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Consider a grinding operation which utilises the following process parameters: wheel speed of 1450m/min, a crossfeed of 5 mm, infeed of 0.07 mm and workspeed of 0.25 m/s. For a cutting wheel of diameter 150 mm with 0.75 grits/mm? active grits per area, calculate: i) the material removal rate; ii) the number of chips formed per unit time for the portion of the operation when the wheel is engaged in the work;

Consider a grinding operation which utilises the following process parameters: wheel speed of 1450m/min, a crossfeed of 5 mm, infeed of 0.07 mm and workspeed of 0.25 m/s. For a cutting wheel of diameter 150 mm with 0.75 grits/mm? active grits per area, calculate: i) the material removal rate; ii) the number of chips formed per unit time for the portion of the operation when the wheel is engaged in the work;

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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e) Consider a grinding operation which utilises the following process parameters: wheel speed of 1450m/min, a crossfeed of 5 mm, infeed of 0.07 mm and workspeed of 0.25 m/s. For a cutting wheel of diameter 150 mm with 0.75 grits/mm? active grits per area, calculate: i) the material removal rate; ii) the number of chips formed per unit time for the portion of the operation when the wheel is engaged in the work; Table 3: Typical Recommended Feeds for Milling (mm/tooth) High Speed Steel Cutters Cemented Carbide Cutters End Mills and Slot End Mills and Slot Face Mills Face Mills Drills Drills Work Material Aluminium Alloys 0.40 0.17 0.60 0.25 Brass 0.35 0.15 0.40 0.19 Cast Iron 0.30 0.18 0.50 0.21 Tool Steel 0.10 0.05 0.15 0.10 (annealed) Mild Steel 0.25 0.15 0.3 0.18 Table 4. Surface Cutting Speeds (m/min) Part Material Aluminium Tool Steel Brass Cast Iron Mild Steel Alloy (Annealed) Tool Material High Speed 120 75 18 15 28 Steel Cemented 250 180 100 80 170 Carbide
Transcribed Image Text:e) Consider a grinding operation which utilises the following process parameters: wheel speed of 1450m/min, a crossfeed of 5 mm, infeed of 0.07 mm and workspeed of 0.25 m/s. For a cutting wheel of diameter 150 mm with 0.75 grits/mm? active grits per area, calculate: i) the material removal rate; ii) the number of chips formed per unit time for the portion of the operation when the wheel is engaged in the work; Table 3: Typical Recommended Feeds for Milling (mm/tooth) High Speed Steel Cutters Cemented Carbide Cutters End Mills and Slot End Mills and Slot Face Mills Face Mills Drills Drills Work Material Aluminium Alloys 0.40 0.17 0.60 0.25 Brass 0.35 0.15 0.40 0.19 Cast Iron 0.30 0.18 0.50 0.21 Tool Steel 0.10 0.05 0.15 0.10 (annealed) Mild Steel 0.25 0.15 0.3 0.18 Table 4. Surface Cutting Speeds (m/min) Part Material Aluminium Tool Steel Brass Cast Iron Mild Steel Alloy (Annealed) Tool Material High Speed 120 75 18 15 28 Steel Cemented 250 180 100 80 170 Carbide
Question 2 Blitz Precision Engineering Ltd manufactures moulds for injection moulding machines. The moulds are made from hardened tool steel due to its high wear and abrasion resistant properties. When hardened, it will offer a hardness in the range 55-62 HRC, however it is machinable in the annealed condition. The first step to machine one of the components of a particular mould involves a milling operation. Specifically, this consists of a face milling operation which is performed on the top surface of a rectangular tool steel workpiece which is 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 centred over 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 the relevant data provided in a handbook by the milling cutter supplier. Some of the data is reproduced in Tables 3 and 4. a) Using the data provided, as a manufacturing engineer employed with the abovementioned company, suggest the appropriate values for the cutting speed and chip load, that need to be used by the machinist in order to satisfactorily face the top 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, and ii. the duration of the feed motion, if an additional approach distance of 20 mm is provided at the beginning of the pass (before cutting begins), and an overtravel distance is provided at the end of the pass equal to the cutter radius plus 25 mm. c) Once hardened, to finish the mould a grinding operation is required to face the cavities. Explain in detail (using diagrams if required) why the specific energy in grinding is greater than in conventional machining. d) What are the consequences of the high working temperatures which are characteristic of grinding operations?
Transcribed Image Text:Question 2 Blitz Precision Engineering Ltd manufactures moulds for injection moulding machines. The moulds are made from hardened tool steel due to its high wear and abrasion resistant properties. When hardened, it will offer a hardness in the range 55-62 HRC, however it is machinable in the annealed condition. The first step to machine one of the components of a particular mould involves a milling operation. Specifically, this consists of a face milling operation which is performed on the top surface of a rectangular tool steel workpiece which is 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 centred over 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 the relevant data provided in a handbook by the milling cutter supplier. Some of the data is reproduced in Tables 3 and 4. a) Using the data provided, as a manufacturing engineer employed with the abovementioned company, suggest the appropriate values for the cutting speed and chip load, that need to be used by the machinist in order to satisfactorily face the top 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, and ii. the duration of the feed motion, if an additional approach distance of 20 mm is provided at the beginning of the pass (before cutting begins), and an overtravel distance is provided at the end of the pass equal to the cutter radius plus 25 mm. c) Once hardened, to finish the mould a grinding operation is required to face the cavities. Explain in detail (using diagrams if required) why the specific energy in grinding is greater than in conventional machining. d) What are the consequences of the high working temperatures which are characteristic of grinding operations?
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