Styrofoam CNC milling: end bits, settings, and advices

Contents:

We had an article about CO2 laser foam cutting and now let’s talk about CNC routers. They are suitable for this kind of operation as well. Here, we will tell you which end mills to use, how to set the equipment, and give you some advice.

What is styrofoam?

Styrofoam is a foamed plastic. There are many densities and rigidities of foam. In general, its composition of air-filled plastic cells accounts for the material’s remarkable low weight. Foam serves both thermal and acoustic insulation purposes. Additionally, if this material becomes damaged in any way, spackling may easily fix it. Foam also may be painted, and etc. It will function like brand-new.

So, there are different types of this material, each serving different purposes. The most common ones to be processes on the CNC router machine are:

1. Expanded polystyrene (EPS). It consists of only 2% polymer and 98% air. This material is excellent for thermal insulation and is also easily recyclable.
2. Extruded polystyrene (XPS). In this case, there is less air, and this type of foam can be colored. As a result, it is inherently heavier.

What it is being used for

The application depends on the type of foam and its characteristics. However, the main areas where it is used include:

• Packaging;
• 3D letters, logos, and advertising: Unlike similar items made of wood, these are lighter, cheaper, and faster to produce;
• Interior and architectural elements: This includes columns, cornices, moldings, balusters, railings, and more. Sometimes, they serve as substitutes for plaster forms;
• Thermal insulation: Foam is used as one of the components in wall insulation;
• Decorations for events, celebrations, theater, or film.

Specifics of milling process

The first thing to note is that foam, like plastic, can burn. It is a flammable material, so its temperature must be carefully monitored. For the operator, this means carefully selecting the settings and tools for CNC milling styrofoam.

End mills

The tool should not overheat; otherwise, it will start melting the material. Therefore, for styrofoam CNC milling in this case, we recommend using single-flute end mills with a large chip removal space. Why?

Firstly, they have a better chip removal. A single-flute end mill removes chips more effectively, which is crucial when working with foam. Poor chip removal can cause them to stick firmly to the tool, which may then heat up.

Secondly, it allows you to avoid uneven wear. Multi-flute instruments can dull unevenly, leading to tool vibration. This can result in poor-quality cuts or increase the risk of ignition due to friction.

Also, it’s best to use tools made of high-speed steel or hard alloys. End mills made from polycrystalline diamond are also suitable.

Settings for styrofoam CNC milling

Knowing all the details about foam mentioned above, let’s look at the settings. You’ll need to find the optimal balance between spindle speed and tool feed rate.

1. It’s better to cut foam in two passes for higher quality and lower risk.
2. The recommended spindle speed for working with foam is between 14,000 and 17,000 RPM.
3. The feed rate can be set between 50 and 100 mm/s. Adjust as needed, and if necessary, proportionally reduce both the feed rate and spindle speed.

One more important detail: it’s best if your end mill does not extend more than 20 mm from the clamp. This reduces vibrations and improves work quality.

Extra information

What else is necessary for efficient and safe styrofoam CNC milling?

1. Aspiration system. It  is an industrial stationary vacuum cleaner with a hose and a brush that are attached to the spindle. It helps remove flammable chips and keeps the workspace safe and tidy. Invest in a good, powerful system.
2. Vacuum table. Foam is a very lightweight material that the spindle can easily displace during operation. Thus, it must be securely fixed on the worktable. Clamps might not be suitable, as they can damage the material during the process. For this reason, we recommend using a vacuum table. It holds the material firmly, touching it only from below.

You can contact our managers for more information about the vacuum table. It can be installed on a Wattsan CNC router machine upon request.

3. Cooling system. You can use a thin stream of air from a compressor to cool the material, ensuring there’s no risk of ignition.

CNC router machines for styrofoam milling

Let’s look at a few examples of machines suitable for working with this material. The choice should be based on the typical sizes in which foam is available in the market. It often comes in dimensions ranging from 30×15 cm to 30×60 cm and from 60×60 cm to 60×125 cm.

Therefore, we recommend three models: the desktop, compact routers 0404 Mini and 0609 Mini, and the larger router 1313 A1.

Mini series are good for both hobby and small business. Their dimensions allow them to be placed on a table or floor inside home, warehouse or office. Wattsan 0404 and 0609 have cast iron bad to provide stability and minimum vibrations. The spindle power is 1.5 kW and 2.2 kW respectively. Both machines have HIWIN 20 mm guideways in the X and Y axes, inductive sensors, NS studio control system, and ball-screw system.1313 A is a bigger model for a production with larger loads. Power here starts at 2.2 kW but may be increased by the wish of the client. Dimensions of the working table allow processing of big styrofoam workpieces. Also, thanks to the ballscrews on Wattsan machines, it is possible to install a more powerful spindle with an increased Z-axis lift of 100 mm, which is very useful when we are talking about thick foam.

Conclusion

1. Styrofoam is a foamed plastic. There are many densities and rigidities of foam. In general, its composition of air-filled plastic cells accounts for the material’s remarkable low weight. Foam serves both thermal and acoustic insulation purposes. However, foam, like plastic, can burn. It is a flammable material.
2. The tool should not overheat; we recommend using single-flute end mills with a large chip removal space. Also, it’s best to use tools made of high-speed steel or hard alloys. End mills made from polycrystalline diamond are also suitable.
3. It’s better to cut foam in two passes for higher quality and lower risk. The recommended spindle speed for working with foam is between 14,000 and 17,000 RPM. The feed rate can be set between 50 and 100 mm/s.
4. it’s best if your end mill does not extend more than 20 mm from the clamp. This reduces vibrations and improves work quality.
5. Use a good aspiration and cooling system. Also, it’s important to make a good fixation of the material. Use clamps or a vacuum table. The last one is recommended.