Design & Technology 0445 | Paper 3 Mock 01 | Materials

The process of annealing mild steel involves three stages:

1. Heating: The mild steel workpiece is heated in a furnace to a cherry red colour, approximately 720 degrees Celsius (above its upper critical temperature). [1] At this temperature, the internal crystal structure of the steel transforms, and the internal stresses built up from previous working (bending, hammering, rolling) begin to relieve.
2. Soaking: The steel is held at this temperature long enough for the heat to penetrate evenly throughout the full cross-section of the workpiece, ensuring a uniform transformation of the grain structure.
3. Slow cooling: The steel is allowed to cool very slowly. [1] This can be achieved by turning off the furnace and leaving the workpiece inside to cool with the furnace (furnace cooling), or by burying the hot workpiece in dry sand, vermiculite, or ite ash, which acts as an insulator to slow the cooling rate. [1]

The result of annealing is that the steel becomes softer, more ductile, and easier to work. The slow cooling allows the grain structure to form large, even crystals (ferrite and pearlite), relieving internal stresses and making the metal less likely to crack during further shaping operations such as bending, pressing, or machining.

(a) Pine is classified as a natural timber, specifically a softwood. [1]

Softwoods come from coniferous (cone-bearing) trees that are typically evergreen and fast-growing. Pine is widely used in furniture, construction, and school workshop projects because it is relatively inexpensive, easy to work with hand and machine tools, and has an attractive grain pattern. As a natural material, it is renewable and biodegradable.

(b) Acrylic is classified as a thermoplastic (a type of polymer / plastic). [1]

Acrylic (also known as PMMA, polymethyl methacrylate) is a synthetic, manufactured material. As a thermoplastic, it softens when heated and can be shaped using processes such as line bending and vacuum forming. It is transparent with excellent optical clarity, relatively lightweight, and available in a range of colours. It is commonly used for display cases, signs, light diffusers, and as a substitute for glass where shatter resistance is needed.

(a) Naming the two methods of seasoning timber:

• Method P is air seasoning (air drying). [1] The diagram shows timber planks stacked outdoors on a raised platform with stacking sticks (thin strips of wood) placed between each layer. The stacking sticks create air gaps that allow air to circulate around every surface of the planks, enabling moisture to evaporate gradually over months or years.
• Method Q is kiln seasoning (kiln drying). [1] The diagram shows timber placed inside a heated, enclosed chamber. Fans circulate warm air around the timber to accelerate the drying process. Temperature and humidity are carefully controlled to achieve the desired moisture content.

(b) The purpose of seasoning timber is to reduce its moisture content to a usable level. [1] Freshly felled (green) timber contains a high proportion of water. If used without seasoning, the timber would shrink, warp, crack, and become susceptible to fungal attack (rot) as it dried out in service. Seasoning brings the moisture content down to a level appropriate for the timber's intended use, typically 10-20%.

(c) Two advantages of Method Q (kiln seasoning) over Method P (air seasoning):

1. Kiln seasoning is much faster: timber can be dried in days or weeks, compared with the months or even years required for air seasoning. [1] This means timber can be processed and made available for use far more quickly.
2. The moisture content can be precisely controlled and reduced to a lower level than air seasoning can achieve. [1] In a kiln, temperature and humidity sensors allow the operator to target an exact final moisture content, whereas air seasoning relies on ambient weather conditions and typically cannot reduce moisture below the equilibrium moisture content of the local climate.

(a) The accuracy of measurement that can be achieved using a steel rule is 1 mm (or 0.5 mm if the rule has half-millimetre graduations). [1] A steel rule is graduated with millimetre markings along its edge, so the smallest division that can be read directly determines the accuracy. Some rules allow estimation to the nearest half millimetre.

(b) One advantage of using a measuring tape instead of a steel rule when measuring the length of a large curved surface:

A measuring tape is flexible, so it can follow the contour and shape of a curved surface, giving an accurate measurement along the actual surface path. [1] A rigid steel rule cannot bend to conform to a curve, so it would only measure the straight-line distance (chord) between two points, not the true surface length. Additionally, measuring tapes are typically much longer than steel rules (often 3-8 metres), so large distances can be measured in a single span without repositioning.

The metal used to make the electrical wire shown in Fig. 11 is copper. [1] Copper is the standard metal for electrical wiring because it is an excellent electrical conductor, meaning electricity flows through it with very low resistance. This efficiency reduces energy losses as heat and ensures reliable delivery of current. Copper is also ductile, so it can be drawn into thin wires without breaking, and it is malleable, allowing the wire to be bent and routed around corners and through conduits during installation. Additionally, copper has good resistance to corrosion, so the wire maintains its conductivity and integrity over a long service life.

This extended-response question is assessed using a levels-based mark scheme. A strong answer addresses all six bullet points with detailed, well-annotated sketches and technical notes. The following indicative content outlines the key knowledge expected at the highest level.

Marking-out tools suitable for metal:

• Scriber: Used instead of a pencil because it scratches a fine, permanent line into the metal surface. Pencil marks would be too thick, easily rubbed off, and difficult to see on shiny stainless steel.
• Engineer's square: Used to mark lines at 90 degrees to the datum edge, ensuring right-angle accuracy.
• Steel rule: Used to measure distances and guide the scriber for straight lines. Steel rules are harder than the workpiece, so they resist damage from the scriber point.
• Dividers / spring dividers: Used to scribe arcs, circles, and transfer measurements. Essential for marking curved shapes such as the ladle bowl outline.
• Surface gauge / scribing block: Used to mark lines at a constant height from the surface plate, maintaining parallel accuracy across the sheet.
• Centre punch: Used to create a small indentation at the intersection of scribed lines to locate drill positions for the hanging-hook holes.

Datum edges and their role:

Two adjacent edges of the steel sheet are designated as datum edges (the bottom and left edges in the figure). All measurements are taken from these fixed reference edges. This eliminates cumulative error that would arise if measurements were chained from one marked point to the next. The datum edges must be straight and at 90 degrees to each other; an engineer's square is used to verify this before marking begins.

Templates and jigs for batch production:

For batch quantities, thin sheet-metal or acrylic templates are made for each utensil shape. The template is placed on the steel sheet, clamped in position, and the scriber is drawn around its edge to transfer the outline accurately. Templates eliminate the need to re-measure each shape individually, ensuring every utensil is identical. A jig could also locate the template at the correct position relative to the datum edges, further speeding up the process and reducing errors.

Tolerances and why they matter:

Tolerances define the permitted range of dimensional variation (for example, length +/- 0.5 mm). For kitchen utensils, tight tolerances are important because the handle must fit comfortably in the hand (ergonomic requirement), parts must align with dies or formers used in subsequent shaping operations, and the finished products must look uniform when displayed as a matching set. Exceeding the tolerance would cause rejection at quality control.

Marking hole positions for hanging hooks:

The position of each hole is located by scribing two intersecting lines (one measured from each datum edge). A centre punch is then struck at the intersection to create an indentation that prevents the drill bit from wandering when the hole is drilled. The centre-punched position is checked against the specification using a steel rule before drilling.

Quality control checks before cutting:

• Verify all dimensions against the working drawing using a steel rule or vernier caliper.
• Check that templates are aligned correctly and have not shifted.
• Confirm all scribed lines are clearly visible and continuous.
• Ensure hole centre-punch marks are in the correct positions.
• Check sufficient material surrounds each shape to avoid deformation during cutting.
• Verify the sheet is flat and free from distortion before committing to cutting.

Levels-based assessment:

Name the joint shown in Fig. 4

Dovetail joint [1]. The dovetail joint consists of interlocking fan-shaped projections (tails) on one piece that fit into corresponding wedge-shaped sockets (pins) on the other. The angled shape of the tails and pins creates a mechanical interlock that resists pulling forces along the joint line, making it very strong even without adhesive. It is commonly used for drawer construction, box corners, and fine furniture where both strength and visual appeal are important.

Two safety rules that must be followed when using the pillar drill:

1. Keep the safety guard in place [1] - The guard, visible in Fig. 20 around the drill bit area, prevents the user's hands, hair, or clothing from coming into contact with the rotating chuck and drill bit. It also contains any debris thrown up during drilling.
2. Clamp the workpiece securely to the drill table [1] - If the material is held by hand, the rotating drill bit can catch and spin the workpiece violently, causing injury to the user. A clamp or machine vice holds the material firmly in position.

Other valid safety rules include: tie back long hair to prevent it being caught in the rotating parts; do not wear loose clothing, jewellery, or ties; wear safety goggles to protect eyes from flying chips; and ensure the correct drill bit is fitted and tightened in the chuck before starting.

(a) A jig is a device that holds and locates the workpiece and guides the cutting tool (such as a drill bit) to ensure each component is manufactured identically. [1] It combines workholding and tool guidance in a single fixture, so the operator does not need to measure, mark out, or align each piece individually. The jig shown has guide holes through which the drill bit passes, ensuring holes are drilled in the same position on every workpiece.

(b) One advantage of using a jig for batch production: [1]

It ensures accuracy and consistency because all holes are drilled in the same position on every component without the need for individual marking out. This saves time (no measuring or marking per piece), reduces the skill level required of the operator, and virtually eliminates positional errors across the entire batch.

(c) The part labelled 'stop' is an end stop (also called a location stop). Its function is to position each workpiece in exactly the same location within the jig before the operation begins. [1] The operator pushes the workpiece against the stop, guaranteeing that every piece is registered in the same position relative to the guide holes. Without the stop, each workpiece could shift to a slightly different position, causing the drilled holes to be inconsistently located from piece to piece.

(a) Name the parts labelled A and B [2]

1. A - Heater element / radiant heater [1]. This provides the heat source positioned above the thermoplastic sheet to soften it before forming.
2. B - Thermoplastic sheet / clamped plastic sheet [1]. This is the material that will be heated and then drawn over the mould by the vacuum.

(b) Describe the stages of the vacuum forming process [4]

1. The thermoplastic sheet is clamped securely in the frame above the platen [1].
2. The heater is positioned above the sheet and heats it until it becomes soft and pliable (it will visibly sag when ready) [1].
3. The mould is raised up into the softened sheet. Air is then sucked out through the small holes in the platen by the vacuum pump, creating a pressure difference that forces the plastic tightly over every surface of the mould [1].
4. The plastic is allowed to cool and harden around the mould. It is then removed from the frame, separated from the mould, and any excess material is trimmed away [1].

(c) Give one advantage and one disadvantage of vacuum forming compared to injection moulding [2]

Advantage (any one for [1]):

• Lower tooling cost / cheaper moulds - vacuum forming moulds can be made from wood or resin rather than expensive hardened steel.
• More suitable for one-off or batch production runs where high initial investment in tooling is not justified.

Disadvantage (any one for [1]):

• Only produces simple, open (single-sided) shapes - complex enclosed forms with undercuts cannot be made.
• Uneven wall thickness / thinning at corners and deep draws - the material stretches thinner where it has to travel furthest over the mould.
• Slower for mass production - cycle times are longer and each piece needs trimming, making it less efficient at very high volumes.

(a) Name the tool labelled A and the material labelled B [2]

1. A - Soldering iron [1]. This is an electrically heated tool with a pointed copper tip (called the bit). It is used to transfer heat to the joint area on the PCB, melting the solder so it flows around the component lead and copper track.
2. B - Solder [1]. Solder is a low-melting-point alloy (traditionally a tin-lead mixture, now often lead-free tin-copper or tin-silver-copper) supplied as wire. When melted by the soldering iron, it flows into the joint by capillary action and solidifies to form a permanent electrical and mechanical connection between the component lead and the copper track on the PCB.

(a) Name the thermosetting polymer commonly used to make the decorative laminated surface labelled A [1]

Melamine / melamine formaldehyde [1]. This thermosetting polymer is produced as thin decorative sheets that are bonded under heat and pressure to a substrate (typically chipboard or MDF) to create laminated worktops and surfaces.

(b) State two properties of this thermosetting polymer that make it suitable for a kitchen worktop surface [2]

Any two from the following, each worth [1]:

• Heat resistant / does not soften when heated - as a thermoset, melamine formaldehyde has permanent cross-linked bonds that do not break down with heat, so hot pans placed on the surface will not cause it to deform or melt.
• Scratch resistant / hard surface - the high surface hardness resists scratching from knives, utensils, and abrasive cleaning, maintaining its appearance over years of use.
• Waterproof / moisture resistant - it does not absorb water, preventing swelling, warping, or degradation in the wet kitchen environment.
• Stain resistant / easy to clean - the smooth, non-porous surface does not absorb food stains, grease, or cleaning chemicals, and can be wiped clean easily.
• Can be produced with a decorative/coloured finish - melamine sheets are available in a wide range of colours, patterns, and textures (including wood grain and stone effects), giving designers visual flexibility.

(a)

1. Name the process: The process shown is press forming (also known as stamping or die cutting). A sheet of metal is placed between a punch and a die, and the press forces the punch down to cut or shape the metal into the required profile. [1]
2. One advantage in a factory: It is fast for large quantities; once the die is made, each pressing takes only seconds. Components are identical and accurate, reducing waste compared with hand cutting and making it cost-effective for mass production. [1]

(b)

1. Scale of production for a single 3D-printed prototype: One-off production. A single, unique item is made, typically at higher unit cost but without the expense of moulds or tooling. [1]
2. Two advantages of 3D printing a prototype rather than making by hand:
   • Complex shapes (internal cavities, thin walls, organic curves) can be produced that would be difficult or impossible to achieve by hand, since the printer builds layer by layer. [1]
   • The prototype is made directly from a CAD file with high dimensional accuracy; design changes can be implemented quickly by modifying the digital model and reprinting. [1]
3. Why 3D printing is unsuitable for 100 000 identical phone cases: 3D printing is slow (each case is built layer by layer over minutes to hours), making very high volumes impractical in terms of time. The unit cost remains constant regardless of quantity, whereas injection moulding has a high initial tooling cost but very low per-unit cost at scale, making it far more economical for mass production.

(c)

1. CNC stands for: Computer Numerical Control. A computer reads coded instructions (G-code) to control the machine tool's movements with high precision and repeatability. [1]
2. Software for creating digital CNC instructions: CAM (Computer Aided Manufacture) software. CAM converts a CAD model into machine-readable tool paths, specifying cutting strategies, feed rates, and depths of cut. [1]

(d)

1. Purpose of a jig: A jig holds and locates the workpiece while guiding the cutting tool, ensuring every component is manufactured identically without the need for individual marking out. [1]
2. Advantage of using a jig for batch quantities: It ensures accuracy and consistency, with all features produced in exactly the same position on every component. It also speeds up production because less time is spent measuring and marking out each piece, and less skilled operators can produce accurate work. [1]
3. Part labelled 'stop' and its function: The stop (end stop / location stop) positions each workpiece against a fixed edge so it is placed in exactly the same position before the operation begins, guaranteeing identical positioning across the batch. [1]

(e)

1. Process shown: Injection moulding. Granules of thermoplastic are heated until molten, then injected under high pressure into a steel mould cavity. The plastic cools and solidifies into the shape of the mould. [1]
2. One product made using this process: Plastic bucket, bottle cap, toy, phone case, comb, ruler, or plastic chair (any suitable mass-produced thermoplastic product). [1]

(f)

1. Scale of production: Mass production (also called continuous production). This is the manufacture of very large quantities of identical products on a continuous or near-continuous basis. [1]
2. Two advantages of mass production compared with one-off production:
   • Lower unit cost: The high initial investment in tooling, moulds, and automated machinery is spread across a very large number of units, drastically reducing the cost per item. In one-off production, all setup costs apply to just one item. [1]
   • Consistency and quality: Automated processes and fixed tooling produce identical products with minimal variation. Every chair meets the same specification, reducing waste and rework. One-off production relies more on individual skill, leading to potential variation. [1]
   • Speed: Automated production lines operate continuously at high speed. 50 000 chairs per week would be impossible to achieve with one-off methods.
   • Less skilled labour: Automated systems require operators rather than highly skilled craftspeople, reducing labour costs.