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Throughout the last decade magnesium alloys have slowly overtaken aluminium alloys, especially in the automotive and aerospace industry. Due to its attractive weight-resistance and weight-hardness characteristics, the global production of Magnesium alloys has grown from 360,000 tons in 1999 to 850,000 tons in 2013. Magnesium alloys AZ91 and AZ31 are the most widely used grades. AZ 91 exhibits a Knoop’s hardness (HK) of 76.2 that is higher to the AZ31 with a 51.1 HK. The manufacturing of AZ 91 is through a casting process whereas AZ31 is manufactured by using an extrusion process. The microstructure of AZ31 and AZ91 are highly influenced by the heat generated during the machining process that also affects the surface hardness due to the high thermal conductivity of the material that range from 62 W/m.k to 96W/m.k. Both materials have a very good machinability where milling, drilling, and turning are commonly used. However, extreme care should be taken in terms of machining conditions as Magnesium alloy is highly flammable. However, a safe machining process can be performed by avoiding very fine chips, magnesium dust and also the usage of water-based coolants that react with the raw material. This paper has widely reviewed the studies that have been conducted since the evolution of magnesium alloys in terms of machining parameters, machining consumables and their effect on the mechanical properties, surface conditions and limitations of the various machining processes.

The improvement of the quality of the surface roughness of the polyurethane board (PB) has always been a challenge in the automotive industry. A suitable combination of the milling parameters is very important in order to get a high grade of smoothness specially when dealing with complex designs such as curved profiles. In this paper, a half factorial design of experiment (DoE) with 16 runs at two levels is applied in the milling operation of the checking fixtures of a car seat belt bracket under a dry cutting condition. The Feed rate, Depth of cut, Spindle speed, Step over and Plunge rate were taken as the variables for the DoE. Two different milling tools, a flat end mill of diameter10 mm for roughing, and a ball nose of diameter 5 mm for the finishing process were used. Minitab software was use to analyze the correlation between the parameters and the surface roughness. The most influential factor in the milling process was observed to be the Step over.

The polyurethane block also known as PB is widely use in the automotive industry to manufacture checking fixtures. This material has a high machinability and a low hardness that can range from 37 to 84 at the shore D hardness. To acquire the appropriate milling parameter for this material has always been a challenge for the manufacturing industry, especially when comes to achieving a certain degree of surface quality as this material is highly porous. In this paper, the most significant milling parameter that affects the surface roughness was studied using DoE. Surface roughness tester was used to evaluate the surface finish. The morphology and composition of the PB were determined by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). It was found that the most significant factor among the milling parameter was the stepover and that the surface quality was heavily dependent on the amount of weight percentage of silicon.