Choosing the Right Material for CNC Milling & Machining

CNC milling is manufacturing where computers are used to operate the drilling machine to shape the material into the desired object. It does this using a milling cutter attached to rotating spindles, which cut into the material of your choice. CNC stands for “computer numerical control”, meaning each part of the device follows instructions from a computer program. This ensures total accuracy of what you’ve instructed the computer to design.

CNC Milling Machine Types

CNC milling machine types can be classified into two categories: CNC vertical machining centers (VMCs) and CNC horizontal machining centers (HMCs). CNC VMCs are installed vertically or at an angle. CNC VMC bed sizes range from 6-ft up to over 10-ft, enabling the CNC mills to work on large CNC parts. CNC HMC bed sizes, however, are much smaller as CNC HMCs are installed horizontally or level to the ground.

The Materials for CNC Milling and Machining

These are typically divided into two main categories: soft and hard. The CNC milling machine uses a tool bit to cut, shape, or make a desired item from the stock material. Tool bits come in different shapes and sizes depending on what it is designed for. CNC machining of wood and plastics requires using CNC milling tools with very sharp edges, while CNC milling of metals requires the CNC milling tools to have a very hard surface, as it is used for cutting and carving.

Why Choose a Specific Material for Your Project?

Choosing the right material for CNC milling and machining is very important. CNC machines are used to cut away materials, so having a sturdy yet consistent material will mean that your project comes out perfect. Keep in mind that the material you use will dictate what type of drill bit you’ll need.

You can contact a CNC milling service to learn more about specific materials. 

How to Select the Right Material for Your Project

One of the first things you do when manufacturing is deciding what material your item will be made of. CNC milling is no exception to this, and CNC mills come in various sizes, speeds and accuracies. This means that different CNC mills are better suited for different materials.

Selecting the right CNC material can be a complicated process depending on what your CNC machine is capable of. For example, if you have a CNC milling machine that can drill extremely precise pockets in a material, you would be restricted in what materials may be used for the project.

There are quite a few different CNC milling materials on the market. Some examples are outlined below:

  • Acrylic: Cuts accurately, and usually requires cooling. Abrasive cut-off wheels can achieve the best result. This material is heat and water-resistant and also cuts smoothly.
  • Sintra or PVC: Cuts are sharp and require cooling. To get the best outcome, abrasive cut-off wheels should be used. Cuts very easily.
  • PVC Foam Board: Cuts well and does not require any cooling because of the low cutting speeds required for this material. Not very durable unless sealed properly.
  • Cedar Wood: Cuts very well on CNC routers. Cuts at high speeds, so it needs cooling in order to prevent burning.
  • Birch Plywood: Cuts well on CNC routers. With a cutting speed of 400 to 600 mph (644 to 966 km/h) required, it is critical that the blade be cooled in order to avoid burning. Cuts are as smooth as glass.
  • Aluminum: Cuts at high speeds, and also needs to be cooled in order to prevent burning. Cuts are smooth and uniform. Requires a hard drill bit, otherwise it will dull quickly. Cuts at a maximum depth of 0.125 inches (3.175 mm)
  • Brass: Cuts well on CNC routers. Cuts at high speeds so it needs cooling in order to prevent burning and can cause tool breakage if the cutting speed is too high.
  • Steel: Cuts well on CNC routers. Cuts at high speeds so it needs cooling in order to prevent burning and can cause tool breakage if the cutting speed is too high. Cuts at a maximum depth of 0.25 inches (6.35mm).

A CNC routing bit made of a harder material (such as HSS or carbide) is more suitable for CNC machining steel on CNC milling machines, whereas softer materials (such as aluminum oxide ceramic and polycrystalline diamond ) are more suited to CNC machining plastics.

Tips on How to Pick the Best Material

Certainly, you’ll want to have the best results when milling an item, so deciding which material to use is paramount. CNC mills can be used on many materials, and here are some tips to help you pick which material is best for CNC milling.

Follow these three simple steps of the material selection procedure:

  • Step 1. Determine the material needs. For example, this includes things like construction materials, insulation levels; as well as cost and surface quality. Consider the part’s environment and the components it will contact.
  • Step 2. Choose a few materials that meet your design criteria.
  • Step 3. Select the material. When it comes to design planning, there will almost always be a compromise between two or more of them, according to cost-effectiveness, durability, etc.

Common Mistakes When Selecting a Material for CNC Milling

  • 1. Using the wrong material for CNC milling in your application, which can damage not only the material but the mill itself.
  • 2. Choosing a low-quality material that will not last.
  • 3. Using the incorrect CNC mill speed and feed, which can cause damage to your CNC mill or affect the quality of CNC milling results. It is always advisable to perform a simple test cut on a representative sample using the same parameters as those required in CNC milling in your design.

Conclusion

CNC milling can create almost any shape imaginable with the right CNC milling tools, but the material that CNC milling is machining must be chosen carefully so that it does not break under CNC milling forces.

Material choice for CNC milling and CNC machining can be quite difficult if you’re new to CNC. CNC milling machines are designed for machine-specific types of materials, and CNC milling materials should be chosen according to the material that the CNC mill is designed for.

Adam Hansen