweight.
Color: White
Features:
- High rigidity, high hardness, and high surface strength, but average notch impact toughness. PP material can withstand tensile stress and is easily welded. Heat-resistant, no deformation from +5°C to +100°C, good chemical stability, excellent electrical properties.
Drawbacks:
- Average oxidation resistance, average wear resistance, embrittlement at low temperatures, average notch impact toughness, PP material can withstand tensile stress but cannot be welded at high frequencies, average adhesive paintability, susceptible to weather conditions.
Applications: Used in pump and valve parts, drinking water and sewage pipes, seals, spray carriers, electroplating processes, toy parts, dental guide tubes, etc.
06 FR-4 (Epoxy Board)
FR-4 is a code for a flame-retardant material grade, indicating that the resin material must be able to self-extinguish in a burning state, a specification of material used in fire-resistant applications.
FR-4 epoxy board is a high-performance, multifunctional insulation material composed of heat-resistant composite materials and fiberglass.
Colors: Green, Yellow, Black
Features:
- Stable electrical insulation performance, good flatness, smooth surface, no pits, standard thickness tolerance. High dielectric properties, heat resistance, and moisture resistance, good mechanical processing and structural stability, most notable for its high flame retardancy.
Applications: Applied in products with high-performance electronic insulation requirements and used as insulation structural components in motors, electrical equipment, such as FPC reinforcement boards, PCB drilling pads, electrical (electronic) equipment insulation boards, electronic switch insulation boards, etc.
07 PA6 (Polyamide Resin/ Nylon)
PA6, also known as nylon 6 or polyamide 6, is a high-performance compound with superior comprehensive properties, including mechanical strength, toughness, mechanical shock absorption, and wear resistance, commonly used in the manufacture of mechanical structural parts and maintainable parts.

Colors: Black, White
Features:
- Hard and low friction coefficient, wear-resistant and pressure-resistant; stable dimensions when not absorbing water, increased ductility and toughness when absorbing water; heat-resistant, stable when heated; high toughness, retains toughness at low temperatures, high tensile strength and elastic modulus.
- Good sliding and energy cushioning properties, good resistance to many oils, butter, and mineral oils; good dielectric properties, easy to process, bond, and weld, insulation.
Drawbacks:
- Rapid water absorption, reduced tensile strength and rigidity with increasing temperature and humidity.
Applications: Widely used in chemical machinery, gear and blank materials for corrosion-resistant equipment, wear-resistant parts, transmission structural parts, household appliance parts, automobile manufacturing parts, screw mechanical parts, chemical machinery parts, chemical equipment, etc.
08 PC (Polycarbonate)
PC is an amorphous, odorless, non-toxic, highly transparent thermoplastic engineering material, known as transparent metal.
Color: Clear
Features:
- A low-crystalline polymer with excellent impact resistance over a wide temperature range, toughness, resistance to creep, mechanical strength, and dimensional stability, transparency/ductility, weather resistance, and high temperature resistance, applicable from -150°C to +120°C. Flame-resistant, radiation-resistant, good electrical insulation.
Drawbacks:
- Sensitive to stress notches; reacts to hydrolysis, poor chemical resistance; prone to scratching, difficult to polish, arc resistance; becomes brittle when immersed in water for a long time/dissolves in hydrogen peroxide solution/cracks when exposed to aromatics/copper/acids.
Applications: Widely used in bulletproof glass, projector parts, mechanical electronics, automobiles, construction, daily necessities, hand model materials, and other high-tech fields. Currently used as windshields, bulletproof glass in aviation, electronics, and machinery, observation windows in instruments, circuit boards, fixtures, models, etc.
How to select proper materials for CNC Machining?

Application Requirements
Firstly, we need to determine the final use of the product and its various components and accessories. For example, medical equipment may require sterilization, food containers need to be heated in microwave ovens, and bearings, gears, etc., need to support weight and undergo repeated rotational friction.
Material Characteristics
After determining the application, research should be conducted on the actual usage of the product, analyzing its technical requirements and environmental conditions, and transforming these requirements into material characteristics. For example, components of medical equipment may need to withstand the extremely high heat of autoclaves; bearings, gears, etc., require materials with high wear resistance, tensile strength, and compressive strength. Analysis can be done primarily from the following points:
Environmental Requirements
Analyze the actual usage scenarios and environment of the product. For example, what are the long-term working temperatures of the product? Are the temperatures high or low? Will the product be used indoors or outdoors? Is there a requirement for UV resistance? Is the environment dry, humid, or corrosive?
Technical Requirements
Based on the technical requirements of the product, analyze the capabilities it needs to possess. This may cover a range of application-related factors. For example, does the product need to have conductivity, insulation, or antistatic capabilities? Is heat dissipation, thermal conductivity, or flame retardancy required? Will it come into contact with chemical solvents?
Physical Performance Requirements
Analyze the physical properties required for the components based on the product’s intended use and environment. For components subjected to high stress or wear, factors such as strength, toughness, and wear resistance are crucial. Components exposed to high temperatures for extended periods require good thermal stability.

Sufficient Material Rigidity
Rigidity is a primary consideration when selecting materials because products require stability and wear resistance in actual operation. Material rigidity determines the feasibility of product design. Depending on the industry, non-standard fixture designs typically use 45 steel and aluminum alloy; fixture designs for mechanical machining often use 45 steel and alloy steel; fixture designs for the automation industry mostly opt for aluminum alloy.
Material Stability
For a product with high precision requirements, instability can lead to deformation after assembly or during use, making it a nightmare. Material stability is crucial, ensuring that the product remains unaffected by temperature, humidity, and vibration-induced deformations.
Appearance and Surface Treatment Requirements
The market acceptance of a product largely depends on its appearance. Different materials offer various color choices, transparency levels, surface finishes, and treatment methods. Rust prevention treatment affects product stability and appearance quality. Surface treatment methods include blackening for 45 steel, painting, powder coating, or using rust inhibitors or sealants.
Consideration of Machinability
Material machinability affects the manufacturing process and precision of parts. Stainless steel, for example, is corrosion-resistant but wears out cutting tools easily, increasing processing costs. Plastics have low hardness but soften and deform easily during heating, leading to poor stability. Material selection should align with processing requirements.
Conclusion
The process of material selection commences with a systematic review of material classifications, encompassing metals, non-metals, and composites. Subsequently, guided by the outcomes of the analysis, materials aligning with the specific requirements of the product are scrutinized. Finally, integrating cost considerations, the optimal material is discerned from the array of candidate materials.
This methodical approach begins with an exhaustive examination of material performance data. However, the exhaustive review of thousands of materials is deemed unnecessary. Instead, a targeted review of pertinent material data is conducted, informed by the product’s specific requirements and preliminary analyses, thereby refining the pool of candidate materials.
Final Thoughts
Selecting the right material for CNC machining is critical for ensuring performance, cost-efficiency, and ease of production. For instance, aluminum alloys are a popular choice for their excellent machinability and lightweight properties, making them ideal for automotive and aerospace parts. Stainless steel, with its superior strength and corrosion resistance, is commonly used for medical devices and industrial applications. At Ultirapid, with 15 years of experience in CNC machining service, we’ve successfully worked with a variety of materials. For example, we recently completed a project for a client in the automotive sector, machining high-strength steel components that met both tight tolerances and durability requirements. Our deep understanding of materials helps us provide the best solutions for each unique project.