# Development of a Staggered PCD End Mill for Carbon Fiber Reinforced Plastic
## 1 Introduction  
CFRP (Carbon fiber reinforced plastic) is widely used in high-performance applications due to its high-grade mechanical and physical properties [1; 2]. Milling is a basic machining operation of CFRP, and the inhomogeneous and anisotropic properties of CFRP present a challenge to the milling process [3]. End mills are mostly used in CFRP milling. The hard machinability of CFRP requires updates to the cutting tools [4]. The fiber of CFRP can be broken by the cutting edge and the fiber will wear the tool, which requires that the cutting edge must be sharp enough and have sufficient strength and wear resistance [5]. High milling force results in fast tool wear and low machining accuracy, so an optimized structure of the tool is preferred. As milling is an intermittent machining process, the tool should have high stiffness and stability. In short, tool structure and materials for milling CFRP should have a sharp cutting edge, low cutting force, good wear resistance and high stiffness and strength. Many studies have been done in recent years concerning the CFRP milling technique. [PERSON] and [PERSON] [6] developed ceramic end mills for CFRP machining, and the influence of flute grinding parameters and tool structural parameters are studied. [PERSON] et al. [7] proposed an evaluation method of cutting edge and machinability of inclined planetary motion milling for CFRP. [PERSON] et al. [8] studied the influence of process parameters on machining forces during milling of CFRP,and a lower feed rate at higher speeds is recommended for optimal milling operation. [PERSON] et al. [9] investigated the influences of machining parameters on cutting force and surface roughness of CFRP milling using finite element method. [PERSON] et al. [10] built a finite element model to investigate the cutting forces, chip formation, and machining damage during CFRP milling. [PERSON] et al. [11] developed two types of DLC (Diamond-like Carbon)-coated end mills with different helix angles for the side milling of CFRP. [PERSON] et al. [12] investigated the relationship between the cutting parameters, conditions and the surface integrity of CFRP. [PERSON] et al. [13] studied the correlation between weave-induced fiber undulation and delamination when milling CFRP. [PERSON] et al. [14] proposed a laser-milling method for CFRP. [PERSON] and [PERSON] [15] presented a mathematical model for the surface delamination and analyzed the influences of machining parameters in milling of CFRP. [PERSON] et al. [16] built a new cutting-forces model for down-milling unidirectional CFRP laminates. [PERSON] et al. [17; 18] proposed a mechanistic force model for milling CFRP with double helix tools. [PERSON] et al. [19] developed a roughness model by response surface methodology. [PERSON] et al. [20], [PERSON] et al. [21] and [PERSON] et al. [22] proposed optimal cutting conditions for milling of CFRP. [PERSON] and [PERSON] et al. investigated the defects generated by different machining processes, tools and machining parameters [23; 24]. Their results show that defects generated during the trimming process with a cutting tool are fibers pull-out and resin degradation, mainly located in layers with fibers oriented at \(-45^{\circ}\) and \(90^{\circ}\), and that the machined surface quality is affected by cutting speed and feed speed. However, in abrasive water jet and abrasive diamond machining, defects are streaks and not related to fiber orientation. [PERSON] and [PERSON] et al. [25; 26] also found that the mechanical strength of specimens trimmed by abrasive water-jet machining is greater than the strengths of specimens trimmed by diamond-cutter machining and conventional cutting tool machining, and abrasive water-jet machining provides greater inter-laminar shear strengths and a low dispersion on the compressive strength. In this work, the influence of tool structure on the milling defect of CFRP is analyzed, a new staggered PCD end mill is designed and the fabrication of the staggered PCD end mill is conducted.