2023 CCEA GCSE Engineering and Manufacturing 0009 模拟试题及答案详解

Aluminium and its alloys do not contain iron, so aluminium alloy is classified as a non-ferrous metal.

[1] Non-ferrous. Do not accept 'ferrous'.

The frame is described as having a 'blue anodised finish'. Anodising is an electrolytic process that thickens the natural oxide layer on aluminium and can be dyed to give a coloured, corrosion-resistant surface.

[1] Anodising. Accept 'anodizing'.

The case study states a 'single-acting pneumatic cylinder is fitted between the frame and the toe plate' to control folding speed.

[1] Single-acting cylinder. Accept 'pneumatic cylinder' alone for [1]; do not accept 'double-acting cylinder'.

A micrometer (micrometer screw gauge) can measure external diameters to a resolution of 0.01 mm; a vernier caliper is also an acceptable precision measuring instrument for this purpose.

[1] Micrometer OR vernier caliper. Reject 'ruler' or 'tape measure' (insufficient precision).

It is practically impossible to manufacture every axle bore to an exact single dimension because of unavoidable variation in machines, tools and materials. A tolerance defines an acceptable upper and lower limit within which the bore will still allow the axle to fit correctly and the wheel to rotate freely, while keeping manufacturing realistic and cost-effective; it also allows interchangeable parts to be produced by different machines/operators and still assemble correctly.

[1] Recognises exact dimensions cannot be achieved consistently in manufacture (practical/cost reason). [1] Recognises a tolerance range still ensures correct fit/function and interchangeability of parts.

Upper limit = nominal + tolerance = 8.00 + 0.10 = 8.10 mm. Lower limit = nominal - tolerance = 8.00 - 0.10 = 7.90 mm.

[1] Upper limit = 8.10 mm. [1] Lower limit = 7.90 mm. Award both marks only if units (mm) are consistent with the question; ECF from a transcription slip in the nominal value.

Anodising deliberately thickens the natural aluminium oxide layer on the surface. This oxide layer is hard and chemically stable, so it protects the aluminium beneath from corrosion caused by moisture and handling, and it also produces a harder, more wear-resistant surface than bare aluminium. The anodised layer can also be dyed, giving the product a consistent, attractive colour that bare aluminium cannot achieve.

[1] Identifies a valid benefit, e.g. improved corrosion resistance / improved wear resistance / allows dyeing for appearance/brand colour. [1] Expands with a reason/consequence linked to the product (e.g. extends service life, maintains appearance in a warehouse environment). Any one benefit developed fully.

Working through production in order: Stage 1 - the mild-steel sheet is marked out using engineer's marking blue and then cut to the blank size using a guillotine (shearing), giving the correct overall length and width. Stage 2 - the blank is punched to produce the fixing holes needed to bolt the toe plate to the hinge, using a punch and die set so all holes are positioned accurately and consistently across the batch. Stage 3 - the front edge of the blank is press-folded (bent) through 90 degrees on a folding machine/press brake to form a stiffening lip and remove the sharp raw edge from the load-bearing face. Stage 4 - the folded plate is deburred (filed/linished) to remove sharp edges left by cutting and punching, before finishing, so the component is safe to handle and ready for finishing.

[1] Stage 1: marking out and cutting (guillotining/shearing) the blank to size. [1] Stage 2: punching the fixing holes using a punch and die. [1] Stage 3: press-folding the front lip through 90 degrees. [1] Stage 4: deburring/finishing sharp edges. Award 1 mark per correctly named/ordered stage with a valid purpose; accept equivalent valid process order (e.g. punching before folding) provided the sequence is logical and each purpose is correct.

Volume = length \( \times \) width \( \times \) thickness = \( 300 \times 250 \times 3 = 225\,000 \text{ mm}^3 \). Convert to m\(^3\): \( 225\,000 \text{ mm}^3 = 225\,000 \times 10^{-9} \text{ m}^3 = 0.000225 \text{ m}^3 \). Mass = density \( \times \) volume = \( 7850 \times 0.000225 = 1.76625 \text{ kg} \), which rounds to 1.77 kg.

[1] Correct volume formula used \( (V = L \times W \times H) \). [1] Correct volume = 225 000 mm\(^3\) (or 0.000225 m\(^3\)) with correct unit conversion. [1] Correct use of mass = density \( \times \) volume. [1] Final answer 1.77 kg (accept 1.76-1.77 kg; accept 1766.25 g). ECF applied throughout.

Moment = force \( \times \) distance from the pivot: \( M = F \times d = 35 \text{ N} \times 0.400 \text{ m} = 14 \text{ N m} \). The distance must be converted from mm to m before substituting (400 mm = 0.400 m). The SI unit of moment is the newton metre (N m).

[1] Correct formula \( M = F \times d \). [1] Correct conversion of 400 mm to 0.400 m. [1] Correct substitution and calculation. [1] Final answer 14 N m with correct unit stated. ECF applied if distance not converted, provided working is consistent.

Cross-sectional area of a circle: \( A = \pi r^2 \), where \( r = 8 \div 2 = 4 \text{ mm} \). So \( A = \pi \times 4^2 = \pi \times 16 = 50.3 \text{ mm}^2 \) (3 s.f.). Stress = force \( \div \) area = \( 900 \div 50.3 = 17.9 \text{ N/mm}^2 \) (1 d.p.).

[1] Correct radius used (4 mm, half of diameter). [1] Correct area calculation \( A = \pi r^2 \approx 50.3 \text{ mm}^2 \). [1] Correct stress formula (stress = force / area) applied. [1] Final answer 17.9 N/mm\(^2\) (accept 17.8-18.0 N/mm\(^2\) / MPa depending on rounding of area). ECF applied throughout.

Function of each part: A, the hinge pivot, is the fixed axis about which the toe plate (B) rotates as it is raised or folded down. B, the toe plate, is the rigid lever arm that carries the load and swings between the vertical (storage) and horizontal (working) positions. C, the pneumatic cylinder body, contains the piston and a chamber of air; it is anchored to the frame at E and provides a controlled resisting force as the piston moves. D, the piston rod, connects the cylinder to a point near the hinge on the toe plate, so as the toe plate rotates, the rod is pushed into (or pulled out of) the cylinder body. E, the frame anchor point, is the fixed pivot that lets the whole cylinder assembly rotate slightly as the geometry of the linkage changes during folding. Operation: when the toe plate is released from the raised position, gravity begins to rotate it about the hinge (A). This rotation forces the piston rod (D) into the cylinder body (C). Because the cylinder is single-acting, air on the piston's downstroke side can only escape through a small restricted flow-control orifice, so the air resists rapid movement of the piston; this converts the toe plate's kinetic energy into the work of forcing air through the restriction, slowing the fall. As a result, the toe plate lowers smoothly and steadily under control rather than dropping quickly and slamming onto the frame, protecting the mechanism and the user's fingers. When needed again, the internal return spring pushes the piston rod back out, ready to resist the next fold.

Detail contained in the description of function/operation [4]: 1 mark each for correctly explaining the role of A (pivot), B (lever/load), C+D (cylinder/rod resisting motion), and the flow-restriction damping principle. Quality/coherence of the explanation as a continuous, logically ordered account of the mechanism in action [4]: marks awarded across four bands for how clearly and completely the sequence of motion (release -> rotation -> piston forced in -> air restricted -> controlled fall) is explained, with correct use of mechanism vocabulary (pivot, lever, resisting force, damping). Annotation/labelling accuracy [4]: 1 mark for each part (A-E, up to 4 of the 5) correctly and specifically linked by letter to its function in the answer, rather than described generically. Quality of written communication assessed: coherent technical account using correct terminology throughout.

Anodising process: the aluminium alloy frame components are first thoroughly cleaned and degreased. They are then immersed as the anode in an electrolytic bath (typically containing dilute sulfuric acid), with a cathode also in the bath. A direct electric current is passed through the bath; oxygen is released at the aluminium surface and reacts with it to build up a controlled, porous layer of aluminium oxide, much thicker than the natural oxide layer that forms in air. While still porous, the component can be immersed in a dye bath (here, blue) so the dye is absorbed into the pores. Finally the component is sealed, usually in hot water or steam, which closes the pores and locks in the colour, leaving a hard, corrosion-resistant, coloured surface.

Reason 1: anodising produces a very thin, extremely hard surface layer that is fused into the aluminium itself (rather than sitting on top of it), so it resists the scratching and abrasion the frame will suffer from repeated warehouse handling, stacking and contact with other equipment far better than a sprayed-on powder coating, which can chip or flake if impacted.

Reason 2: because the anodised layer is very thin (a few microns) and does not build up on the surface, it does not affect the close tolerances needed at the hinge and folding joints of the toe-plate mechanism; a powder coating is a much thicker applied film that could clog fine clearances or fastener threads on moving/folding parts, causing the mechanism to bind or requiring extra masking during finishing.

Levels of response (12 marks). Level 1 (Basic) [1-3]: brief or partial description of anodising and/or a simple, undeveloped reason for its choice; limited technical vocabulary. Level 2 (Satisfactory) [4-6]: a mostly correct description of the anodising process (electrolytic bath, oxide layer forms, may mention dyeing/sealing) with one reason for choosing it over powder coating explained with some development. Level 3 (Good) [7-9]: a clear, mostly complete description of anodising including electrolytic action, dyeing and sealing, with two reasons discussed, at least one well developed and linked to the product's use. Level 4 (Excellent) [10-12]: an accurate, well-sequenced description of the full anodising process (cleaning, electrolysis/oxide growth, dyeing, sealing) and two clearly developed, product-specific reasons for choosing anodising over powder coating (e.g. hardness/wear resistance from handling, no build-up affecting folding-mechanism tolerances), written with accurate specialist terminology, good organisation and few errors of spelling, punctuation or grammar (QWC).

Vacuum forming uses air removed from beneath a heated sheet stretched over a mould (B). Sand casting pours molten metal into a sand mould formed around a pattern (A). Injection moulding forces molten plastic under pressure into a sealed mould cavity (D). Blow moulding inflates a heated parison inside a mould to form hollow shapes such as bottles (E). Extrusion forces material through a shaped die to give a constant cross-section, as used for the frame uprights (C).

[1] each for 1-B, 2-A, 3-D, 4-E, 5-C. Maximum [5].

Low carbon steel is a ferrous alloy, ductile and weldable, widely used for panels and brackets (B). Aluminium alloy is a lightweight, corrosion-resistant non-ferrous alloy used for extruded frames such as the EcoHaul 150 uprights (C). Acrylic is an optically clear thermoplastic used for guards/screens (A). MDF is a manufactured board used in flat-pack furniture (D). GRP is a composite material used for lightweight, corrosion-resistant shells such as boat hulls (E).

[1] each for 1-B, 2-C, 3-A, 4-D, 5-E. Maximum [5].

British Standard working drawings must clearly communicate manufacturing information such as key dimensions, the scale used, the projection method (first or third angle) and title block details.

[1] Any one valid item, e.g. key dimensions, scale, projection method (first/third angle), title block (drawing number/date/name), tolerances.

A CNC laser cutter directs a focused beam of light at the sheet material to melt/vaporise a narrow kerf, cutting accurate 2D profiles under computer control.

[1] Laser cutter.

Indirect costs are costs not directly tied to making one specific unit, such as management, administration, marketing or general business expenses.

[1] Any one valid indirect cost, e.g. management, administration, marketing, insurance, rent/overheads.

Just-in-time production supplies materials and manufactures products only when needed to meet actual demand, reducing stored stock and warehousing costs.

[1] Just-in-time / JIT.

Ear defenders (or ear plugs) protect an operator's hearing from the noise generated by machinery such as a pillar drill.

[1] Ear defenders / ear plugs / hearing protection.

A reservoir stores a supply of compressed air so that it is immediately available to the system when required, helping to maintain a steady supply pressure.

[1] Stores compressed air (for use on demand) / smooths pressure fluctuations.

First, CAD allows a design to be modified quickly and accurately: dimensions, shapes and tolerances can be changed on screen without redrawing everything by hand, and every copy generated remains precise and consistent, reducing costly errors. Second, a 3D CAD model can be shared directly with computer-aided manufacture (CAM) software to drive CNC machines, and can be used to check that components (such as the toe plate and hinge) fit and move correctly together through virtual assembly/interference checking, catching design problems before physical prototypes are made, saving time and material.

[1] Valid benefit 1 identified (e.g. speed/accuracy of modification, consistency of dimensioning). [1] Valid benefit 2 identified (e.g. direct link to CAM/CNC manufacture, virtual assembly/interference checking). [1] At least one benefit developed with a clear reason/consequence linked to reduced error, time or cost.

First, CAM-controlled machines (such as a CNC router or mill) follow the same digital toolpath every time, so every uprights in a batch is cut to the same high accuracy; this repeatability is far harder to achieve consistently by hand, reducing scrap from human error. Second, once set up, CAM machines can run continuously and often unattended (or with one operator overseeing several machines), cutting parts faster than manual methods and reducing the direct labour cost and time needed per unit, especially over a large batch or mass-production run.

[1] Advantage 1 identified (e.g. accuracy/repeatability/consistency across batch). [1] Advantage 2 identified (e.g. speed, reduced labour cost, can run unattended). [1] At least one advantage clearly developed/explained rather than simply stated.

When the rectangular toe-plate blank is punched from a larger sheet, the offcuts around and between the holes cannot be used in that product and become scrap. This scrap steel has already been purchased at full material cost, so every kilogram wasted is effectively money the manufacturer has spent without it becoming part of a saleable product, reducing profit margin per unit. In addition, disposing of or recycling the scrap may itself incur a further cost (transport, processing). For these reasons, a manufacturing proposal must calculate and try to minimise waste, for example by nesting blanks efficiently on the sheet, so that the true cost of producing the toe plate is accurately reflected and controlled.

[1] Waste material has already been paid for/represents lost material cost even though unused. [1] Disposal/recycling of waste can add a further cost. [1] Explains the consequence for the manufacturer (e.g. reduced profit margin, need to minimise waste through efficient nesting/design) linked to the product.

The EcoHaul 150 can carry loads up to 150 kg. If the loaded barrow tips, or a load slips and falls, an unprotected foot could be crushed or struck causing serious injury. Safety footwear with reinforced (steel or composite) toe-caps protects the operator's toes and forefoot from impact and crushing forces in this situation, and non-slip soles also reduce the risk of the operator slipping while manoeuvring a loaded barrow.

[1] Identifies the hazard (heavy load/barrow could fall onto or crush the foot). [1] Explains how safety footwear (reinforced toe-cap) protects against this specific hazard.

Aluminium alloy has a good strength-to-weight ratio: it is much lighter than steel of the same volume, so the EcoHaul 150 is easier for a user to lift, carry when folded and manoeuvre, while the alloying elements still give the frame sufficient strength to carry a 150 kg load. Aluminium also has good natural corrosion resistance, because it forms a thin, stable, self-protecting oxide layer on its surface (further enhanced by anodising), which is important because the product will be used and stored in warehouse or outdoor conditions where a ferrous metal would rust. Its ductility also allows it to be extruded into the constant cross-section profile needed for the uprights.

[1] Property 1 identified (e.g. good strength-to-weight ratio, corrosion resistance, ductility/extrudability). [1] Property 2 identified (a different valid property from the list above). [1] At least one property explained with a clear link to why it benefits the EcoHaul 150 specifically.

Quality control involves inspecting, measuring or testing parts (such as checking a toe plate's punched hole positions against a specification) after they have been made, to check whether they meet requirements and to reject or rework any that do not; it is therefore a reactive check on the finished item. Quality assurance is broader: it is the overall system of planned procedures, standards and checks built into every stage of production (e.g. calibrated machine settings, staff training, documented processes) that is designed to prevent defective parts being produced in the first place, rather than just catching them afterwards.

[1] Quality control correctly described as inspecting/testing finished parts against a specification (reactive). [1] Quality assurance correctly described as the planned system of procedures to prevent defects occurring (proactive).

Density = mass \( \div \) volume = \( 22.8 \text{ g} \div 20 \text{ cm}^3 = 1.14 \text{ g/cm}^3 \). Since \( 1 \text{ g/cm}^3 = 1000 \text{ kg/m}^3 \), density = \( 1.14 \times 1000 = 1140 \text{ kg/m}^3 \).

[1] Correct use of density = mass / volume, giving 1.14 g/cm\(^3\). [1] Correct final answer 1140 kg/m\(^3\) with correct conversion/unit.

Total material used = useful material + waste = \( 9.0 + 1.5 = 10.5 \text{ kg} \). Percentage waste = \( \dfrac{\text{waste}}{\text{total}} \times 100\% = \dfrac{1.5}{10.5} \times 100\% = 14.2857...\% \), which rounds to 14.3%.

[1] Correct total material calculated (10.5 kg). [1] Correct percentage = 14.3% (accept 14.2-14.3%, or exact fraction \( 100/7\% \)).

Direct costs = materials + labour + service resources = 12.50 + 8.00 + 1.50 = GBP22.00. Total cost = direct costs + indirect costs = 22.00 + 4.50 = GBP26.50.

[1] Direct costs correctly totalled as GBP22.00. [1] Correct formula applied (total cost = direct costs + indirect costs). [1] Final answer GBP26.50 with correct working shown. ECF applied if direct cost total is carried forward correctly.

Volume of one cylindrical pin: \( V = \pi r^2 h \), where \( r = 10 \div 2 = 5 \text{ mm} \) and \( h = 120 \text{ mm} \). \( V = \pi \times 5^2 \times 120 = \pi \times 25 \times 120 = 9424.8 \text{ mm}^3 \) (1 d.p.). For 25 pins: \( 9424.8 \times 25 = 235\,619.4 \text{ mm}^3 \). Converting to cm\(^3\) (divide by 1000): \( 235\,619.4 \div 1000 = 235.6 \text{ cm}^3 \) (1 d.p.).

[1] Correct volume of one pin calculated using \( V = \pi r^2 h \) (\( \approx 9424.8 \text{ mm}^3 \)). [1] Correctly multiplied by 25 pins. [1] Final answer 235.6 cm\(^3\) with correct mm\(^3\) to cm\(^3\) conversion (accept 235.5-235.7 cm\(^3\)).

In its first year, demand for a new product like the EcoHaul 150 is uncertain and likely to be lower than for an established product. Batch production allows a set quantity (a batch) to be manufactured using flexible, general-purpose machines and jigs that can later be reset to make a different product or a modified version, without committing to the very high cost of dedicated, single-purpose mass-production tooling and assembly lines. This keeps financial risk lower while the manufacturer confirms that customer demand justifies scaling up to mass production.

[1] Identifies a valid advantage of batch production over mass production for a new/uncertain-demand product (e.g. lower tooling investment, flexibility to change product, matches uncertain demand). [1] Advantage explained/developed with a reason linked to the EcoHaul 150's situation (new product, first year, uncertain demand).

Introducing a pick-and-place robot to fit the axle pins is likely to increase the speed and consistency of assembly, since the robot repeats the same precise movement every cycle without fatigue, reducing assembly errors and improving output rate; it also reduces the risk of repetitive-strain injury to a human operator who would otherwise perform this repetitive task all day. However, the robot requires a high initial capital investment to purchase and install, along with skilled staff to program, set up and maintain it, which raises fixed/indirect costs. There may also be a negative social impact, since fewer human operators are needed for this repetitive assembly task, potentially reducing the number of jobs on the line, and any robot failure or reprogramming need can stop the whole line.

[1] Valid positive impact (e.g. faster, more consistent/accurate assembly; reduced risk of RSI to workers). [1] Valid negative impact (e.g. high initial investment; need for skilled programming/maintenance staff; possible job losses). [1] At least one impact explained with a clear reason/consequence rather than simply stated.

Mass production refers to the method of manufacture itself: identical products (e.g. thousands of identical EcoHaul 150 frames) are made continuously on a dedicated production line using specialised, often automated, tooling, giving a high output rate and low cost per unit once set up. Just-in-time (JIT), in contrast, is a stock-control strategy: rather than holding large stores of components such as wheels, axle pins or hinges in advance, JIT arranges for suppliers to deliver these components to the factory only as they are needed on the line. One benefit of combining JIT with mass production is that it reduces the amount of money tied up in stored stock and the warehouse space needed to store it, lowering the manufacturer's overall costs.

[1] Mass production correctly described as continuous, high-volume manufacture of identical products on a dedicated line. [1] JIT correctly described as a stock-control approach where components arrive only when needed rather than being stored in advance. [1] Valid benefit of JIT stated (e.g. reduced stock-holding cost/storage space, reduced money tied up in stock).