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Production Activity Control. Chapter 5. MPC System with PAC (VBW, figure 5.1). PAC Framework. PAC concerns execution of material plans, a ided by use of shop-floor computers, EDI, and the Internet. Usual linkage is to MRP system.

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pac framework
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.
pac responsibilities
PAC Responsibilities
  • Execution
    • Scheduling
    • Dispatching
  • Control
    • Work order progress – move tickets
    • Labor efficiency – labor tickets
    • Quality – scrap/rework tickets
    • Shop status – machine/tool tickets
planning for shop order release
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)
planned lead time
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
scheduling focus
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.
pac techniques
PAC Techniques
  • Basic shop-floor concepts:
    • Essential inputs—routing and lead time data (see figure 5.3)
    • Queue/wait times often accounts for 80%+ of total lead time.
    • Operations setback chart—based on each part’s lead times.
    • Work center schedules—based on various elements of lead-time elements
pac techniques9
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 problem—updating.
      • Computer systems can bring updating into real-time and to the shop floor.
pac techniques10
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.
pac techniques11
PAC Techniques
  • Finite loading system—detailed 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
pac techniques finite loading continued
PAC TechniquesFinite Loading (continued)
  • Vertical versus horizontal loading:
    • Vertical—scheduling w/c job by job.
    • Horizontal—scheduling jobs (by priority) across all w/c’s.
  • Front versus back scheduling:
    • Front—load an order as soon as w/c capacity was available.
    • Back—load a job backward from its due date.
  • Optimized Production Technology (OPT) approach may be used.
pac techniques13
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.
pac techniques14
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 utilization—but not too much.
    • System queue times are often over-stated.
dispatch system
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
schedule adjustments
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
pac database
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).
concluding principles
Concluding Principles
  • PAC system design must be in concert with the firm’s 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.
concluding principles19
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.
concluding principles20
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.
chapter 5 assignments
Chapter 5 Assignments
  • Problems 5.2 and 5.12
  • Due Tuesday, November 12