Mechanical Technology Grade 12 NSC June 2024 Memo (English)

SENIOR CERTIFICATE EXAMINATIONS/ NATIONAL SENIOR CERTIFICATE EXAMINATIONS MECHANICAL TECHNOLOGY: WELDING AND METALWORK MAY/JUNE 2024 MARKING GUIDELINES MARKS: 200 These marking guidelines consist of 17 pages. Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 2 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) 1.1 A ✓ (1) 1.2 B ✓ (1) 1.3 A ✓ (1) 1.4 D ✓ (1) 1.5 C ✓ (1) 1.6 C ✓ (1) [6] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 3 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 2: SAFETY (GENERIC) 2.1 First aid: • When illness occurs. ✓ • When an injury is sustained. ✓ • When an accident occurs. ✓ (Any 2 x 1) (2) 2.2 Bench grinder: A. A fire extinguisher should be available. ✓ B. Safety glasses must be worn. ✓ C. Maximum grinding wheel speed. ✓ D. Maximum distance between tool rest and grinding wheel. ✓ (4) 2.3 Drill press: • Never try to stop/hold the work piece by hands when the drill bit get stuck during drilling. ✓ • Don’t force a drill bit into the work piece. ✓ • Keep loose clothing and hair away from revolving parts. ✓ • Never leave the machine running if it is unattended. ✓ • Use a brush or wooden rod to remove chips from the drill. ✓ • Do not put hands near moving parts. ✓ • Never clean or adjust the machine while it is in motion. ✓ • Never try to stop the drill/chuck by hands. ✓ (Any 2 x 1) (2) 2.4 Surface grinder: • Never clean or adjust the machine while it is in motion. ✓ • Know how to stop the machine in an emergency. ✓ • Do not use excessive force when grinding the work piece. ✓ • Immediately report any dangerous defects of the machine. ✓ • Stop using defective machinery until it has been repaired by a qualified person. ✓ • Ensure that the grinding wheel is not submerged in coolant. ✓ • Never leave the machine running if it is unattended. ✓ • Do not put hands near moving parts. ✓ (Any 2 x 1) (2) [10] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 4 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 3: MATERIALS (GENERIC) 3.1 Critical temperature: 3.1.1 Hardening: Above ✓ (1) 3.1.2 Tempering: Below ✓ (1) 3.1.3 Normalising: Above ✓ (1) 3.2 Machining test: • The chips heating colour ✓ • The chips curl ✓ (2) 3.3 Material tests: • Sound test ✓ • Bending test ✓ • Filing test ✓ • Hardness test ✓ • Density test ✓ • Weight measurement ✓ • Magnetic test ✓ • Visual inspection/observation ✓ • Scratch test ✓ (Any 3 x 1) (3) 3.4 Quenching methods: • Carburising ✓ • Nitriding ✓ • Cyaniding ✓ (Any 2 x 1) (2) 3.5 Heat treatment temperature: • Pyrometer ✓ • Crayons ✓ • Visually ✓ • Magnet ✓ (Any 1 x 1) (1) 3.6 Heat-treatment steps: • Heat the metal. ✓ • Soak the metal. ✓ • Cool the metal. ✓ (3) [14] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 5 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) 4.1 D✓ (1) 4.2 B✓ (1) 4.3 B✓ (1) 4.4 A✓ (1) 4.5 D✓ (1) 4.6 A✓ (1) 4.7 C✓ (1) 4.8 B✓ (1) 4.9 D✓ (1) 4.10 A✓ (1) 4.11 C✓ (1) 4.12 C✓ (1) 4.13 B✓ (1) 4.14 D✓ (1) [14] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 6 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 5: TERMINOLOGY(TEMPLATES) (SPECIFIC) 5.1 Labeling of roof truss: A - Roof sheeting ✓ B - Ridging ✓ C - King post ✓ D - Tie beam/main tie ✓ E - Internal bracing ✓ F - Rafter ✓ G - Gusset plate ✓ (7) 5.2 Brass ring calculations: 5.2.1 MeanØ = OutsideØ − plate thickness = 380 − 15 ✓ = 365 mm✓ (2) 5.2.2 Mean circumfere nce = π  Mean Ø = π  365 ✓ = 1146,68 ✓ = 1147 mm ✓ (3) 5. 3 Weld symbol: ✓ ✓ ✓ ✓ (4) 5.4 Supplementary weld symbols: • Indicate additional ✓ information about a weld. ✓ • Supplementary ✓ information about a weld. ✓ (Any 1 x 2) (2) 5.5 Advantages of using templates: • Quicker to use to improve mass production. ✓ • Accurate production. ✓ • Cheap to manufacture. ✓ • Unskilled labour will be able to use it. ✓ • Avoid unnecessary wastages / cost effective. ✓ • It gives uniformity in production. ✓ • Can be reused. ✓ (Any 2 x 1) (2) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 7 DBE/May/June 2024 SC/NSC – Marking Guidelines 5.6 Template machine tools: • Planer ✓ • Circular saw ✓ • Drilling machine ✓ • Jig saw ✓ • Sanding machine ✓ • Shears ✓ • Cut off saw ✓ • Bench grinder ✓ • Hydraulic press ✓ (Any 3 x 1) (3) [23] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 8 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 6: TOOLS AND EQUIPMENT (SPECIFIC) 6.1 Working principles: 6.1.1 Power driven guillotine: • Activated by foot pedal. ✓ • Driven by an electric motor, flywheel, gearbox and axle. ✓ • Top cutting blade moves downwards. ✓ • Uses eccentric motion for the cutting stroke. ✓ (4) 6.1.2 Pyramid bending rolls: • A bending roll has three rollers mounted in a horizontal position. ✓ • At the bottom there are two fixed rollers next to each other, rotating in unison. ✓ • The top roller is adjustable (up and down) applying downward pressure on the metal. ✓ • That causes the metal to deflect and ultimately form the round shape desired. ✓ (4) 6.2 Uses of the hydraulic press: • Installing components. ✓ • Removing components. ✓ • To press profiles. ✓ • Bending. ✓ (Any 2 x 1) (2) 6.3. Types of hardness testers: • Rockwell Hardness tester ✓ • Brinell Hardness tester ✓ • Vickers Hardness tester ✓ (Any 2 x 1) (2) 6.4 Labels for gas welding: A – Filler rod/Welding rod/Brazing rod ✓ B – Welding tip/Welding nozzle ✓ C – Flame ✓ D – Parent metal/Work piece ✓ (4) 6.5 Function of the plasma cutter: Cuts ✓ through electrically conductive materials. ✓ (2) [18] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 9 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 7: FORCES (SPECIFIC) 7.1 Beams: 7.1.1 Distributed load: 10 x 3= 30 N ✓ (1) 7.1.2 Reaction (RL): Take moments about RR: ✓ ✓ ✓ RL x 10 = (25 x 2 ) + (30 x 6,5) + (15 x 8) = 50 + 195 + 120 10 RL 365 ∴ = 10 10 RL = 36,5 N ✓ Reaction (RR): Take moments about RL: ✓ ✓ ✓ RR x 10 = (15 x 2) + (30 x 3,5) + (25 x 8) = 30 + 105 + 200 10 RR 335 ∴ = 10 10 RR= 33,5 N ✓ (8) 7.1.3 Shear force: SFA = 36,5 – 15 ✓ = 21,5 N ✓ SFB = 36,5 – 15 – 30 ✓ = –8,5 N ✓ SFC = 36,5 – 15 – 30 – 25 ✓ = –33,5 N ✓ (6) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 10 DBE/May/June 2024 SC/NSC – Marking Guidelines 7.1.4 Scale: Space diagram 1 m = 10 mm Shear force 1N = 1 mm A B ✓ C ✓ 36,5 N 21,5 N ✓✓ CROSS HATCHING ✓ 0 ✓ 0 - 8,5 N ✓ -33,5 N ✓ Note to marker: . Marker must redraw the shear force diagram according to given scales for marking purposes. (8) ` Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 11 DBE/May/June 2024 SC/NSC – Marking Guidelines 7.2 Stress and Strain: 7.2.1 Stress: πD 2 A = 4 π  0,036 2  = 4 = 1,01787602  10−3 m 2    F Stress =  A  110  10 3   = 1,01787602 x10 −3   = 108068171,2 Pa     =108,07 MPa     (5)  7.2.2 Strain:   ΔL  ε =  OL  0,6   ε = 125  = 0,0048  (3)             Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 12 DBE/May/June 2024 SC/NSC – Marking Guidelines 7.3 Simple frame: 7.3.1 Space diagram: A  B  D 30°   60°   C    (Scale)  NOTE: Draw to scale on transparency for  marking purpose. Mark allocation  for scale and each member with arrows showing  strut or tie.   (4)    7.3.2 Force diagram:   a    ✓ ✓ ✓ d c ✓ ✓ Note to marker: Marker must redraw the space and force diagrams according to given scales for marking purposes. b (4) 7.3.3 Magnitude and nature of force: Member Force Nature AD 100 N ✓ Strut ✓ BD 174 N ✓ Strut ✓ CD 86 N ✓ Tie ✓ NOTE: Allow ± 2 mm tolerance. (6) [45] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 13 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 8: JOINING METHODS (INSPECTION OF WELD) (SPECIFIC) 8.1 Prevent incomplete penetration: • Use correct travel speed. ✓ • Use narrow/correct joint. ✓ • Use correct welding current. ✓ • Use correct electrode angle. ✓ • Use correct weaving technique. ✓ • Clean the base/parent metal. ✓ (Any 3 x 1) (3) 8.2 Visual inspection of welds: • Cracks ✓ • Lack of fusion ✓ • Excessive spatter ✓ • Undercutting. ✓ • Craters ✓ (Any 2 x 1) (2) 8.3 Fusion: The proper bonding of the weld metal ✓ with the base metal. ✓ (2) 8.4 Undercutting: • Adjust the welding parameters. ✓ • Control heat input. ✓ • Ensure proper electrode angle. ✓ (3) 8.5 Purpose of the nick break test: • To assess the ductility. ✓ • To check penetration. ✓ • To check for fusion. ✓ • To check porosity. ✓ • To check for undercutting. ✓ (Any 2 x 1) (2) 8.6 Width and height of a weld bead: To provide structural integrity ✓ and proper strength ✓ distribution along the joint. ✓ (3) 8.7 Inspection of welds: • Clean bead. ✓ • Constant width and height. ✓ • Fusion and penetration. ✓ • Absence of cracks. ✓ • Undercutting. ✓ • Craters ✓ (Any 3 x 1) (3) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 14 DBE/May/June 2024 SC/NSC – Marking Guidelines 8.8 Liquid dye test on a welded joint: • Clean the surface to be tested. ✓ • Spray the liquid dye penetrant onto the surface and allow liquid dye to penetrate. ✓ • Remove excess dye with a cleaner. ✓ • Spray a developer onto the surface to bring out the colour. ✓ • Observe surface for defects. ✓ (5) [23] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 15 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 Stress relieving: • To reduce/eliminate residual stresses in welded structures. ✓ • To improve their dimensional stability. ✓ • To improve resistance to distortion. ✓ (3) 9.2 Factors contributing to distortion and residual stress: • Material properties. ✓ • Joint design. ✓ • Welding process. ✓ • Parameters. ✓ • Rate of cooling. ✓ (Any 3 x 1) (3) 9.3 Mechanical properties: • Hardness ✓ • Strength ✓ • Ductility ✓ • Malleability ✓ • Elasticity ✓ (Any 4 x 1) (4) 9.4 Factors influencing the grain size: • The amount of temperature and duration of the annealing process. ✓ • The composition of the steel. ✓ • Its melting point. ✓ (3) 9.5 Cause of shrinkage: The cooling of the weld metal, which leads to contraction. ✓ (1) 9.6 Welding methods: • Tack welding. ✓ • Intermittent welding. ✓ • Back-step welding. ✓ • Do not over weld. ✓ • Place welds near neutral axis. ✓ • Use as few passes as possible. ✓ • Anticipate shrinkage forces. ✓ • Use strongbacks. ✓ • Use clamps, jigs and fixtures. ✓ (Any 4 x 1) (4) [18] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 16 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 10: MAINTENANCE (SPECIFIC) 10.1 Failure in machines: • Lack of lubrication or incorrect lubrication. ✓ • Overloading. ✓ • Friction. ✓ (Any 2 x 1) (2) 10.2 Power driven guillotine: • Test for correct operation. ✓ • Check that all guards are in place and operational. ✓ • Check if operating instructions are displayed. ✓ • Ensure that ancillary equipment is closely located. ✓ • Check if appropriate PPE is kept close by. ✓ • Check if housekeeping equipment is readily available. ✓ • Ensure that the guillotine is properly secured to the floor. ✓ • Tighten loose nuts and bolts. ✓ • Lubricate the machine adequately. ✓ • Clean the machine. ✓ (Any 4 x 1) (4) 10.3 Failure of rollers: • Worn or damaged bearings. ✓ • Misalignment. ✓ • Contamination. ✓ • Excessive load. ✓ • Inadequate lubrication. ✓ (Any 2 x 1) (2) [8] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 17 DBE/May/June 2024 SC/NSC – Marking Guidelines QUESTION 11: TERMINOLOGY (DEVELOPMENT) (SPECIFIC) 11.1 Square ✓ to round. ✓ (2) 11.2 Cone: 11.2.1 Type of cone: • Conical frustrum ✓ • Truncated cone ✓ (Any 1 x 1) (1) 11.2.2 Conical frustrum: A – Vertical height ✓ B – Top radius/Small radius ✓ C – Slant height ✓ D – Base radius/Large radius ✓ (4) 11.3 Hopper: 11.3.1 A-1    A − 1 = 480 + 700 + 700 2 2 2 = 230400 + 490000 + 490000 = 1210400  = 1100,18 mm  (5) 11.3.2 C-3    C − 3 = 250 + 120 + 700 2 2 2 = 62500 + 14400 + 490000 = 566900  = 752,93 mm  (5) 11.3.3 X1-X2   X1 − X 2 = 480 2 + 700 2 = 230400 + 490000 = 720400  = 848,76 mm  (4) [21] TOTAL: 200 Copyright reserved