1. No category

Coimisiún na Scrúduithe Stáit
State Examinations Commission
Leaving Certificate Examination 2006
Technical Drawing
Paper 2A - Higher Level
(Engineering Applications)
Marking Scheme
and Sample Solutions
(Other valid solutions are acceptable and marked accordingly)
MARKING SCHEME: QUESTION 1
(a)
(b)
(c)
(d)
ASSEMBLY
SECTIONAL ELEVATION
ADDITIONAL REQUIREMENTS
OPERATION/MODIFICATION
TOTAL
ASSEMBLY
Gasket in position
Cover in valve body
Spindle piston in cover
Valve seat in body
Valve on spindle
Nut and washer on spindle
Valve in closed position
(7)
1
1
1
1
1
1
1
SECTIONAL ELEVATION
(23)
BODY
Body outline
Internal features
Fillets
7
3
3
1
GASKET
Left area
Right area
2
1
1
COVER
M75 thread convention & chamfer
Ø100 mm x 10 mm flange
Nut portion of cover
3
1
1
1
VALVE SEAT
Outline
Ø 40mm hole & chamfer
2
1
1
VALVE
Chamfer & body
Boss & spindle hole
2
1
1
7
23
15
5
50 Marks
SPINDLE
Piston end areas
Ø 4 mm hole
Ø 20 mm x 45 mm shank
M12 thread end
4
1
1
1
1
WASHER
Washer outline
1
1
M12 NUT
Three faces on nut
Curves on faces
2
1
1
ADDITIONAL REQUIREMENTS (15)
Centre lines
1
Hatching of components
3
Parts item referenced
3
(Leaders; Terminations; Numbers)
Title supplied
2
(G=1; Ex=2)
Overall presentation
6
(F=4; G=5; Ex=6)
OPERATION /MODIFICATION
Flow direction
Purpose of 4 mm hole
Suitable modification suggested
Method shown in sketch
Sketch presentation
(5)
1
1
1
1
1
MARKING SCHEME: QUESTION 2
(a)
(b)
CAM & DISPLACEMENT DIAGRAM
MECHANISM
TOTAL
30
20
50 Marks
CAM
(30)
MECHANISM
(20)
DISPLACEMENT DIAGRAM
Twelve appropriate divisions
Correct heights
S.H.M construction
S.H.M curve drawn & correct
Dwell
U.A.R construction
U.A.R curve drawn & correct
Dwell
Instantaneous fall
Identification system
Presentation
14
2
1
2
1
1
2
1
1
1
1
1
LAYOUT
Centre lines
Crank OD
Link AB
Link BC
4
1
1
1
1
CAM PROFILE
Rotation correct
Angular divisions 00 to 3600
Nearest approach correct
Heights projected and swung
Roller followers drawn
S.H.M drawn/correct
Dwell arc drawn/correct
U.A.R drawn/correct
Dwell arc drawn/correct
Instantaneous fall/correct
Camshaft
Identification system
Presentation
(G=1; Ex=2)
16
2
2
1
1
1
1
1
1
1
1
1
1
2
LOCUS
Circle OD divided into 12 parts
Rotation OD correct
Location of points B on arc AB
Location of points C
Location of points P
Locus drawn & correct
Indexing
Presentation
(G=1; Ex=2)
16
1
1
3
3
3
2
1
2
MARKING SCHEME: QUESTION 3
(a)
(b)
(c)
(d)
(e)
GIVEN VIEWS
TRUE LENGTHS
DEVELOPMENT
SHEET SIZE
SHEET METAL JOINT
TOTAL
GIVEN VIEWS
Elevation correct
Plan correct
End elevation correct
(6)
2
2
2
TRUE LENGTHS
Surface divided into triangles
True lengths obtained/identified
T/L layout
Identification system
(12)
2
8
1
1
DEVELOPMENT
Triangular area correct (17 triangles)
One piece development
Seam correct
Identification system
Presentation
(G=1; Ex=2)
(22)
17
1
1
1
2
SIZE OF RECTANGULAR SHEET (3)
Minimum sheet size shown/stated 3
SHEET METAL JOINT
Single grooved seam sketch
Suitable seam allowance shown
Allowance indicated both ends
Sketch presentation
(7)
3
2
1
1
6
12
22
3
7
50 Marks
MARKING SCHEME: QUESTION 4
(a)
(b)
ISOMETRIC DRAWING
PIPE BEND
30
20
Total 50 Marks
ISOMETRIC DRAWING
(30)
PIPE BEND
(20)
Body
Front face outline
25 mm x 65 mm cut out
Left base area
Left slot
Right base area
Left side area
Top area
Ø 20 mm hole
Other profiles
10
2
1
1
1
1
1
1
1
1
ELEVATION
Top flange
Bottom flange
Ø50 mm pipe bend
Hidden detail bore
Hidden detail flanges
5
1
1
1
1
1
Height Adjusting Nut
Isometric circles
Screw threads
Tangents
Knurling
5
2
1
1
1
SIDE ELEVATION
Top flange OD
Four bolt holes
Bottom flange
Ø50 mm pipe
Hidden detail Ø40 bore
Hidden detail flanges
6
1
1
1
1
1
1
Support
Support head Vee
Support head chamfers
Support head thickness
Support shank & threads
Isometric arcs
6
1
1
1
1
1
VIEW DETAILS
Isometric drawing provided
Correct viewpoint
Method of assembly shown
Construction for isometric circles
Construction of angles
Centre lines
Presentation
(G=1; Ex=2)
9
1
1
1
2
1
1
2
ADDITIONAL REQUIREMENTS 9
Drawing in 1st/3rd angle projection 1
Centre lines
1
Welding symbols
1
Dimensions
4
Overall presentation
2
(G=1; Ex=2)
MARKING SCHEME: QUESTION 5
(a)
(b)
HELICAL CHUTE
BOARD GAME PIECE
TOTAL
HELICAL CHUTE
(38)
LAYOUT
Centre line
Chute inlet
Chute outlet
Outside diameter
Root diameter
Division of circles
Divisions of pitches
Projection lines for crest
Projection lines for root
Indexing
10
1
1
1
1
1
1
1
1
1
1
CHUTE HELIX
Helix rotation correct
1st crest helix plotted
2nd crest helix plotted
1st root helix plotted
2nd root helix plotted
Crest flats drawn
Root flats drawn
17
3
3
3
3
3
1
1
FINISHED CHUTE
Drawing of finished visible profile
Drawing of hidden profile
Drawing of column
Finished plan
Presentation
(G=1; Ex=2)
11
3
2
2
2
2
38
12
50 Marks
BOARD GAME PIECE
Equilateral triangle in plan
Find centre in plan
Establish apex and draw elevation
Find ‘X’ circumcentre in elevation
Determined angle 109o ±2o
(12)
2
2
3
3
2
MARKING SCHEME: QUESTION 6A
(a)
(b)
GEAR AND RACK
CLUTCH
TOTAL
28
22
50 Marks
GEAR AND RACK
(28)
CLUTCH
(22)
SPUR GEAR TEETH
Centre lines
PCD
Addendum circle
Dedendum circle
Base circle
Tooth thickness
Construction of tooth profile
(involute curve or any recognised
approximate method acceptable)
Root radii drawn
Second tooth drawn
Presentation
(G=1; Ex=2)
13
1
1
1
1
1
1
2
PARTS LIST
12 parts identified (1 mark each)
Presentation / lettering
13
12
1
CLUTCH OPERATION
Operation explained
Sketches of clutch
6
3
3
1
2
2
THRUST BEARING
Sectional sketch
3
3
RACK
Pitch line on gear pcd
Addendum line
Dedendum line
Tooth thickness
Pressure angle
Three teeth correctly drawn
Teeth correctly meshing
Presentation
9
1
1
1
1
1
2
1
1
TABLE OF GEAR VALUES
Calculations and formulae shown
Gear Data (6 off x ½ mark each)
Table drawn
Presentation
6
1
3
1
1
MARKING SCHEME: QUESTION 6B
(a)
(b)
(c)
(d)
SHORT CAD QUESTIONS
3D MODEL
CAD COMMAND PAIRS
CAD PROFILE
12
10
11
17
Total 50 Marks
SHORT CAD QUESTIONS
(i)
Four advantages of CAD
(12)
2
(ii)
Parametric CAD system
2
(iii)
Line types
2
(iv)
Layers
2
(v)
Ordinate dimensioning
2
(vi)
Drawing template
2
(vii)
Oblique angle
2
(viii) Hyperlink
Maximum 12 marks
2
3D MODEL
(10)
CAD package
1
Commands used to draw the model 9
(Explanation 5)
(Sketches
4)
CAD COMMAND PAIRS
(i)
Scale/Zoom
(11)
2
(ii)
Text Align/Text Fit
2
(iii)
Associative/Non associative 2
dimensions
(iv)
Wireframe/Solid models
2
(v)
Raster/Vector files
3
CAD PROFILE
Sheet size
Circle
Ellipse
Lines
Extend
Trim
Arc
Polygon
Line
Offset
Fillets
Array
Presentation
(17)
1
1
3
1
1
1
1
2
1
1
1
2
1