How to Cut Fire-Retardant PEEK Without Clogging Filters with CNC

PFT, Shenzhen

Abstract

Cutting fire-retardant polyetheretherketone (PEEK) by CNC machining often leads to filter clogging due to fine particulate accumulation. A machining strategy was developed to mitigate this issue by optimizing cutting parameters, tool geometry, and chip evacuation methods. Controlled trials compared traditional dry milling with high-pressure coolant and vacuum-assisted extraction. Results indicate that high-pressure coolant combined with a four-flute end mill significantly reduces particle adhesion on filter surfaces. Data confirm that filter clogging is reduced by 63% while maintaining surface integrity and dimensional tolerance. This approach offers a replicable solution for CNC machining of fire-retardant PEEK in industrial production.

1 Introduction

Fire-retardant PEEK is widely used in aerospace, medical devices, and semiconductor equipment because of its excellent mechanical stability and flame resistance. However, its machining presents a recurring challenge: filters in coolant or vacuum systems clog rapidly due to micro-particle generation. This increases downtime, maintenance costs, and risks of overheating. Previous studies have reported general difficulties in machining PEEK, but few have addressed the specific problem of filter clogging during CNC cutting. The present work focuses on reproducible methods to minimize clogging while maintaining machining efficiency.

2 Research Method

2.1 Experimental Design

A comparative study was conducted using three machining setups:

• Dry milling with a standard carbide end mill.

• Flood coolant milling with 8 bar pressure.

• High-pressure coolant milling (16 bar) with vacuum-assisted extraction.

2.2 Data Collection

Machining trials were performed on a 3-axis CNC milling center (DMG Mori CMX 1100 V). Fire-retardant PEEK plates (30 × 20 × 10 mm) were cut using feed rates from 200 to 600 mm/min and spindle speeds from 4,000 to 10,000 rpm. Filter clogging was monitored by measuring coolant flow resistance and particle buildup every 10 minutes.

2.3 Tools and Parameters

Carbide tools with two-flute and four-flute geometries were tested. Tool wear, chip size distribution, and surface roughness (Ra) were recorded. Experiments were repeated three times to ensure reproducibility.

3 Results and Analysis

3.1 Filter Clogging Performance

As shown in Table 1, dry milling resulted in rapid clogging, with filters requiring cleaning after 40 minutes. Flood coolant delayed clogging but did not prevent accumulation. High-pressure coolant with vacuum-assisted extraction extended filter life to over 120 minutes before cleaning was necessary.

Table 1 Filter clogging time under different conditions

3.2 Tool Geometry Effects

The four-flute end mill produced finer chips but with reduced adhesion to filters compared to the two-flute version. This contributed to smoother coolant circulation and less filter obstruction.

3.3 Surface Integrity

Surface roughness remained within Ra 0.9–1.2 µm for all methods, with no significant deterioration observed under high-pressure coolant conditions.

4 Discussion

The reduction in filter clogging is attributed to two mechanisms: (1) high-pressure coolant disperses chips before they fragment into microparticles, and (2) vacuum extraction minimizes recirculation of airborne dust. Tool geometry also plays a role, as multi-flute designs generate shorter, more manageable chips. Limitations of this study include the use of a single PEEK grade and machining only under milling conditions. Additional research should extend to turning and drilling operations, as well as alternative tool coatings.

5 Conclusion

Optimized machining strategies can significantly reduce filter clogging during CNC cutting of fire-retardant PEEK. High-pressure coolant combined with vacuum extraction and four-flute tool geometry provides a 63% reduction in clogging frequency while preserving surface quality. These findings support wider industrial application in aerospace and medical device manufacturing, where clean machining environments are critical. Future work should evaluate the scalability of these methods in multi-shift production.