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A studied analysis into a case calling for optimized plant layouts.
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Case: http://books.google.co.in/books?id=Dh19GaFCzrIC&printsec=frontcover&source=gbs_summary_r&cad=0#PPA63,M1
Established in 1949 Core business being manufacturing of
rotating machinery Acquired general engineering plant in 1989 New products to be manufactured Mr. Lamba appointed to develop a new
layout
Mr.Lamba found out that 6000 components were required in final products out of which 5000 components were to be fabricated on Indus facilities
The approach followed was Gathering reasonably accurate forecast figures Using stratified random sample (4%) for the purpose of
evaluation Using Schnieder’s method for developing alternate layout Getting the proposal checked by production department
Used data to create routing table, a load matrix and adistance matrix chart
Using Table 2 and Table 3, a load distance matrix was developed and
Schnieder’s method was applied to it.
All the primary operation centers (handling maximum load) are placed as close to raw material stores as possible
Similarly, the secondary operation departments are placed close to primary operation departments
Using this method, the existing layout was transformed into a new layout
The plant’s efficiency improved from 43% to 85.4% The moves distance per time period for path
reduced from 2803.8 to 1403.09 Material handling efficiency reduced from 1023005
unit-load move feet to 517210 unit-load move feet Cost of material handling came down by 50%
The factory plant and production personnel pointed out
that the location of the mechanical assembly andassembly erection departments didn’t allow smoothmovement of painted products.
Time constraint: Only six weeks for making the decision
Information constraint: Lack of information from Product division and Process planning departments
Sampling: Stratified data was assumed to be correct
Factors Considered:• Load and Cubic space utilization• Distance
Factors not Considered:• Safety factors• Working condition for workers • Cost• Flexibility • Concern of other departments • Customized orders• Optimum usage of floor space
Schnieder’s Method has both pros and cons
Pros: Ensures smooth flow of materials through different
operations The high preference given to proximity between primary
operations and raw materials reduced the to-fro movement
Cons: Approach focused at minimizing material handling alone Does not account the costs for shifting from the existing
layout
Total material handling effort (TMHE) - single most important and frequently used criterion for layout planning
We look at an alternate layout that is based on a heuristic method that could reduce the time required to bring out a product
Tried to create a “hybrid” layout which looks to introduce a hint of assembly line in a process-based layout
Reason: Continuous lines are usually preferred when time is a factor, since they act to reduce the time spent on a particular WIP when compared to process layouts
Data regarding sub-divisions of factors (like product mix, market accessibility, etc) is not available, hence ignored
Main factory has not been included in calculations
Assumed portability of units, in line with Lamba’s approach
Looked at the most frequent and repetitive sequences of departments in the material flow
Arrived at an arrangement that makes the WIP flow between most of them akin to an assembly line, without much back-and-forth between departments
To →
From ↓
RMS M/c HT Process Shop
Project Stores
Welding Total
RMS 0 7 0 0 0 1 8
M/c 0 0 2 2 3 0 7
HT 0 0 0 7 0 0 7
Process Shop
0 0 0 0 12 0 12
Project Stores
0 0 0 0 0 0 0
Welding 0 0 0 1 0 0 1
Total 0 7 2 10 15 1
Preceding table based on Table 5.1 in given sample data
A pattern is seen along the diagonal (in red), that enables us to make an arrangement that is in a continuous chain
Important to keep in mind not only the frequencies, but also the loads that are transferred between the departments
Keeping this in mind, arrived at an alternate layout that is continuous and yet would not involve carrying heavy loads too far
Had to resort to some trial-and-error to get there
The pseudo “line”
Pro:◦ Objection raised by production personnel about
Mechanical Assembly and Assembly Erection departments may be mitigated to a large extent
Con:◦ Load-distance efficiency is less (64%) as
compared to Lamba’s method (85%)
Minimization of total space occupied, by area (square footage)
If area is considered, problem is analogous to sheet-cutting problem (pieces of different shapes and sizes need to be cut from a single sheet while minimizing the sheet area used)
Qualitative method that considers five key factors:
◦ Product (P): What is to be produced?
◦ Quantity (Q): How much of each item will be made?
◦ Routing (R): How will each item be produced?
◦ Supporting services (S): What support will be required for production?
◦ Time (T): When will each item be produced?
SLP procedures
Some well known computer programs that use algorithms based on heuristic/qualitative data to optimize layouts are ALDEP (Automated Layout Design Program) and CORELAP (Computerized Relationship Layout Planning).
Gives a ‘relative importance’ of parameters with each other
Based on the premise that not all factors are equally important, while designing a layout
Factors can be divided into sub-factors and relative weights can be calculated, however not performed here due to lack of data
Step 1: Formation of AHP initial matrix, based on investigator’s judgment
Step 2: Calculation of proportionate worth of criteria. This is the result
Step 3: Verify result. Multiply initial matrix by average worth
Step 4: Divide final matrix of step 4 by average worth to get l
Consistency Index (CI) = (lavg – n) / (n – 1), where n is the order of the matrix.
Consistency Ratio (CR) = CI/RI (Random Index) If CR << 0.1, then results can be held valid
Initial Matrix:
No. of items Volume Distance Weight
No. if items 1 0.5 0.5 0.5
Volume 5 1 0.5 0.8
Distance 7 5 1 1
Weight 7 3 1 1
No. of items Volume Distance Weight Avg Worth
No. if items 0.05 0.05 0.15 0.15 0.10
Volume 0.25 0.10 0.15 0.25 0.19
Distance 0.35 0.50 0.35 0.30 0.37
Weight 0.35 0.35 0.35 0.30 0.33
No. of items Volume Distance Weight Avg Worth
No. if items 0.05 0.05 0.15 0.15 0.10 0.1195
Volume 0.25 0.10 0.15 0.25 x 0.19
= 0.1820
Distance 0.35 0.50 0.35 0.30 0.37 0.3585
Weight 0.35 0.35 0.35 0.30 0.33 0.3300
lavg = (2.295+0.95+0.96+1) / 4 = 1.026
Consistency Index (CI) = (lavg – n) / (n – 1), where n is the order of the matrix.CI = (1.026 – 4)/3 = -0.9913
Consistency Ratio CR = CI / RI = -0.9913 / 0.90 = -1.101
Since -1.101 << + 0.10, the results are acceptable.
Calculation of l
Possible Implications
Since buildings cannot be altered, no extra construction or demolishing costs involved
Size of the buildings is immaterial for location of the departments
The process of developing a new layout can still be complicated if we have length and breadth constraints for the blocks
TMHE is the only criteria under consideration in the current method while other factors like minimization of moves,etc. can also be considered
‘Not properly located to allow painted products to move out smoothly’ can signify that movement is obstructed due to space constraint or due to narrow exit entrances
The Mechanical and Assembly erection departments which are farther away from the road and aisle can be located much closer
Also check if the material handling equipment is proper and allows smooth flow
Assumption
1. No volume restriction, only weight restriction (2000 kg per truck)2. Trucks are considered as the only material movement equipment3. Load is considered in tons4. Main Factory is situated as per layout given below5. The jth department has Nj machines which work simultaneously and
take Tj time to finish one product6. Speed of a truck is considered to be constant at “v” feet / minute7. Dedicated trucks are provided between the nodes and the number of
trucks moving between node i and node j are represented by Xi
8. The main criteria for deciding the number of trucks is the total cost of acquiring the trucks, which is calculated by multiplying the total number of trucks in to the cost of one truck (K). The total cost is to be minimized
Machine Assembly
Machine Shop
Welding Shop
Process Shop
Project Store
Assembly Errection
HT Plant
RMS
Blade
Plastic
Main Factory
Fig 2 Load – Hop Distance Map
Objective Function:
Minimize Z = (X12+X13+X14+X15+X16+X17+X24+X26+X27+X29+X32+X36+X37+X39+X46+X47
+X49+X48+X52+X59+X63+X67+X78+X79+X73+X76+X98+X9,10+X10,8) * K, it should be minimized
K = Cost of a power vehicle
Constraints Number of vehicles running from ith node to jth node >= (( Time of round trip from ith node to jth node / Time of operation of machine at jth node ) * number of machines at jth node) Example:
X12 >= ((4d/v)/T2)*N2
Where X12 = Number of vehicles running from 1st node to 2nd
noded = 1 hop distancev = speed of power trucksT2= Time of operation of a machine at 2nd nodeN2 = Number of machines at 2nd node
NOTE:
Also we need to consider the recurring cost of truck operations over a long period of time. X12 trucks are moving in between node 1 and 2 which will cost us P= X12*K for acquiring the trucks. Now for example say cost of moving a truck for 1 hop costs C. So total cost for X12 trucks will be (2*(73/X12)*C). So if we consider M period as the life time of the truck, then total recurring cost for X12 will be R= (2*(73/X12)*C)*M. So after M period
R <= P
Thank you! Questions at [email protected] please