Automation

1
Automation

• Definition The process of having machine follow
  a predetermined sequence of operation with little
  or no human labor, using special equipment and
  devices that perform and control manufacturing
  processes.

2
Implementation areas

• Manufacturing processes automation (CNC)
• Material handling (Robots, conveyors..)
• Inspection
• Assembly
• Packaging

3
Goals of automation

• Integration of various aspects of manufacturing
  operations to reduce labor cost
• To improve productivity or efficiency
• To improve quality
• To reduce human involvement therefore human error
• To reduce work piece damage that manual handling
  caused.
• To raise the safety level
• To economize of floor space

4
Application of Automation

• Automation can be applied to manufacturing of all
  types. The decision to automate a facility
  requires some considerations
• The type of the product
• The quantity and rate
• Particular phase of automation
• Skill level of workers available
• Reliability and maintenance
• Economics
• Selective automation rather than total automation
  is selected

5
Production quantity

• Crucial to determining the type of machinery and
  level of automation required the knowledge of
  quantity.
• Total production quantity means total number of
  parts to be made.
• This quantity can be produced in individual
  batches of various lot sizes.
• Small quantities per year can be produces in job
  shops, by using general purpose of machining
  tools in lot sizes 50 or less.

6
Production quantity(continue)

• When parts involve a large labor component,
  their production is called labor intensive.
• Small batch production quantities range from
  10-100.
• Batch production 100-5000.
• Mass production over 100 000, needs special
  purpose machining called dedicated machines and
  and automated components.

7
Assembly lines

• Two types of assembly lines Manual and
  Automated.
• Fundementals of assembly lines
• Series of work stations work part moves from one
  station to other, the production rate of the line
  is determined by the slowest station (bottleneck)
• Conveyor or mechanical transfer device is used.
  In manual usually parts are moved manually.

8
Product variation

• Single model line no variation, produce one
  model.
• Batch model lineone or more different production
  in batches. From one model produces some number
  then the system reconfigured to produce from the
  other model.
• Mixed model linemore than one model production
  simultaneously on the same line.

9
Advantages of mixed over batch model

• Downtime between models is minimized
• High inventories of some models are avoided
• Production rates and quantities of two models can
  be controlled accordance to changes in demand
• Disadvantages of mixed over batch model
• Work assigning to the stations is complex
• Sequence of the model(scheduling) and getting
  right part to station (logistic) is difficult.

10
Methods of work transfer

• Manual By hand
• Mechanized
• Lift and carry devices
• Pick and place mechanism
• Powered conveyors can be calssified into 3
  groups
• 1)Synchronous transfer system
• 2)Asynchronous transfer system
• 3)Continuous transfer system

11

• Synchronous transfer system
• Work parts moved between stations with a quick,
  discontinuous motion. Called intermittent
  transfer. Stressful to human workers, good in
  automated operations.
• Asynchronous transfer system
• Work parts moved between stations when its job
  completed. Independent move. Called power and
  free system. Queues form in front of the work
  stations. Good for both manual and automated
  operations.
• Continuous transfer system
• Continuous conveyor moving by a constant velocity
  Vc, fixed parts on conveyor moved from the
  conveyor to the work station, or worker moves to
  the part.

12
Determining the min number of work stations

• RpActual Average Production Rate (units/hour)
• RpAnnual demand/(work week in a year number of
  shifts per week hours per shift)
• Tp Average Production Time (time/unit)
• Tp60 / Rp

13
Determining the min number of work
stations(continue)

• A year 52 weeks but machine can not be available
  all the time.Can be some electrical or mechanical
  failures, tool wearing out, power outages or
  malfunctions. Therefore, to catch the same
  production units per hour the lines must operate
  faster than Tp.
• E line efficiency
• Tc Cycle time
• Tc E. Tp

14
Determining the min number of work stations
(continue)

• Lets assume a piece need to be operated in nmin
  (integer) work stations. Each takes Tc times
• nmin ? Twc /Tc
• Where Twc , work content time, means the total
  time to make the product on the line.
• To achive is very unlikely, because
• Tc not always same
• A worker performs differently w.r.t time
• Different workers perform differently
• Defected pieces pullback
• Sometimes work part needs positioning

15
Manual assembly lines

• One of the biggest problem is line balancing.
• Means, assigning tasks to individual workers,
  therefore, each worker will have an equal amount
  of work.
• Each station must have ? Tc
• Precedence constraints,( means order of the
  production phase a product to follow. For examle,
  a screw hole should be open before assembling the
  bolts) complicates the line balancing problem.

16
Manual assembly lines(continue)

• Total available service time w. Ts
• w number of workers on line
• Ts MaxTsi
• Ts ? Tc
• because we have Tr positioning time,
  therefore
• Tc Ts Tr
• Assume Eb balancing efficiency (measure of the
  total idle time)
• Eb Twc / w.Ts
• Eb1 , perfect balance, typically, Eb0.90-0.95

17
Manual assembly lines(continue)

• Sometimes, if a job large, it requires more than
  one worker, therefore the number of workstations
  is not equal to the number of workers on the same
  line. The number of the workers assigned to each
  station called manning level (Mi). Average
  manning level
• Mw/n (wworkers, n stations)
• Usage of automation decreases labor but increase
  the need for more technical labor
• Inventory buffer use helps for service time
  variability.

18
Automated assembly lines

• Consists of
• Automated work stations
• Connected by transfer line
• Operates under computer control
• Line balancing is also a problem in automated
  lines. In automated systems tasks generally
  simpler than the ones in manual lines. Also,
  automated lines has less stations which make
  rather less complex problem. Significant problem
  is reliability if one machine down, the system
  is down.

19
Automated assembly lines(continue)

• Assume
• Tc ideal cycle time
• Tr repositioning time (called transfer line)
• Tsi service time at station (i)
• Tc Tr maxTsi

20
Automated assembly lines(continue)

• F breakdown frequency causing line stoppage
• Td average time line down (downtime), including
  repair time
• Actual Average Production Time
• Tp Tc F. Td
• Average Production Rate
• Rp 60/ Tp
• Ereliability Tc /(Tc F. Td )

21
Automated assembly lines(continue)

• F is related to failures at individual
  workstations.
• pi probability of failure at station i
• F(p1 p2 ... pn )
• If average pi p , therefore Fn.p
• Comments
• F increase with increased number of stations
• Efficiency decrease with incerased number of
  stations.