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Pattern Development: Sheet Metal Level 1 by Brian Coey is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.
© 2021 Brian Coey
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Pattern Development: Sheet Metal Level 1 by Brian Coey was funded by BCcampus Open Education.
BCcampus Open Education began in 2012 as the B.C. Open Textbook Project with the goal of making post-secondary education in British Columbia more accessible by reducing students’ costs through the use of open textbooks and other OER. BCcampus supports the post-secondary institutions of British Columbia as they adapt and evolve their teaching and learning practices to enable powerful learning opportunities for the students of B.C. BCcampus Open Education is funded by the British Columbia Ministry of Advanced Education and Skills Training and the Hewlett Foundation.
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When wanting to build a project, we need to first imagine it. The process of pattern development gives us the ability to take that visual representation and actually create the object. It allows us to turn two-dimensional metal, into three-dimensional objects, which is the basis for everything we fabricate.
Learning Objectives
Layout Terms
I
As a sheet metal worker, we work with different lines, angles and shapes. We work with geometry. Be it in the field or in a shop, geometry is a tool we use in many different ways. From creating 2D patterns of 3D objects, to making sure roof panels are installed square, to locating duct runs and penetrations, geometry is used everyday by a sheet metal worker. This is the foundation for which all layout is done. Craftspeople who excel at this stage are able to quickly transform any complex ideas into reality.
Learning Objectives
Geometric Terms
Circle Facts:
In geometry we deal with many different shapes. All shapes are made up of various points, lines and angles.
We can define a point (A) as a single location on a shape or line.
A line (A-B) is made up of 2 points. There are different types of lines:
We also have lines which are parallel or equal distance apart and lines which are perpendicular or at right angles to one another.
An angle is formed at a point at where 2 lines meet (vertex). We deal with three different types of angles:
With a combination of points, lines, and angles, we start to create shapes. Triangles (A-B-C), squares or rectangles (A-B-C-D), and circles are some of the most common shapes seen in the sheet metal industry. It is a combination of points, lines, and angles that make up different shapes —or in our case, our patterns.
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If we think of a hexagon inside a circle, it has a radius equal to the length of any given side. This makes it quite easy to construct.
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II
When wanting to build a project, we need to first imagine it. The process of pattern development gives us the ability to take that visual representation and actually create the object. It allows us to turn two-dimensional metal into three-dimensional objects, which is the basis for everything we fabricate.
Consider a globe and a map. The map is a 2D representation of a 3D object. What should the map look like? Is it truly flat? Well, maybe some would argue, but a map is not a true representation of the Earth until we remove some of it. The actual shape of the map will have numerous “cut outs” which would allow it to form a sphere. This is a form of pattern development.
Learning Objectives
Layout Terms
The process of pattern development is the way we turn 2D sheets of metal into 3D objects. A parallel line is one of the basic forms of layout. We use it when element lines (bends) on an object are indeed parallel. The two ends of the part must be the same. Consider a gutter: It may have curves and bends and angles, but each end is the same shape. The element lines and bends are all parallel. This is the only factor which will allow parallel line pattern development to be used.
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III
In Parallel Line Pattern Development, we required parallel element line or bends. Some objects are of a conical shape and parallel line will not work on them. Rather, we will look at using Radial Line Pattern Development.
In radial line, we develop patterns for shapes that have a taper, all element lines (bends) must radiate back to a common point, a radius point. We need two things for this process to work:
So, when we find ourselves determining if radial line will work, we look at those two things. If the cone is a scalene or oblique cone, it will not work. If a radius point is 40 feet away, it is not worth the effort with this process, another should be chosen, but if it will fit in our bench space, then it will work.
Being one of the simplest forms of layout, it allows us to create these patterns with accuracy and speed. If we can use radial line, it is an effective and efficient choice.
Learning Objectives
Terms
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IV
When we looked at both parallel line and radial line pattern development, we saw fairly simple and limited layout process. We have conditions that must be met in order to use them. Triangulation is the process used when nothing else works. There are very few conditions in which triangulation will not work. It is the most complex and time consuming, but it allows us to create patterns of endless possibilities. When all else fails, triangulation will work.
Learning Objectives
Triangulation Terms
Triangulation is defined as using two known points to create a third. If we think back to geometric construction, we created triangles such as a 3-4-5 in this manner. The development of patterns using triangulation is an extension of that process. Developing one triangle after another, we build 2D patterns for 3D objects.
In this unit, we will focus on Triangulation from plan view.
Let’s look at a right triangle in orthographic terms. If we look down on a triangle (plan view), we only see the one leg of the triangle. If we look from the front (elevation view), we see the other leg. When we look from the right side, we see a full view of the triangle, with all three legs. The right side is the only view that gives enough information to see the whole triangle.
The same is true when we think of these ideas in relation to a 3D object. With few exceptions, we don’t actually see true lengths of the element lines for an object in the plan or elevation views. They are representations. Think again of the triangle in orthographic projection. If only the hypotenuse was drawn, not a full triangle, the plan and elevation views would still look the same as it did when we looked at the triangle. This is true of any 3D object. The plan and elevation views only show a representation of the hypotenuse from different views. Remember that the element lines or edges only represent the outside of the object.
So, to triangulate a pattern for an object, we must find the outside lengths of all the element lines, the hypotenuses. We must get all element lines from an object into a right side view. With a 3D object, this takes rotating the object over and over, putting each line individually into a right side view. This would take a tremendous amount of work, but, we can do this quite easily by using what is called a true length diagram. This is know as finding true lengths and is the foundation that all triangulation is built upon.
For triangulation, we must find the true lengths of the element line before we create any triangles. And the true lengths are the hypotenuses between the plan length and vertical height. This is the way we triangulate from plan view.
If we again think of the plan view, we have the length of one leg. It doesn’t matter how the line is orientated, it is shows us how much the outside edge (hypotenuse) is leaning. We also have the vertical height of the triangle in the front view. So, if we take these two known lengths and place them in a 90° corner, it shows us the same as the right side. It show us the hypotenuse. It shows us the true view of the element line. This is known as a true length diagram.
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an angle/triangle with an angle smaller than 90°
the material needed for a specific component-“We must allow this much extra”. Usually a seam for connection
the intersection point of a cone, as seen in the elevation view
a portion of a circumference
an extra element line added, different from the standard divisions
to divide in half
a straight line from 2 points on a circumference
the distance around a circle, perimeter of a circle
the distance across a circle at center, twice the radius
the number of pieces of a round elbow times 2 then minus 2(# of pcs x 2-2) gives us the number of gores in the elbow
a line representing an edge or bend
looking at the front or side of something, to have elevation (height), 2D
a cone with the top cut parallel to the base
a part of a round elbow which allows us to calculate the miter angle
a line/plane level with the horizon. Flat, level
an intersection of 2 pieces- an irregular cut on the end of something
an angle/triangle with an angle larger than 90°
a line/plane that is equal distance from another
the shape of the object, still in 2D form
a line/plane which is 90° to another
looking down at something, a “birds eye view”, “floor plan” (2D)
a straight line that touches the circle at only one point
a half of a plan view, drawn on the outside of an object
a sector which equals one quarter of the area of a circle
the distance from center to any point of the circumference, half the diameter
an angle/triangle which has a 90° angle
the area of a circle bound by 2 radii and an arc
the area of a circle bound by an arc and a chord
the hypotenuse of a cone, outside edge. The slant height is always a true length in the elevation view
a shape which has been “stretched out”, to take a perimeter and make it straight
the angle or arc which encompasses a radial line pattern
a line which touches only 1 point of a circumference
the length of an element line, set 90° to the vertical height, gives the true length of that line
a dimension or line that is not distorted by the view
a 90° corner in that we use to find the actual length of a line
the point at which an angle is formed
a line/plane straight up and down, vertically level (plumb)
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