The success of a CNC machining project depends on a lot of factors, one of which is the choice of material. This singular factor determines the durability and performance of your final product. There is a wide range of materials you can choose for your CNC machining task. This is why you must understand the strengths and weaknesses of each material to find the best fit.
In this guide, we will provide an in-depth knowledge of the different types of CNC machining materials available and how to choose the right one for your project.
Metal Materials Used for CNC Machining
CNC machining is widely used across several industries due to its high level of precision and efficiency. Different metal types are compatible with CNC process. However, each metal type has its unique properties, strength and performance, and is suitable for different metal CNC projects. Here are the metal types commonly integrated in CNC machining projects.
Aluminum
Aluminum is a common metal known for its lightweight and corrosion resistant properties. It is a great material option for CNC machined parts due to its machinability. The most common aluminum types are alloy 6062 and 7075. These are popularly used in automotive, aerospace, and consumer products due to their high strength-to-weight ratio.
Aluminum also has good electrical and thermal conductivity. It is an affordable material choice that offers great properties. Another important benefit of this CNC machined metal is that you can easily coat it for enhanced surface protection.
Copper
Copper, a material that with great thermal and electrical conductivity excels in a lot of applications. However, you can find copper difficult to machine because of its softness. During machining, this material can stick to cutting tools, making the machining process difficult. However, you can achieve good results with copper if you implement the appropriate machining strategy and cutting tools.
Copper is a good choice for medical applications due to its antimicrobial properties. It has a reddish look that makes it useful for aesthetic purposes.
Bronze
Bronze is an easy-to-machine alloy made of tin and copper. It is durable, strong, and corrosion resistant, making it suitable for producing intricate components like bearings and gears. Also, this material has weather-resistant properties which help it excel in high-demand applications like marine and aerospace.
Although bronze isn’t a popular option as aluminum for CNC metal machined parts, it has high strength and wear resistance. You can use this Bronze for components with high friction.
Steel
Steel is a durable metal with high tensile strength and corrosion-resistant properties. There are different types and grades of steel, ranging from carbon steel, tool steel, and mild steel. Consequently, Steel is a reliable material, and as such, you can use it in manufacturing automotive parts, medical equipment, and heavy-duty components.
Steel is a cheaper alternative for manufacturing parts compared to some materials like titanium. Also, you can easily weld this. Steel doesn’t need additional coating or treatments due to its ability to resist corrosion. The grade or type of steel you are working on will determine its machinability. While some steel types are easier to machine, you may find it difficult to machine other types.
Stainless Steel
Stainless steel contains chromium, which makes it corrosion resistant. This material is strong and durable. However, SS grades are difficult to machine, unlike regular steel. This is because of its toughness. Common grades like 316 or 304 are suitable for manufacturing food processing equipment and medical devices.
CNC machining stainless steel is a popular choice because of its high performance and lifespan. Stainless steel has non-reactive surfaces, which makes it a good choice in applications where cleanliness is a major concern.
Magnesium
This is a lightweight metal that is easy to machine. Although it has low density, magnesium has a good strength-to-weight ratio. Therefore, it is a good material option for applications where less weight is important. For instance, manufacturers like to use magnesium for producing automotive parts and aerospace components. You must be very careful when machining metals like magnesium because it is very flammable when it is in powder form.
Titanium
Titanium is a hard metal with good biocompatibility and corrosion resistance properties. It is commonly used for producing aerospace components, high-performance engineering parts, and medical implants. Therefore, titanium is a highly reliable material that maintains its properties regardless of temperature fluctuation. Titanium grades can resist corrosion, making them ideal for marine applications.
However, you need high-performance tools and great experience to machine this material. Titanium can withstand any harsh conditions due to its toughness.
Plastic Material Types Used for CNC Machining
Plastic is one of the most popularly used CNC machining materials in precision manufacturing due to its excellent properties. Naturally, plastics can withstand corrosion. These lightweight CNC materials are available in different types, with each having different mechanical and chemical properties.
When it comes to CNC machining, you must understand the properties of each plastic. This will help you choose the best plastic that meets the requirements of your CNC machining projects. Here is the CNC material list.
ABS (Acrylonitrile Butadiene Styrene)
ABS is an affordable choice of plastic with food impact resistance. This tough plastic is very easy to machine, which makes it ideal for designing consumer product prototypes. ABS doesn’t perform well in applications where there is exposure to extreme heat and UV.
PC (Polycarbonate)
Polycarbonate can withstand impact and vibration. This plastic features optical clarity and heat-resistance, and as such, you can consider it a great choice for electronic components and automotive parts. Polycarbonate is easy to machine, but it can crack due to heat. Therefore, you need to ensure it cools properly during machining.
PMMA (Acrylic)
Acrylic is well known for its smooth surface finish and durability. Due to its high optical clarity, you can use this plastic as a good alternative to glass. This material is versatile and easy to machine, making it a good choice for CNC machining. However, acrylic can crack when it is under stress.
POM (Polyoxymethylene, also known as Acetal or Delrin)
This plastic features great properties like low friction, dimensional stability, and high strength. POM is an ideal material choice for making automotive parts like bearings and gears. Additionally, it performs well in applications exposed to moisture and corrosion.
PA (Nylon)
Nylon is a flexible and impact-resistant type of plastic used in different applications. Due to its ability to resist wear and surface lubricating properties, you can use this material in parts that experience friction, like gears, sliding surfaces, and bushings. However, nylon has low dimensional stability because it can absorb moisture from the air.
PE (Polyethylene)
Polyethylene is an easy-to-machine material that is chemically resistant. There are different types of polyethylene, which are low-density polyethylene (LDPE) and high-density polyethylene. In general, you can use polyethylene for wear-resistant parts like liners and containers. Due to its softness, you may find it challenging to machine.
PEEK (Polyetheretherketone)
This is a type of thermoplastic that features great thermal stability. PEEK can tolerate high temperatures, making it a suitable option for parts used in medical, aerospace, and automotive industries. It can survive in high-stress environments due to its mechanical and chemical properties. You can use them as an alternative to some metals in certain applications.
PP (Polypropylene)
Polypropylene is a common CNC material used in producing piping systems and medical equipment. It has good moisture and chemical resistance, making it ideal for applications exposed to corrosive elements. However, this plastic type is very soft and can be very difficult to machine.
HDPE (High-Density Polyethylene)
HDPE features properties like a high strength-to-density ratio and good chemical resistance. This type of plastic is ideal for making moving or sliding parts due to its low friction coefficient. However, you need to take caution when machining HDPE because of its ability to deform.
HIPS (High Impact Polystyrene)
HIPS is very easy to machine due to its structural features. Although this plastic isn’t as strong as others, it can resist impact. It is a low-cost material, and as such, you can use it in packaging and prototyping.
LDPE (Low-Density Polyethylene)
LDPE is very soft and flexible. You can use it for producing tubing, lids, and foils. However, this material has some challenges during machining. This is because of their softness and flexibility.
PBT (Polybutylene Terephthalate)
PBT has good dimensional stability and mechanical strength. This type of plastic is easy to machine due to its mechanical properties. PBT is a good plastic choice for manufacturing parts in automotive, electronic, and medical devices.
PPA (Polyphthalamide)
This is a type of nylon that features chemical resistance. It is a reliable option for producing engine components used in the automotive and electronics industries. PPA has better mechanical and thermal properties compared to regular nylons. You can use PPA in high-temperature CNC applications.
PAI (Polyamide-imide)
PAI is a very strong thermoplastic with great dimensional stability. This plastic can withstand extreme temperatures and mechanical stress. You can use them in manufacturing aerospace components and high-speed machinery parts. However, this thermoplastic is difficult to machine due to its high strength.
PET (Polyethylene Terephthalate)
PET is a common type of plastic used in packaging food and beverages. This plastic has good wear resistance and dimensional stability. As a lightweight material, you can easily machine PET and achieve smooth finishes as a result.
PPS (Polyphenylene Sulfide)
PPS is an easy-to-machine plastic with great mechanical strength and chemical resistance. Also, the PPS CNC-machined plastic components are ideal for manufacturing chemical processing equipment and electrical insulators due to their ability to withstand harsh conditions without degrading.
PS (Polystyrene)
Polystyrene is popularly used in the food and packaging industries for making disposable cutlery, cups, and packaging. This plastic type can’t resist impact. That’s why it can easily crack or break. Polystyrene offers smooth finishes when machined, which makes it great for prototyping.
PVC (Polyvinyl Chloride)
PVC is an affordable plastic material that offers flame retardancy. This material has a high strength, making it a good choice for manufacturing valves, pipes, and construction parts. Also, it can withstand chemicals and high impact. You can use this for enclosures, chemical tanks, walking surfaces, and custom fittings.
PTFE (Teflon)
PTFE is a common type of plastic with non-stick and low friction properties. This makes it great for producing moving and sliding components like seals and bushings. However, you can’t achieve a tight tolerance with this material because of its softness. PTFE performs well in applications that are exposed to chemicals.
UPE (Ultra-High Molecular Weight Polyethylene)
UPE, or UHMW-PE, is a strong plastic material that has the ability to resist wear and impact. It also has a low-friction property, which is key for making moving parts like liners and conveyor systems. This material’s softness makes it quite challenging to machine.
Bakelite (Phenolic Resin)
Bakelite is a strong plastic known for its heat resistance and electrical insulating features. However, you can find this plastic difficult to work with due to its brittleness. It remains one of the oldest and most reliable plastic CNC materials.
FR-4 (Fiberglass-Reinforced Epoxy Laminate)
FR-4 is a strong plastic comprising epoxy resin and woven fiberglass cloth. This material features electrical insulation and flame resistance properties. It has common uses in the production of printed circuit boards. You need to be very careful with FR-4 during machining. This is because fiberglass, an important component of FR-4, is abrasive and can cause wear to cutting tools.
Other Materials Used for CNC Machining
Although Plastics and metals are included in the popular CNC machining materials list used in CNC machining, this machining process is also compatible with other materials. CNC machines can work with different materials while offering smooth finishes and precise results. Below are other materials that you can use CNC machining for.
Graphite
Graphite is a popular option for creating electrical discharge machining (EDM) molds used for metal casting. It is a soft material that serves as a good electrical conductor due to its high-temperature resistance.
You can achieve tight tolerances when working on graphite. However, it requires proper containment during machining since it produces fine dust. Graphite is a great option in applications exposed to extreme temperatures due to its ability to resist thermal shock.
Wood
This is another material you can easily machine without much difficulty. There are different types of wood, which are softwood, hardwood, and engineered wood. With CNC mills, you can create intricate designs with wood. You can make furniture parts, cabinetry, and engravings with extreme precision.
One of the great benefits of wood is that it is easy to machine. However, it isn’t dimensionally stable due to its moisture content, which can pose some problems during machining. Wood is great for architectural and artistic applications when machined properly.
Silicone
This material looks like rubber and has similar flexibility. Rubber is great for making molds, seals, and gaskets used in automotive parts and medical devices. Silicone in its soft form isn’t ideal for machining. Hence, CNC machining works on harder silicone like high-durometer types. You need specialized CNC tooling to achieve great results. Silicone is good for use in an environment exposed to heat and chemicals.
Rubber
Rubber has an elastic nature, which makes it difficult to machine. However, you can machine harder rubber forms like vulcanized rubber sheets. They are ideal for making industrial parts. The best way to proceed with the rubber is through CNC waterjet cutting. This CNC machining method prevents rubber from distortion. Rubber can withstand impact, which makes it a great choice in applications that experience vibration.
Ceramics
Ceramics are very strong CNC materials with thermal stability. Also, ceramics such as zirconia and alumina offer great results when you machine them. However, ceramics require specialized processes and tooling to machine. You need slow feeds and diamond tooling to machine this because of its hardness.
Ceramics are commonly used in aerospace, medical, and electronics industries. They don’t corrode and experience wear, making them suitable for manufacturing components used in harsh conditions.
Phenolic
Phenolic is a glass or paper reinforced thermosetting plastic. It is a machinable material with great mechanical strength and electrical insulation. You can use phenolics for manufacturing mechanical fixtures and electrical housing. Although it is abrasive in nature, you can achieve a clean finish with the right tooling. However, phenolic can wear out tools, and as such, you need to handle it carefully during machining.
Stone
Stone can be in its natural or engineered form. You can machine this material for artistic or architectural applications. The best machining method for stones is CNC waterjet and CNC router tooling. These machines can cut stone precisely and offer a clean finish. Stone like marble or granite is great for intricate designs like plaques and countertops.
However, the hardness of stone makes it difficult to machine. Therefore, you have to use the right tools and coolant systems to prevent wear. Diamond-tipped tools will help you maintain precision and enhance the finishing of the stone.
Foam
There are different types of foams, like polyurethane and high-density modeling foam. These foams are mainly used for packaging inserts, molds for composites, and prototypes. Foam is a lightweight material with ease of machinability. It is an affordable option for creating large, lightweight components. However, foam usually produces dust during machining.
Epoxy Resins
Manufacturers use epoxy resins for composite parts and mold creation. Epoxy resins have good strength and are heat resistant when cured. These materials are great for creating master patterns for prototyping in the aerospace and automotive industries. You can easily achieve tight tolerances with resin. This makes them a perfect choice in applications that need repeatable accuracy.
Carbon Fiber
Carbon fiber is a stiff and strong material with good thermal stability. In most cases, raw carbon fiber fabric usually needs resins to make it easy to machine. When machining carbon fiber, you need specialized tools to achieve great results. Also, carbon fiber is abrasive and has a high tendency to produce dust. Therefore, it is necessary to have proper dust management when machining this material.
Gypsum
Gypsum is a great choice for artistic and architectural applications. You can find it easy to machine gypsum boards and plaster of Paris (POP). These materials are very soft and brittle. With CNC machining, you can create intricate designs and complex shapes with gypsum. Also, gypsum is suitable for ornamental pieces, roofs, and theater props.
Important Factors to Consider When Choosing CNC Machining Materials
Selecting the best material for your CNC machining isn’t just about choosing either plastic or metal. Whatever material you choose affects everything, including the appearance, cost, longevity, and performance. Here are the main factors to look into when choosing the most suitable material for your CNC machining project.
Manufacturing Parts Requirements
Before you choose a material, make sure you understand the material requirements of whatever parts you’re manufacturing. Will it function under high stress, withstand very heavy loads, work in harsh or extreme temperatures?
The component’s intended strength, performance, as well as dimensional stability greatly affect the choice of material. For example, aerospace components need lightweight CNC materials that have great strength, while food-grade CNC-machined components must not be toxic and be resistant to corrosion.
Weight Requirements
Weight plays a very important role in several industries, including robotics, automotive, and aerospace. If you need a lightweight part without having to sacrifice strength, then it is advisable to choose materials such as magnesium, aluminum, or some plastics like nylon or PEEK. Also, if weight becomes an issue and you need durability, then titanium or stainless steel would be the best choice. Make sure you consider the ratio between the strength and weight of whatever application you’re working with.
Corrosion Resistance
Corrosion can reduce the lifespan of a part dramatically, most especially in areas exposed to salt, chemicals, or moisture. It is important to use materials that are resistant to corrosion for applications in food processing, medical, or marine industries. Titanium, stainless steel, as well as several high-performance plastics of high performance, such as PEEK and PTFE, provide great resistance to corrosion, ensuring that parts are safe and functional over time.
Part Applications
The use of the part largely affects your choice. For example, electronics need materials that have great insulating properties, like phenolic resins or FR-4. Medical devices may require biocompatible materials such as PEEK or titanium.
Also, automotive parts may require metals that resist heat, i.e. steel or high-performance plastics such as PPS. Having a good understanding of the part’s functional demands and operational environment is important for avoiding performance failure.
Cost
The cost of materials may vary. Metals such as aluminum are usually more affordable, while high-performance options such as engineering plastics or titanium are much more expensive. There’s a need to balance your performance needs with your budget, most especially in high-volume manufacturing. In addition, you should consider the cost involved in machining; these include cycle time and tool wear, which could be affected by the material’s machinability and hardness.
Machinability
It is not easy to machine some materials. Some softer options, such as aluminum are less expensive to machine and can be completed quickly; however, they may not have the desired durability or strength required for some specific applications. Also, harder materials such as titanium need special tooling, as well as more time for machining, increasing the costs of production. Good machinability helps to reduce the lead time and the total costs, most especially for complex parts.
Environmental Impact
Sustainability is now an increasing issue across different industries. Several materials are more eco-friendly compared to others. i.e. aluminum, which is very recyclable. Selecting materials that have a lower environmental footprint will support initiatives related to green manufacturing. Also, check if the material releases harmful byproducts while machining, like PVC fumes, and make sure that there are effective environmental and safety measures in place.
Material Properties
Mechanical properties like elasticity, hardness, and tensile strength have to align with your part’s performance requirements. For example, high-tensile strength is very necessary for load-bearing components. Also, you may require elasticity for parts that absorb shock. Based on the application, chemical resistance, electrical insulation, and thermal conductivity are also important features to look into.
Availability
It might be difficult to source some high-performance materials in the quantities or sizes required, thereby causing an increase in cost and possibly delaying the manufacturing process. Standard CNC machining materials such as ABS, aluminum, and stainless steel are available and usually offered in different grades and forms. Make sure you check the material’s global or local availability before using it for your design.
Tolerance and Accuracy of Parts
Some materials have tighter tolerances compared to others. For example, aluminum provides great dimensional stability. Also, softer plastics such as polypropylene may lose form while machining or after the process. If the design needs very tight tolerances, importantly for several parts in fluid systems or mechanical assemblies, select a material that will stay stable even during environmental changes and machining stress.
Thermal Expansion
Thermal expansion deals with how much a material experiences size changes in size when there are fluctuations in temperature. In precision applications like optical devices and components of engines, it is preferable to use materials having a low coefficient of thermal expansion, like some ceramics.
Plastics seem to expand more compared to metals, which could result in alignment or fitting problems in temperature-variable environments. This factor is very important in high-precision projects that are highly sensitive to temperature.
Product Aesthetics
There are several cases where the way the part looks is very important, as is the way it operates. For consumer products, visible machine parts should look attractive and clean. Materials such as acrylic provide optical clarity, while anodized aluminum delivers a modern and sleek finish.
Several metals and plastics also accept polishing, dyes, or coatings to achieve some aesthetic goals. How compatible the finish is, color alternatives, and surface texture should all be involved when making decisions.
Type of Surface Finish
Your surface finish of choice won’t only affect the part’s look but affects its performance with respect to wear, sealing, and friction. Several materials machine into a better and smoother finish compared to others. For example, aluminum and brass usually yield a better finish in contrast to rougher materials such as fiberglass or cast-iron composites. Also, some finishes, such as plating, painting, etc., might just be compatible with some materials. Lastly, make sure you consider your post-processing requirements when choosing your preferred base material.
Cost Implications of Different Machining Materials
You can’t determine the CNC machining cost just by machine time alone. The type of material used plays a critical role in shaping overall manufacturing expenses. Each material comes with its own price point and machining challenges, influencing cost in different ways.
Here’s how different material types impact the cost:
Common metals (e.g., mild steel, aluminum):
- Easy to machine
- Relatively low raw material cost
- Cost-effective for most applications
Harder metals (e.g., stainless steel, titanium):
- Higher raw material cost
- Increase tool wear
- Require slower machining speeds
Standard plastics (e.g., nylon, ABS):
- Fast and easy to machine
- Generally affordable
High-performance thermoplastics (e.g., PTFE, PEEK):
- More expensive materials
- Need precise, slower machining
- Often leads to higher overall costs
Brittle or composite materials (e.g., ceramics, carbon fiber):
- Require specialized tooling and techniques
- Result in higher scrap rates
- Increase machining time and complexity
Other cost-driving considerations include:
- Material availability and lead times
- Post-processing and finishing needs
- Waste management and material utilization
Impact of a Material’s Properties on Machining Techniques
CNC machinable materials usually differ in terms of their physical and chemical properties. These properties determine the machining tools and strategy to use. Also, they determine how you should set parameters like cutting speeds and the cooling system. Every decision you make during the machining process depends on the properties of the material. While some others can tolerate stress, heat, and impact, some can’t.
| Material Property | Effect on Machining | Recommended Approach |
|---|---|---|
| Hardness | Increases tool wear; requires lower speeds. | Use slower cutting speeds and wear-resistant tools (e.g., coated tools). |
| Softness | Can deform or gum up tools at high speeds. | Apply higher speeds carefully; use sharp tools and proper fixturing. |
| Brittleness | Risk of cracking or chipping at high feed rates. | Use slower feeds and precise cutting techniques. |
| Toughness | Generates more heat during cutting. | Ensure effective cooling and use durable tools. |
| Heat Resistance | Poor heat dissipation (e.g., stainless steel) increases tool wear. | Use coolants/lubricants to manage heat. |
| Elasticity | Flexible materials may deflect, causing dimensional errors. | Secure fixturing and reduce cutting pressure. |
Addressing Issues Relating to Machining Different Materials
CNC machining of materials presents different challenges, with each needing specific solutions to ensure the best results and performance. Each material behaves uniquely under specific cutting conditions. Here are some of the common machining problems and how you can solve them effectively.
| Challenge | Description | Solution |
|---|---|---|
| Material Deformation | Thin or soft materials may warp, bend, or flex during machining. | Use accurate fixturing, reduce cutting force, select proper tool geometry, and apply low feed. |
| Tool Wear | Hard/abrasive materials accelerate tool degradation. | Use coated carbide, ceramic, or diamond tools; reduce speed; ensure proper coolant application. |
| Surface Finish Quality | Surface defects vary by material — tearing, chipping, or fracturing. | Use sharp tools, high spindle speeds, shallow finish passes, and apply polishing if needed. |
| Temperature Control | Excessive heat causes expansion, distortion, and tool wear. | Use cutting fluids; if coolant is limited, reduce cutting speed or use intermittent cutting. |
| Heat Generation | Harder materials generate more heat due to resistance. | Optimize speed, feed, and depth of cut; maintain sufficient coolant flow. |
| Vibrations & Chatter | Leads to poor finish, reduced tool life, and dimensional errors. | Use rigid fixtures, reduce spindle speed, increase feed rate, use tools with variable flute pitch. |
| Dimensional Accuracy | Material behavior like expansion/shrinkage affects tolerances. | Apply thermal compensation, finish passes, and precision measuring tools. |
| Material Waste | High material costs demand efficient material use. | Use smart nesting, proper fixturing, roughing strategies, and simulate toolpaths with CAM. |
| Burr Formation | Unwanted edges form, especially in metals and plastics. | Use sharp tools, optimize angles and feed rates; use manual or automated deburring. |
| Hard Material Machining | Materials like titanium or ceramics are difficult to cut. | Use rigid machines, high-performance tools, optimize parameters, or apply advanced techniques. |
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Conclusion
It is important to choose the best CNC machining material to get the best performance, cost-efficiency, and durability. When you understand the properties of each material, as well as how they affect CNC machining, then, you will be able to make positive decisions and achieve a better product. Whatever you’re working with, be it composites, plastics, or metals, aligning your choice of material with the requirements of the product helps to achieve reliable results.
