CNC stands for “Computer Numerical Control”. CNC machines are controlled by a computer that converts the human idea into a physical product using some programming codes. The efficiency and quality of a CNC machined part depend largely on selecting the appropriate CNC machining materials.
Although the selection process might be a little difficult due to the availability of various materials, this article will provide a well-detailed guide that will help you choose the best CNC machining material for your projects.
Key Factors That Can Affect CNC Material Selection
Before choosing one of the many CNC materials available in the market, some factors can aid your selection. Below are a few important ones you need to consider:
This factor denotes the level of interaction between the material and CNC machining. The right material should have high machinability as this will increase productivity and reduce damage to parts.
Examples of machinable materials include light metals such as aluminum, brass, copper, and some plastics. On the contrary, tough metals and strong plastics like carbon fiber have a low level of machinability.
Machining a material with low machineability can reduce the quality of parts and machining efficiency and destroy metal parts. Furthermore, such materials often require unique cutting tools (common with titanium), which will increase production costs.
Another major factor you should consider when selecting a CNC machining material is the material strength. There are several ways to measure the strength of the material, whether plastics or metals, and the following are the various ways to measure it and choose the right material.
- Tensile strength measures the level of resistivity of a material to external forces；
- Compression shows how much a material can accommodate under a steady load；
- The level of toughness is the level of resistance of a material to wearing and tearing；
- Elasticity property shows the material’s ability to return to its original shape after deformation under a heavy load.
3. Heat Resistance
Heat resistance is another factor affecting a CNC material’s selection process. It measures the level of adaptability of material to temperature changes. The right CNC materials will show regular contraction and expansion when temperature changes. As a result, there will be no deformation due to the heat generated during machining.
4. Corrosion resistance
Corrosion resistance is the capability of a CNC material to withstand odd substances or resist chemical exposure. Water, alongside other substances, including salt, oil, grease, acids, alcohol, etc., can cause corrosion. Corrosion resistance will determine the application of the material. For example, stainless steel material is suitable for marine applications.
5. Material Hardness
This factor measures the ability of a CNC material to resist surface loads. Furthermore, it predicts the range of materials a CNC machine can cut through.
Extremely hard materials are not appropriate for CNC machining because they can damage the cutting part of the CNC machine. Also, they are highly nonmachinable and might require unique cutting machines, such as the use of diamond cutting tools to reduce surface roughness.
6. Dimension Tolerance
Dimension tolerance also known as machining tolerance and dimensional accuracy is the level of variation in the part dimension that is permitted without affecting the function of such parts. Materials that guarantee the achievement of tight dimensional tolerance have high machinability and low variability.
7. Physical Appearance
Although it is not a major consideration for CNC material selection, producing some products, specifically consumer goods, might be necessary. The physical appearance of a material comes from its color and determines the final part’s uniformity. Metals often have a uniform surface finish but don’t come in various colors, unlike plastics.
8. Cost of the Material
The cost of the material is the most crucial factor when choosing from CNC materials. Generally, metals are costlier than plastics. Nevertheless, you should ensure you choose a material of optimum quality while falling within your budget.
Categories of CNC Machining Materials
There are three major categories of CNC machining materials. In this section, we will look at the categories of materials that are compatible with CNC machining.
Category #1: Metal Materials for CNC Machining
Metals are CNC materials with special attributes. However, there are varieties of metals that are compatible with the CNC machining process. The following are popular metals, along with their properties and applications:
Alloys of aluminum have excellent properties like a high strength-to-weight ratio, high corrosion resistance, and good conductors of heat and electricity. Although these properties vary depending on the exact type of alloy, an example is the comparison between aluminum 6061 vs. 7075. Aluminum 6061 has lower corrosion resistance than aluminum 7075.
Aluminum is widely applicable in the automobile and aerospace industries for manufacturing parts like quality frames and equipment.
Brass is an alloy of zinc and copper, a budget-friendly CNC material with high resistance to foreign substances. In addition, it has a low coefficient of friction and low strength and is highly machinable due to its softness.
Brass is suitable for producing parts used in the medical industry (surgical equipment and tools) and strings used in musical instruments.
1.3 Stainless steel
Stainless steel alloys can resist corrosion unlike steel and wear and tear effectively in the CNC machining process. Furthermore, most stainless-steel alloys accommodate heat well, except the alloy 303 stainless steel applicable in creating nuts, bolts, gears, and shafts, and 304 stainless steel is known instead for its high machinability and weldability.
Stainless steel is widely applicable in the automobile and aerospace industries. Furthermore, it is applicable in producing surgical tools.
Titanium alloys are renowned for their special properties like high toughness, strength, biocompatibility, etc. Unlike aluminum, it is more expensive and has a lower level of machinability. Unlike the previous metals, titanium requires special cutting tools during machining. It has low weldability, which makes steel a better option for CNC machining materials.
Applications of titanium include rapid prototyping of parts in the military field and making equipment, parts, and devices for the medical and aerospace fields.
Copper is a good conductor of electricity and heat and is known for its corrosion resistance. However, it has low resistance to substances like acids, sulfides, ammonia, and halogens.
Due to its high ability to conduct electricity, it is widely applicable for producing parts in the electronic industry. It is suitable for making heat exchangers and cooling systems used in the automobile industry.
Category #2: Plastic Materials for CNC Machining
Plastic polymers including thermoset and thermoplastics are more suitable for CNC machining and are widely popular in several industries due to their aesthetic attributes and versatility. Below are the popular plastic materials compatible with CNC machining, their properties, and applications:
2.1 ABS (Acrylonitrile Butadiene Styrene)
This is a thermoplastic polymer with high chemical and abrasion resistance. Although they are more compatible with the injection molding process, they are also compatible with CNC machining. Aside from that, they are very cheap and can’t resist heat for long, unlike other plastic materials.
ABS plastic is applicable in making toys and automobile parts. They are also applicable to manufacturing sporting products and devices in the sports sector.
Nylon or polyamide is a highly machinable plastic polymer with high strength and an appropriate level of heat resistance. It is suitable for manufacturing parts like insulators, wheels, bearings, and casings for electronic devices.
2.3 Polymethylmethacrylate (PMMA)
PMMA or acrylic is a strong, impact/wear-resistant material with a transparent-like structure, making it suitable for replacing glass. Although useful, its major disadvantage is that it is prone to deformities caused by heat.
Applications of acrylic include the production of display screens and transparent enclosures. Furthermore, due to the absence of Bisphenol-A, it is suitable for making food storage containers.
This is a plastic polymer with a semi-crystalline form, a high level of machinability, excellent stability, chemical resistance, and wear and tear resistance. PEEK is commonly used to manufacture parts like switches, sockets, and connectors.
PVC is a special CNC material, with high chemical resistance, cost-effectiveness, dimensional stability, etc. It is applicable in the construction and consumer industry.
Category #3: Composites for CNC Machining
Composites are synthetic materials such as glass fibers and carbon fibers that contain two or more individual materials with different chemical and physical properties. Below is a list of common composites, their properties, and their applications.
3.1 Thermoplastic Composites
This composite type can take on desired forms even after subjecting them to heating, softening, molding, and cooling. It also resists stress, corrosion, and chemicals. They are applicable in making electronic accessories, fuel tanks, rotor blades, satellite structures, etc.
3.2 Glass-fiber Reinforced Composites
As its name implies, the composite comes from different formulations of silica-based glass. Depending on some specific properties, the main ones include alkali glass, chemical glass, electrical glass, etc.
3.3 Carbon-fiber Reinforced Composites
They comprise long chains of carbon. Unlike glass fibers, they are strong, rigid, and light in weight. They also can resist extreme temperatures and chemicals. They are majorly applicable in power generation. Automobile and aeronautics industries
Other CNC Machining Materials And Their Applications: A Quick Chart
Apart from the CNC materials mentioned above, there are also other CNC machining materials with good qualities. Below is a table that represents each of the materials, their properties, and their application areas.
|CNC Machining Materials||Properties||Applications|
Requires careful machining
|Engine components of a space shuttle
High dimensional stability
Needs special cutters
|Areas that require testing|
Very high melting point
Good tensile strength
|Molybdenum||Low thermal conductivity
It’s an alloy comprising about 36% nickel and 64% iron
Considerations on Choosing Machining Materials for CNC Parts
Choosing the right machining materials is a critical factor when machining CNC parts because it can impact the quality, durability, and cost-effectiveness of the final product. Here are some factors to consider when choosing machining materials for CNC parts:
1. Consider the Requirements for Manufacturing Parts
The basic needs of the parts to be processed are a crucial part of CNC machining, and they also create a guide for the type of material to use. The common part requirements include:
Make sure that the CNC material you intend to use is suitable for the intended application and its environment. For example, let’s examine the comparisons between stainless steel and carbon steel when they want to be used to manufacture components in the marine sector.
Both materials are highly machinable, but stainless steel will be more appropriate since it has a higher level of resistance to corrosion. However, carbon steel will be a better option in a regular, dry environment because it is more durable and stronger.
The weight of the part affects the CNC material selection, as it can impact the machining process and the overall performance of the part. Heavier parts typically require stronger, denser materials to ensure they can withstand the load. For lighter-weight parts, materials with lower density may be used, such as aluminum or titanium, to reduce weight and improve performance.
Part Accuracy and Tolerance
Some materials are more difficult to machine to tight tolerances than others. For example, materials that are prone to warping, such as certain types of plastics (PVC), may require more significant machining allowances to achieve the desired tolerances.
On the other hand, materials such as steel or titanium are often preferred for applications that require high accuracy and tight tolerances.
The properties required for the part depend on its intended use and the environment in which it will be used. Factors such as strength, toughness, and wear resistance are crucial for parts that will be subjected to high stress or wear.
Materials such as steel, titanium, and certain plastics, such as nylon or acetal, are known for their strength and durability, making them suitable for these types of applications. For parts that will be exposed to high temperatures, materials with good thermal stability, such as ceramics or certain metals, may be preferred.
2. Consider Surface Treatment Options for Machined Parts
Although machined parts have a process-inbuilt finishing, you can also consider other surface treatment options.
Furthermore, the choice of material can also influence the available surface treatment option. For example, aluminum alloys such as 6082 and 7075 are often subjected to treatment such as anodizing. Other surface treatment options include electroplating, powder coating, galvanization, and sandblasting.
3. Select Common Machining Materials
Instead of worrying about choosing from the myriad of materials available, you can select common machining materials which top rated engineers identified and conclude that it works well for machining and is widely accepted for such applications.
Common metals include brass, copper, stainless steel, and aluminum. Common plastics include PEEK, Acetal, Nylon, ABS, and Polycarbonate.
Get the Right CNC Machining Material for Your Projects
If you are struggling to choose the right CNC materials for your projects, WayKen is here to help you. We can provide 30+ engineering metals and plastics and have well-experienced machinists and engineers who help recommend materials for your project within your budget range.
Furthermore, with our one-stop CNC machining services to meet your expectations, you can confidently get CNC machined parts with high quality and accuracy. Have any specific questions about material machining, please feel free to contact us.
What are the factors to be considered when selecting a CNC material?
It would be best if you considered many factors, including environmental, uses, machinability, tolerances, and the cost of the material.
Which aluminum alloy is the best for CNC machining?
Aluminum 6061-T6 is a commonly used aluminum alloy, and it is known to be a standard grade for CNC machining. Its properties, like lightness in weight, resistance to corrosion, versatility, and machinability, make it applicable in the automobile and aerospace industries.
What types of materials can a CNC machine cut?
A standard CNC machine can cut soft metals like stainless steel and aluminum, plastics like ABS, PEEK, and PVC, and other materials, which include ceramics, wood, and foams.