e) Consider a grinding operation which utilises the following process parameters: wheelspeed of 1450m/min, a crossfeed of 5 mm, infeed of 0.07 mm and workspeed of0.25 m/s. For a cutting wheel of diameter 150 mm with 0.75 grits/mm? active gritsper area, calculate:i) the material removal rate;ii) the number of chips formed per unit time for the portion of the operation whenthe wheel is engaged in the work;Table 3: Typical Recommended Feeds for Milling (mm/tooth)High Speed Steel CuttersCemented Carbide CuttersEnd Mills and SlotEnd Mills and SlotFace MillsFace MillsDrillsDrillsWork MaterialAluminium Alloys0.400.170.600.25Brass0.350.150.400.19Cast Iron0.300.180.500.21Tool Steel0.100.050.150.10(annealed)Mild Steel0.250.150.30.18Table 4. Surface Cutting Speeds (m/min)Part MaterialAluminiumTool SteelBrassCast IronMild SteelAlloy(Annealed)Tool MaterialHigh Speed12075181528SteelCemented25018010080170Carbide Question 2Blitz Precision Engineering Ltd manufactures moulds for injection moulding machines. Themoulds are made from hardened tool steel due to its high wear and abrasion resistantproperties. When hardened, it will offer a hardness in the range 55-62 HRC, however it ismachinable in the annealed condition. The first step to machine one of the components of aparticular mould involves a milling operation. Specifically, this consists of a face millingoperation which is performed on the top surface of a rectangular tool steel workpiece whichis 315 mm long, 70 mm wide and 30 mm thick.To mill this component, the machinist has decided to:use a cemented carbide tool that has 5 teeth and a diameter of 80 mm.set up the machine and workpiece so that the cutter follows a path that is centredover the workpiece with a roughing depth of cut value of 4 mm.In addition, to select the relevant processing parameters, the machinist has to refer to therelevant data provided in a handbook by the milling cutter supplier. Some of the data isreproduced in Tables 3 and 4.a) Using the data provided, as a manufacturing engineer employed with theabovementioned company, suggest the appropriate values for the cutting speed andchip load, that need to be used by the machinist in order to satisfactorily face thetop surface of the workpiece. State any rationale/assumptions made.b) Using the parameters selected in (a) above, determine the following:the actual cutting time to make one pass across the surface,i.ii.the maximum metal removal rate during the cut, andii.the duration of the feed motion, if an additional approach distance of 20 mmis provided at the beginning of the pass (before cutting begins), and anovertravel distance is provided at the end of the pass equal to the cutterradius plus 25 mm.c) Once hardened, to finish the mould a grinding operation is required to face thecavities. Explain in detail (using diagrams if required) why the specific energy ingrinding is greater than in conventional machining.d) What are the consequences of the high working temperatures which arecharacteristic of grinding operations?

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