CNC Dust Collection-How to Build the Perfect System

CNC Dust Collection-How to Build the Perfect System

CNC Dust Collection-How to Build the Perfect System

If you are a hobbyist or small shop owner who owns a CNC router, there's nothing that would make your life easier than a working CNC dust collection system.

The dust and debris produced while cutting using a CNC router can substantially affect the router's performance and also your health.

Large-scale shops have custom-built elaborate dust collection systems that collect dust and debris from multiple machines and tools.

If you are a hobbyist or small shop owner, designing a dust collection system can appear overwhelming.

In this article, I discuss everything you need to consider for creating the perfect dust collection system for your shop.

Dust Collector or Shop-Vac for CNC machines?

Dust Collector vs Shopvac
Dust Collector vs Shopvac

Dust collectors and shop vacs are different classes of equipment. The primary goal of both systems is dust collection, but they differ in various aspects.

Shop vacs are designed to be used intermittently and clean up the debris in intervals during the machining process. 

Dust collectors are designed for continuous operation for prolonged periods. Further, they can be used for multiple tools and stations simultaneously with an elaborate system of ducts.

CNC machines are used when you require automation. A dust collector becomes an obvious choice for such an operation as you do not need to perform dust collection manually.

Dust collectors are significantly more expensive than shop vac systems. But the efficiency of a shop vac is higher than most dust collectors.

However, for small operations like engraving and cutting small workpieces which require short periods of operation, a shop vac is the economical and efficient choice.

If you operate 4x8 CNC router machines then you are likely to work with full-size sheet materials.

You definitely need a dust collection system in that case.

Building a CNC Dust Collection System

There are three parts to a CNC dust collection system:

These three components function together to keep the work area clean and help improve the efficiency of your CNC router machine.

Part 1- Picking the CNC Dust Shoe

Dust shoe
Dust shoe

CNC Dust shoes attach to the spindle or gantry and surround the immediate area around the cutter.

They have a curtain made of brush or flexible material that prevents the dust and debris from flying off and contains them within the dust shoe.

You can connect the dust shoe to a dust collector to remove the dust contained within the dust shoe. This prevents the dust and debris from spreading and maintains a clean work surface.

Sometimes instead of a dust shoe, you have a dust shroud.

Dust shrouds are similar to dust shoes in function.

The difference is that the curtain surrounding the dust shoe in shrouds is made of narrow sheets of fabric, plastic, or silicon loosely hanging from the edges of the dust shoe.

Whereas in dust shoes the curtain is made of brushes.

You must keep in mind the following parameters while choosing a dust shoe for your CNC router.

1. Shoe size

Shoe size is an important factor to be considered while selecting a dust shoe. It depends upon the size of the tool you are using and the process.

When using tools with large diameters, more chips and dust are produced; hence they require a large dust shoe.

Make sure the shoe is large enough to hold all the dust and debris produced while cutting.

2. Vacuum Port Size

The dust and debris contained within the dust shoe is evacuated through the vacuum port using a dust collector.

Make sure the vacuum port is large enough to accommodate the required duct size. For example, a 4" duct is needed for large debris. If the dust and debris size is small, you can use a 2.5" port.

3. Length of the brush

The length of the brush determines the effectiveness of the dust shoe. Therefore, make sure you select a brush size that is slightly longer than the length of the tool when it touches the surface.

Most dust shoes are height adjustable so set the height of the shoe in such a way that no gap exists between the brush and the surface.

If there is a gap between the surface and the brush, dust and debris can escape through the gap.

If the length is too large, the compression on the brush will be more, which will cause more restriction on the movement of the spindle over the workpiece.

4. Material of the brush

The brushes for dust shoes can be made from different materials. Some common materials for dust shoe brushes are nylon, plastic, horsehair, and silicon.

Among these materials, nylon is preferred by most CNC router users due to its durability, flexibility, and cost.

Choose a brush that has enough rigidity to stop the debris from flying away and, at the same time, enough flexibility to allow smooth travel over the work surface.

If you use a brush with high rigidity, the brush may get stuck when the direction of movement is reversed.

5. Build

Dust shoes are made from various materials that include aluminum, ABS, HDPE, plywood, acrylic, and polycarbonate.

The dust shoes are typically installed onto the spindle on the Z-axis or onto the Z-axis gantry.

Ensure the dust shoe does not add much weight to the axis or the gantry, as this can affect the accuracy of the machine.

I always prefer a lightweight construction for your dust shoe. Further, a see-through material like polycarbonate or acrylic will allow you to monitor the cutting process.

6. Mounting

Dust shoes typically come in two parts, a mount and the detachable dust shoe. Such a design helps in easy removal and attaching of the dust shoe when tool changing is required.

The mounts can be fixed to the gantry or the Z-axis. You must prefer attaching the mount to the gantry.

If the mount is attached to the Z-axis, it will add additional load on the Z-axis and affect your CNC router's performance. 

Part 2- CNC Dust Collection Hose

The hose is what connects the dust shoe to the dust collector.

The size and material of the piping have a huge effect on the efficiency of the system.

The hose is also called as duct.

Vacuum hose
Vacuum hose

All the dust and debris from the dust shoe travels through the hose into the dust collector.

1. Diameter of the Hose

The diameter of the hose has a direct influence on the velocity of airflow. Smaller the diameter, the higher the velocity.

Velocity and pressure are inversely proportional, and a higher velocity translates to lower pressure.

When low pressure is created, air will try to gush in to equalize the pressure drop, and this causes a higher amount of suction.

The diameter also depends on the size and quantity of the dust and debris created by your machining process.

The typical range of duct size required for hobbyists and small shop applications range between 2.5" and 4".

For a single machine that produces moderate amounts of dust and debris, like machining aluminum or plastics using a Shapeoko or similar models, you can use a 2.5" duct.

If you are woodworking using an Avid CNC machine with a 4 hp spindle or more, a 4" system would be a better choice.

2. Length of the Hose

The more the length of the duct, the more is the surface area that the air comes in contact with. Hence the length adds resistance to the airflow.

Keep the length as short as possible. But, at the same time, ensure that there is enough length for your CNC router to perform smoothly.

If you need long ducts, use a duct with a large diameter and reduce the diameter at the CNC router side using a reducer. 

A larger diameter will reduce the resistance but will reduce suction. But, the reducer used at the router side will increase the suction.

3. Mounting 

Make sure you mount the ducts away from heat sources and moving equipment. It is best to route the ducts through walls using brackets.

Leave enough slack when you are placing brackets, as this will help you modify the ducting if needed.

If you need bends in the ducting, the ideal angle for bends is a maximum of 60°. However, if required, you may make bends up to 90°.

It is always best to avoid bends greater than 90° as this will reverse airflow direction and cause unnecessary energy loss.

When attaching the duct to the dust shoe on your CNC machine, an overhanging duct is a better choice.

An overhanging duct produces the least amount of resistance to the gantry movements.

You can use a bracket suspended from the ceiling directly above the center of your CNC router's work area to direct the duct to the router.

4. Material of construction

Typically vacuum ducts are made from plastics or PVC. However, certain applications like large-scale milling of metals would require metallic or hard ducts.

Metal chips can be sharp, and when they travel at high speeds, they can tear through the duct, especially at the bends.

For most hobbyists, small shop applications, and woodworking a plastic construction is sufficient. 

5. Grounding

Duct with ground wire
Duct with ground wire

When the dust particles move inside the ducts, they rub against the surface of the ducts. This creates static charge buildups on the ducts.

Static charge buildups are a shock hazard. If you come in contact with the ducts, there is a risk of you getting an electric shock, but it won't be anything major.

However, if the static charge buildup on the ducts were to discharge through sensitive electronic equipment, it can cause damage to such equipment.

You must make sure that the ducts are properly grounded. A good way to ensure this is to run a copper wire along the entire length of the duct and connect it to the metallic body of the dust collector.

The body of dust collectors is usually grounded through the earth terminals, and you can use them to ground the ducts.

Part 3- Picking the Dust Collector

Single-stage dust collector
Single-stage dust collector

Dust collectors are powerful vacuum pumps that suck air in from the dust shoe via the hose. 

The dust and debris contained within the dust shoe is sucked into the dust collector and is stored inside it. 

While selecting a dust collector for your CNC machine, you must keep the following factors in mind.

1. Power of the Dust Collector

The power of the dust collector determines how quickly it can remove dust from your work area. 

You might think that more power is always good. But, that is seldom true. So, what is the use of more power if you were never to use it?

A typical one-person shop would require a dust collector with a maximum power of 2 hp. However, if you want to operate multiple machines and tools simultaneously, you can use dust collectors with higher powers.

However, for a single machine, a 1.5 hp collector can provide sufficient suction.

2. Type of Dust Collector

Single-stage dust collector: These dust collectors suck in air from the work area directly into a collection bag. The dust and debris are deposited in the bag, and the air is pushed out via a filter.

In single-stage collectors, the chips and dust come in direct contact with the impeller blades of the motor and can damage the motor.

Furthermore, the air leaving the collection bag has more dust which can clog the filter and need you to change or clean the filter more frequently. 

Two-stage dust collector: These collectors have an additional dust collection stage that separates large particles and chips before entering the dust collector.

For separating large particles and chips, a cyclonic separator is used. The air from the work area enters the separator and is swirled around, the heavier particles fall to the sides, and clean air leaves the chamber through the center.

The advantage of 2 stage collectors is that the impeller is protected from debris from the work area.

Additionally, the air that reaches the filter has less amount of dust in it and extends the filter's life.

3. CFM of Dust Collector

CFM stands for Cubic Feet per Minute. It is the volume of air that is evacuated by the vacuum in a minute.

The CFM of the dust collector determines the suction and the amount of dust that is cleared out per minute.

If the CFM is too low, all the dust produced will not be cleared out and spread out into the surrounding area.

Ideally, for cutting wood on a single CNC router, you will require a dust collector with atleast 400 CFM of evacuation.

Machining metals produce chips rather than dust, and they do not demand high CFM as wood and other soft materials that produce fine dust.

4. Filter size

The filter size is measured in microns. It determines the size of particles that the filter will allow to pass.

You can use a filter with a size of fewer than 4 microns with your CNC machine as that will stop most particles.

You must also note that as the filter size reduces, the frequency you need to clean or change them also increases. This is because smaller filters tend to clog up more easily. 

The size of the filter also determines the quality of air that is expelled out of the dust collector.

If you are machining materials that produce harmful fumes, you will require cartridge filters with a filter size of around 0.3 microns.

5. Exhaust air setup

The air sucked in by the dust collector is also dumped out. Consider the setup of your shop before deciding on the dust collector.

Check whether you can direct the exhaust air outside the shop and into the open air. The exhaust will be noisy, so letting it out near a neighbor is not a good idea.

It would be better if you can find a spot for letting the air out into the open. However, if you are forced to let it out inside your shop, you will need to use HEPA filters at the exhaust.

The exhaust air can have fine dust particles that could be toxic depending on the material you are cutting, and inhaling them could be dangerous.

A HEPA filter will filter out most particles and fumes and give you clean, breathable air.

In conclusion, choosing a dust collector depends on the requirements of the projects you intend to undertake, the material removal rate of your CNC router, and the setup of your workplace.

If you consider the factors discussed in this article, it will help you immensely in selecting a good dust collector for your CNC applications.

Why Do CNC Routers Need Dust Collection?

1. Health Hazard

Various dust particles pose health hazards to the human body. The dust particles suspended in the air can settle down on our skin, or you may inhale it. 

When the dust from certain materials like some woods settles on your skin or eyes, it can cause irritation, itching, or allergic reaction in that area.

Some common skin problems caused by CNC dust are acne, rashes, redness, itching, dryness, and scaling.

Some materials can be toxic, and CNC routing produces fine dust particles, and these dust particles, if inhaled, can cause short-term and long-term respiratory problems.

Further, if you have respiratory problems, inhaling dust from CNC routers can elevate such problems.

Therefore, to prevent such eventualities, you must use a dust collection system or wear masks while using your CNC router.

Wood Health Effects
Alder (common, black, red)Dermatitis (black alder), decreased lung function (red alder)
BeechDermatitis due to lichens on the bark of beech trees, rhinitis, asthma, nasal cancer
BirchIrritant dermatitis
Cedar (western red)Asthma, contact dermatitis, allergic reactions, decreased lung function, eye irritation, rhinitis
Fir (grand, balsam, silver, alpine)Skin irritation, dermatitis, rhinitis, asthma
MahoganyDermatitis, allergic reactions
MapleRhinitis, asthma, Maple Bark Stripper’s disease
OakNasal cancer
Pine (white, lodgepole, jack)Skin irritation, contact dermatitis, rhinitis, asthma
PoplarContact dermatitis, allergic reactions
RosewoodEczema, allergic contact dermatitis
SpruceSkin irritation, decrease in lung function
TeakToxic, dermatitis, allergic reaction
Walnut (black)Skin irritation, rhinitis
YewIrritation of skin, dermatitis

Possible Health effects of some common woods

2. Fire Hazard

Concentrated clouds of dust suspended in the air are highly combustible and burn explosively.

The particles are small enough to ignite spontaneously, and the amount of air available makes it burn instantly.

This can cause severe injury to you or the person working in the room. 

A dust collection system will prevent such instances from happening.

A messy CNC router
A messy CNC router

3. Equipment Performance

The presence of dust can affect the performance of your CNC router and other equipment in your store.

The dust and debris can lodge between the moving parts of your router, jamming it and affecting its accuracy.

The dust buildup on tools in your shop can reduce the tool's life and cause performance issues. The tools most affected by dust are the rotary tools.

Frequently Asked Questions (FAQ)

How many cfm of dust collection does a cnc router need?

Ideally, for cutting wood on a single CNC router, you will require a dust collector with at least 400 CFM of evacuation. The CFM of the dust collector determines the amount of dust that is cleared out per minute. Low CFM can result in dust escaping out.

What size ductwork should be used?

You should use a duct that is as big as the inlet of your dust collector and run it to your CNC machine. If the dust shoe on your CNC router requires a smaller diameter you can use a reducer to match the diameter of duct and dust shoe.

You must not use a duct with a smaller diameter than the inlet of dust collector for the entire length. A reduced diameter should only be used at the CNC router end.

Should the ductwork be glued together?

Typically, ductwork for dust collection are not glued together. The ducts and connectors usually have a snug fit, which is enough to provide a leak free conduit for air.

If your ductwork is prone to loading or other stress you may use glue. But, gluing down the ductwork would make it difficult for future modifications and upgrades.

About John

Hey I'm John. I talk about CNC's and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNC's and writing about CNC's for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNC's. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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John

Hey I'm John. I talk about CNC's and Power Tools at Mellowpine. I'm a CNC hobbyist who has been making CNC's and writing about CNC's for a while. I currently also work as a consultant for business owners and hobbyists setting up their own CNC's. If you have any questions related to CNC, I'd be happy to answer them. Reach me at john@mellowpine.com

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