Production Activity Control

1
Production Activity Control

• Chapter 5

2
MPC System with PAC (VBW, figure 5.1)
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PAC Framework

• PAC concerns execution of material plans, aided
  by use of shop-floor computers, EDI, and the
  Internet.
• Usual linkage is to MRP system.
• Shop-floor and vendor activities begin when an
  order is released.
• Feedback status information and warning signals.
• JIT may limit the need for most PAC activities.
• Primary PAC objective is managing material flows
  (JIT, material velocity) other objectives may
  include efficient use of capacity.

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PAC Responsibilities

• Execution
• Scheduling
• Dispatching
• Control
• Work order progress move tickets
• Labor efficiency labor tickets
• Quality scrap/rework tickets
• Shop status machine/tool tickets

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Planning for Shop Order Release

• Review planned orders
• Material availability
• Order quantity and due date
• Routing and tooling availability
• Capacity data and labor standards
• Verify lead times
• Authorization for release creates an open shop
  order (scheduled receipt)

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Planned Lead Time

• Job order setup time and run time
• Work center queue time
• Material handling wait time and move time
• Longer lead time leads to more jobs in the
  system, which leads to longer queue and more
  work-in-process inventory

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Scheduling Focus

• Scheduling individual jobs need dates, release
  dates, processing times, priority adjustments,
  performance measures, etc.
• Scheduling the shop work-in-process, average
  lead time, labor efficiency, machine utilization,
  percent early/late, etc.

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PAC Techniques

• Basic shop-floor concepts
• Essential inputsrouting and lead time data (see
  figure 5.3)
• Queue/wait times often accounts for 80 of total
  lead time.
• Operations setback chartbased on each parts
  lead times.
• Work center schedulesbased on various elements
  of lead-time elements

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PAC Techniques

• Gantt charts (or bar charts) Figure 5.4
• Show a schedule based on lead time assumptions
  (maybe omit queue, wait, and move times)
• Often shown on a schedule board.
• Primary problemupdating.
• Computer systems can bring updating into
  real-time and to the shop floor.

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PAC Techniques

• Priority sequencing rules which job to run next
  (usually determined as the current job is being
  completed).
• Earliest operation due date.
• Earliest part due date.
• Order slack (based on all part data).
• Slack per operation (all part data).
• Critical ratio (time/work).
• Shortest operation time.
• PAC creates a dispatch list that shows the
  priority sequence for the work center.

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PAC Techniques

• Finite loading systemdetailed schedule for each
  work center based on work center capacity and
  other scheduled jobs. (Will only schedule work
  up to w/c capacity.)
• May conduct a simulation of each w/c for the
  planning horizon
• May consider jobs coming from upstream w/c as
  well as the current queue
• Matching parts may have inconsistent due date

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PAC TechniquesFinite Loading (continued)

• Vertical versus horizontal loading
• Verticalscheduling w/c job by job.
• Horizontalscheduling jobs (by priority) across
  all w/cs.
• Front versus back scheduling
• Frontload an order as soon as w/c capacity was
  available.
• Backload a job backward from its due date.
• Optimized Production Technology (OPT) approach
  may be used.

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PAC Techniques

• Vendor scheduling and follow-up
• Similar to SFC system, but customer demands are
  managed by the vendor with its MPC system.
• Schedule and priority changes must be sent to the
  vendor, but may be contractual limits to the
  amount of change allowed.

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PAC Techniques

• Lead time management.
• All elements except setup and run times (which
  may only be 10-20 of total lead time) can be
  compressed with a good PAC system.
• Lead time and WIP are directly related.
• Some WIP may be needed to ensure capacity
  utilizationbut not too much.
• System queue times are often over-stated.

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Dispatch System

• Create and maintain an open shop order for each
  scheduled receipt.
• Maintain a dispatch list.
• Basis for priority control
• Identify required resources, work units, work
  contents
• Perform status and audit reports
• Open order status
• Exception reports

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Schedule Adjustments

• Reschedule order release
• Reschedule due date
• Vary lost size
• Relocate labor
• Alternative equipment or routing
• Overlap operations (move portion of lot)
• Lot splitting

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PAC Database

• Relation to MPC system (see figure 5.9.)
• Open shop orders with due dates.
• Routing files.
• Standard operations (run) time estimates.
• Move, wait, and queue time data.
• Work center information.
• Data acquisition and feedback
• Automate WIP data collection (bar coding).
• Decentralized computer systems.
• Base scheduling on real-time transactions
• Integrate other systems (quality, maintenance,
  CAD/CAM/CIM).

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Concluding Principles

• PAC system design must be in concert with the
  firms needs.
• The chop-floor control system should support
  users and first-line supervisors, not supplant
  them.
• Vendor capacities should be planned and scheduled
  with as much diligence as are internal
  capacities.
• Lead times are to be managed.

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Concluding Principles

• Organizational goals and incentives must be
  congruent with good PAC practice.
• Discretion and decision-making responsibilities
  in PAC practice need to be carefully defined for
  both shop and vendors.
• PAC performance should be defined and monitored.
• Feedback from PAC should provide early warning
  and status information to other PAC modules.

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Concluding Principles

• Automated reading systems and and distributed
  computers should facilitate data acquisition and
  shop-floor decision making.
• Database design and integrity must be assessed
  for PAC systems to be effective.
• The ongoing evolution in PAC systems as firms
  increasingly adopt world class manufacturing
  methods is reduced detail, smaller databases, and
  simpler systems.

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Chapter 5 Assignments

• Problems 5.2 and 5.12
• Due Tuesday, November 12