CNC machining is a great way to turn innovative designs into precise working models. However, users can only extract the full advantages of the process if they use the right CNC machining materials. The right material can lead to products that exceed your expectations. On the other hand, making the wrong choice can be an utter disappointment when you see and use the finished part.
CNC machining and CNC milling are processes with high versatility. You are not limited to just a couple of choices, there is a wide range of CNC machining materials. The exact material you should use for a project can depend on a lot of factors.
This article will help in making the current decision when choosing between CNC Machining materials. With the information provided here, you can create the best CNC machining project without any problems.
Factors That Affect The Choice of CNC Machining Materials
There are many factors that affect the decision of which CNC materials to use. After reviewing these factors for your particular scenario, you can easily choose which material to use.
First and foremost, the purpose of the component will shortlist the materials that you can use for it. For instance, if you are making toys, you cannot really use metal materials for the body. If you are making insulation-related components, you are restricted to use parts that have a low conductivity.
Indoors vs Outdoors
Outdoor components require materials that are resistant to weather conditions such as sun, UV rays, rain, and other elements. These parts require rugged material properties and a strong design. On the other hand, parts that are used indoors have controlled environmental conditions without sun or rain. Therefore, there are more options for indoor materials.
Calculate the amount of stress that the part will have to bear. Many manufacturers forget to account for the load-bearing stress on the part, leading to complete part failure. If the part is supposed to handle high stress, it requires strong materials such as metals, alloys, or high-strength plastic materials.
Every material has a dimensional tolerance that will affect the overall accuracy of the manufactured part. For most situations, dimensional tolerance might not be important enough to consider. However, certain applications such as research and development or medical equipment require highly precise parts. It is important to note that tolerance comes at a price. If you require extremely low tolerance, it is possible with CNC machines but will require specialized cutting tools and more time, piling up costs
If precision is a concern for your requirement, use a material with adequate dimensional tolerance. In addition, remember that accounting for proper tolerance initially is cheaper than paying for having the part resized later on.
Materials with high hardness and high strength might seem like the ideal way to go. However, they are often difficult to machine and require a longer time and cause more wear and tear of the cutting tools. Therefore, if you want fast production and minimum maintenance, using materials with good machinability is the better way to go.
CNC machining often creates parts that are turned into complex components in a later assembly. This later assembly is done with fasteners, due to which accommodating fastening measures are incorporated into the CNC design. However, not every material supports fastening. Additionally, certain properties such as galvanic corrosion resistance can be important for some fastening use cases. Therefore, choose a material that supports your particular fastening requirements.
Consider the operating temperature range for the final product and its environmental conditions. The CNC machining material should be able to handle this operating temperature with ease along with some temperature compensation due to the variations that can occur at times.
The material should not only handle the operating temperature, but also the temperature changes. For instance, some plastic materials can handle certain operating temperatures, but break down or warp when the temperatures are changed frequently.
Not to forget, CNC machining processes like CNC milling use cutting tools that can heat up significantly. Therefore, make sure that your material can handle these temperatures during the processing without distortion.
Chemical resistance is just as important as resistance to high temperatures. If your CNC machined components will be used in a chemically reactive environment such as labs or research facilities, it is important to choose chemical-resistant materials. For instance, using metal materials in an acidic environment is never a good idea.
For environmental conditions with high humidity, focus on the corrosion resistance characteristics of the material. Materials with poor corrosion resistance can rust and degrade easily. If you require high-strength metals but the working environment has high humidity, replacing them with their corrosion-resistant alloys can be a good option.
The weight of the material and its weight capacity are important factors for most projects. In use cases where the part will bear a heavy weight, it is important to choose a sufficiently strong material. These materials will have a higher weight in themselves. In case the weight of the part is a concern, using a material with a high strength-to-weight ratio is a good practice.
Durability and Strength
Manufacturing the part isn’t enough, it is important that the part should last for its intended lifespan. Therefore, evaluate the strength and durability requirements of the application and choose a material that meets these characteristics. These are the factors you should consider:
- Tensile Strength: Tensile strength is the amount of tension that a material can handle before breaking down.
- Wear Resistance: Wear resistance or abrasion resistance makes the object resistant to natural wear and tear during its lifespan.
- Endurance Strength: Endurance strength dictates how much stress an object can absorb. If the endurance strength of the part is high, use an impact-resistant material.
When aesthetics are a concern, it is important to choose a material that can provide a high surface finish. For example, metals can be smoothened for a glossy surface or can be matte surface treated. The same is not the case for many plastic-based materials.
Raw Material Cost
Lastly, the cost is the deciding factor that dictates the material you can choose for CNC machining. In case the project budget is limited, you can only opt for plastics and ceramics. Metals and their alloys, while having exceptional physical properties, are expensive CNC materials.
What are the Different Material Options for a CNC Machining Project?
To understand the types and properties of CNC materials, they are divided into basic classes: metals, plastics, woods, foams, ceramics, and composites. Let us study these different classes one by one along with the particular CNC materials that fall under that class.
Metal parts can provide the best precision and ruggedness among all CNC machining materials. However, they come at a high cost and with vulnerabilities such as corrosion in humidity. However, metal alloys eliminate these vulnerabilities quite well. Here are the common metals and their alloys used in CNC machining:
Aluminum and aluminum alloys are some of the most common materials used in CNC machining projects. Aluminum is known for its high strength-to-weight ratio, meaning that aluminum parts will be lightweight but can handle high stress. It has very good machinability and low raw material costs, leading to cheaper mass-production projects than other metals. There are many different types of aluminum alloys available for CNC milling, such as:
- Aluminum 6061
- Aluminum 7075
- Aluminum 6082
- Aluminum 5083
Applications of CNC machining of aluminum are:
- Consumer electronics
- Medical device
- Aerospace frames
- Automotive components
Steel is an alloy made of iron and carbon, highly improving the strength and corrosion resistance characteristics of iron. It is extensively used in CNC machining in different forms like sheets, bars, cylinders, and blocks. There are many different types of steels with varying amounts of carbons.
Some common types include:
- stainless steel
- steel 1018
- steel 12L14
- carbon steel
- carbon steel 1045
Carbon steel contains a high amount of carbon as compared to other steels. Therefore, carbon steel has high strength and hardness characteristics, while being more brittle.
Characteristics of steel include very high strength, high ductility (ability to draw into wires), excellent machinability, high wear resistance, high corrosion resistance, and good surface finishing. However, it can be costly to produce parts made out of steel in high volume.
A few applications of CNC machining of steel are:
- Automotive components
- Car Accessories
- Aircraft components
Stainless steel is one of the most widely used types of steel in CNC machining, with its volume comparable to many other materials like wood. Therefore, it requires a cursory understanding of its own.
It comes in many different grades such as Stainless Steel 303, Stainless Steel 304, Stainless Steel 316, Stainless Steel 416, marine grade stainless steel, and so on.
The most sought after quality of stainless steel is its ability to resist wear and abrasions. It offers high precision when manufacturing parts, but can be costly for mass production model.
Applications of stainless steel include:
- Medical industry
- Aircraft construction
- Tankers and vessels
- Food and catering utensils and equipment
Brass is one of the expensive materials to CNC. Some common types of brass include C3604 and C3602. It is the preferable choice for art and aesthetics based projects that do not have a restriction on project budget and do not require mass production.
It has a smooth surface finish that can be easily polished to look quite superior. Brass is easy to machine material, reducing the operational costs when using it for CNC machining. Other appealing qualities of brass are its high corrosion resistance and low friction. The overall qualities of Brass make it usable for:
- Art installations
Titanium is a metal with very high toughness. As such, it is often applied in applications that require high strength and durability. Titanium also has a high hardness and is highly corrosion-resistant. Additionally, it is possible to utilize a lot of different surface finishing options for titanium.
Common applications of CNC machined titanium are:
- Aerospace industry
- Sporting equipment like golf clubs
Copper is one of the most conductive materials and of the more common materials for CNC machining. This includes both- electrical conductivity and thermal conductivity. Additionally, it has high ductility and malleability along with high corrosion resistance. However, the cost of copper can be quite high compared to other materials including metals, making it quite expensive for mass-producing metal parts.
Applications of CNC machining copper are:
- Electrical connectors
- Insulation components
- Heat exchangers
Other Metals and Alloys
Besides these common materials for CNC machining, there are other metals and alloys that can find fewer applications. These include:
While metals have good physical properties, they can be quite expensive to mass-produce parts. For mass production, plastics tend to be the cheaper option. Modern-day plastic resin compounds can offer sufficient strength and other physical properties that make them a good replacement for metals. Here are the common plastics used in CNC machining:
Acrylonitrile Butadiene Styrene (ABS)
ABS plastics are one of the most common forms of plastic used in CNC machining. It is a thermoplastic with good physical properties. Additionally, it is very easy to machine with CNC machining. Compared to many other plastics, ABS holds well in a wide range of temperatures. The cost of ABS raw materials is very low, making it cheap for mass production.
Common applications of ABS include:
- Vacuum components
- Keyboard keys
- Electronics housing
- 3D building
Thermoplastic Polyvinyl Chloride (PVC)
PVC is another extensively used plastic in CNC machining and other mass production methods. Its standout quality is its sturdiness and resistance to chemicals, corrosion, and even flames. It is cheap to use, making it a suitable material for limited budgets.
Applications of PVC include:
- Medical device
- Electronics housing
- Automotive industry interiors
- Seat coverings
Acetal- Delrin (POM)
Polyoxymethylene is commonly known as acetal, polyacetal, Delrin, or POM. It is a thermoplastic material that provides very high precision, high dimensional stability, and low friction. It is used to mass-produce components via CNC machining and injection molding.
- Sports gear
- Mechanical components like screws, chains, gears, etc.
- Small scale models
- Medical equipment
Polymethyl Methacrylate, known as PMMA or Acrylic PMMA, is a common thermoplastic material. It is visually transparent, giving it the name Acrylic Glass. Several trademarked brand names such as Plexiglass, Lucite, and Perspex use this material. It has high tensile strength, flexural strength, and UV tolerance, scratch resistance, and abrasion resistance.
- LED lights
- Healthcare industrial applications
- Automotive parts such as lighting
Polycarbonates (PC) are similar to PMMA acrylics to some extent, as certain grades of polycarbonate materials can be visually transparent. They have very high machinability, making them easy to mold into different parts.
Applications of polycarbonate include:
- Dome lights
- Insulation components
- Sound walls
- 3D printing
- Eyeglass and sunglass lenses
Noryl is a material made by blending a plastic resin such as PPO or PPE with polystyrene. They have good dimensional stability, machinability, and low density. Additionally, they can be designed to be resistant to high temperatures along with electrical insulation properties.
Some applications of Noryl are:
- Electrical equipment
- Water pumps
Polypropylene (PP) is the most widely produced plastic after polyethylene. It has high ruggedness, heat resistance, and chemical resistance. The high strength and rigidity of propylene makes it usable for pure water piping systems. It is also resistant to chemical leaching and corrosion.
Some applications of Propylene are:
- Potable plumbing
- Hydronic heating
- Lab equipment
- Bottle caps
- Loudspeaker drive units
Polytetrafluoroethylene, commonly known as Teflon, is a very popular polymer. It is a hydrophobic material that is not affected by water or other water based liquids. It has an extremely low coefficient of friction, lower than most other solids.
- Wire insulation
- Bearings seals
- Musical instruments
- Kitchen accessories
High-Density Polyethylene (HDPE)
HDPE, also known as PEHD, is a common thermoplastic polymer. It has a high corrosion resistance and a high strength-to-density ratio. It is commonly recycled and consumed in large amounts globally. Its applications are:
- Milk Jugs
Ultra High Molecular Weight Polyethylene (UHMWPE)
UHMWPE, also called High Modulus Polyethylene, is a type of thermoplastic polyethylene. It is the most impact resistant among all thermoplastic materials. It also has a very high toughness. It is chemical resistant to most acids and alkalis.
Its common applications are:
- Fibers for parachuting and fishing lines
- Medical implant biomaterial
- Marine infrastructure
Nylon is a thermoplastic with a silk-like texture. Its physical properties can vary significantly due to the addition of different materials. Some common types are nylon 6, nylon 66, nylon 510, and 1,6. Its applications include:
- Machine screws, gears, and gaskets
- Car composite parts
- String trimmers
Other plastics that can be CNC machined are:
- Polyvinylidene fluoride (PVDF)
- Polyetherimide – Ultem (PEI)
- Polyether ether ketone (PEEK) – with a high level of resistance to corrosive substances and a high melting point PEEK is a popular material for different machining parts and projects.
- Phenolics (Bakelite)
Woods such as plywood and solid wood used to be common materials for CNC machining. However, environmental factors, availability, and cost related factors have shifted the focus to metals and plastics. Even so, wood as a CNC machining material finds several applications in industries like:
- Making furniture frames
- Legs for tables, chairs, and beds
- Decoration pieces
CNC machining material selection is not just limited to hard materials. Even softer substances like foam are a great material for CNC machining in industrial applications. This includes both rigid foams and carving foams. Some common applications of CNC foam machining are:
- Packaging elements
- Decor items
Ceramics are not only aesthetically beautiful, but their physical properties also make them great for a variety of applications. They are good insulators for heat as well as electricity. Additionally, they have a very high compressive endurance.
Common applications for ceramic CNC machining are:
- Decor pieces
- Insulator elements
- Jewelry pieces
- Electrical component housing
Composites, such as FRP have become common nowadays for their exceptional physical properties, ability to withstand pinpoint surface loads, mechanical properties, tensile strength, and many other factors. They can be the right materials if the job requires a rugged, low cost solution. Their applications include:
- Decor pieces like fountains
- Glass replacement
- Aerospace applications like radar and antenna
- Aircraft industry
- Wind turbine blades
Tips for Optimizing Material Selection for CNC Machining
Here are some tips that will improve the material selection process for you and add more value to the project:
Go Beyond Metals
Many people immediately jump to metals when they think of a CNC machining project. In recent years, nonmetallic materials are providing better value for money by offering similar physical properties as metals at a lesser cost and an easier machining process.
Choosing the Right Material Grades
Many materials are available in multiple grades. If you have decided on a material for your project, say steel or foam, make sure you choose the adequate subtype since they can vary greatly in their properties. For instance, rigid foam and carving foam have entirely different purposes and finished parts.
Many materials, such as composites, wood, and even metals generate a huge amount of dust when going through CNC machining processes. This dust can be harmful to the workforce and even the finished part in many cases like aerospace, aircraft components, and R&D applications. When choosing materials that are going to generate dust, follow proper dust removal protocol to ensure the safety of the workplace and preserve the integrity of the parts.
Which is the Best Material For a CNC Machining Project?
There is no material that can be deemed absolutely best when it comes to CNC Machining. This is because different materials have diverse properties and purposes. Materials like aluminum can be said to be the most widely used since their properties are flexible and suitable for most requirements.
All the available materials and the factors for choosing materials that are right for the job can seem like tough knowledge to acquire. However, once you go through all this information and understand it, the project result will be astounding. Not only does the right material eliminate part failure, it also provides a smoother operation and precision unlike anything else.
It is also important to understand that the benefits of the right material will only hold true if you are using the right machining services. 3ERP is the best available solution in this regard. 3ERP is a CNC machining service provider that can handle any requirement and offers every possible material that you might need.
Frequently Asked Questions (FAQs)
Here are the answers to some commonly asked questions regarding the right material for CNC manufacturing process:
1. What is the most common material used for CNC machining?
Common materials used in CNC manufacturing processes are steel, aluminum, and plastics.
2. What are the hardest materials to machine?
Heat-treated alloys are generally the hardest materials to machine. This includes alloy steel and cobalt based alloys.
3. Which material has the highest machinability?
Free machining steel is a material that has one of the highest machinability. While materials like plastics and composites are easier to cut, they can react badly to high temperatures in the cutting process.
4. Which is the most durable material that can be CNC machined?
Maraging steel is one of the most durable material for CNC machining.
5. Which CNC machining material has the best heat and temperature resistance?
Ceramics are a great CNC machining material that have one of the highest heat and temperature resistance.