Mechanical Technology Grade 12 Eastern Cape Mock 2020 Memo

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 SEPTEMBER 2020 MECHANICAL TECHNOLOGY: WELDING AND METALWORK MARKING GUIDELINE MARKS: 200 This marking guideline consists of 18 pages.

Downloaded from hlayiso.com 2 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) QUESTION 1: MULTIPLE-CHOICE QUESTIONS (GENERIC) 1.1 C (1) 1.2 B (1) 1.3 C (1) 1.4 A (1) 1.5 B (1) 1.6 C (1) [6] QUESTION 2: SAFETY (GENERIC) 2.1 Gas welding (PPE)  Eye protection   Overall / leather apron   Safety boots   Gloves  (Any 2 x 1) (2) 2.2 Safety rules that must be followed while the surface grinder is in operation:  Make sure that the sparks pose no danger to co-workers.   Do not force the material onto the grinding wheel.   Do not plunge grind.   Bring the material slowly into contact with the grinding wheel.   Never clean or adjust the machine whilst it is in motion.   Use cutting fluid.   Know where the emergency stop is located.   Stop machine before any adjustment   Keep tools clear from moving parts.  (Any 2 x 1) (2) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 3 2.3 Completing a task on any machine Switch the machine off.  (1) 2.4 TWO safety precautions before switching on the angle grinder  Make sure that there are no cracks or chips on the disc.   Make sure that the emery disc that is fitted is rated above the revolutions at which it is turned by the motor.   Make sure that the space between the tool rest and the emery disc does not exceed 3 mm.   Ensure that guards are in place   When switching on the machine, do not stand in front of it, until it reaches its full speed.   Do not force or bump the work piece against the emery disc.   Grind only on the front surface of the wheel, not the sides.   All grinding machines must have a sign indicating the revolutions at which the spindle rotates.  (Any 2 x 1) (2) 2.5 Importance of a welding helmet  To protect your eyes and face from ultra-violet rays and radiation  (1) 2.6 Types of workshop layouts:  Process layout   Product layout  (2) [10] Copyright reserved Please turn over

Downloaded from hlayiso.com 4 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) QUESTION 3: MATERIALS (GENERIC) 3.1 DIFFERENT TYPES OF TESTS MATERIALS Sound Filing Bend Cast iron Very dull sound  Easy  Cannot bend / Snaps/breaks / Fractures easily  Mild steel Medium metallic Easy  Bends easily  sound  (6) 3.2 Heat treatment process  Is the heating and cooling of metals in their solid state so as to change their properties.  (1) 3.3 Hardness factors:  Workpiece size   Quenching rate   Carbon content  (Any 2 x 1) (2) 3.4 Heat treatment processes: 3.4.1 Tempering  Is a process applied to steel and it relieves the strain induced during the hardening process.   It decreases the degree of hardness   It increases toughness   It reduces brittleness   It gives steel fine grain structure  (Any 2 x 1) (2) 3.4.2 Annealing  Relieves internal stress   Softens the metal   Makes metal ductile   Refines the grain structure   Reduces brittleness  (Any 2 x 1) (2) 3.5 Hardness of steel depends upon  Carbon content  (1) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 5 QUESTION 4: MULTIPLE-CHOICE QUESTIONS (SPECIFIC) 4.1 A (1) 4.2 D (1) 4.3 C (1) 4.4 C (1) 4.5 D (1) 4.6 B (1) 4.7 D (1) 4.8 D (1) 4.9 A (1) 4.10 A (1) 4.11 A (1) 4.12 B (1) 4.13 B (1) 4.14 A (1) [14] Copyright reserved Please turn over

Downloaded from hlayiso.com 6 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) QUESTION 5: TERMINOLOGY (TEMPLATES) (SPECIFIC) 5.1 Template loft: Is the heart of the structural workshop. (2) 5.2 THREE qualities of a good template loft:  Accuracy   Quietness   Better lighting   Separate from main building   Wooden floor with black matt finish   Large space to accommodate required work  (Any 3 x 1) (3) 5.3 Web template  Is used to mark out the positions of holes on the webs of the channel iron and girder sections.  (2) 5.4 A steel ring: 5.4.1 Dimensions of the required material: Mean diameter = Outside diameter – Plate thickness  = 500 – 30  = 470 mm  Mean circumference = π x Mean diameter  = π x 470  =1 476,55 mm  (6) 5.4.2 Make a neat sketch of the steel ring indicating the mean diameter, outside diameter and the thickness of the material: 1476,55 mm of 30 x 30 mm square steel bar is required to fabricate the ring. Material 30 mm thickness (4) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 7 5.5 Fillet weld on T-joint: Arc  10  60 – 100     (6) [23] Copyright reserved Please turn over

Downloaded from hlayiso.com 8 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) QUESTION 6: TOOLS AND EQUIPMENT (SPECIFIC) 6.1 Uses of the machines 6.1.1 Guillotine  To cut sheet metal   To cut plate metal  (2) 6.1.2 Bench grinder  Hand grinding-cutting tools   Sharpening cutting tools  (2) 6.1.3 Press machine  Is used to install or remove components such as bearings or bushes in machines or mechanical devices  (2) 6.2 Joining equipment labels: 6.2.1 A – Gauges  B – Outlet  C – Inlet  D – Bonnet  (4) 6.2.2  Oxygen regulator  (1) 6.3 Function of stock and dies:  They are used to cut internal and external threads of the bolt and nut.  (1) 6.4 Function of regulators: To reduce the cylinder pressure to operating or working pressure.  (2) 6.5 Operating principle of plasma cutter: The process involves creating an electrical channel of ionised gas;  that is the plasma cutter itself, through the work piece that is being cut; this forms an electric circuit back to the plasma cutter via a grounding clamp;  accomplishing this via air that is blowing towards the work piece through a focused nozzle.  (4) [18] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 9 QUESTION 7: FORCES (SPECIFIC) 7.1 Term definition 7.1.1 Force: is an influence which changes or tends to change the state of rest of a body or motion  OR It is often more convenient to think about a “pull” or “push” (Any 1 x 2) (2) 7.1.2 Hooke’s law: Strain is directly proportional to the stress it caused, provided the limit of proportionality is not Exceeded.  (2) 7.2 Stress and strain 7.2.1 𝝅𝑫𝟐 Area = 𝟒 𝜋 x (0,024)2 = 4 = 4,525 x 10−4 𝑚2 𝐹𝑜𝑟𝑐𝑒 Stress = 𝐴𝑟𝑒𝑎 60 𝑥 103 =  4,525 𝑥 10−4 = 132,579 x 106 Pa  (2) 7.2.2 Change in length Strain = Original length 0,22 x 10−3 =  212 x 10−3 = 1,038 x 10−3 = 1,04 x 10−3  (2) 7.2.3 𝑆𝑡𝑟𝑒𝑠𝑠 Young’s modulus of elasticity (E) =  𝑆𝑡𝑟𝑎𝑖𝑛 132,58 x 106 =  1,04 x 10−3 = 127,48 x 109  = 127,48 GPa  (4) Copyright reserved Please turn over

Downloaded from hlayiso.com 10 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) 7.3 Calculations of the reactions, bending moments and shear force 7.3.1 Moments about RL: RR X 8 = (2 x 4) + (6 x 5) + (3 x 6)  = 8 + 30 + 18 = 56  RR = 7 N  Moments about RR: RL X 8 = (3 x 2) + (6 x 3) + (2 x 4)  = 6 + 18 + 8 = 32  RL = 4 N  (6) 7.3.2 The bending moments at points A, B and C. 𝐵𝑀𝐴 = (4 x 4) = 16 N  𝐵𝑀𝐵 = (4 x 6) – (2 x 2) – (6 x 1) = 14 N  𝐵𝑀𝐶 = (4 x 7) – (2 x 3) – (6 x 2) – (3 x 1) = 7 N  (3) 7.3.3 Shear forces at points, A, B and C 𝑆𝐹𝐴 = 4 2 = 2  𝑆𝐹𝐵 = 4 – 2 – 6 = -4  𝑆𝐹𝐶 = 4 – 2 – 6 – 3 = -7  (3) Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 11 7.3.4 (5) 7.3.5 (5) Copyright reserved Please turn over

Downloaded from hlayiso.com 12 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) 7.4 100 kN A B D 25kN 75kN 7000 Space diagram = 1 mark a   c d   b Member Force Nature AD 29 kN  Strut  BD 76 kN  Strut  CD 14 kN  Tie  (11) [45] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 13 QUESTION 8: JOINING METHODS (INSPECTION WELD) (SPECIFIC) 8.1 Arc welding  Rate of rod burning and the progress of the weld   Amount of penetration and fusion   The way the weld metal is flowing   The sound of the arc, indicating correct current and voltage for the particular weld  (Any 2 x 1) (2) Oxy-acetylene  Correct flame for the work on hand   Correct angle of blowpipe and rod, depending on the method being used   Depth of fusion and amount of penetration   The rate of progress along the joint  (Any 2 x 1) (2) 8.2  HAZ (Heat-affected zone)   Centreline cracks   Crater cracks   Transverse cracks  (Any 2 x 2) (4) 8.3 A – Penetration  B – Width  C – Height  D – Weld bead  E – Base metal  (5) 8.4  Shape of profile   Uniformity   Overlap   Undercutting   Penetration bead   Root groove  (Any 2 x 1) (2) 8.5 8.5.1 Spatter Caused by voltage being too low  or amperage being too high.  (2) 8.5.2 Incomplete penetration  The weld bead does not penetrate the full depth of the weld or into the root of the weld.   Two opposing weld beads do not inter-penetrate.   The weld does not penetrate to the toe of a fillet weld but only bridges across it.  (Any 2 x 1) (2) Copyright reserved Please turn over

Downloaded from hlayiso.com 14 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) 8.6 Arc welding  Rate of rod burning and the progress of the weld   Amount of penetration and fusion   The way the weld metal is flowing   The sound of the arc, indicating correct current and voltage for the particular weld  (Any 2 x 1) (2) 8.7 Testers 8.7.1 Nick-break test is done to: Determine the internal quality of the weld metal  and can reveal the internal defects  (2) 8.7.2 Machinability test is done to: Determine the hardness  and strength of the welded joint. (2) [25] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 15 QUESTION 9: JOINING METHODS (STRESSES) (SPECIFIC) 9.1 Term definition 9.1.1 Weld distortion: Takes place in a welded joints due to uneven expansion and contractions  as a result of intense heat of the arc or oxy-acetylene flame. (2) 9.1.2 Residual Stress: Is the internal stress distribution locked into the material; these stresses are present even after all external loads or forces have been removed.  (2) 9.2 Factors affecting grain size  The prior amount of cold work  The temperature and time of the annealing process   Composition and constitution   Its melting point  (Any 2 x 1) (2) 9.3 Low carbon steel  0,15 – 0,30%  Medium carbon steel  0,31 – 0,70%  High carbon steel 0,71 – 1,5% (Any 2 x 2) (4) 9.4 Quenching mediums  Brine   Water   Oil   Metal salt   Air  (Any 2 x 1) (2) 9.5 Factors affecting shrinkage in welding  Size of work piece   Weld thickness   Thermal conductive properties of parent metal  (Any 2 x 1) (2) Copyright reserved Please turn over

Downloaded from hlayiso.com 16 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) 9.6 9.6.1 Transverse shrinkage (2) 9.6.2 Longitudinal shrinkage (2) [18] QUESTION 10: MAINTENANCE (SPECIFIC) 10.1 Keeping records assists in upholding warrantees and guarantees because service requirements inevitably form part of agreements.  (1) 10.2 Due to the danger associated with a large machine, it is critical to isolate the machine completely before any maintenance is undertaken  to ensure nobody can turn on the machine.  (2) 10.3 Friction can be reduced by applying cutting fluid or light oil to the drill bit.  (1) 10.4 10.4.1 Cutting plate of excessive thickness  or hardness will overload both the blade and hydraulic system.  (2) 10.4.2 The feed speed which is higher than the rate at which the power saw can cut,  effectively results in the blade being forced into the materials.  (2) [8] Copyright reserved Please turn over

Downloaded from hlayiso.com (EC/SEPTEMBER 2020) MECHANICAL TECHNOLOGY: WELDING AND METALWORK 17 QUESTION 11: DEVELOPMENT (SPECIFIC) 11.1 11.1.1 Cˆ  70 EC  BC  BE  2 1   1m EC EC  Cos 70  DC  DC Cos 70 1 DC  DC  2.92m Cos 70 (5) 11.1.2 BC Cos 70  AC BC AC   Cos 70 2 AC  Cos 70  AC  5.85m (4) 11.1.3 Circumf .  D   (4)   12.57m (3) Copyright reserved Please turn over

Downloaded from hlayiso.com 18 MECHANICAL TECHNOLOGY: WELDING AND METALWORK (EC/SEPTEMBER 2020) 11.2 Square-to-round transition piece: 11.2.1 The true length FG is firstly needed to draw the pattern. IK  300 (2 units) IH  150 (1unit) HK  1 3 (1unit 3 ) The true length FG : Plan length FG  FG  GK   400  300  100 mm  The true FG is equal to H' F H' F 2  H' G2  GF 2   800  100 2 2  H' F  650 000 True length FG  806 mm  (5) 11.2.2 To determine the plan length CI, the sides CE and EI of triangle CEI must first be calculated. CE  CF  EF  400  150  250 mm  But EI  FH FH  FK  HK  400  259,8  140,2 mm  True length CI  FH 2  EI2   2502  140,22  82156,04  286,63 mm  (4) [21] TOTAL: 200 Copyright reserved Please turn over