03_Design of Production Systems Flashcards

1
Q

What is a Work System?

A
  • smallest organizational unit of the production system
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2
Q

Examples for Master Data

A
  • capacity info
  • bill of materials
  • process plans
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3
Q

Examples for Transaction Data

A
  • demand data
  • volumes, due dates
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4
Q

Examples for Feedback

A
  • quality produced
  • due date adherence
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5
Q

3 types of production systems

A
  1. Job Shop
  2. Manufacturing Cells
  3. Flow Shop
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6
Q

Job Shop

Functional Layout

A
  • spatial concentration of similar work systems
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7
Q

Flow Shop

Object layout, uniform material flow

A
  • arrangement of work systems according to the work flow
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8
Q

Cellular manufacturing

Object Layout, production-dependant material flow

A

arrangement of product families to machine groups

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9
Q

Production Segment

A

sybsystem of the production system that is organized according to specific layout type

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10
Q

Job Shop
Characteristics

A
  • more flexible
  • high workload fluctuation
  • low production vol
  • low division of labout
  • high product variety
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11
Q

Flow Shop Characteristics

A
  • more efficient [assembly line sequence]
  • low workload fluctuation
  • low product variety
  • high division of labout
  • high production vols
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12
Q

Cellular Manufacturing
Characteristics

A
  • medium workload fluctuation, production volume, product variety, division of labour
  • often combinations of layout types to leverage benefits of both systems
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13
Q

Pros for Job Shop

3 items

A
  • flexibility
  • low monotony of work
  • investment (automation) is low

Suitable for one-of-a-kin and small series appications

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14
Q

Facility layout planning
(determining in-plant locations)

A
  • grid division of the floor space
  • distance measure: mostly rectangular along the in-plant traffic lanes

Note:
- Aerial vs. rectangular distance

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15
Q

Objective of Factory Layout

Job Shop

A
  • Minimization of the entire proxy criterion
  • proxy defined as product of transport of quantity and transport distance summed up over all types of goods
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16
Q

Greedy Method
(Construction Heuristic)
5 Steps

Job Shop

A
  1. determine object i’ with heaviest transport relation from/to all other objects
  2. assign i’ to a grid square at center of floor space
  3. determine yet unassigned object i’’‘ which shows strongest transport relations from/to already assigned objects
  4. assign i’’ to grid square closest to already assigned objects so that proxy criterion between i’’ and to the already assigned objects is minimized
  5. if all obects are assigned STOP
17
Q

Types of Line Production

Flow Shop

A
  • Unpaced Lines: Sequential Layout
  • Paced Lines:
    1. Discrete material flow: Transfer lines
    2. Continuous Material Flow: Flow Lines
  • open vs closed stations
18
Q

Tranportation Systems

Flow Shop 3 items

A
  • Continuously moving conveyor (e.g. automotive final assembly lines) conveyer belt
  • Synchronous transport (e.g. automated transfer lines)
  • Asynchronous transport (e.g. manual lines)
19
Q

Cycle Time C
+ Calculation

Flow Shop - Single product line

A
  • time it takes to complete one task
  • maximum duratin per work station
  • including producing and wait stages

**C = T / X **

X = production volume e.g 30 pieces
T = effective operation time e.g. 360 min per day

C = 360 min / 30 = 12 min / piece

20
Q

Determine the theoretical minimal # of work stations given total assembly time

Job Shop - single-product line

A

M = 𝜏 / C

  • where x is the smallest integer number
  • lower bound for # of workstations
  • 𝜏 = ∑ of the task times of all work stations
21
Q

Up to which lower limit could the cycle time C be reduced?
Minimum cycle time

A
  • choose highest task time among work stations
22
Q

What is the utilization p if the theoretical minimal number of work stations M = 4 could be realized?

What is the ulization p if M=5 work stations have to be set up?

𝜏 = 46 min total assembly time
C - 12 min cycle time

A

**p = 𝜏 / M*C **

e.g. 46 min / 4 workstations * 12 min = 95.8% line utilization

23
Q

Popular Priority Rules
when selecting assignments of feasible tasks to stations

Flow Shop

A
  • maximum standard time
  • maximum # of immediate Successors
  • maximum total number of successors
  • position weight
  • etc.
24
Q

Throughput rate of 6 products / h
Calculate Cylce Time C

Flow Shop - Single product line balancing

A

6 units / h = 6/60 min
-> 10 min / unit
C = 10min

25
Q

What to do when assigning tasks to work station and there is a tie in priority value and no tie-breaker?

Flow Shop - single-product line balancing

A
  • most likely task with lowest task number
26
Q

Line balancing for a mixed model assembly line

Flow Shop - mixed model balancing

A
  • variants of basic product types e.g. size (clothing), optional equipment (automotive), colours, technical performance (electrical devices)
  • different product variants are manufactured on same line
  • no changeovers between different product variants are necessary
  • product variants differ in task sequences and task times
27
Q

How to balance mixed-model assembly line

Flow Shop

A
  • generate hybrid with task times corresponding to variant-specific task times
  • use the demand ratios of the variants as weighting factors
  • priority rule for the precedence relationship e.g. max # of all successors
28
Q

Ranked positional weight technique

mixed-model assemblu line

A
  • priority rule based procedure for determining next task to be assigned to work station
  • e.g. ∑ of all task times of the succeeding tasks + task itself
29
Q

3 types of infeasibilities when assigning product variants to

Mixed-model Assembly Line

A
  1. Task-casued infeasibility
    - single task takes longer than cycle time C
    - e.g 14 min for task 2 > C=13
  2. Variant-Caused Infeasibility
    - variant total task time exceeds capacity
    - e.g. 35, 31, 54 min < 4 * 13 = 52min
  3. Assignemnt-caused Infeasibility
    - combination of tasks > cycle time
    - you can live with infeasibilities with smart sequencing if average workload overall stations and product variants = cycle time
30
Q

Cellular Manufacturing
In depth Characteristics

A
  • spatial consolidation of limited # of working systems or machines
  • product families based on similarity of machine requirements
  • machine groups with respect to specific product family
  • based on machine-product incidence matrix
31
Q

Cons or Cellular Manufacturing

A
  • **challenging process
  • may have to replicate machines in several cells**
  • monotony of work
  • investment (automation)
  • generation of product families and machine groups
  • capacity utilization
32
Q

Types of Production Centers

Cellular Manufacturing

A

1. Machining center - single machine

2. Machining Center - multiple machines
2.1. Flexible manufacturing system (highly automated)
2.2. Manufacturing Cell: low cost as not automataed and manually moved

33
Q

Method for generating product families and machine groups

Cellular Manufacturing

A

Binary Sorting
- aim to generate block-diagonal-structure
- sort row first -> sort column

34
Q

What to do with tasks that are in the wrong machine / product group after the binary sorting?

Cellular Manufacturing

A
  • **calculate additional costs of transporting the production volumes or buying a a new machine **
  • if smaller transport
  • if bigger buy an additional machine to avoid transportation costs