aplicatiile analizei valorii-4-optimizarea volantului concasorului-autori: florin chichernea &...

8/9/2019 Aplicatiile Analizei Valorii-4-Optimizarea Volantului Concasorului-Autori: Florin Chichernea & Alexandru Chichernea

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FUNCTIONAL ANALYSIS AND AESTHETICS IN DESIGN

Florin CHICHERNEA1

Alexandru CHICHERNEA

1

1) Universitatea Transilvania din Brasov

Abstract: Value Analysis (VA) is a method that provides

an operating technique using a creative and organized

approach. It is managed by a group, each of them selected

by their expertise in specific subjects and coordinated by a

Value Analysis expert.

The paper presents a complete study of Value Analysisapplied concretely to a selected piece of equipment. The

phases and iterative operation of the Value Analysis

method are presented.

Value Analysis combines both Engineering and

Economics without, however, placing neither Engineering

or Economics first. They both are similarly important, as

can be concluded by the end of this paper.

KEYWORDS:value analysis, optimum variant


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VALUE ANALYSIS APPLIED TO THE DESIGN OF A JAW CRUSHER

Further on an example of Value Analysis is presented, applied to the redesign of a jaw crusher used for

primary crushing of a wide variety of materials in the mining, iron and steel and pit and quarry industries.

Next the establishing mode of the optimum constructive solution is presented from the technical andeconomic viewpoint for a part participating in a function of over-dimensioned cost.

Value Analysis (VA) is a method that provides an operating technique utilizing a creative and organized

approach.

It is managed by a group, each of them selected by their expertise in specific subjects and coordinated by a

Value Analysis expert.

The VA group activity is managed in seven stages:

formation and functional analysis, creativeness, evaluation and selection of the proposals, the creative phase, development of the selected proposals, presentation of the selected proposals, set in order by priority, implementation phase.

ESTABLISHING THE LIST OF FUNCTIONS AND DIMENSIONS

Table 1 presents the list of functions of the jaw crusher.


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Table .1. List of functions.

Symbol Function*:FSService function;FCConstraint function;

FEEstimation function.

Type of

Function*

Technical dimension of function

Name UM Value

F1 Ensure milling FS blast degree - 3 - 10

F2 Ensure protection of

machinery

FC moment,

force

daN*m

daN

300

200

F3 Ensures adjustment FC length mm 15 - 30

F4 Supports the assembly FS weight daN 30.000

F5 Aesthetics FE colour, form, - -

F6 Supplies working energy FS moment daN*m 80

F7 Ensure uniformity of themovement

FS revolutionpulsation

rpmrad/sec

F8 Capability of work FC volume m3

1,2

F9 Wear resistance FC eroded material g/year

F10 Part evacuation FS debit m3 /h 0,50,7

ESTABLISHING THE LEVELS OF IMPORTANCE OF THE FUNCTIONS

Table 2 presents the value weighting of the functions.The following percentage values of the functions value weighting result:

XF1 = 25 %, XF2 = 10,7 %, XF3 = 7,1 %, XF4 = 17,8 %, XF5 = 3,5 %, XF6 = 21,4 %, XF7 = 14,2 %.

The product value is equal to the sum of the functions levels and is equal to 28.

Foto 1 and figure 1 shows the studied jaw crusher [1].


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Table 2. Value weighting of the functions (* - X coordinate).

Functions F1 F2 F3 F4 F5 F6 F7 Total

Number of points 7 3 2 5 1 6 4 28

Ratio 0,25 0,107 0,071 0,178 0,035 0,214 0,142 1

*Percentage % 25,00 10,71 7,14 17,85 3,57 21,42 14,28 100

Foto 1.Jaw crusher.


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Fig. 1Jaw crusher:1 -flywheel; 2 - eccentric shaft; 3, 5 - walls of the crushing zone; 4, 14 - wearing parts6 - moveable crushing jaw; 7fixed crushing jaw; 8, 9 - adjustable wedge system; 10 - toggle;

11, 13 - the bar; 12the bearing.

ECONOMIC DIMENSIONING OF THE FUNCTIONS

Costs were assigned to the various functions by means of the functions-costs matrix shows in table 3.

The percentage values of the functions participation in the total cost are:YF1 = 26,13 %,YF2 = 9,20 %, YF3 = 5,90 %, YF4 = 18,18%, YF5 =1,13 %, YF6 = 17,84%, YF7 = 21,59%.


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Table 3. Distribution of costs on functions (*Y coordinate, ** monetary units).

No.Parts Cost/

part**

F u n c t i n s

F1 F2 F3 F4 F5 F6 F7

1 Fixed crushing jaw 500 450 45 52 Walls 100 95 5

...

6 Belting 150 5 65 5 5 70

7 Flywheel 1500 300 20 430 750

Total cost 4.400 1150 405 260 800 50 785 950

Ratio 1 0,261 0,092 0,059 0,181 0,011 0,178 0,215Cost of functions % 100 26,13 9,20 5,90 18,18 1,13 17,8421,59

COMPARISON OF THE FUNCTIONS VALUE AND COST WEIGHTINGS

The valuecosts relationship needs to identify: The functions that are very expensive in relation to the others [2], The functions that are too expensive in relation to their contribution to the value of the product, The functions that are too expensive in relation to the existing technical possibilities of achievement.


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DIAGRAMS

Further on the construction of the diagrams is presented.

Based on the values for coordinates x i and yi presented in table 4 the diagrams of figures 2, 3, 4 and 5 are

plotted.The parameters have the following computed values: a = 0,8943, 41,8

o, S = 601,7 S' = 0.

Table 4 provides the necessary values for constructing the following types of diagrams:

1) In figure 2 the diagram of the value weighting of functions,2) In figure 3 the diagram of the cost weighting of functions,3) In the figure 4 the diagram of the value and cost weighting of functions,4) In figure 5 the diagram of the comparing the values and costs weighting of functions.Figure 2 shows the ranking of the functions by their value [3].

Figure 3 shows the ranking of the functions by their functional cost.

Table 4. Computational elements for plotting the diagrams. *S' =2 * a *(Xi)22 * Xi * Yi

No.Computational

elements

F u n c t i o n s Total

valueF1 F2 F3 F4 F5 F6 F7

1 X i 25 10,71 7,142 17,85 3,571 21,42 14,28 100

2 Y i 26,13 9,204 5,909 18,18 1,136 17,84 21,5999,96

3 (X i)

2

625 114,8 51,02 318,88 12,75 459,18 204,0 1785,74 X i * Y i 491,25 26,786 43,82 527,5 46,64 136,35 324,5 1596,9

5 (Y i - a*Xi)2

7,327 50,149 0,063 184,16 97,34 163,84 98,89 601,7

6 S' * 135,3 151,75 3,595 -484,7 -70,47 548,58 -284,1 5E-13


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The diagram allows significant comparisons of the functions total costs, and, within the total costs, of the

work and material costs, highlighting:

The very expensive functions with the highest weighting in the total cost of the product, The secondary functions that are very expensive in relation to the objective functions, or even more

expensive than these, The functions the achievement of which requires disproportionate material or work costs.The diagram reveals a Pareto type distribution, meaning that 20 - 30% of the total number of functions

include 70 - 80% of the total costs of the functions [4].

These functions are F4, F7 and F1.

In the case of such a distribution, the first functions in the order of costs, representing 20 - 30% of the total

number of functions (in the above example functions F4, F7 and F1) are considered to be very expensive

functions.

The real situation is represented by the shape of the straight line in figure 4, plotted by means of the smallestsquares method, and showing disproportions in the distribution of costs and in the contribution of the various

functions to the value of the product [5].

An analysis of the diagram of figure 4 shows that functions F7, F4 and F1 are located above the regression

line, indicating high costs, not justifiable in relation to the value.

The disproportions are highlighted also in the diagram of figure 5, where it can be noticed that functions F 3,

F5, F6 i F7 have disproportionate costs (5,9 %, 1,13 %, 17,84 %, 21,59 %) in relation to their respectivecontributions to value (7,14 %, 3,57 %, 21,42 %, 14,28 %).

These aspects allow the assumption that these functions are deficient, hence the solutions to be identified are

to focus on those assemblies, parts, materials and technological operations that contribute, within the general

structure of the product, to the achievement of these functions [6].


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3,57

7,14

10,71

14,28

17,85

21,42

25

0

5

10

15

20

25

30

F1 F6 F4 F7 F2 F3 F5

Functions

Funct

ionsvalueweighting%

Fig.2. Diagram of the value weightingoffunctions.
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26,13

21,6

18,2 17,8

9,2

5,9

0

5

10

15

20

25

30

F1 F7 F4 F6 F2 F3

Functions

Functio

nscostweighting%

Fig.3. Diagram of the cost weighting of functions.
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F5(3,5; 1,1)

F3(7,1; 5,9)

F2(10,7; 9,2)

F7(14,2; 21,5)

F4(17,8; 18,1)

F6(21,4; 17,8)

F1(25; 26,1)

y = 0,9812x + 0,0083

R2

= 1

0

5

10

15

20

25

30

0 10 20 30

functions value %

fu

nctionscosts%

Y

X

Fig. 4. Value and cost weightings of functions.
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14,2

21,4

3,57

25

10,7

7,14

17,8

1,13

21,59

17,1

9,20

26,13

5,90

18,18

0

5

10

15

20

25

30

F1 F2 F3 F4 F5 F6 F7

Functions

Value&

functionalcostweighting%

Value Costs

Fig.5. Comparison of values weighting (x---) and costsweighting of functions (y- - -).
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A basic criterion of Value Analysis is obtaining a minimum value for S.In order to diminish estimator S the points need to be aligned as perfectly as possible along the straight liney = a * x, with a tilt of 45

o.

Firstly, in order to diminish costs those functions will be redesigned that are located above the straight line

[7].For the points below the line the problems is more complicated. By diminishing the cost of the functions

above the straight line, it may change its tilt and the points initially located below the line may appear above

it.

It is also evident, that by diminishing the cost of certain functions the total costs of the product decreases, the

weighting of the functions that were not modified increasing implicitly. This is another cause for some points

relocating from below the straight line to above it, without, however, any modification occurring in the

absolute value of the costs of these functions.

Secondly, the minimization of S needs to be understood in the sense ofgrowththe value/cost ratio as muchas possible, and not in the sense of imposing S = 0.Thirdly, Value Analysis also admits the increase of the costs of some functions, provided their value

increases at a faster rate than the costs.

Practically, the criterion of minimization of S leads most often to cascading Value Analysis studies, theoptimisation of the constructive solution being thus an iterative process.

At first the functions above the regression straight line are analyzed and their costs reduced, then the

regression line is re-plotted and the functions relocated above it are noted; these functions too are analyzed in

view of reducing their costs, followed by the re-plotting of the regression line, etc. etc.

Hence the constructive solution is improved from one iteration to the other.


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ESTABLISHING THE FUNCTIONAL -TECHNOLOGICAL FORM OF THE PARTS IN

VIEW OF COST REDUCTION

Further on an analysis from the technical and economic viewpoint will be carried out in order to select a

technically optimum variant for one of the parts: the flywheel [1].Four constructive variants of flywheel will be studied and eventually the most cost effective and the most

competitive one from the technical and economic viewpoint will selected.

Prior to the actual study a number of basic ideas of creative engineering will be presented in short.

Figures 6 and 7 presents a flywheel made from the welded semi-products.

Fig. 6. Flywheel made from the welded semi-products.

.


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Fig. 7. Flywheel made from the welded semi-products

The functional characteristics for this type of part, are the following:

maximum diameter, diameter of egagement, geometrical elements of connecting gear, internal diameter of wheel hub, concentricity between flywheel axis and and diameter of egagement, wearing resistance, reconditioning method.Figure 8 presents a flywheel screw assembled and figure 9 presents a flywheel made from a cast semi-

product.


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Fig. 8. Flywheel screw assembled.

. Fig. 9. Flywheel made from a cast semi-product.


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All variants are technological and the selection of one of them depends on the level of endowment of the

company. Thus the variants presents the aspects enumerated below:

The analysis of the constructive variants for the flywheel of figures 6, 7, 8 and 9 is presented further on.

The example above represents an analysis on the influence of the semi-product on the constructive form and

functional characteristics of part.By analyzing the welded variants by the criterion UNDER WHAT CONDITIONS IS IT ACHIEVED ?,

valid conclusions follow also for other parts made from such semi-products:

The welded semi-products are usually obtained by welding simple parts made from rolled semi-products. In

order to ensure a good weldability steels with reduced contents of carbon are used for welded constructions,

like OL 37 (C = 0,150,22%); even if the additive material has an identical composition to that of the basematerial, these semi-products cannot be hardened or hardened-annealed in order to achieve the imposed wear

resistance, only subsequent to cementing the surfaces that require a higher hardness.

The welding seams need to be protected during cementing in order to avoid the occurrence of cracks during

and after heat treatment. The solution of heat treating constructions welded from low carbon steels is not

applicable due to the required large number of technological conditions. On the other hand, any welded

construction is subjected to a relaxation heat treatment in order to eliminate the welding stress and ensure

stability of form.

Using for the simple welded parts rolled semi-products of hardening-annealing high carbon steels like OLC

45, 25MoC11 does not ensure a good weldability. These steels allow superficial hardening-annealing or

hardening by high frequency currents or oxy-acetylene flame. This is not a correct solution as the mechanical

strength of the part is not ensured by classical welding procedures.

Using a rolled semi-product of OLC 45 for disks and of OL 37 for the ribs does not ensure a strong joining

as the steels have different carbon contents (OLC 45 has 0,45% C, and OL 37 has 0,15-0,22% C).


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Such solutions need to be completely avoided as cracks occur in the welding seam due to welding stress. The

imposed characteristics are not ensured for the studied part.

In order to avoid obtaining a fragile welding seam by rapid cooling particularly when rolled semi-products

with large differences of cross-sections and different carbon contents are used, a pre-heating of the part to

200-300o

C is required, while the cooling needs to take place slowly, in the furnace or by wrapping the part inasbestos. The pre-heating is successfully applied in all described cases.

Finally it can be argued that the welded construction variant is not one to ensure all imposedcharacteristics.

Dimensional precision is obtained in any welded construction by machining of the functional surfaces, of the

central bore and of the mounting surface of the sole only after welding and relaxation and never prior to

welding, as at times is wrongly done. Prior to welding only the contour of the simple parts is machined if

these have been cut with oxy-acetylene flame, as well as their joining surfaces. A series of mechanical

machining operations is eliminated by mechanical cutting. From the viewpoint of achieving the assembly ofthe flywheel the welded variant is technological, as the welding ribs are not positioned with a hidden

welding.

Further analyzing the variants by the FROM WHAT IS THE PART MADE ? criterion the following can be

established:

Flywheel can be achieved only from a semi-product cast of OT 45 or OT 55. In this semi-product casting

defects appear observable after machining, and that can be eliminated by welding followed again by

machining.

The constructive variant of figure 9 obtained from a cast semi-product ensures the best functional

characteristics, if the technical conditions for heat treatment are provided. It has, however, the disadvantagethat it allows only one solution for reconditioning: build-up welding and re-machining to the initial

functional dimensions.


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COMPARISON OF THE VARIANTS

Table 5 presents the denoting by 9 assessment criteria of the analyzed constructive variants of a flywheel [2].

The cost variant of figure 9 has obtained the highest score, and will thus be selected as the constructive

solution within the assembly of the jaw crusher.The cost of the final variant of figure 9 presented in table 6 (step 2 of the Value Analysis VAstudy) is of1100 monetary units and has a weighting of 18,75% of the final cost as compared to the initial situation of

1500 monetary units with a weighting of 21,59%, for function F7 presented in table 3 (step 1 of the VA

study) [3].

Table 5. Synthetic table with the analyzed constructive variants

No. Analysis criteria Fig.6 Fig.7 Fig.8 Fig.9

1 Functional characteristics 4 4 4 42 Semi-product 1 2 3 4

3 Mechanical machining 1 2 3 1

4 Mounting 4 4 4 4

5 Repair 4 4 4 4

6 Rigidity 3 3 2 4

7 Ergonomics 2 2 2 4

8 Aesthetics 3 3 3 4

9 Cost 1 2 3 4

TOTAL 23 26 28 33


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Table 6. Cost distribution on functions (partial) (*Y coordinate, ** monetary units).

No.Parts Cost/

part**

F u n c t i o n s

F1 F2 F3 F4 F5 F6 F7

7 flywheel 1100 200 20 330 550

... ...Total cost 4.000 1050 405 260 800 50 685 750

Ratio 1 0,262 0,101 0,06 0,2 0,012 0,17 0,18

Cost of functions % 100 26,25 10,12 6,5 20 1,25 17,12 18,75

The final situationstep 2 of the VA study

By introducing the new data into table 7 the four diagrams of figures 10, 11, 12 and 13 are plotted.

These diagrams will be compared to those of figures 2, 3, 4 and 5 [4].

Table 7. Computational elements for plotting the diagrams.* S' =2 * a *(X i)22 * Xi * Yi

No.

Computational

elements

F u n c t i o n s Total

valueF1 F2 F3 F4 F5 F6 F7

1 X i 25 10,71 7,14 17,85 3,57 21,42 14,28 100

2 Y i 26,25 10,12 6,5 20 1,25 17,12 18,75 99,99

3 (X i)2

625 114,8 51,02 318,8 12,75 459,1 204,0 1785,7

4 X i * Y i 656,2 108,4 46,42 357,1 4,464 366,8 267,8 1807,45 (Y i - a*Xi)

20,89 0,525 0,532 3,708 5,592 20,87 18,40 50,53

6 S' * -47,3 15,52 10,42 -68,7 16,89 195,8 -122,6 1E-12


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The parameters have the following computed values: a=1,0122, 45,346o, S = 50.539, S'=0.

It can be noticed that S and S' have smaller values than in the initial variant.

Table 7 provides the necessary values for the plotting of the following types of diagrams:

1) The diagram of the value weighting of functions (figure 10). This diagram has not changes, as the valueof the system and of the functions has remained the same,2) The diagram of the cost weighting of functions (figure 11). The diagram of figure 11 presents thefunctional costs of the new variant, step 2.

3) The diagram of the cost weightings of functions, step 1 and step 2 (figure 12). Figure 12 presentscomparatively the old variant, step 1 and the new one, step 2.

4) The diagram of the comparison of values weighting (x---) and costs weighting of functions (y- - -) (figure13) [5].

Only the costs are represented in order to not overload the diagram and to observe the decrease of the value

of cost of function F7, from 21,59 %, in the first step of VA study to 18,75 % in the second step of VA study.


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3,577,14

10,71

14,28

17,85

21,42

25

0

5

10

15

20

25

30

F1 F6 F4 F7 F2 F3 F5

Functions

Func

tionsvalueweighting%

Fig. 10. Diagram of the value weighting of functions.
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26,25

20

17,1

10,12

6,5

1,25

18,75

0

5

10

15

20

25

30

F1 F4 F7 F6 F2 F3 F5

Functions

Func

tionscostweighting

%

Fig. 11.Diagram of the cost weighting of functions.
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26,25

20

18,75

17,12

10,12

6,5

26,136

18,18

21,5

17,8

9,2

5,9

1,251,13

0 10 20 30 40 50 60

F1

F4

F7

F6

F2

F3

F5

functions

functions costs %

Step 2 Step 1

Fig. 12.The diagram of the cost weightings of functions, step 1 and step 2.
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5,9

17,8

1,13

9,2

21,6

18,2

26,13

18,8F7

1,25F5

6,5F3

10,12F2

17,1F6

26,25 F1

20F4

0

5

10

15

20

25

30

0 3,57 7,14 10,71 14,28 17,85 21,42 25

Functions value weightins %

Functionscostweightins%

Step 1 Step 2

Y

X

Fig. 13. Comparison of values weighting (x---) and costs weighting of functions (y- - -).
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The economic dimension or the cost of the function represents the main criterion for the critical evaluation of

functions.

These evaluations aim at identifying those functions, the too costly technical solutions of achievement of

which affect the total manufacturing cost of the analyzed product.

A correctly completed critical evaluation will directly lead to the identification of what can be called thedeficient functions of the analyzed product, that is of those functions that include useless costs.

The deficient functions from the economic viewpoint appear as:

very expensive functions in relation to the others, too expensive functions in relation to the existing technical possibilities of achievement.Evaluation by the criterion of economic dimension can be achieved in several ways, presented below:

1) comparison of costs per function, by meansof the diagram presented in figure 12,

This diagram allows comparisons of:

the costs of the functions and comparisons of the total cost and the cost of each function, work and material costs, highlighting the very expensive costs, with the highest weighting in the total cost

of the product,

functions the achievement of which requires disproportionate costs, of either work or material,2) comparison to the functions of otherproducts,

Other products refer to:

products of the same typo-dimensional range or family, manufactured by that company, products similar to the analyzed one, manufactured by other companies, products with other destinations, but having some functions similar to those of the analyzed product.3) Theoretical evaluation of the costs of thefunction.


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CONCLUSIONS

In two steps of Value Analysis study one componentof jaw crusher, who contribute at the function F7

(Ensure uniformity of the movement) was redesign and optimized [6]:

1

from engineering viewpoint, from variant of flywheel of figure 7 consists of four welded modules, one

complicated part (many components, mechanical machining, turning of metal parts complicated, long and

very expensive, etc.) to the variant of figure 10 consists of cast semi-product (one component, mechanical

machining, turning of metal parts simple, short and less expensive than the flywheel of figure 7, etc.).

2from the economic viewpoint: the cost of function F7 (figures 12 and 13) decrease from 21,59 %, in thefirst step of Value Analysis study to 18,75 % in the second step of Value Analysis study (decrease with

13,15 %).

3in the third step of Value Analysis study are analyzed other functions above the regression straight line(for exemple F2) and their costs reduced, then the regression line is re-plotted and the functions relocated

above it are noted; these functions too are analyzed in view of reducing their costs, followed by the re-plotting of the regression line, etc. etc.

4 in the fourth step of Value Analysis study are analyzed other functions (for exemple F 4) above theregression straight line and their costs reduced, then the regression line is re-plotted and the functions

relocated above it are noted; these functions too are analyzed in view of reducing their costs, followed by the

re-plotting of the regression line, etc. etc.

5 in the five step of Value Analysis study are analyzed other functions (for exemple F 1) above theregression straight line and their costs reduced, then the regression line is re-plotted and the functions

relocated above it are noted; these functions too are analyzed in view of reducing their costs, followed by there-plotting of the regression line, etc. etc.


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At the end of the Value Analysis study the points are aligned as perfectly as possible along the straight

line y = a * x, with a tilt of 45o, this is the optimal situation, the values weighting of functions and the

functions cost weighting are equal, the final interest in Value Analysis study.

REFERENCE

[1].Bejan V.,Tehnologia fabricrii i a reparrii utilajelor tehnologice, vol.I i vol.II, Oficiul de InformareDocumentar pentru Industria Construciilor de Maini, Bucureti, 1991;

[2].Chichernea Fl.,Analiza Valorii, Editura Universitii Transilvania din Braov, 2002, ISBN 973 812459X;

[3].Chichernea Fl.,Analiza valorii, ISBN (10) 973 - 635 - 850 X, ISBN (13) 978 6358500, EdituraUniversitii Transilvania Braov, 2007

[4].Chichernea Fl.,Analiza valorii, Universitatea Transilvania Braov, sept., 2007, suport electronic CD; [5].Chichernea Fl., Analiza Valorii. Partea I, Bramat 2007, Proceedings-International Conference on

Materials Science and Engineering, Braov, Romnia, 22-24.feb.2007, vol.I, ISSN 1223-9631, P_1_11[6].Chichernea Fl.,Analiza Valoriidiagrame FAST. Partea IV, Revista Metalurgia, nr.5, 2005, pg.30.[7]. www.miningbasics.com/html/single-toggle_jaw_c[8]. Chichernea Fl.,Analiza Valorii. Partea II, Bramat 2007, Proceedings-International Conference on Materials

Science and Engineering, Braov, Romnia, 22-24.feb.2007, vol.I, ISSN 1223-9631, P_1_12

aplicatiile analizei valorii-4-optimizarea volantului concasorului-autori: florin chichernea &...

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