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Surface Developments 1
Surface Developments
Sacramento City College
Engineering Design Technology
2
Surface Developments
A surface development is a full-size layout of an object made on a single flat plane. Refer to Figure 18-1.
Example: bookcover
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Surface Developments
Surface developments are also called: Stretchouts
Developments
Surface developments are an important part of industrial drafting.
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Surface Developments
Many different industries use surface developments.
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Surface Developments
These items are made using developments. Pipes.
Air conditioning ducts.
Aircraft.
Automobiles.
Storage tanks.
Cabinets.
Boxes and cartons.
Frozen food packages.
Many other items.
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Surface Developments
A surface development is first drawn as a pattern.
The pattern is then cut from flat sheets of material, that can be folded, rolled or otherwise formed into the required shape.
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Surface Developments
Pattern materials include: Paper.
Cardboard.
Plastics and films.
Metals.
Wood.
Fiberboard.
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Surface Developments
The packaging industry uses surface developments extensively.
Creating packaging requires engineering and artistic skills.
Each package must meet many requirements. The package must protect the contents.
It must look attractive for sales appeal.
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Surface Developments
Packaging must also protect the contents during shipping.
Packaging must also be durable. One use package.
Multiple use package.
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Surface Developments
Designers use many different materials in various thicknesses. Thin paper stock.
Medium thickness paper stock.
Material can be folded easily into the desired shape. Tabs.
Glueless tabs.
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Surface Developments
Packages require allowances for the material thickness.
Bend marks are shown with a circle on the fold line.
Refer to Figure 18-4.
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Figure 18.4
Surface Developments 14
Sheet Metal Pattern Drafting
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Sheet Metal Pattern Drafting
Many different metal objects are made from sheets of metal that are laid out, cut and formed into the required shape and then fastened together. Computer cases
Automobiles
Air conditioning ductwork
Toys
File cabinets
Etc.
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Sheet Metal Pattern Drafting
For each sheet-metal object to be produced, two drawings are usually made. Pictorial drawing.
Shows the product as a picture.
Development or pattern. Used to actually cut out the sheet metal which is
then bent and assembled into the final shape
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Sheet Metal Pattern Drafting
Pictorial drawing Shows the appearance of the final product.
Development or pattern Shows the shape of the object as a flat
sheet, that after rolling, folding and fastening, will form the finished object.
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Figure 18-6
Pictorial
Drawing
Pattern
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Sheet Metal Pattern Drafting
Many thin metal objects are formed by die stamping.
Die Stamping Is pressing a flat sheet into the desired
shape under great pressure.
The flat stock is inserted into a die, which is a mirror image of the final product.
Many thin metal objects are die stamped.
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Sheet Metal Pattern Drafting
Die Stamping examples Brass cartridge cases.
Household utensils.
Wheelbarrows.
Automobile fenders, hoods, doors.
Aircraft parts.
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Sheet Metal Pattern Drafting
Making sheet-metal objects can involve many operations.
All are done with machines.
Refer to Figure 18-7.
Most industrial plants now use mass production with highly complex automatic machines.
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Sheet Metal Pattern Drafting
Sheet Metal Operations Squaring.
Folding.
Wiring.
Box and Pan Brake.
Burring.
Forming.
Setting-down machine.
Turning machine.
Doubling-seaming machine.
Beading machine.
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Shaping
Shaping: Shearing
Cutting
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Shaping
Shaping: Bending
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Shaping
Shaping: Folding
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Sheet Metal Pattern Drafting
Fastening: Riveting
Seaming
Soldering
Welding
Surface Developments 33
Seams and Laps
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Seams and Laps
Knowledge of Wiring.
Hemming.
Seaming.
is also required.
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Sheet Metal Pattern Drafting
Wiring involves reinforcing open ends of articles by
enclosing a wire in the edge.
See Figure 18-11A.
The drafter must add a band of material equal to 2.5 times the wire diameter.
Hemming Method of stiffening edges
Refer to Figure 18-11B and C.
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Wiring
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Seaming
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Seaming
Surface Developments 39
Pattern Development
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Sheet Metal Pattern Drafting
Sheet Metal patterns are developed using surface geometry.
There are two classes of patterns: Plane.
Flat, rectangular, non-spherical objects
Curved. Spherical objects.
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Sheet Metal Pattern Drafting
Plane surfaces: Sides of a cube.
Top and bottom of a cylinder.
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Sheet Metal Pattern Drafting
Curved surfaces: Surfaces that can be rolled in contact with a
plane surface.
Side of a cylinder.
Side of a cone.
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Sheet Metal Pattern Drafting
Double curved surfaces: Spheres.
Spheroids.
Exact surface developments cannot be made for objects with double-curved surfaces. Drafters can make approximations.
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Double-Curved Approximations
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Pattern for a Cube
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Pattern for a Cube
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Making Paper Patterns
Patterns can be laid out on stiff drawing paper.
Cut out pattern and fold to make a solid.
Secure the joints with tape.
Surface Developments 48
Pattern Line Development
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Parallel Line Development
Parallel-Line Development is a simple way of making a pattern by drawing the edges of an object as parallel lines. Refer to Figure 18-9 and 18-12.
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Parallel Line Development
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Parallel Line Development
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Parallel Line Development
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Prisms
Patterns for prisms are made by parallel-line development.
Refer to Figure 18-13.
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Parallel Line Development Procedure
1. Draw the front and top views full-size. Label the points.
Refer to Figure 18-14A.
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Parallel Line Development Procedure
2. Draw the stretchout line (SL). The stretchout line shows the full length of
the pattern.
Find the lengths of sides 1-2, 2-3, 3-4, 4-1.
Measure these lengths off on SL.
Refer to Figure 18-14B.
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Parallel Line Development Procedure
3. At points 1, 2, 3, 4 and 1 on the stretchout line, draw vertical crease lines. Make them equal in length to the height of
the prism
Refer to Figure 18-14C.
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Figure 18.14C
Vertical lines = prism height
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Parallel Line Development Procedure
4. Project the top line of the pattern from the top of the front view. Make it parallel to SL.
Darken all outlines until thick and black.
Refer to Figure 18-14D.
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Figure 18.14D
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Parallel Line Development Procedure
5. Add the top and bottom to the pattern by transferring distances 1-4 and 2-3 from the top view. Refer to Figure 18-14E.
Add laps or tabs as necessary for assembly of the prism.
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Figure 18.14D
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Figure 18.15
Surface Developments 64
Cylinder Patterns
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Cylinder Patterns
In the pattern for cylinders, The stretchout line is straight.
The stretchout line is equal in length to the circumference of the cylinder.
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Cylinder Patterns
If the base of the cylinder is perpendicular to the axis, its rim will roll out to form the straight line.
If the base is not perpendicular to the axis, You will have to make a right section to get
the stretchout line.
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Figure 18.16
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Truncated Cylinder
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Truncated Cylinder Patterns
To develop a truncated cylinder, imagine that the cylinder is a many-sided prism.
Each side forms an edge called an element.
Because there are so many elements, they seem to form a smooth curve on the surface of the cylinder.
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Cylinder Patterns
Refer to Figure 18-17.
Mark off elements at convenient equal spaces around the circumference of the cylinder.
Then, add up these spaces to make the stretchout line.
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Figure 18.17
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Cylinder Patterns
Refer to Figure 18-18.
This figure is a pictorial view of a truncated right cylinder Notice the imaginary elements.
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Figure 18.18
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Cylinder Patterns
Figure 18-19 shows the steps to draw the pattern.
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Figure 18.19
Surface Developments 76
Drawing Truncated Cylindrical Patterns
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Truncated Cylinder Patterns
1. Draw the front and top views full size. Divide the top view into a convenient number
of equal parts.
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Truncated Cylinder Patterns
2. Begin the stretchout line. You will determine its actual length later.
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Truncated Cylinder Patterns
3. Using dividers, find the distance between any two consecutive elements. Mark off this distance along SL.
Repeat for each elements in the top view, along the SL.
Label each point.
From each point, draw a vertical construction line upward.
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Truncated Cylinder Patterns
4. Project other lines downward from the elements on the top view to the front view. Label the points where they intersect the
front view.
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Truncated Cylinder Patterns
5. From the intersection points, project horizontal construction lines toward the development.
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Truncated Cylinder Patterns
6. Locate the points where the horizontal construction lines intersect the vertical lines from the SL. Connect these points in a smooth curve.
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Truncated Cylinder Patterns
7. Darken outlines and add laps as necessary.
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Truncated Cylinder Patterns
Since the surface of a cylinder is a smooth curve, the pattern will not be completely accurate.
The pattern was made by measuring distances on a straight line rather than on a curve.
Surface Developments 86
Right Rectangular Pyramids
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Figure 18-29
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Figure 18-29
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Figure 18-30
Surface Developments 90
Triangulation
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Triangulation
Triangulation is a method used for making approximate developments of surfaces that cannot be developed exactly. Maps
Approximations of spherical surfaces
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Triangulation
In Triangulation the surface is divided into triangles, by finding the true length of the sides.
The triangles are “connected” to form the object.
The triangles approximate the shape of the object.
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Triangulation
Maps of the Earth are often represented using triangulation.
Surface Developments 94
Transition Pieces
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Transition Pieces
Transition pieces are used to connect pipes of different shapes to pipes of other shapes.
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Transition Pieces
Transition pieces have a surface that is a combination of different forms. Planes
Curves
Refer to Figure 18-36.
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Transition Pieces
Figure 18-37 shows the making of a transition piece.
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Transition Pieces
Figure 18-39 shows a transition piece to connect a round pipe with a rectangular pipe.
Surface Developments 99
Drawing a Transition Piece
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Transition Pieces
Also known as a square to round, this transition piece is a duct component that provides a change in shape from square or rectangular to round.
Transition pieces may be designed to fit any given situation, but the pattern development technique is always as follows.
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Transition Pieces
Accuracy and the use of a number system is very important.
Do all lay-out work using construction lines FIRST, then darken in object lines when you know your figure is correct.
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Figure 18-55
Assignment
Page 18-55A
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Pattern Development
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Transition Piece - Step 1
Step 1 Draw the top and front views.
Divide the circle in the top view into twelve
equal parts.
Connect the points in each quarter of the
circle to the adjacent corner of the square.
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Transition Piece - Step 1
Project the same corresponding system to the front view.
Number and letter each point in each view as shown in Figure 24-55.
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Transition Piece - Step 1
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Transition Piece - Step 1
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Transition Piece - Step 1
The transition piece shown in Figure 24.55 is made up of a series of triangles 1,A,D.
1,2,A.
2,3,A.
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Transition Piece - Step 1
The development progresses by attaching the true size and shape of each triangle together in order.
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Transition Piece - Step 1
This technique is known as triangulation.
There is no stretch-out line.
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Transition Piece - Step 2
Each element of the development must be in true length.
Establish the true-length diagram using revolution as shown in Figure 24.56.
Only one set of true-length elements is required because the given problem is a right transition piece (symmetrical about both axes).
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Figure 24.56
Establishing
True Length
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Establishing
True Length
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Transition Piece - Step 3
Begin the pattern development on a sheet in an area where there is a lot of space.
Start with the true size and shape of triangle 1,A,D.
The true lengths of 1-A and 1-D are the same and may be found in the true-length diagram.
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Transition Piece - Step 3
The true length of A-D is in the top view (See Figure 24.57.)
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Transition Piece - Step 3
Work both ways from triangle 1,A,D in Figure 24.57 to develop the adjacent triangles.
From points A and D draw arcs equal to A-2 and D-12, respectively.
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Transition Piece - Step 4
Set a compass for the distance from 1-2.
Keep this compass setting as it is used several times.
With this setting, scribe two arcs from point 1 that intersect the previously drawn arcs.
These intersections are points 2 and 12.
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Transition Piece - Step 4
Connect points 2-A and 12-D.
Do not connect points 1,2 and 12 yet.
(See Figure 24.58.)
Do all work with construction lines until complete
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Transition Piece - Step 5
Continue the same procedure, working both ways around the transition piece until the entire development is complete.
Every triangle must be included
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Transition Piece - Step 5
The pattern will end on both sides with the element 7-X, which is true length in the front view.
The two final triangles are right triangles, because each is half of the full side that is an equilateral triangle.
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Transition Piece - Step 5
Every line transferred from the views to the pattern must be true length.
Use the numbering system be used to avoid errors.
When all points have been established, the outline may be darkened.
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Transition Piece - Step 5
When all points have been established, the outline may be darkened.
A series of points form the inside curve.
Connect these points with an irregular curve.
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Transition Piece - Step 5
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Transition Piece - Step 5
If any point is out of alignment with the others, you have made an error at this location.
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Error at this point
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