Design & Technology (9-1) 0979 | Paper 4 Mock 41 | Graphic Products

(a)(i) The handles of the tin opener operate as a first class lever. [1] In a first class lever, the fulcrum (pivot point) is positioned between the effort and the load. On the tin opener, the central pivot pin sits between where the user squeezes (effort) and where the cutting wheel meets the can rim (load).

(a)(ii)

• Effort: at the ends of the handles where the user squeezes them together. [1] The user applies a compressive gripping force at the far ends of the handles to operate the opener.
• Load: at the cutting wheel where it pierces and cuts through the metal can rim. [1] The resistance of the metal rim being punctured and sheared is the load force that the lever must overcome.

(a) An alloy is a mixture of two or more metals, or a metal combined with a non-metal, that is produced to achieve improved or different properties compared to the individual elements. [1] For example, chromoly steel is an alloy of iron with small amounts of chromium and molybdenum added to increase strength and fatigue resistance beyond what plain carbon steel can achieve.

(b)(i) Two mechanical properties that make chromoly steel suitable for a bicycle frame: [2]

1. High tensile strength - chromoly allows thin-walled tubes to be used that still support the rider's weight and the dynamic forces of pedalling, cornering, and braking without permanently deforming. Thin walls mean a lighter frame. [1]
2. Good fatigue resistance - the frame is subjected to repeated stress cycles from road vibrations, pedalling loads, and impacts over thousands of kilometres. Chromoly's fatigue resistance means the frame can endure these cycles over a long service life without developing cracks. [1]

(b)(ii) Two advantages of titanium over steel for a bicycle frame: [2]

1. Titanium is significantly lighter than steel (approximately 45% less dense), reducing the overall weight of the frame, which is a critical performance factor in competitive cycling. [1]
2. Titanium has excellent corrosion resistance and does not rust. The frame does not need a protective coating (paint or powder coat), saving additional weight and eliminating the risk of corrosion under chips in the finish. [1]

(c)(i) TIG stands for Tungsten Inert Gas. [1]

(c)(ii) Description of TIG welding: [3]

1. A non-consumable tungsten electrode is held in the welding torch. An electric arc forms between the tungsten tip and the workpiece, generating intense, focused heat that melts the parent metal (chromoly steel) at the joint. Unlike MIG, the electrode does not melt and is not consumed. [1]
2. A separate filler rod of matching or compatible material is fed manually by the welder's other hand into the molten weld pool to build up the joint and fill any gap between the tube ends. [1]
3. An inert shielding gas (usually argon) flows through the torch nozzle and surrounds the tungsten electrode and weld pool. This gas shield prevents atmospheric oxygen and nitrogen from reacting with the molten metal, which would cause oxidation, porosity, and a weak, contaminated weld. The result is a clean, high-quality, precisely controlled weld bead. [1]

(d)(i) Two stages of preparation before welding the frame tubes: [2]

1. Clean and degrease the tube ends to remove oil, grease, fingerprints, and other surface contaminants. Any contamination in the weld zone would vaporise during welding and create gas pockets (porosity) that weaken the joint. [1]
2. File or machine the tube ends to the correct mitre angle so they fit tightly together with minimal gaps. A close-fitting joint ensures the weld penetrates evenly and the tubes maintain their designed alignment. [1]

(d)(ii) Work hardening occurs when a metal is deformed at room temperature (cold working), such as being bent, hammered, rolled, or repeatedly stressed. The deformation distorts the metal's internal crystal grain structure, forcing dislocations in the lattice to pile up and tangle. [1] This makes the metal harder and stronger but more brittle, reducing its ductility. If further cold working continues without relief, the metal may crack. In the area around a weld, thermal expansion and contraction during cooling can introduce internal stresses that have a similar effect. [1]

(e)(i) Normalising process and its purpose: [3]

1. The welded steel frame is heated in a furnace to above its upper critical temperature (approximately 900 degrees C for medium carbon steel) and held at this temperature until the heat has soaked through the entire frame evenly. [1]
2. The frame is then removed from the furnace and allowed to cool in still air (not quenched in water or oil, and not left in the furnace). [1]
3. The purpose is to relieve the internal stresses introduced by welding and to refine the grain structure. The reheating allows the distorted grains to recrystallise into a uniform, fine-grained microstructure, restoring consistent mechanical properties (strength, ductility, toughness) throughout the frame, including the heat-affected zones around each weld. [1]

(e)(ii) Difference between normalising and annealing: [2]

Both processes involve heating steel above its critical temperature, but they differ in cooling rate. Normalising cools the steel in still air, which produces a finer grain structure and a slightly harder, stronger material. [1] Annealing cools the steel very slowly inside the furnace (or buried in sand/vermiculite), producing a coarser grain structure that makes the metal softer and more ductile. Annealing is used when the metal needs to be as soft as possible for further machining or forming, while normalising produces a tougher, more refined structure suited to a finished component. [1]

(f)(i) Stages of the powder coating process: [3]

1. The steel frame is thoroughly cleaned, degreased, and surface-prepared. Any rust, mill scale, or old coatings are removed by shot blasting or chemical treatment to create a clean, bare metal surface. [1]
2. The frame is given an electrostatic charge (grounded), and dry thermoplastic or thermosetting powder is sprayed from a gun that imparts an opposite electrostatic charge to the powder particles. The charged particles are attracted to the grounded metal surface and adhere evenly, building up a uniform layer of powder. [1]
3. The coated frame is placed in a curing oven at approximately 180 to 200 degrees C. The powder particles melt, flow together into a continuous film, and chemically cure (cross-link) to form a hard, smooth, durable coating that is bonded to the metal surface. [1]

(f)(ii) Two advantages of powder coating compared to traditional wet paint: [2]

1. Powder coating produces no volatile organic compounds (VOCs) or harmful solvent emissions, making it significantly more environmentally friendly and safer for workers than solvent-based wet paints. [1]
2. The resulting coating is thicker and more durable than most wet paint finishes, providing better resistance to chipping, scratching, fading, and weathering. [1]

(g) The two main metals in duralumin are aluminium and copper. [1] Duralumin is significantly harder and stronger than pure aluminium because the copper atoms disrupt the aluminium crystal lattice, preventing dislocations from moving easily. This gives the handlebars greater rigidity and resistance to bending under the rider's grip and steering forces, while retaining much of aluminium's low density. [1]

(a) Aluminium is a non-ferrous metal. [1] Non-ferrous metals are those that do not contain iron as their primary element. Aluminium is lightweight, corrosion-resistant, and non-magnetic, all characteristic properties of non-ferrous metals.

(b) Acrylic is classified as a thermoplastic. [1] Thermoplastics soften when heated and harden when cooled, and this process can be repeated. Acrylic (PMMA) can be heated and formed into curves using line bending or vacuum forming, making it ideal for the phone stand in this product.

(c) One property of MDF that makes it suitable for the base of the desk organiser: MDF has a smooth, flat surface that can be easily coated with melamine laminate, producing a clean, professional finish with no visible grain or surface imperfections. [1] Unlike solid timber, MDF has no grain direction, so it does not split, warp, or move with changes in humidity, ensuring the base remains perfectly flat.

(a) The logic gate shown in Fig 5 is an AND gate. [1]

The symbol shows the characteristic D-shaped body with a flat back and a curved front. An AND gate produces a high output (logic 1) only when all of its inputs are high simultaneously. This makes it the correct choice for the security system described: the alarm sounds only when both the pressure pad (A) and the door switch (B) are activated at the same time. If either input is low, the output remains low and the alarm stays silent.

(b) Completed truth table: [2]

The AND gate outputs 1 only in the final row, where both inputs are 1. In all other combinations, at least one input is 0, so the output remains 0. This truth table confirms that both conditions must be met simultaneously for the alarm to activate.

(a)(i) The hand layup process for manufacturing the kayak hull from CFRP composite: [4]

1. A release agent is applied to the female mould surface to prevent the cured laminate from bonding to the mould. [1]
2. Layers of carbon fibre mat or woven cloth are cut to shape and carefully placed into the mould, following the contours of the hull profile. [1]
3. Epoxy resin is applied to each layer using a brush or roller, thoroughly wetting out the fibres to ensure complete saturation. The roller also removes trapped air bubbles. [1]
4. Successive layers are built up to the required wall thickness. The completed layup is left to cure (harden) either at room temperature over several hours or in a heated oven to accelerate the chemical cross-linking of the epoxy. [1]

(a)(ii) Two reasons why a female mould is used rather than a male mould for the outer hull surface: [2]

1. A female mould produces a smooth outer surface on the hull because the outer face of the laminate forms directly against the polished mould surface. A smooth hull reduces hydrodynamic drag in the water, which is critical for competitive racing speed. [1]
2. The external dimensions are controlled accurately by the mould cavity, ensuring a consistent, precise hull shape from one kayak to the next, which is essential for meeting racing class regulations and maintaining predictable handling. [1]

(b)(i) The composite structure of CFRP is suitable for a racing kayak because: [3]

1. CFRP has an excellent strength-to-weight ratio, meaning the hull can be made extremely strong while adding very little mass. [1]
2. The hull is stiff enough to resist flexing during the high paddling forces of sprint racing, maintaining its designed hydrodynamic shape and transferring the athlete's power efficiently. [1]
3. The composite can be moulded into complex curved shapes, allowing designers to optimise the hull cross-section, bow entry angle, and stern rocker for minimum drag. [1]

(b)(ii) Two properties of CFRP that make it superior to a steel frame: [2]

1. CFRP is much lighter (lower density) than steel, significantly reducing the overall mass the athlete must propel through the water. Every gram matters in competitive sprint events. [1]
2. CFRP does not corrode in fresh or salt water, unlike a steel frame which would need protective coatings that add weight and require maintenance. [1]

(c)(i) Two surface preparation steps before applying epoxy adhesive: [2]

1. Both bonding surfaces must be cleaned and degreased to remove oils, dust, fingerprints, or residual mould release agent that would prevent the adhesive from wetting the surface and forming a strong bond. [1]
2. Both surfaces should be lightly abraded (sanded) with fine abrasive paper to roughen the surface, creating a mechanical key that increases the contact area and allows the adhesive to grip. [1]

(c)(ii) Adhesive bonding is more appropriate than mechanical fixings inside a thin composite shell because: [3]

1. Mechanical fixings such as screws or bolts would require drilling holes through the thin laminate, creating stress concentrations that weaken the shell and could initiate cracking or delamination under the dynamic loads of paddling. [1]
2. Adhesive bonding distributes the load over a larger area of the joint, avoiding the localised stress peaks that occur around bolt holes, resulting in a more durable connection. [1]
3. Drilling through the composite laminate could also allow water ingress between the carbon fibre layers, leading to delamination, fibre damage, and progressive structural degradation. [1]

(d)(i) Two quality control checks on the finished composite hull: [4]

1. Visual inspection of the outer surface for cracks, dry patches (areas of unsaturated fibre), surface blemishes, or resin-rich/resin-starved zones. Surface defects indicate manufacturing faults that may compromise structural integrity. [1]
2. Tap testing: the hull is tapped systematically with a coin or small hammer. A consistent, sharp sound indicates solid laminate; a dull or hollow sound at any point indicates delamination or a void, where layers have separated internally. [1]
3. Additional checks include: measuring the hull wall thickness at key points using an ultrasonic thickness gauge to ensure uniformity across the laminate [1]; and checking overall dimensions and symmetry against the design drawing to confirm the hull meets the specified tolerances and class regulations [1].

(d)(ii) If air pockets become trapped between layers of carbon fibre during layup: [2]

1. The air pockets (voids) create weak spots in the laminate where the fibre and resin are not bonded together, reducing the local strength and stiffness of the hull wall. [1]
2. Under the repeated loading of paddling, these voids can initiate delamination or cracking, causing layers to separate and the hull to fail progressively, potentially leading to catastrophic structural failure during a race. [1]

(e) Three advantages of vacuum bagging over hand layup for producing composite structures: [3]

1. Vacuum bagging compresses the laminate more evenly across the entire surface, significantly reducing voids and trapped air pockets compared to manual roller consolidation. [1]
2. The compression produces a higher fibre-to-resin ratio, because excess resin is squeezed out. This results in a stronger, stiffer, and lighter finished part because carbon fibre (not resin) carries the structural loads. [1]
3. Vacuum bagging gives a more consistent laminate thickness across the entire hull, reducing variations in wall thickness that can cause uneven performance and localised weakness. [1]

(a) The joint most commonly used at the front corners of a high-quality drawer is the dovetail joint (either through dovetail or lapped dovetail). [1] The lapped dovetail is particularly common at the drawer front because the joint is hidden from the front face, while the through dovetail may be used at the back corners where appearance is less critical.

(b) Two reasons why the dovetail joint is suitable for a frequently opened drawer: [2]

1. The interlocking trapezoidal shape of the tails and pins creates a strong mechanical lock that directly resists the pulling force applied when the drawer is opened. The wider end of each tail faces outward, meaning the joint physically cannot be pulled apart along the direction of the pull. [1]
2. The interlocking fingers create a large glue surface area, giving a very strong adhesive bond that reinforces the mechanical interlock and ensures the joint remains tight over years of repeated use. [1]

The type of drawing that shows surfaces at their true size with no perspective:

Orthographic projection (also called orthographic drawing). [1] In orthographic projection, each view (front, plan, side) shows one face of the object at its true size and shape, with no perspective distortion or foreshortening. All lines are drawn at their actual measured length, so dimensions can be taken directly from the drawing and used to mark out and cut materials accurately. This makes it the standard format for working drawings and manufacturing instructions, where precise measurements are essential.

(a) The gears shown in the figure are spur gears. [1] Spur gears have straight-cut teeth arranged around the circumference of a cylindrical wheel. They are the simplest and most common type of gear, used to transmit rotary motion and force between two parallel shafts. The teeth mesh along a line of contact parallel to the shaft axis, which is why they are called "spur" gears.

(b) The driven gear rotates anti-clockwise (counter-clockwise). [1] When two meshing spur gears are in contact, their teeth interlock at the point where the two circles meet. As the driver gear turns clockwise, its teeth push against the teeth of the driven gear at the meshing point, forcing the driven gear to rotate in the opposite direction. This reversal of direction is a fundamental property of all externally meshing gear pairs: the driving teeth on one gear push the driven teeth on the other gear in the opposite rotational sense.

The process used to create a clean fold line in card before folding:

Scoring [1] - scoring involves running a blunt-pointed tool (a scoring tool, bone folder, or the back of a craft knife blade) along a straight line on the card surface, using a steel rule as a guide. This compresses the card fibres along the intended fold line without cutting through the material. When the card is then folded along the scored line, it bends cleanly and sharply, producing a crisp, accurate fold without cracking, tearing or producing a rough edge.

(a) The machine used to cut the vinyl lettering and logo:

Vinyl cutter (also called a plotter cutter or cutting plotter). [1] The machine uses a small, computer-controlled blade that follows a vector path generated from the digital design file. It cuts through the top vinyl layer but not through the backing paper beneath (known as kiss cutting).

(b) How the vinyl lettering is applied to the foamboard surface:

1. The unwanted vinyl around the letters is peeled away (a process called weeding), leaving only the cut letters and logo on the backing paper. Transfer tape (a low-tack adhesive sheet) is then applied over the top surface of the letters to hold them in their correct relative positions. [1]
2. The backing paper is peeled away from the underside, exposing the adhesive face of the vinyl. The letters are then positioned precisely on the foamboard surface and pressed down firmly using a squeegee or roller, working from the centre outward to remove air bubbles and ensure a strong, smooth bond. The transfer tape is then carefully peeled off, leaving the vinyl letters adhered to the foamboard. [1]

(a) The LED must be connected with the correct polarity because it is a semiconductor diode that only allows current to flow in one direction (from anode to cathode). [1]

If connected the wrong way round (reverse-biased), the LED blocks current flow and will not emit light. Unlike a filament bulb, which works regardless of polarity, an LED's internal P-N junction only conducts when the anode is connected to the positive terminal and the cathode to the negative terminal of the supply.

(b) A resistor (current-limiting resistor) must be connected in series with the LED. [1]

(c) Without the current-limiting resistor, too much current would flow through the LED, causing it to overheat and burn out almost immediately. [1]

A 9V battery can supply far more current than a standard LED can safely handle (typically 20 mA maximum). The LED's forward resistance is very low once it begins conducting, so without a resistor to restrict the current, the power dissipated in the LED's junction would exceed its rating, permanently destroying the component.