Types of CNC Coolants: Which One to Choose?

When you run a CNC machine, heat is always a challenge. To overcome this, you need the right CNC coolant. But with so many types available, how do you choose the best for your application?

In this guide, we’ll explain what CNC coolant is, why it’s important, and the different types of CNC coolants you can use.

What is CNC Coolant?

CNC coolant is a liquid used in machining to reduce heat and friction. The friction between the cutting tool and the material creates high temperatures, which can damage tools and reduce accuracy.

It also helps remove chips from the cutting area and prevents tool wear. The right coolant can improve surface finish, extend tool life, and keep your machine running efficiently.

The Importance of CNC Machining Coolant

Using the right CNC coolant is important for the following:

• Prevents overheating and maintains material properties.
• Reduces friction between the tool and the workpiece.
• Flushes away metal chips, preventing damage to the tool.
• Protects machine parts and workpieces from rust.
• Ensures clean, precise cuts

How Does the Coolant System Work?

When your CNC machine is running, the coolant flows over the cutting area to keep the tool and workpiece cool and lubricated. At the same time, it washes away chips and debris.

After that, the used coolant collects in a sump at the bottom of the machine.

From there, a pump then moves it through a filtration system that removes metal shavings, tramp oil, and other contaminants before sending it back to the cutting area through nozzles or a through-spindle system to be used again.

There are two main types of cooling systems– a single-machine system and a central coolant system.

A single-machine system is smaller and only serves one machine. These systems don’t always have advanced filtration, so they get dirty faster and need more frequent maintenance.

A central coolant system supplies coolant to multiple machines and usually has better filtration and oil separation so it’s more efficient for larger operations.

No matter which system you use, regular cleaning and proper filtration are important to keep your coolant effective and your machine running smoothly.

Types of CNC Machining Coolants

There are several types of CNC coolants, each with different benefits. Let’s discuss further below.

Water-Soluble Oils

Water-soluble oils are a mix of oil and water, usually containing 5-10% oil. They are the most commonly used CNC coolants because they provide both cooling and lubrication.

Prós:

• They offer good lubrication, reducing tool wear.
• These coolants help prevent rust on metal surfaces.
• They work well for many different materials and machining operations.

Contras:

• Bacteria can grow over time, causing bad odors and coolant breakdown.
• Regular maintenance is needed to prevent contamination and extend coolant life.

Synthetic Coolants

Synthetic coolants contain no oil and are made from chemical compounds designed for maximum cooling. They are ideal for high-speed machining and work well with materials like aluminum and stainless steel.

Prós:

• They provide excellent cooling, reducing heat buildup during cutting.
• Synthetic coolants last longer and resist bacteria growth.
• They leave less residue, keeping machines and workpieces cleaner.

Contras:

• They don’t lubricate as well as oil-based coolants.
• Some synthetic coolants can cause skin irritation if not handled properly.

Semi-Synthetic Coolants

Semi-synthetic coolants are a mix of synthetic chemicals and a small amount of oil. They offer a balance between cooling, lubrication, and cleanliness.

Prós:

• They work well for both light and heavy machining applications.
• These coolants resist bacterial growth better than water-soluble oils.
• They provide better lubrication than pure synthetics.

Contras:

• Hard water can cause scum deposits, reducing coolant effectiveness.
• They tend to foam more than other coolants, which can affect lubrication.

Straight Oils or Neat Coolant

Straight oils, also called neat coolants, are 100% oil-based and do not mix with water. They are mainly used for heavy-duty machining and cutting tough materials.

Prós:

• They provide the best lubrication, reducing friction and tool wear.
• These coolants help achieve a smooth surface finish.
• They work well for deep cuts and slow-speed machining.

Contras:

• They don’t cool as effectively as water-based coolants.
• Straight oils can produce smoke, so proper ventilation is needed

Mist Coolants

Mist coolants use a fine spray of lubricant or a small amount of coolant mixed with air. They are often used in high-speed machining where minimal coolant is needed.

Prós:

• They reduce coolant waste and mess.
• Mist coolants are great for light-duty machining.
• They lower coolant costs and are more environmentally friendly.

Contras:

• They don’t provide enough cooling for heavy cuts.
• Less lubrication means tools may wear out faster.

Various Coolant Delivery in CNC Machines

Different CNC machines use different coolant delivery methods depending on the material, cutting speed, and required precision.

Choosing the right coolant delivery system is important because too much coolant can waste resources, while the wrong pressure can damage the workpiece or cutting tools.

Here are some of the common coolant delivery methods used in Máquinas CNC:

Mist Cooling System

The mist cooling system uses low pressure to deliver coolant as a fine mist. This method works best when heat and chip removal are not major concerns.

Because there is no high-pressure force, mist cooling does not add extra stress to the tool or workpiece. It is often used for light machining or when a small amount of lubrication is enough to get the job done.

Air Cooling System

Air cooling does not provide lubrication but helps reduce heat and remove chips from the cutting area. Since it does not use oil or water-based coolant, it is less effective than other methods.

However, air cooling is useful when machining delicate materials that may be damaged by liquid coolant. It is also a good choice for plastics, which can expand or contract when exposed to sudden temperature changes.

Minimum Quantity Lubrication (MQL) System

Many CNC shops use the MQL system to improve efficiency, reduce waste, and lower costs. This method delivers only the necessary amount of coolant in a fine mist or aerosol form.

MQL is an environmentally friendly option because it minimizes coolant use while still providing enough lubrication for cutting operations.

It is commonly used for high-speed machining and applications where excess coolant is not needed.

High-Pressure Coolant System

A high-pressure coolant system uses pressure above 1000 psi to blast coolant directly into the cutting zone. This method is highly effective for chip removal and cooling deep cavities.

It is often used in CNC drilling and other deep-cut operations. However, high pressure can damage small-diameter tools, so it is important to use it only when necessary.

This system is usually connected to a built-in coolant tank or an external coolant supply.

Machine Coolant Concentration Chart

To get the best results, you need to use the right coolant concentration for your machining process and metal type.

Each machine and coolant have different manufacturer recommendations, but here’s a general guideline for common machining operations:

Factors to Consider When Choosing a CNC Coolant

When choosing the right CNC coolant, you must think about the material, the machining speed, and how the fluid affects the environment. To know more about these factors, keep reading!

Compatibilidade de materiais

Different materials need different coolants to work properly. Hard metals like high-tensile steel create a lot of heat so you need oil-based coolants to keep them cool and lubricated. Sometimes, you might need additives to prevent overheating or fire risks.

Softer metals like aluminum, copper, and brass work better with water-based coolants. But be careful– some fluids contain chlorine or sulfur, which can stain these metals. Also, different materials produce different sizes of metal chips. Steel creates bigger chips than copper alloys so it’s easier to clean.

Machining Operation Type

High-speed operations, like milling and grinding, generate a lot of heat. You need synthetic coolants because they cool the workpiece the best.

Slower operations, like gear-cutting and threading, need more lubrication than cooling. Oil-based coolants work better for these processes. You should always consider whether cooling or lubrication is more important based on the material and type of machining.

Environmental and Health Considerations

Coolants can affect both workers and the environment. Some coolants create smoke or cause allergic reactions so it’s uncomfortable or even unsafe to work near them. Others leave a sticky residue that is hard to clean and may pollute the workspace.

To keep your workspace safe and clean, choose coolants that are both effective and environmentally friendly. The right coolant helps you machine efficiently, protects workers, and keeps the environment free from harmful substances.

Water-Based Cutting Fluids vs. High-Pressure CNC Coolants

Both water-based cutting fluids and high-pressure CNC coolants are commonly used in CNC machining, but they work in different ways.

Water-based cutting fluids are great at removing heat and reducing friction. They are also more environmentally friendly and cost-effective compared to high-pressure coolants.

However, water-based cutting tools can lead to bacterial growth over time and may cause corrosion on certain metals if not properly maintained.

High-pressure CNC coolants, on the other hand, are designed to improve cutting speeds, extend tool life, and provide better chip control. These systems use pressures above 1000 psi that’s why they are ideal for deep-hole drilling and tapping operations.

While high-pressure CNC coolants significantly boost productivity, they also come with higher costs and require regular maintenance. Operating a high-pressure coolant system also takes skill to ensure safe and efficient use.

DEK - Your Reliable CNC Machining Partner

Em DEK, we understand the importance of precision and reliability in Maquinação CNC. Our expert team is here to help you machine custom components using the right coolant. Contact us today to find the right solution for your specific application.

Conclusão

Choosing the right CNC coolant helps keep your machine cool, protects your tools, and makes cutting easier. You can use water-based, synthetic, or high-pressure coolant; however, you need to think about the material, machining speed, and how it affects the environment and your safety.

Regular cleaning and good filtration will make your coolant last longer and keep your machine working well.

FAQs

Can I use the same coolant for different materials?

Not always. Different materials need different coolants to work best. If you use the wrong coolant, your tools may wear out faster, or your parts may not turn out right. Always check what works best for the material you are machining.

How often should I replace or maintain CNC coolants?

You should check your coolant regularly to keep it working well. Watch for changes in color, bad smells, or dirt in the coolant. Most water-based coolants last between 6-12 months, but this depends on how often you use them. Testing the coolant’s pH and concentration can help you know when to change it.

Are there eco-friendly alternatives to traditional CNC coolants?

Yes! Some coolants are better for the environment, such as supercritical carbon dioxide (scCO₂) and alcohol-based coolants. They reduce waste and leave no residue. Just make sure they work with your machine.