What Is The Difference Between A CNC Mill And A CNC Router?

We have covered CNC routers and helped folks learn to make money from their garage with a CNC router. 

CNC machining is experiencing increased popularity in both manufacturing facilities and small hobby shops.

Adding CNC capabilities to your business can unlock new profits.

As you shop for your first CNC router, you are going to run across CNC milling machines. Here is an overview of them, with a comparison of their features.

A CNC router uses higher rotational speeds to make faster cuts in softer materials such as wood and plastic. A CNC milling machine uses lower rotational speeds and more torque to mill steel and thick metals.

What Does CNC Mean?

CNC means computer numerical control. CNC machines receive a set of coordinates, generally inputted from a computer. It then performs a series of cuts based on those programmed instructions.

In most cases, the product will be designed using Computer-Aided Manufacturing (CAM) or Computer-Aided Design (CAD) software such as AutoCAD. A CNC machinist will then extract the coordinates from that software and input them into the CNC machine.

What Are CNC Machines?

CNC machines are computer-controlled lathes or routers that mill, cut, drill, and grind raw materials such as aluminum, steel, plastic and wood to create new products for the end-user.

Since the material is removed to create a new end product, this is called subtractive manufacturing. A CNC milling machine removes material instead of adding material as a 3D printer would (additive manufacturing).

All aspects of the CNC machine are programmed into the coordinates are on an x-y grid (and some large machines also have a “z” grid for 3-dimensional milling.). But more than just the location of the cuts, the programmed instructions encode the rate of movement, drilling depth, speed of rotation and the path of the cutting head.

Both have similar functions. We will discuss the key differences.

CNC Routers

CNC routers are designed to handle sheet materials. Rarely, this includes a lathe that spins the material while the router head moves above it.

The CNC router is used to cut softer materials. These are popular for wood, plastic, foam, soft metals, and acrylic. Generally, the material will be clamped to a larger surface, and the cutting heads will move around it in an x,y,z Axis.

The cutting tool also spins at high speeds. It may spin at 20,000 RPMs to perform a cut in plywood, where a mill might move at only 1,000 RPMS when working in steel.

CNC Router Summary:

  • More Affordable
  • Only the spindle moves around a stationary workpiece
  • Used to cut soft materials including wood, foam, plastic and aluminum
  • Cuts along X, Y-axis and sometimes also a Z-axis
  • The Head operates at a high rotational speed
  • Less Torque
  • It can be outfitted with a laser cutter

Routers tend to use a gantry frame design, while mills have the more durable C-frame structure. The gantry moves the bit in the x and y-axis with some limited ability to move on the z-axis.

A CNC router replaces the router work that a carpenter would generally do. This automation can speed up the woodworking shop.

Router Workspace Area

The CNC router uses a wide flat work area suitable for carving signs and even large acoustic wall panels. They tend to have less Z-axis, limiting the thickness of the wood for which they are suited. This makes the CNC router better suited for thin board work such as cabinets and signs. They are not as suited for large wood blocks and for carving 3D shapes (although specific models can be purchased for these tasks at a higher price point.)

The router can use various cutting bits, and it is important to match the bit-type with the routering task being performed. Some of the bit examples would include rabbeting bits, beading bits, chamfer bits and straight bits. Each bit is going to have a maximum speed that makes it ideal for the task.

Spending more money on a higher-quality bit can prolong their usability, decrease downtime for bit changes, allow fore resharpening, and decrease chatter and artifacts on the finished product.

CNC Milling Machines

bridgeport torqcut1 cnc milling machine

While the CNC mill can perform many of the same functions as a CNC router, CNC mills tend to be used for metalworking. The cutting heads tend to move more slowly, emphasizing torque and power instead of speed.

They way hundreds of pounds more than the router does.

CNC mills do not use a stationary table. Instead, these machines hold the material and can rotate it to any angle so that it is accessible by the cutting head. These CNC mills move in an X-Y pattern above the workpiece.

While operating speeds are slower, it means they can perform thicker cuts in harder materials.

CNC Mill Summary:

  • Used to cut hard metals and tougher materials
  • Workpiece moves
  • Used for thicker cuts
  • Slower operational speed
  • Has Increased clearance over Z-axis
  • Makes cuts using higher torque
  • More precision
  • Better for complex shapes

CNC Milling Machine WorkSpace Area

The CNC mill has a large central chamber that admits larger pieces of source materials. Generally, there are plexiglass covers over this area to protect the operator from flying debris. This Axis design allows for a greater Z-axis clearance.

Often a CNC mill can flip the material, letting it be carved on multiple surfaces. Most of the machine is constructed from die-cast iron to provide the structure needed for the high-torque operation.

A Milling machine uses an end mill instead of a router bit. These milling cutters look a lot like drill bits and deliver the added torque of the CNC mill. These end mills come in common configurations, such as flat or ball end mills. These influence factors such as chip load and feed rate.

Ultimately, the operator and the quality assurance team must inspect each product to check for bit wear that can create defects. In some cases, bits will need to be swapped multiple times in one milling session.

Working with metal takes more practice and more oversight from a trained CNC operator.

CNC Router Vs Mill – Choosing The Correct Machine

image of vertical milling machine

Both machines remove human error, improve accuracy and makes it easy to produce highly replicable products. Both machines create complex products that cannot be easily made by hand. From automotive brackets to cabinet doors, these machines save thousands of person-hours and increase profitability.

Both machines give you the accuracy of being a Computer Numerical Control. CAD software removes human error and provides a high amount of repeatability to the supply chain.

Parts can be cut to exact specifications. Measurements can be inputted exactly, and complex cuts can be executed flawlessly, making it possible to create unique, limited-run parts with a fraction of the workforce previously required.

CAD software requires highly skilled and highly paid individuals. However, the CAD designs can be input into the machines by lower-paid machinists, lowering the overall labor costs for an organization.

Both machines are loud and require a dust capture system. Operators need to wear proper protective equipment, and the machines and operating area will need daily cleaning to remove product shaving build-up.

During operation, machines should be closely observed for shaking and skipping. The CNC machinist needs to know how to stop the machine, resolve errors, and restart it without losing its spot.

The main difference is that a CNC Router is designed for flat, soft, thinner materials. A CNC mill is designed for thick and metal material.

  • Materials – A CNC router is best for soft materials such as wood, plastic and foam. A CNC mill is best for hard materials such as steel, titanium, cast iron and brass.
  • Speed – A CNC router is the fastest option. If you need many copies of a part, a router will cut those quickly. A CNC mill is going to move more slowly and with greater precision.
  • Accuracy – While both tools offer a high degree of accuracy when used at the proper speed and with the proper bits, A CNC mill provides greater accuracy. A mill can cut on multiple axes and provide more intricate designs than a router will do. The precision of either tool will be dictated by the accurate parts of which they are constructed. For example, THK rails are more accurate than round rails on a CNC router.
  • Cutting Area – The largest routers can handle flat material 5 feet by 8 feet or larger. However, they don’t generally offer much drilling depth. For greater depth, a milling machine is the better option. The CNC mill has a greater Z-axis, which allows for more 3D work.
  • Expense – While both machines are available in a wide array of price points, CNC routers tend to have the most affordable entry-level models for DIY use

Why You Need Both

The first thing you noticed about the difference is e type of materials each handle.

A CNC router is going to be the better choice in woodworking. It lets you offer a better product than your competitors. CNC routers provide a deep level of intricacy from cabinet doors to signage, drawer fronts, and chair spindles.

CNC mills tend to be used for creating components that will be used in other products. From aircraft gearing to automotive brackets, the CNC mill allows for the complex milling of high-value products. The significant difference is that CNC mills have greater rigidity but a smaller work envelope than routers.

All machines are a compromise in functions. It is a matter of getting the right tool for the type of job you perform most.

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