Elif Temiz, 030070195, 9th Week definitions-Part 2

3-Maximum Material Condition

New Definition (Geometric Tolerance Feature)(Better)

 

The symbol for MMC is shown in Figure 42-6. The symbol dimensions are based on percentages of the recommended letter height of dimensions.

 If a geometric tolerance is required to be modified on an MMC basis, it is specified on the drawing by including the symbol immediately after the tolerance value In the feature control frame, Figure 42-6.

A form tolerance modified in this way can be applied only to a feature of size; it cannot be applied to a single surface. It controls the boundary of the feature, such as a complete cylindrical surface or two parallel surfaces of a flat feature. This permits the feature surface or surfaces to cross the maximum material boundary by the amount of the form tolerance. If design requirements dictate that the virtual condition be kept within the maximum material boundary, the form tolerance must be specified as zero at MMC, Figure 42-7.

 Application of MMC to geometric symbols is shown in Figure 42-8.

Application with Maximum Value

It is sometimes necessary to ensure that the geometric tolerance does not vary over the full range permitted by the size variations. For such applications, a maximum limit may be set to the geometric tolerance, and this is shown in addition to that permitted at MMC, figure 42-9.

( C. H. Jensen,Jay D. Helsel,Ed Espin, Interpreting Engineering Drawings, pp.347-348)

 Previous Definition

MMc is that condition of a par tor feature which contains the maximum amounth of materail ,e.g. minimum size hole , or a maximum size shaft. In certain cases its use allows an increase in the specified tolerances if it is indicated that the tolerance applied to the feature at its maximum material condition.

The maximum material principle take into account the mutual dependence of tolerances of size , form orientation and/or location and permits additional tolerance as the cosidered feature departs form its maximum material condition.

(Manual of engineering drawing , Colin H. Simmons,Dennis E. Maguire,Neil Phelps ; pg. 183 , first edition)


4-Annual Cost Method 

New Definition (Financial Decision Method)  (Better)

Alternatives that accomplish the same purpose but that have unequal lives must be compared by the annual cost method. The annual cost method assumes that each alternative will be replaced by an identical twin at the end of its useful life (infinite renewal). This method, which may also be used to rank alternatives according to their desirability, it is also called the annual return method or capital recovery method.

Restrictions are that the alternatives must be mutually exclusive and repeatedly renewed up to the duration of the longest-lived alternative. The calculated annual cost is known as the equivalent uniform annual cost (EUAC) or just equivalent annual cost. Cost is a positive number when express exceed income. 

(John A. Camara, Computer Engineering Reference Manual for the Electrical and Computer PE Exam, p. 39.15)

Previous Definiton

Equivalent uniform annual cost spreads the cost of all items (initial startup costs,user fees,maintanence,and anticipated rehabilitation costs) annually over the life cycle of project.An analysis using equivalent uniform annual cost more effectively compares alternates with different service lives.However when making such comparisons the user must understand that during analysis it is assumed that the same set of activities will be repeated indefinitely.(Tushar K. Ghosh,Mark A. Prelas;Energy resources and systems:Fundementals and non renewable,p:55)