# Micro-Slit Cutting in an Aluminum Foil Using an Un-Traveling Tungsten Wire
## 1 Introduction  
Aluminum and its alloys are widely used in many industries owing to its excellent thermal conductivity, electrical conductivity, extensibility and low density [1, 2]. For instance, aluminum is used in producing heat sinks with multislit structure [3]. Though it has a poorer thermal conductivity than copper, its low density makes aluminum become more popular in aviation and aerospace [4]. In microelectromechanical systems (MEMS) field, aluminum is processed into various shapes as a core mandrel, which can be utilized to electrochemical forming small and microparts with complex internal cavities, such as corrugated horn antennas and micro waveguides, etc. [5]. Besides, precision aluminum disks are used extensively for hard-drives in the computer industry and precision aluminum mirrors are used in numerous optical applications as in lasers and rotating mirrors in copying machines [6, 7].  
However, aluminum microstructures are difficult to cut in certain aspects due to its low hardness and deformability, especially for those from aluminum foils [8]. Traditional wire/blade saw cutting uses wire or blade made by cemented carbide or diamond as tools to cut workpiece by tool traveling or spinning, which cannot fulfill the feature scale as well as machining accuracy, and serious bending deformation will appear because of vibrations from the relative motion and extrusion between tool and foil [9, 10]. What is more, slits with microscales are difficult to fabricate in aluminum foils due to the limitation of tool size. As a result, straight and smooth slits cannot be stably machined in aluminum foils with a thickness of 100 \(\upmu\)m. Wire electrical discharge machining (WEDM) and wire electrochemical machining (WECM) are two typical contactless cutting methods. In WEDM, the material is melted and vaporized by the heat generated in electric spark and the material removal rate is relatively fast compared with WECM. However, the overlapping machined surface is made up of the recast layer and heat-affected zones, leaving poor surface roughness [11, 12]. Contrary to WEDM, WECM removes material by controlled electrochemical reactions rather than thermal energy. The anode material isdissolved into electrolyte ionic by ionic. Though it avoids the trouble of white layer and heat-affected zones, low efficiency, and stray corrosion are the main drawbacks in cutting aluminum foils [13; 14]. Besides, either in WEDM or WECM, the wire electrode needs to move along the axial direction to refresh electrolytes and remove processing products. When fabricating microstructures, the especially designed fixture is required to avoid vibration of the micro-wire electrode [15]. Laser cutting is another contactless machining method that employs a focused laser beam to generate high power and vaporize the material. The advantage of this method is that it has high efficiency and machining accuracy. However, the equipment cost of laser cutting is rather expensive, especially femtosecond laser machining. Besides, as aluminum has a low absorption rate of laser and low melting point, the processing speed is limited, and spherical slags will appear around slit edges [16].  
In this study, a new cutting method is proposed where an ordinary tungsten micro-wire is utilized as the tool to cut aluminum foil without tool traveling or spinning. It is assumed that a tungsten wire with a diameter as small as a cutting tooltip could cut aluminum foil merely by a feeding movement along with the slit profile, as tungsten has much higher strength than aluminum [17; 18]. This study aims to analyze the brief principle of this proposed method and experiments are carried out to verify its performances on yielding micro-slits in aluminum foils. Further, process parameters are optimized in order to obtain straight and smooth slits.