Sunday, July 20, 2008
History Of Engineering Drawing
An engineering drawing is a type of drawing that is technical in nature, used to fully and clearly define requirements for engineered items, and is usually created in accordance with standardized conventions for layout, nomenclature, interpretation, appearance (such as typefaces and line styles), size, etc. Its purpose is to accurately and unambiguously capture all the geometric features of a product or a component. The end goal of an engineering drawing is to convey all the required information that will allow a manufacturer to produce that component.
Engineering drawings are often referred to as "blueprints" or "bluelines". However, the terms are rapidly becoming an anachronism, since most copies of engineering drawings that were formerly made using a chemical-printing process that yielded graphics on blue-colored paper or, alternatively, of blue-lines on white paper, have been superseded by more modern reproduction processes that yield black or multicolour lines on white paper.
The process of producing engineering drawings, and the skill of producing them, is often referred to as technical drawing, although technical drawings are also required for disciplines that would not ordinarily be thought of as parts of engineering.
posted by yjlevia at 1:54 AM
The layout of an engineering drawing
It is important that you follow some simple rules when producing an engineering drawing which although may not be useful now, will be useful when working in industry.
All engineering drawings should feature an information box. An example is shown below.
Common information recorded on an engineering drawing
- TITLE
- The title of the drawing.
- NAME
- The name of the person who produced the drawing. This is important for quality control so that problems with the drawing can be traced back to their origin.
- CHECKED
- In many engineering firms, drawings are checked by a second person before they are sent to manufacture, so that any potential problems can be identified early.
- VERSION
- Many drawings will get amended over the period of the parts life. Giving each drawing a version number helps people identify if they are using the most recent version of the drawing.
- DATE
- The date the drawing was created or amended on.
- SCALE
- The scale of the drawing. Large parts won't fit on paper so the scale provides a quick guide to the final size of the product.
- PROJECTION SYSTEM
- The projection system used to create the drawing should be identified to help people read the drawing. (Projection systems will be covered later).
- COMPANY NAME
- Many CAD drawings may be distributed outside the company so the company name is usually added to identify the source.
posted by yjlevia at 1:46 AM
Orthographic projection
The aim of an engineering drawing is to convey all the necessary information of how to make the part to the manufacturing department. For most parts, the information cannot be conveyed in a single view. Rather than using several sheets of paper with different views of the part, several views can be combined on a single drawing using one of the two available projection systems, first angle, and third angle projection.
The diagram below demonstrates how the projection systems work
posted by yjlevia at 1:41 AM
Hatching
On sections and sectional views solid area should be hatched to indicate this fact. Hatching is drawn with a thin continuous line, equally spaced (preferably about 4mm apart, though never less than 1mm) and preferably at an angle of 45 degrees.
Hatching a single object
When you are hatching an object, but the objects has areas that are separated, all areas of the object should be hatched in the same direction and with the same spacing.
Hatching Adjacent objects
When hatching assembled parts, the direction of the hatching should ideally be reversed on adjacent parts. If more than two parts are adjacent, then the hatching should be staggered to emphasise the fact that these parts are separate.
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| Reverse hatching | |
Hatching thin materials
Sometimes, it is difficult to hatch very thin sections. To emphasise solid wall the walls can be filled in. This should only be used when the wall thickness size is less than 1mm
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Hatching large areas
When hatching large areas in order to aid readabilty, the hatching can be limited to the area near the edges of the part.
posted by yjlevia at 1:38 AM
Sectioning - Introduction
Sections and sectional views are used to show hidden detail more clearly. They are created by using a cutting plane to cut the object.
A section is a view of no thickness and shows the outline of the object at the cutting plane. Visible outlines beyond the cutting plane are not drawn.
A sectional view, displays the outline of the cutting plane and all visible outlines which can be seen beyond the cutting plane. The diagram below shows a sectional view, and how a cutting plane works.
posted by yjlevia at 1:37 AM
Which Sectional View?
Before proceeding, consider the diagrams below and select the correct sectional view.
posted by yjlevia at 1:37 AM
Types of sectioning
Sectional View in a single plane
The example below shows a simple single plane sectional view where object is cut in half by the cutting plane. The cutting plane is indicated on a drawing using the line style used for centre lines, but with a thick line indicating the end of lines and any change in the direction of the cutting plane. The direction of the view is indicated by arrows with a reference letter. The example below shows a sectional view of the cutting plane A - A.
Sectional View in two planes
It is possible for the cutting plane to change directions, to minimise on the number of sectional views required to capture the necessary detail. The example below shows a pipe being cut by two parallel planes. The sketch shows where the object is cut.
Half Sectional views
Half sections are commonly used to show both the internal and outside view of symmetrical objects.
Part Sectional views
It is common practice to section a part of an object when only small areas need to be sectioned to indicate the important details. The example above shows a part sectional view to indicate a through-hole in a plate. Notice that the line indicating the end of the section is a thin continuous line.
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posted by yjlevia at 1:34 AM
Tolerancing
It is not possible in practice to manufacture products to the exact figures displayed on an engineering drawing. The accuracy depends largely on the manufacturing process used and the care taken to manufacture a product. A tolerance value shows the manufacturing department the maximum permissible variation from the dimension.
Each dimension on a drawing must include a tolerance value. This can appear either as:
- a general tolerance value applicable to several dimensions. i.e. a note specifying that the General Tolerance +/- 0.5 mm.
- or a tolerance specific to that dimension
The method of expressing a tolerance on a dimension as recommended by the British standards is shown below:
posted by yjlevia at 1:31 AM
Dimensioning Radii
All radial dimensions are proceeded by the capital R. All dimension arrows and lines should be drawn perpendicular to the radius so that the line passes through the centre of the arc. All dimensions should only have one arrowhead which should point to the line being dimensioned. There are two methods for dimensioning radii.
(a) shows a radius dimensioned with the centre of the radius located on the drawing.
(b) shows how to dimension radii which do not need their centres locating.
posted by yjlevia at 1:29 AM
Dimensioning Holes
When dimensioning holes the method of manufacture is not specified unless they necessary for the function of the product. The word hole doesn't have to be added unless it is considered necessary. The depth of the hole is usually indicated if it is isn't indicated on another view. The depth of the hole refers to the depth of the cylindrical portion of the hole and not the bit of the hole caused by the tip of the drip.
posted by yjlevia at 1:27 AM
Dimensioning circles
All dimensions of circles are proceeded by this symbol; 
. There are several conventions used for dimensioning circles:
(a) shows two common methods of dimensioning a circle. One method dimensions the circle between two lines projected from two diametrically opposite points. The second method dimensions the circle internally.
(b) is used when the circle is too small for the dimension to be easily read if it was placed inside the circle. A leader line is used to display the dimension.
(c) the final method is to dimension the circle from outside the circle using an arrow which points directly towards the centre of the circle.
The first method using projection lines is the least used method. But the choice is up to you as to which you use.
posted by yjlevia at 1:23 AM
Types of dimensioning
Parallel DimensioningParallel dimensioning consists of several dimensions originating from one projection line. | | |
Superimposed Running DimensionsSuperimposed running dimensioning simplifies parallel dimensions in order to reduce the space used on a drawing. The common origin for the dimension lines is indicated by a small circle at the intersection of the first dimension and the projection line. In general all other dimension lines are broken. The dimension note can appear above the d imension line or in-line with the projection line  | | |
Chain DimensioningChains of dimension should only be used if the function of the object won't be affected by the accumulation of the tolerances. (A tolerance is an indication of the accuracy the product has to be made to. Tolerance will be covered later in this chapter).  | | |
Combined DimensionsA combined dimension uses both chain and parallel dimensioning.  | | |
Dimensioning by Co-ordinatesTwo sets of superimposed running dimensions running at right angles can be used with any features which need their centre points defined, such as holes.  | | |
Simplified dimensioning by co-ordinatesIt is also possible to simplify co-ordinate dimensions by using a table to identify features and positions.  | |
Dimensioning Small Features
When dimensioning small features, placing the dimension arrow between projection lines may create a drawing which is difficult to read. In order to clarify dimensions on small features any of the above methods can be used.
posted by yjlevia at 1:22 AM
Friday, July 4, 2008
SOLID EDGE 3D Tutorial Video
Labels: video
posted by yjlevia at 6:32 AM
Wednesday, July 2, 2008
- Draw line between two center.
- Draw arc through these center.
- Draw circle with R59-R39 to intersect
the arc at D.
- Draw line AD and project until E.
- Draw parallel line AE and BF.
- EF is line of tangency between two
circle.
How to draw a line tangency to a circle
Source: Engineering-Drawing.blogspot.com
posted by yjlevia at 12:11 AM