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production > MANUFACTURING CELLS > Flashcards

MANUFACTURING CELLS Flashcards

1
Q

What is the Manufacturing Cells?

A

Group of machines (cell) of different types that completely fabricates a range of “similar” products or parts (FAMILIES)

Remarks:
*Machines are grouped and placed according to the product/part families manufactured.

*Inter-cellular flows (from one cell to another one) are not “allowed”

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2
Q

How is it possible to group the different machines in order to create the manufacturing cells?

A

Manufacturing cells (together with product/part families) are constituted by applying models of GROUP TECHNOLOGY (GT)

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3
Q

What about the features of GROUP TECHNOLOGY?

A
  • GT is strongly related to cellular manufacturing (also known as “group manufacturing”)
  • GT has a wide operation range both in terms of volume and product mix
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4
Q

How products/parts are grouped?

A

Parts/products are grouped into PART/PRODUCT FAMILIES

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5
Q

Based on what are the machines grouped?

A

Machines with different technologies are grouped based on the Processing requirements of each product family.

So we get machines with different technologies are grouped within the same manuf. cell.

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6
Q

Is the inter-cell moving allowed?

A

NO. In manufacturing cells the mahcines are dedicated to manufacture the same product type, creating thus a Product layout.

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7
Q

What does it mean the Product Layout in manuf. cells?

A

NON inter-cell moving: Each product has its own routing within the cell.
This allows to avoid material interweave ( which is a drawback in Job Shops).

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8
Q

Based on which conditions are the Manuf. Cell applied?

A
  • When there is a limited range of product variants.

* Customer’s demand remains stable

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9
Q

Strengths?

A
  • Rationalization of material flow
  • Setup time reduction
  • Production managmeent is easier w.r.t Job Shops
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10
Q

Strengths w.r.t the Job Shops?

A
  • WIP reduction
  • Lead Time (LT) reduction
  • More reliability in estimating the delivery lead times:
    Since WIP is lower.
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11
Q

Why is there a higher razionalitacion of material flow?

A
  • Because when NON-inter cell moving is aplied (case of completely cell independence), all the material’s flow remains within the same cell.
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12
Q

Which are the benefits of the Rationalization of material flow?

A
  • This leads to a reduction in interweave of material w.r.t Job shops
  • Time reduction and more productivity in material’s handling sincethe machines to be visited are closer.
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13
Q

Why is there a setup time reduction?

A

Because it is possible by means of using a Family of Tools (tools used for the same product family), since the machines are focused on the same product type/family.

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14
Q

Why is the production management easier in Manufactu. Cell w.r.t Job Shops?

A
  • Reduced size of the cell system.
  • Reduced set/variety of parts/products manufactured within the cell.
  • Reduced WIP: Guarantees that machines are sufficiently fed up and utilized.
  • Machines are closer so there is a higher quality control.
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15
Q

More stengths?

A
  • Job enlargement + job enrichment for employees: SInce machines are closer and workers have more responsabilities (like quality control).
  • Team work within the cell
  • Unification of product and process responsibilities
  • More control on the quality characteristics of the products
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16
Q

Regarding the job enrichment of workers w.r.t Job Shops?

A

In JOb Shops: , The division in functional departments (based on technological capacity of machines), leads to alimitiation in the worker’s responsabilities. Therefore they loss control of the whole product proces.

Conversely, in Manuf. Cells: Workers working within the same cell and focused on the same product type, have a higher number of responsabilities and have a higher control of the product process.

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17
Q

Weaknesses?

A
  • Difficult in balacing thw workload b/w cells.
  • Problems related to production mix variability
  • In some cases, more machines are neeeded w.r.t Job Shops.
  • Difficulties related to manage technological operation outside the cells
  • Problems related to breakdowns.
18
Q

Why is the worload balancing difficult?

A
  • Due to the NON inter-cell moves.
  • Cells are designed based on product families.

In Job Shops, is easier to assign a production lot/batch to the underloaded machines thanks to the alternative routing. (flexibility in routing and materials handling)

19
Q

Why are there problems related to Production mix variability?

A

Because if the production volume changes for a specific product type (if its demand varies), it will lead to unbalance w.r.t the workload in other cells which faricate other product types.

20
Q

Why may more machines be needed w.r.t Job Shops?

A

it is related to the possible worload unbalance b/w cells. In Job Shop the overall worload is balanced by all the product types, therefore if there is any unbalance in some location, it may be baanced in another one.

21
Q

Why are there problems related to breakdowns?

A

As opposed to Job Shops, the number of machines of the sme technology is lower. So, in case of a breakdown, replaces some machine would be more difficult.

22
Q

By which aspects is it possible to identify a Man. cell?

A
  • A team of operators belongs to a cell (the operators “own” the cell)
  • Input / output areas are defined
  • Products have an obvious identity
  • Clear physical boundaries help to highlight ownership of the cell
  • Notice boards display cell information
23
Q

Aspect to consider in Manuf. Cell design -> SIZE OF CELL: How many machines and operators must be located at each cell?

A
  • less than 15 machines
  • Less than 10 operators (per shift)

Remark: there could be b/w 2 to 20 cells in a plant.

24
Q

Aspect to consider in Manuf Cell design -> Why CELL SIZE RESTRICTION IS A KEY TO ACHIEVE GOOD PERFORMANCES ?

A
  • Scope and activities can be understood easily by all operators
  • Key decisions made by most knowledgeable operators
  • Local objectives: operators see progress & improvements
25
Q

Aspect to consider in Manuf Cell design -> What about the MATERIALS FLOW based on the cell size?

A
  • Cell size allows easy material movement
  • Control of material flow is easier
  • Normally cells employ local material control e.g.“kanban”
26
Q

What is GROUP TECHNOLGY (GT) ?

A

Group Technology (GT) is an approach to manufacturing and engineering management that helps managing diversity by identifying similarities of parts/products and required activities/operations.

  • GT allows to group items/parts which share common features.
  • GT facilitates the rationalization of activities/operations in a wide variety of functional areas, including purchasing, design, and manufacturing.

Concerning Manufacturing cells: By means of GT, manuf cells can be created.

27
Q

Which are the steps in GROUP TECHNOLOGY (GT)?

A
  1. Data collection regarding the production mix and
    technological routings
  2. Classification of products
  3. Standardization of products
  4. Standardization of technological routings
  5. Identification of product families
  6. Identification of machine groups forming the cells
  7. Sizing of single cells
28
Q

Which are the methods used in GT?

A

*Visual methods:

  • Geometrical features
  • Technological features
  • Part coding methods:
  • Monocode
  • Polycode
  • Hibrid code
  • Production Flow Analysis (PFA)
  • Matrix formulation
    º ROC (Rank Order Clustering)
    º Similarity coefficients
  • other methods.
29
Q

What does the Visual Method consist?

A

It is based on either:

  • geometrical features: Shape and dimensions
    This method is not only useful to identify part families but, as previously discussed, it helps also to standardize production components such as fixtures (i.e. similar shapes & dimensions
  • Technological features: Materials, processing requirements .
    Even if the dimensions or shapes are different, allows to identify part families.
30
Q

What does the Part Coding Method consist? and its PROS and CONS?

A

Part Coding assigns a numerical or alphabetic value to item characteristics in order to facilitate classification

PROS
*Independent from the person coding parts
*Reproducible
*Accessible for PC through keywords
*Almost unlimited number of parts that can be coded
(Most common in industry; also for other purposes)

CONS

  • Time consuming
  • Complicated
  • Expensive
  • Long time for implementation
31
Q

What about the different types of Part Coding methods?

A

*Monocode (hierarchical code or tree code):
the meaning of each symbol (digit) depends on the value assigned to previous ones, i.e., each digit amplifies the information given in the previous digit

-with a relatively small numbers of digits, a large amount of information can be stored (preferred for morphological information)

  • usually for permanent information (ditto)
  • difficult to construct
  • Polycode: (chain code or attribute code): all symbols (digits) are independent, i.e., each digit is independent of all others, thus, presents information not dependent on previous ones
  • easier to understand immediately and remember
  • easier to accommodate change

*Hybrid (or mixed) code
it has some digits forming monocodes, but strings them together in the general arrangement of a polycode

32
Q

Opitz code ?

A

Opitz code include a morphological (form) part and a technology part:

33
Q

For what can be Part codign method useful?

A
  • To help with blueprint design reuse
  • To form components families
  • To form the basis for cellular manufacturing design
  • To allocate new components to existing cells and easily plan process
34
Q

What about the different types of Part Coding methods?

A

Production Flow Analysis (PFA) is a three stage technique:

1) Factory flow analysis
2) Group flow analysis
3) Line analysis

35
Q

What is the 1st stage of the Produc Flow Analysis (PFA) method?

A

*Factory flow analysis:

  • Broad sub-division of plant into departments
  • Only really necessary for large systems
36
Q

What is the 2nd stage of the Produc Flow Analysis (PFA) method?

A
  • Group flow analysis

- Machine families based on routing regardless of sequence (e.g. ROC, SLC)

37
Q

What is the 3rd stage of the Produc Flow Analysis (PFA) method?

A
  • Line analysis
  • Flow between machines to provide sequence
  • Flow may be obvious
  • Can use From/To Chart technique
38
Q

which are the Product Flow Analysis (PFA) methods (of the 2nd phase.. Group Flow Analysis)?

A
  • MATRIX METHODS:
  • Rank Order Clustering (ROC) et similia

ºMatrix manipulated directly by ordering and interchanging rows or columns

ºEasier to understand and to computerize

  • Single Linkage Clustering (SLC) (SImilarity coefficients) et similia

ºCluster analysis is based on the idea of calculating similarity index and grouping accordingly

  • other methods (e.g., graph theory)
39
Q

Which are the assumption done in Product Flow Analysis (PFA) ?

A
  • Each component is equally important in terms of cost
  • Lot size & its associated cost are not directly related to grouping procedure
  • Routing is assumed to be optimal
40
Q

After the machines have been grouped by means of Matrix Methods (2nd phase: Group Flow analysis), what is the following step?

A

I it necessary to look at the flow rates and directions between resources in order to establish the best relative positioning of the machines within the cell.

This can be done manually (by “common sense”) or using techniques such as “To/From” analysis”, that allows to position Worcenters trying to linearize flows.

41
Q

Ideal vs. real cells ?

A
  • Some cells are not completely self contained:
  • Can sub-contract work or permit inter-cell movement
  • Sharing of staff should be avoided
  • Loss of control must be avoided
  • Duplication of resources:
  • Duplication is a possibility
  • Could duplicate (cheap) resources to avoid imperfect cells
  • Exceptions are made in terms of products and processes:
  • Accommodate parts / products which do not fit into groups
  • Some production processes cannot be integrated in cells, e.g. heat treatment
42
Q

Virtual cellular manufacturing ?

A

In Virtual Cellular Manufacturing the machines that belong to a cell are not physically located together, but are identified as a group only by the Production Planning and Control system.

Virtual Manufacturing Cells (VMC) are an alternative to traditional manufacturing cells, with the purpose to be more responsive with production mix variability.

Virtual cells can achieve the benefits of repetitive processes without the layout rearrangement of a job shop

virtual cells, with subsequent advantages due to cell autonomy and rationalization of material flows (low intertwining).

production (4 decks)

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