4/6/2020
Fayoum University
Faculty of Engineering
Mechanical Engineering Department
FACILITIES PLANNING
Lec_7: Cellular Layout
Direct Clustering Algorithm
Mohammed Abdelghany
Assistant Lecturer – Mechanical Engineering Department
E-mail/ m.abdelghany@fayoum.edu.eg
Tel./ 002 – 01144876702
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Types of Plant Layouts
1. Process layout
2. Product layout
3. Group/Cellular layout
4. Fixed position layout
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Group Technology - concepts
• Similar parts are identified and grouped together to take
advantage of their similarities in design and production.
• Similarities among parts permit them to be classified into
part families.
• In each part family, processing steps are similar.
• Machines are grouped into cells, each cell specializing in the
production of a part family. [cellular manufacturing]
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When to use Cellular Manufacturing?
• The plant currently uses traditional batch production and a
process type layout. This results in:
- much material handling effort,
- high in‐process inventory, and
- long manufacturing lead times.
Process Layout
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Cellular Layout
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When to use Cellular Manufacturing?
• The plant currently uses traditional batch production and a
process type layout. This results in:
- much material handling effort,
- high in‐process inventory, and
- long manufacturing lead times.
• The parts can be grouped into part families.
- A necessary condition to apply group technology
- Each machine cell is designed to produce a given part family, or a
limited collection of part families, so it must be possible to group parts
made in the plant into families
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Part Family
• A collection of parts that possess similarities in
geometric shape and size, or in the processing steps
used in their manufacture.
• Part families are a central feature of group technology.
• There are always differences among parts in a family,
• But the similarities are close enough that the parts can
be grouped into the same family.
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Part Family
Example_1
Example_2
• Two parts that are identical • Ten parts are different in
in shape and size but quite
size, shape, and material,
different in manufacturing.
but quite similar in terms of
manufacturing.
• (a) 1,000,000 units/yr,
tolerance = ±0.010 inch,
1015 CR steel, nickel plate
• (b) 100/yr, tolerance =
±0.001 inch, 18‐8 stainless
steel
• All parts are machined from
cylindrical stock by turning;
some parts require drilling
and/or milling.
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Approaches for cells formation:
1.
Visual inspection
Using best judgment to group parts into appropriate families, based on the parts or photos of
the parts
2.
Parts classification and coding
Grouping of parts into classes or part families based on design attributes. Coding is the
representation of these attributes by assigning numbers or symbols to them.
3.
Production flow analysis
A procedure for forming part families by analyzing the operation sequences and the
production routing of a part or component through the plant.
4.
Clustering techniques
Lists parts and machines in rows and columns and interchanges them based on some
criterion such as similarity coefficients.
5.
Heuristic procedures
6.
Mathematical models
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Direct Clustering Algorithm (DCA)
• DCA is based on a machine-part matrix.
• 1 indicates that the part requires
processing
by
the
indicated
machine;
• Blank indicates the machine is not
used for the particular part.
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Direct Clustering Algorithm (DCA)
Step 1; Order the rows and columns:
1) Sum the 1s in each column and in each row of the
machine-part matrix.
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Direct Clustering Algorithm (DCA)
2) Order the rows (top to bottom) in descending
order of the number of 1s in the rows.
Where ties exist, break the ties in descending
numerical sequence.
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Direct Clustering Algorithm (DCA)
3) Order the columns (left to right) in ascending
order of the number of 1s in each.
Where ties exist, break the ties in descending
numerical sequence.
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Direct Clustering Algorithm (DCA)
Step 2; Sort the columns:
Beginning with the first row of the matrix, shift to the left
of the matrix all columns having a 1 in the first row.
Continue the process row by row until no further
opportunity exists for shifting columns.
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Direct Clustering Algorithm (DCA)
Step 3; Sort the rows:
Column by column, beginning with the leftmost column,
shift rows upward when opportunities exist to form
blocks of 1s.
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Direct Clustering Algorithm (DCA)
Step 4; Form cells:
Look for opportunities to form cells such that all
processing for each part occurs in a single cell.
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Direct Clustering Algorithm (DCA)
Machines can be grouped into two cells:
• Parts 3, 5, and 6 being
processed in a cell made up of
machines 2, 4, and 5.
• Parts 1, 2, and 4 being
processed in a cell consisting of
machines 1 and 3.
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Direct Clustering Algorithm (DCA)
Formation of cells where conflicts exist
Initial machine-part matrix
Final machine-part matrix
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Direct Clustering Algorithm (DCA)
Formation of cells where conflicts exist
Formation of cells with conflict in machine 2 or 3
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Direct Clustering Algorithm (DCA)
Removing conflicts with machine duplication
Duplicate of machine 2
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Direct Clustering Algorithm (DCA)
Removing conflicts with machine duplication
Duplicate of machine 3
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Direct Clustering Algorithm (DCA)
Removing conflicts with machine duplication
Formation of cells with duplicate of
machine 2
Formation of cells with duplicate of
machine 3
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