Design & Technology 0445 | Paper 4 Mock 01 | Graphic Products

(a) A suitable tool for scoring fold lines on card:

Scoring tool / bone folder [1] - a scoring tool creates a shallow indentation along the fold line without cutting through the card. This compresses the fibres along the line, allowing the card to fold cleanly and sharply without cracking or tearing. An empty ballpoint pen or the back of a craft knife blade can also be used.

(b) How the hexagonal end panels are cut out accurately:

1. The hexagonal shape is marked out on the card using a ruler, compass and protractor to ensure each of the six sides is equal in length and the internal angles are correct (120 degrees for a regular hexagon). [1]
2. Each straight edge of the hexagon is then cut out using a craft knife guided along a steel rule, working on a self-healing cutting mat. The ruler is repositioned for each edge to ensure a clean, straight cut along every side. [1]

(a)(i) How a 3D printer produces a product from a digital design file:

1. A 3D digital model (CAD file) of the phone case is created on computer, then slicing software divides the model into many thin horizontal layers (typically 0.1-0.3 mm thick). [1]
2. The printer builds the product layer by layer: for FDM (fused deposition modelling), a thermoplastic filament is melted and extruded through a nozzle, depositing a thin bead of material that traces the cross-section of each slice. [1]
3. Each new layer bonds to the one below as the build platform lowers (or the print head rises) by one layer height. The process repeats, building up the three-dimensional shape progressively. [1]
4. When all layers are complete, the finished object is removed from the build platform and any support material is broken away or dissolved. [1]

(a)(ii) The digital file format commonly used:

STL (stereolithography) file. [1] This format represents the surface geometry of the 3D model as a mesh of small triangles, which the slicing software then processes into layer-by-layer instructions for the printer.

(b) Two advantages of 3D printing a prototype compared to making it by hand:

1. A prototype can be produced directly from the CAD file in a matter of hours, much faster than hand-shaping from raw material using workshop tools. [1]
2. Complex shapes with internal features, thin walls or undercuts can be produced that would be very difficult or impossible to achieve by hand. [1]

(c) Why 3D printing is not suitable for mass production of the phone case:

1. 3D printing is slow, producing one item at a time over several hours per part, making it far too slow for mass production volumes. [1]
2. The unit cost remains high regardless of quantity (no economies of scale), and the surface finish and mechanical properties of 3D-printed parts are generally inferior to injection-moulded parts. [1]

(d)(i) The missing stage (dashed box) in the production flow chart:

Quality control inspection / check finished product [1] - visual and dimensional inspection of the moulded cases to verify they meet specification before packaging.

(d)(ii) Why this stage is essential in mass production:

1. It catches defective products (dimensional errors, surface defects, flash, warping) before they are packaged and dispatched to customers. [1]
2. In mass production, a single undetected fault in the mould or process settings could produce thousands of faulty products. Without this quality gate, defective stock would reach the market, causing customer returns, reputational damage and financial loss. [1]

(e) Lean manufacturing explained:

1. Lean manufacturing is a systematic approach that aims to minimise all forms of waste (materials, time, movement, overproduction, inventory, defects) while maximising productivity and value. [1]
2. It focuses on producing only what is needed, when it is needed, to the quality required, eliminating activities that do not add value to the final product. [1]
3. A specific lean technique: Just-In-Time (JIT) delivery, where raw materials arrive only when needed for immediate production, reducing inventory holding costs and warehouse space requirements. Other valid techniques include Kaizen (continuous improvement), 5S workplace organisation, and Kanban scheduling. [1]

(f) The role of CNC in producing the injection mould:

1. A detailed CAD model of the mould cavity (the negative of the phone case shape) is created on computer, specifying all dimensions, draft angles, gate locations and cooling channels. [1]
2. CAM software converts this 3D model into a precise program of tool paths and cutting instructions (G-code). [1]
3. The CNC milling machine follows these instructions automatically to cut the complex mould cavity from a solid block of tool steel, achieving the high precision (typically ±0.01 mm) needed to produce accurate, repeatable mouldings. [1]

(g)(i) Comparing quality control and quality assurance:

• Quality control (QC) inspectors check samples of finished products against the specification to identify defects after production has occurred. QC is reactive, catching problems after they happen. [1]
• Quality assurance (QA) is a proactive, preventive system embedded throughout the entire production process. It establishes standards, procedures, training and documentation at every stage to prevent defects from occurring in the first place. [1]

(g)(ii) A statistical quality control method:

1. Random sampling: At regular intervals (e.g. every 100 units, or every 30 minutes), a set number of products are randomly selected from the production line. [1]
2. These samples are measured and tested against the specification. If the defect rate in the sample exceeds a pre-defined acceptable quality level (AQL), the entire batch is flagged and the production line may be stopped for investigation and correction. [1]

(h) Organising production to switch between three colours efficiently:

1. The factory uses batch production for the different colours, manufacturing all cases of one colour before switching to the next. [1]
2. Between colour changes, the injection moulding machine barrel is purged of the previous colour granules by running the screw mechanism until only the new colour material is emerging. [1]
3. Production is planned to minimise changeover waste: lighter colours are typically produced first (e.g. white, then yellow, then black), because a small amount of residual dark pigment in a light batch is more visible and wasteful than light residue in a dark batch. [1]

(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) When using a lathe to turn a metal bar, the correct PPE is safety goggles (eye protection). [1] Hot metal swarf is thrown off the workpiece at high speed during turning, and safety goggles prevent these sharp, hot fragments from reaching the operator's eyes. (Also acceptable: face shield.)

(b) When cutting wood on a circular saw, the correct PPE is ear defenders (ear protection). [1] Circular saws produce high noise levels that can cause permanent hearing damage with prolonged or repeated exposure. (Also acceptable: safety goggles, dust mask.)

(c) When applying spray paint in a spray booth, the correct PPE is a respirator or spray mask with an appropriate filter cartridge. [1] Spray painting atomises the paint into very fine droplets and releases solvent vapour, both of which can be inhaled deep into the lungs. A respirator with organic vapour and particulate filters prevents inhalation of both the paint mist and the solvent fumes. (Also acceptable: safety goggles to protect eyes from overspray.)

(a) A suitable permanent mechanical fixing for joining the steel bracket to the tubes is a rivet (or pop rivet). [1] Rivets are inserted through pre-drilled holes and deformed to lock the bracket permanently in place. Welding is also acceptable, though it is a joining process rather than a discrete fixing component.

(b) A permanent fixing is preferred over a temporary fixing for this structural joint because it ensures the joint cannot loosen or come apart under the loads and vibrations that the outdoor storage shelter will experience over its service life. [1] A structural frame joint that loosens could cause the shelter to distort or collapse, so permanence is essential for safety and long-term rigidity.

(c) Two reasons why bolts are suitable temporary fixings for attaching the door mechanism to the steel structure: [2]

1. Bolts allow the door mechanism to be removed for maintenance or replacement without damaging the structural tube, since the bolt simply unscrews from its nut. [1]
2. Bolts can be tightened to a specific torque to resist vibration while still being removable, providing a secure but adjustable connection that can be re-tightened or repositioned if needed. [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) 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)(i) The gear ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear:

\[ \text{Gear ratio} = \frac{\text{Driven teeth}}{\text{Driver teeth}} = \frac{48}{12} = 4 : 1 \]

[1] for the correct formula or method, [1] for the correct answer. The driven gear B has four times as many teeth as the driver gear A, so it turns four times slower.

(a)(ii) The speed of gear B:

\[ \text{Speed of B} = \frac{\text{Speed of A}}{\text{Gear ratio}} = \frac{80\,\text{rpm}}{4} = 20\,\text{rpm} \]

[1] for the correct method, [1] for the correct answer. For every four turns of the small driver gear A, the large driven gear B completes one turn. This speed reduction is accompanied by a fourfold increase in torque at the output, which provides greater drilling force at a controlled speed for the hand drill.

(a) The centre of gravity is the point through which the entire weight of an object appears to act, or the single point at which the object would balance perfectly. [1]

Every particle in an object is pulled downward by gravity. The centre of gravity is the point where all these individual gravitational forces can be considered to act as a single resultant force. For a uniform, symmetrical object, the centre of gravity is at its geometric centre. For irregular or non-uniform objects, the centre of gravity shifts toward the heavier parts.

(b) Two ways to improve the stability of the display board: [2]

1. Widen the base of the display board to increase the area of support. A wider base means the vertical line through the centre of gravity is more likely to remain within the footprint of the base when the board is tilted by a small force. The board must be tilted through a greater angle before it topples, making it more stable.
2. Lower the centre of gravity by moving the heavy brochure holders to a lower position on the board, or by adding weight (such as sandbags or a heavy plinth) at the base. A lower centre of gravity means the board must be tilted further before the line of action of its weight passes beyond the edge of the base. This increases the restoring moment that returns the board to its upright position.

(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.

(a) The adhesive used to join two pieces of acrylic sheet together is solvent cement (also known as Tensol cement or acrylic cement). [1] This is a specialised adhesive based on dichloromethane that works specifically on acrylic (PMMA).

(b) The solvent cement is applied along the joint edge using a fine brush or syringe applicator. The solvent chemically dissolves the surface of both acrylic pieces at the joint line, softening the polymer chains in both faces. [1] As the solvent evaporates, the dissolved surfaces fuse together at the molecular level, creating a bond that is almost as strong as the original material. This is not a conventional adhesive bond where a separate material bridges two surfaces; instead, the two pieces effectively become one continuous piece of acrylic at the joint. [1]

(a) A cam and follower mechanism converts the rotary motion of the handle into the up-and-down motion of the figure's arm. [1] This is the standard mechanism for producing controlled reciprocating or oscillating output from a rotary input, and it is widely used in toys, engines, and automated machinery.

(b) A cam is a specially shaped disc (or lobe) fixed to the rotating handle shaft. As the handle turns, the cam rotates with it. The cam profile has a varying radius from its centre: some portions bulge outward (the "rise") while others sit closer to the centre (the "fall"). [1] A follower, which is a rod or lever connected to the figure's arm, rests against the cam surface. As the cam rotates, the changing radius pushes the follower upward when the high-radius lobe passes underneath it, then allows the follower to drop back down (under gravity or spring return) as the low-radius portion comes around. [1] This continuous rotation produces the repetitive waving motion of the arm.

(c) Bevel gears transmit rotary motion through a 90-degree angle. [1] A pair of bevel gears has cone-shaped teeth cut along angled faces, and the two gear shafts meet at right angles. When one bevel gear turns, its angled teeth mesh with the partner gear and redirect the rotation by 90 degrees, making them ideal for driving the horizontal turntable from the vertical handle shaft.

(d) The gear ratio is calculated by dividing the number of teeth on the driven gear by the number of teeth on the driver gear:

\[ \text{Gear ratio} = \frac{\text{Teeth on driven gear}}{\text{Teeth on driver gear}} = \frac{36}{12} = 3 : 1 \]

The turntable gear is three times larger than the handle gear. [1]

(e) 3 complete turns of the handle are needed for one full rotation of the turntable. [1] Because the gear ratio is 3:1, the driven gear (turntable) turns three times slower than the driver gear (handle). For every three rotations of the smaller 12-tooth gear, the larger 36-tooth gear completes exactly one rotation. This speed reduction also means the torque at the turntable is three times greater than the torque applied at the handle, though speed is sacrificed.