For example, I might say that a certain whole is a counter sink, but if my factory is over in China, they do not know what "counter sink" means, unless they want to use a translator which would take more time. So we use symbols to identify hole types so all cultures and languages can understand what we are trying to say in a description of a hole. What advantage is there to using algebraic equations instead of numerical values when defining the dimensions of a CAD model?
The advantage in using algebraic equations instead of numerical values when defining the dimensions of a CAD model is that you can use the algebraic equation to find the dimensions of other components of an object and also the dimensions can be more accurately calculated. What three types of constraints can be applied to CAD sketches or models?
The three types of constraints that can be applied to CAD sketches or models are geometric constraints, numerical constraints, symmetrical constraints. What advantages do CAD drawings have over paper sketches? Some advantages that CAD drawings have over paper sketches include, being more neat, more precise, quicker to make, more available space to work with, unlimited resources to work with, easy availability to apply constraints to a sketch, easier sharing of work ex: email, picasa, etc.
These thin, unbroken lines are started about one sixteenth of an inch from the outline of the object and extend about one eighth of an inch beyond the outermost dimension line. They are drawn parallel to each other and perpendicular to the distance to be shown. In unusual cases, extension lines may be drawn at other angles if their meaning is clear. As far as practical, avoid drawing extension lines directly to the outline of an object.
When it is necessary for extension lines to cross each other, they should be broken exceptions to this rule have been adopted since the development of CAD software. A dimension line, terminating at either end in a long, pointed arrowhead, is inserted between each pair of extension lines.
Occasionally, when the radius of an arc is to be indicated, there is an arrow at only the end of the line that touches the arc. The other end, without an arrow, terminates at the point used as the center in drawing the arc. The arrowhead on a dimension or leader line is an important detail of a drawing. If these arrowheads are sloppily drawn and vary in size, the drawing will not look finished and professional. The size of the arrowhead used on a drawing may vary with the size of the drawing, but all arrowheads on a single drawing should be the same size, except occasionally when space is very restricted.
The arrowheads used on Navy drawings are usually solid, or filled in, and are between one eighth and one fourth of an inch long, with the length about three times the spread. With a little practice, you can learn to make good arrowheads freehand, Referring to figure , first define the length of the arrowhead with a short stroke as shown at A.
Then draw the sides of the arrowhead as indicated at B and C. Finally, fill in the area enclosed by the lines, as shown at D. Leaders are used to connect numbers, references, or notes to the appropriate surfaces or lines on the drawing. From any suitable portion of the reference, note, or number, a short line is drawn parallel to the lettering. From this line the remainder of the leader is drawn at an angle dog leg to an arrowhead or dot.
In this way, the leader will not be confused with other lines of the drawing. If the reference is to a line, the leader is always terminated at this line with an arrowhead, as shown in figure However, a reference to a surface terminates with a dot within the outline of that surface. The size of the graphic representation of an object is often reduced usually for the purpose of economizing on paper space by the use of adevice called a break. If you drew in the full length of the rectangle, you would need a sheet of paper in.
By using a break, you can reduce the length of the figure to a feasible length, as shown in figure On the original object, the ratio of width to length is You can see that on the drawing the ratio is much larger roughly about However, the break tells you that a considerable amount of the central part of the figure is presumed to be removed. The thick, wavy lines shown in view A , figure , are used for a short break. A short break is indicated by solid, freehand lines, and is generally used for rectangular sections.
For wooden rectangular sections, the breaks are made sharper serrated appearance rather than wavy. For long breaks, full, ruled lines with freehand zigzags are used, as shown in view B , figure For wider objects, a long break might have more than one pair of zigzag lines.
For drawings made to a large scale, special conventions are used that apply to drawing breaks in such things as metal rods, tubes, or bars. The methods of drawing these breaks are shown in figure Phantom lines are used most frequently to indicate an alternate position of a moving part, as shown in the left-hand view of figure The part in one position is drawn in full lines, while in the alternate position it is drawn in phantomlines.
Phantom lines are also used to indicate a breakwhen the nature of the object makes the use of the conventional type of break unfeasible. An example of this use of phantom lines is shown in the right-hand view of figure Sometimes the technical information conveyed by a drawing can best be shown by a view thatrepresents the object as it would look if part of it were cut away.
A view of this kind is called a section. The track can connect with other tracks by the indents on it. Miniature Train Feb Summary of the Project: The goal of this project was to model a miniature toy train based on specifications of the provided design.
Discussion Question Responses: Question: Why are drawings composed of different line conventions? Answer: The different line conventions relay different meanings about the drawing. Object lines convey a different meaning than center lines or hidden lines. Question: What is the purpose of a sectional view? Answer: Sectional views provide an enlarged view of a specific section of a part or assembly.
This is usually used to dimension parts that are very small. Question: What is the purpose of an auxilary view? Answer: The auxilary view is used to deminsion features on a slanted suface of a part that would not be entirely visible in the six most common views.
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