Mechanical Technology Nov 2024 (Welding & Metal Work) MG Eng

NATIONAL SENIOR CERTIFICATE GRADE 12 MECHANICAL TECHNOLOGY: WELDING AND METALWORK NOVEMBER 2024 MARKING GUIDELINES MARKS: 200 These marking guidelines consists of 19 pages. Copyright reserved Please turn over

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

Mechanical Technology: Welding and Metalwork 3 DBE/November 2024 NSC – Marking Guidelines QUESTION 2: SAFETY (GENERIC) 2.1 Horizontal band saw (Already been switched on): • Never leave the band saw unattended while in motion. ✓ • Switch off the band saw when leaving. ✓ • Use a brush or wooden rod to remove chips/swarf/filings. ✓ • When reaching around a revolving band saw, be careful that your clothes do not get caught in the blade.  • Don't stop a revolving bandsaw blade with your hand. ✓ • Don't adjust the band saw while working. ✓ • Don't open any guard while in motion. ✓ • Keep hands away from action points. ✓ • Do not force the band saw blade into the material. ✓ • Apply cutting fluid if required. ✓ • Avoid overcrowding of persons around the machine. ✓ • Do not lean on the machine. ✓ • Check if the machine is running smoothly. ✓ (Any 2 x 1) (2) 2.2 First aid basic treatment: • Examination ✓ • Diagnosis ✓ • Treatment ✓ (3) 2.3 Oxygen fittings with oil and grease: It forms a flammable mixture. ✓ (1) 2.4 Disadvantages of the process layout: • Production is not always continuous. ✓ • Transportation costs between process departments may be high. ✓ • Additional time is spent in testing and sorting as the product moves to the different departments. ✓ • Damage to fragile goods may result from extra handling. ✓ (Any 2 x 1) (2) 2.5 Advantages of the product layout: • Handling of material is limited to a minimum. ✓ • Time period of manufacturing cycle is less. ✓ • Production control is almost automatic. ✓ • Control over operations is easier. ✓ • Greater use of unskilled labour is possible. ✓ • Less total inspection is required. ✓ • Less total floor space is needed per unit of production. ✓ (Any 2 x 1) (2) [10] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 4 DBE/November 2024 NSC – Marking Guidelines QUESTION 3: MATERIALS (GENERIC) 3.1 Filing test: 3.1.1 Files easily  (1) 3.1.2 Hard to file  (1) 3.1.3 Files easily  (1) 3.2 Heat treatment: It is the heating  and cooling  of metals under controlled conditions / as to change their properties.  (3) 3.3 Heating of metal: If metal is heated too fast, the outside of the metal becomes hotter  than the inside,  then it is very difficult  to achieve a uniform structure.  (4) 3.4 Case hardening: • Low-carbon steel / Mild steel  • Low-alloy steel  (2) 3.5 Tempering: • It is to relieve the strains induced during the hardening process.  • Increase toughness.  • Decrease brittleness.  • Achieve a finer grain structure.  (Any 1 x 2) (2) [14] Copyright reserved Please turn over

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

Mechanical Technology: Welding and Metalwork 6 DBE/November 2024 NSC – Marking Guidelines QUESTION 5: TERMINOLOGY (TEMPLATES) (SPECIFIC) 5.1 Template loft separation: • It is quieter. ✓✓ • The lighting is better. ✓✓ • All equipment is readily available. ✓✓ • It is a permanent base. ✓✓ • Marking on the floor enhances accuracy. ✓✓ • Specialists works in the template loft. / More specialised work is done in the template loft. ✓✓ (Any 1 x 2) (2) 5.2 Template loft tools: (Due to the large number of alternatives, marker discretion must be used - discuss with IM). • Hand saws ✓ • Chisels ✓ • Plane ✓ • Drill and drill bits ✓ • Steel tape ✓ • Straight edge ✓ • Compass ✓ • Trammel pins ✓ • Carpenter's square ✓ • Protractor ✓ • Chalk line ✓ • Clamps. ✓ (Any 3 x 1) (3) 5.3 Steel ring calculations: 5.3.1 Mean Ø = Outside Ø − Plate thickness = 980 − 25 ✓ = 955 mm ✓ (2) 5.3.2 Mean circumfere nce = π × Mean Ø = π × 955 ✓ = 3000,22 ✓ = 3000 mm ✓ (3) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 7 DBE/November 2024 NSC – Marking Guidelines 5.4 Factors for selecting materials for templates: • Durability ✓ • Cost effective ✓ • Light weight ✓ • Moisture resistant ✓ • Flexible ✓ • Size ✓ • Accuracy required ✓ (Any 2 x 1) (2) 5.5 Fillet weld on T–joint: ✓ ✓ ✓ 50 ✓ ✓ 10 – 100 ✓ Arc ✓ ✓ ✓ (9) 5.6 Welding symbols: 5.6.1 Spot weld: X ✓ (1) 5.6.2 Seam weld: ✓ (1) [23] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 8 DBE/November 2024 NSC – Marking Guidelines QUESTION 6: TOOLS AND EQUIPMENT (SPECIFIC) 6.1 Working principles of: 6.1.1 Punch and cropping machine: • Cropping machines are electrically driven. ✓ • Uses a heavy fly wheel/hydraulics and clutch system. ✓ • It engages various blades/punches. ✓ • Uses shearing/punching motion to cut the various profiles. ✓ (4) 6.1.2 Resistance welding machine: • Current flows through a resistance to fuse plates together.  • Two copper electrodes are pressed against the plates.  • Heavy current is passed between the electrodes.  • The two plates melt and fuse together, forming a weld nugget or spot weld.  (4) 6.2 Uses of the drill press: • Drilling ✓ • Ream work ✓ • Countersinking ✓ • Sawing – hole saw ✓ • Sanding ✓ • Wire brushing ✓ • Buffing/Polishing ✓ • Boring ✓ • Tapping ✓ • Spot facing ✓ • Honing ✓ (Any 3 x 1) (3) 6.3 Types of taps: • Taper tap/starting tap/first tap ✓ • Intermediate/second tap ✓ • Plug or bottoming tap ✓ (3) 6.4 Brinell hardness test procedure: • Makes use of a steel ball as indenter. ✓ • A load is applied to the test piece. ✓ • The diameter of the indentation is measured with a microscope. ✓ • The diameter is used to determine the Brinell reading. ✓ (4) [18] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 9 DBE/November 2024 NSC – Marking Guidelines QUESTION 7: FORCES (SPECIFIC) 7.1 Beams: 7.1.1 Calculate the reaction left (RL): Take moments about RR: ✓ ✓ ✓ RL ×10 = (50 × 2) + (75 × 5) + (60 × 8) = 100 + 375 + 480 955 RL = 10 = 95,5 N ✓ Calculate the reaction right (RR): Take moments about RL: ✓ ✓ ✓ RR ×10 = (60 × 2) + (75 × 5) + (50 × 8) = 120 + 375 + 400 895 RR = 10 = 89,5 N ✓ (8) 7.1.2 Bending moments: BMB = (95,5  2 ) − (60  0) = 191 Nm ✓ BM C = (95,5  5 ) − (60  3) − (75  0) ✓ = 297,5 Nm ✓ BMD = (95,5  8 ) − (60  6) − (75  3) − (50  0) ✓ = 179 Nm ✓ (5) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 10 DBE/November 2024 NSC – Marking Guidelines 7.1.3 Bending moment diagram: 297,5 Nm ✓ ✓ 191 Nm 179 Nm ✓ ✓ ✓ ✓ 0 0 Note to marker: Marker must redraw the bending moment diagram according to given scales for marking purposes. (6) 7.2 Stress and Strain: 7.2.1 Area: πD 2 A= 4 π(0,038) 2  = 4 = 1,13 × 10 -3 m 2   (2) 7.2.2 Stress:   F Stress =  A  120  10 3   = 1,13  10 -3 m 2    = 106,19 MPa    (3)          Copyright reserved Please turn over 

Mechanical Technology: Welding and Metalwork 11 DBE/November 2024 NSC – Marking Guidelines 7.2.3 Strain: Δl ε = ol 0,55  ε = 125  = 0,0044 or 4,4 ×10 -3  (3)  7.2.4 Calculation of  Young's  Modulus: stress   E = strain  106,19  =   4,4 10 -3     = 24,13 GPa  (3)                Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 12 DBE/November 2024 NSC – Marking Guidelines 7.3 Simple frame: 7.3.1 Space diagram: 800 N A B   D      C      400 N 400 N 3 MARKS FORARROWS   1 MARK FOR DRAWING TO SCALE ✓ (4)     7.3.2 Vector diagram:   a        d  c                 b    NOTE: Draw to scale on transparency for marking purpose Tolerance of 2 mm.     (5)   Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 13 DBE/November 2024 NSC – Marking Guidelines 7.3.3 Magnitude and nature of force: Member Force Nature AD 810 N(790-830) ✓ Strut ✓ BD 810 N(790-830) ✓ Strut ✓ CD 700 N(680-720) ✓ Tie ✓ (6) [45] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 14 DBE/November 2024 NSC – Marking Guidelines QUESTION 8: JOINING METHODS (INSPECTION OF WELD) (SPECIFIC) 8.1 Factors to consider during the inspection of welds: • Bead ✓ • Width • Height ✓ • Fusion • Penetration ✓ • Pits ✓ • Undercutting ✓ • Distortion ✓ • Cracks ✓ • Spatter ✓ • No Slag inclusion ✓ • Proper start of weld ✓ • Termination of weld ✓ (Any 2 x 1) (2) 8.2 Welding defects: 8.2.1 Weld spatter: • Too low welding voltages. ✓ • Too high welding current. ✓ • Arc length too long. ✓ • Not applying anti-spatter spray. ✓ • Electrode angle too small. ✓ • Welding speed incorrect. ✓ • Wrong polarity (DC). ✓ • Contaminated surface. ✓ • Wet electrodes. ✓ • Inadequate consumables. (e.g wrong electrodes, not enough shielding gas, etc.) ✓ (Any 2 x 1) (2) 8.2.2 Cracks: • Wrong selection of electrode. ✓ • A restrained welded joint. ✓ • Fast cooling. ✓ • Improper welding technique. ✓ • Absence of preheating and post-heating of the joint. ✓ • Parent metal of poor weldability/High carbon content. ✓ • High residual stress on the base metal. ✓ (Any 2 x 1) (2) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 15 DBE/November 2024 NSC – Marking Guidelines 8.3 Preventions for welding defects: 8.3.1 Incomplete penetration: • Use correct arc length. ✓ • Use correct electrode angle. ✓ • Use correct current setting. ✓ • Use correct travel speed. ✓ • Use correct joint preparation/Remove mould scale/Clean joint. ✓ (Any 2 x 1) (2) 8.3.2 Undercutting: • Decrease arc travel speed. ✓ • By raising arc voltage. ✓ • By lowering arc voltage. ✓ • By lowering the current. ✓ • Ensure proper joint preparation/Remove mould scale/Clean joint. ✓ • Use correct electrode angle. ✓ (Any 2 x 1) (2) 8.4 Label weld dimension: A. Penetration ✓ B. Width ✓ C. Height/Reinforcement/Cap height/Overfill ✓ D. Weld bead/Deposited metal ✓ E. Base metal/Work-piece/Test piece/Parent metal ✓ (5) 8.5 Machinability test for welded joints: • To evaluate the surface finish. ✓ • To evaluate the integrity of the weld. ✓ • To evaluate defects such as porosity, inclusions or excessive hardness. ✓ • To determine the ease of machining. ✓ (Any 2 x 1) (2) 8.6 Free-bend test on a welded joint: • To determine the percentage elongation of a welded metal. ✓ • It measures the ductility of the weld deposit. ✓ • It measures the heat affected area adjacent to the weld. ✓ (Any 2 x 1) (2) 8.7 Label X-ray test: A. Gamma ray/X-rays ✓ B. Radioactive source/X-ray machine ✓ C. Test piece/Work piece ✓ D. Photographic film/Film ✓ (4) (23) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 16 DBE/November 2024 NSC – Marking Guidelines QUESTION 9: JOINING METHODS (STRESSES AND DISTORTION) (SPECIFIC) 9.1 Factors affecting grain size of steel: • The prior amount of cold work. ✓ • The temperature and time of the annealing process. ✓ • The composition/Type of steel. ✓ • The melting point. ✓ (4) 9.2 Factors that affect distortion and residual stress: • Welding current ✓ • Type/Size of electrode ✓ • Cooling rate ✓ • Size/Thickness of the material ✓ (Any 3 x 1) (3) 9.3 Label iron-carbon equilibrium diagram: A. Carbon percentage ✓ B. Temperature in degrees Celsius ✓ C. AC3 / Higher critical temperature ✓ D. AC1 / Lower critical temperature ✓ (4) 9.4 Quenching media: • Oil ✓ • Water ✓ • Brine ✓ • Air ✓ • Liquid salts ✓ • Sand ✓ • Ash ✓ • Lime ✓ • Molten lead ✓ • Nitrogen air-infused air ✓ (Any 2 x 1) (2) 9.5 Stress relieving: • Annealing ✓ • Tempering ✓ • Normalising ✓ (Any 1 x 1) (1) 9.6 Definition of terms: 9.6.1 Distortion: Distortion is the warping ✓ of the base plate caused by heat. ✓ (2) Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 17 DBE/November 2024 NSC – Marking Guidelines 9.6.2 Elastic deformation: Is the ability of a material to regain its shape ✓ after the stresses have been relieved. ✓ (2) [18] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 18 DBE/November 2024 NSC – Marking Guidelines QUESTION 10: MAINTENANCE (SPECIFIC) 10.1 Maintenance in operating systems: • It helps prolong the lifespan of hardware. ✓ • Minimizes downtime. ✓ • Improves system security. ✓ • Ensures efficient operation. ✓ • Improves safety. ✓ (Any 2 x 1) (2) 10.2 Lack of lubrication: • It causes increased friction between moving parts. ✓ • It causes excessive heat. ✓ • It causes wear. ✓ • Potential damage to components. ✓ (Any 2 x 1) (2) 10.3 Overloading machine: • Premature failure of machine components. ✓ • Decreased lifespan. ✓ • It can create a safety hazard. ✓ (Any 2 x 1) (2) 10.4 Maintenance guidelines for a power saw: • Visual checks of electrical wiring. ✓ • Clearing the workspace. ✓ • Lubricating moving parts. ✓ • Monitor wheel bearings. ✓ • Checking hydraulic oil. ✓ • Repairing any existing leaks. ✓ • Check blade tension. ✓ • Check for proper alignment. ✓ • Inspect belts for wear. ✓ • Daily inspect the chip removal system/band guides. ✓ • Align vice to blade. ✓ • Check that guards are in place. ✓ • Blade condition. ✓ (Any 2 x 1) (2) [8] Copyright reserved Please turn over

Mechanical Technology: Welding and Metalwork 19 DBE/November 2024 NSC – Marking Guidelines QUESTION 11: TERMINOLOGY (DEVELOPMENT) (SPECIFIC) 11.1 Gravity flow: To discharge ✓ its content at the bottom. ✓ (2) 11.2 Value of X: X = 40 2 + 30 2 ✓ = 1600 + 900 ✓ = 2500 ✓ = 50 mm ✓ ✓ ✓ (3) 11.3 ✓ ✓ Square to square off centre hopper: ✓ 11.3.1 B-3: ✓ ✓ ✓ B − 3 = 300 + 600 + 850 2 2 2 = 90000 + 360000 + 722500 = 1172500 ✓ = 1082,82 mm ✓ (5) ✓ 11.3.2 X-Y: ✓✓ ✓ ✓ ✓ X - Y = 250✓ + 850 2 2 = 62500 + 722500 = 785000 ✓ = 886 mm ✓ (4) ✓ 11.3.3 C- 4: ✓✓ ✓ ✓ ✓ ✓ 2 + 850 2 C - 4 = 700 2 + 350 = 490000 + 122500 + 722500 = 1335000 ✓ = 1155,42 mm ✓ (5) ✓ 11.4 Square to square ✓ hopper on ✓ centre. ✓ (2) ✓ [21] ✓ TOTAL: 200 Copyright reserved