Machinery Design
EGTE 435
Spring, 2001
UD

Design Project
Supplemental Material
 

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Project Descriptions Drawing Requirements
Drawings are required as part of your project.  You must generate a drawing for each component in you design as well as an assembly drawing of your system.   Each drawing must have a standard title block.

If you chose to make a component or do a test in the shop, any injury or any cut that draws blood must be reported to the shop personnel. Before returning to work, you must go to the "Student Health Center" (Infirmary) and fill out an accident report.


Tolerances and Surface Finish

  Tolerances and surface finish play a key role in any design.  A majority of the time the two go hand in hand.  Close tolerance specifications often time require a machining method that results in a higher quality surface finish.  They play a role in the function, operation, assembly and overall appearance of a design.  In order to obtain finer surface finishes and closer tolerances there needs to be better control of the machining parameter.  The initial quality of new equipment, and wear in older equipment can also have an effect on achieving the needed surface finish and tolerance.  The figure below shows tolerance capacity of various processes.  Typically, saw cutting is assumed to provide a tolerance ranging from 1/16" to 1/32".  
    Figure 1.  Tolerance capability of various processes.  Source: S. Kalpakjian, Manufacturing Engineering and Technology, 3rd ed. Addison-Wesley, 1995
A few key things to keep in mind are that closer the tolerances and the finer the surface finish, the higher the cost and time to produce become.  Figures 2 gives a general idea towards how this tolerance versus cost trend behaves, while Figure 3 shows the typical surface roughness attributed to various machining operations.  
 
   
Figure 2. Relationship between relative machining cost and tolerance. Source: S. Kalpakjian, Manufacturing Engineering and Technology, 3rd ed. Addison-Wesley, 1995     Figure 3.  Range of surface roughness obtained in various machining processes. Source: S. Kalpakjian, Manufacturing Engineering and Technology, 3rd ed. Addison-Wesley, 1995.