OCR A Level in Design and Technology: Design Engineering H404/01 Principles of Design Engineering . QUESTION PAPER AND ANSWERS.

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Answer all the questions. 1 Fig. 1.1 shows a cordless electric screwdriver. illumination light on/off trigger reverse switch soft grip handle battery inside handle epicyclic gearbox inside ca... se motor inside case Fig. 1.1 (a) (i) Designers often aim to make their products inclusive so that they are easy-to-use by a wide range of users. Identify two ways in which the electric screwdriver in Fig. 1.1 has been designed to be an inclusive and easy-to-use product. 1 ........................................................................................................................................ ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... [2] 3 © OCR 2021 Turn over (ii) One million electric screwdrivers are manufactured every year using a high-volume production process. The production runs continually for 365 days per year. Calculate the average time in seconds to manufacture one electric screwdriver. Give your answer to 2 decimal places. Show your working. Average time ...................... seconds [2] 4 © OCR 2021 (b) The specification for the electric screwdriver is given in Table 1.2. Battery 3.6 V lithium-ion rechargeable Output speed 215 rpm Maximum torque 4.5 Nm Table 1.2 The electric screwdriver uses an epicyclic gear system. (i) Explain two reasons why the designer chose to use an epicyclic gearbox in this product. 1 ........................................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... 2 ........................................................................................................................................ ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... [4] (ii) The epicyclic gearbox in the electric screwdriver consists of two identical stages. Each stage has a gear ratio of 7:1. Use the information in Table 1.2 to calculate the rotational speed of the motor in the electric screwdriver. Give your answer in rpm and show your working. Rotational speed of motor .............................. rpm [3] 5 © OCR 2021 Turn over (c) A new electric screwdriver is being developed. The current drawn by the motor is measured as the torque load on the motor is varied. Fig. 1.3 is a graph of the results. 0 0.5 1 1.5 Torque load on motor (Nm) Motor current (A) 2 2.5 3 0 0.02 0.04 0.06 0.08 0.1 0.12 Fig. 1.3 (i) Use Fig. 1.3 to identify the current of the motor when the load on the motor is 0.04 Nm. Motor current ............................................... A [1] 6 © OCR 2021 (ii) An electronic system is being developed to monitor the torque load on the motor. Fig. 1.4 shows part of the circuit diagram for the new electronic system. 0.1 c 0V Vs 0V output to amplifier M Fig. 1.4 Calculate the voltage across the 0.1 Ω resistor when the motor current is 2.5 A. Show your working. Voltage .................................. V [2] (iii) Component c in Fig. 1.4 is a capacitor. Explain one reason why a capacitor is used in electronic systems. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] 7 © OCR 2021 Turn over (iv) The output voltage signal from the circuit in Fig. 1.4 is fed into an amplifier subsystem with a voltage gain of 4. Describe the effect the amplifier will have on the voltage signal. ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] 8 © OCR 2021 (d) During the development of an electric screwdriver, 3D block models would be made to test ergonomic factors and to communicate ideas with stakeholders. Use annotated sketches and/or notes to show how a non-functional model of an electric screwdriver, such as the type shown in Fig. 1.1, could be made. Identify any relevant equipment, materials and processes. [6] 9 © OCR 2021 Turn over 2 (a) A metal part is being manufactured using an old working drawing which has measurements in inches. A hole is required with a diameter of ¼ inch. The drill bits available are: 3 mm 4 mm 5 mm 6 mm 7 mm 8 mm (i) Assuming 1 inch = 25.4 mm, identify the drill bit that will drill a hole closest to the required size. Show your working. Drill bit .............................. mm [2] The tolerance for the ¼ inch hole is ± 5%. (ii) Determine whether the drill bit you specified in part (a)(i) would produce a hole that is within this tolerance. State Yes or No. Show your working. Within tolerance ..................................... [3] 10 © OCR 2021 (b) A polymer moulding manufacturer produced a batch of 5000 gears. Each gear was inspected and 80 gears were found to be faulty. (i) Calculate the probability of a gear being faulty in the batch. Probability ..................................... [1] (ii) Use your answer to part (b)(i) to calculate the minimum number of gears which should be inspected if the probability of a faulty gear remains the same. Show your working. Minimum number of gears ..................................... [2] (c) Fig. 2.1 shows the basic design for a zip-line for a children’s play park. 2.5° start point zip-line end point 2.8 m 30 m h Fig. 2.1 (not to scale) (i) Calculate the height h in m. Give your answer to 1 decimal place and show your working. Assume that the zip-line does not sag. h ................................. m [3] 11 © OCR 2021 Turn over (ii) Fig. 2.2 shows construction details of the start point for the zip-line. 3 m d guy line zip-line support pole 66° 69° Fig. 2.2 (not to scale) Calculate the distance d in m. Give your answer to 2 decimal places and show your [Show More]

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