Practical Knowledge

Cutting Styrofoam with CNC Hot Wire

EPS is the easiest material for hot wire cutting - but correct settings still matter.

EPS - The Ideal Material for Hot Wire Cutting

EPS Styrofoam is the most commonly used material in CNC hot wire cutting. It melts evenly, is forgiving of minor setting errors and can be cut at high speed. Nevertheless the basic rules apply here too: correct cutting speed, correct cutting gap and the shortest possible wire length. Anyone observing these three factors consistently achieves good results with EPS.

Guideline Values for EPS and Styrofoam

Cutting speed: approx. 450-500 mm/min
Optimal cutting gap: approx. 2 mm
Wire length: as short as possible for the workpiece size
Temperature: set practically on the material - no fixed value
At higher density: reduce speed or increase temperature
Fresh blocks: let dry for at least 48 hours before cutting

How the Setting Is Done in Practice

The setting procedure is always the same: first set the cutting speed to approx. 450-500 mm/min. Then make a short test cut and observe the cutting gap. If the gap is smaller than 2 mm, increase the temperature. If it is larger than 2 mm, reduce the temperature. Repeat until the cutting gap is a consistent approx. 2 mm. This process takes only a few minutes and prevents scrap in production.

Density Affects the Setting

EPS comes in various densities - typically 15 to 30 kg/m³. The higher the density, the more heat the wire needs to melt the material away cleanly. With heavy EPS, either reduce the cutting speed or increase the temperature until the optimal cutting gap of 2 mm is reached. The guideline values serve as a starting point - always set practically on the actual material.

EPS vs. XPS - the Most Important Difference

EPS is considerably more forgiving of small setting errors than XPS and Styrodur. That does not mean the settings do not matter - but there is more leeway. Important: never transfer EPS settings to XPS. XPS needs a slower speed (350-400 mm/min) and reacts more sensitively to long wire lengths.

Common Mistakes When Cutting EPS

EPS also has its typical mistakes. The most common one: setting the temperature too high in order to cut faster. The result is too large a cutting gap - surfaces become rough. Second common mistake: cutting fresh or damp blocks straight away. Damp EPS blocks have uneven cutting resistance - dimensional deviations occur. Third mistake: choosing an unnecessarily long wire length. With EPS too, a short wire produces better results than a long one.

Frequently Asked Questions

The key questions and answers on this topic.

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How do I cut styrofoam with the hot wire?

Set the cutting speed to approx. 450-500 mm/min, make a test cut, observe the cutting gap and adjust the temperature until approx. 2 mm gap is reached. Choose the wire length as short as possible.

What is the correct speed for EPS?

For EPS and styrofoam we recommend approx. 450-500 mm/min as a starting point. At higher density, reduce the speed. Always set practically on the material.

What is the difference between EPS and XPS when cutting?

EPS is more forgiving than XPS and can be cut at a higher speed. XPS needs a slower speed (350-400 mm/min), a shorter wire length and more precise temperature setting.

Why should I let fresh EPS blocks dry?

Fresh EPS blocks can be damp inside. Damp areas have different cutting resistance - dimensional deviations occur. Let them dry for at least 48 hours before cutting.

Can I cut all EPS grades with the same settings?

No. Different densities require different settings. Always make a test cut and adjust the temperature until the optimal cutting gap of 2 mm is reached.

Getting started in EPS production

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