Production Activity Control “The time comes when plans must be put into action”

Production Activity Control Responsible for executing the: Master Production Schedule (MPS) Materials Requirements Plan (MRP) At the same time: Make good use of labor, machines and materials Minimize work-in-process inventory Maintain customer service

Production Activity Control Release work orders to the shop for manufacturing Control work orders to complete on time Control detailed the flow of orders through manufacturing Carrying out the plan Controlling the work as it progresses to completion Manage day-to-day activity and provide support

Priority planning and production activity control Master Production Scheduling Planning Material Requirements Planning Input/ Output Control Implement and Control Production Activity Control Purchasing Operation Sequencing Figure 6.1 Priority planning and production activity control

Planning To meet delivery dates Ensure: Schedule: The required materials, tooling, personnel and information Schedule: Start and completion times for each shop order Develop load profiles for the work centres`

Implementation Gather information needed to make the product Release orders to the shop floor MRP authorized “Dispatching”

Control The production order has been released Is corrective action necessary? Rank the orders by priority Establish a dispatch list Track performance to planned schedule Replan, reschedule, adjust capacity Monitor and control WIP, lead times, queues Report work center effciency, scrap, times

PRODUCTION ACTIVITY CONTROL PLAN Schedule Replan EXECUTE Work Authorization CONTROL Compare Decide Dispatch Feedback MANUFACTURING OPERATIONS Figure 6.2 Production control system

Manufacturing Systems Flow manufacturing Intermittent manufacturing Project manufacturing

Flow Manufacturing High volume Standard products Repetitive or Continuous (production of high volume standard product) = repetitive manufacturing eg. Cars and appliances, if the goods are made in a continuous flow (eg. Gasoline) : continuous manufacturing

Flow Manufacturing Routings are fixed Work centers arranged according to the routing Dedicated to a limited range of products specifically designed equipment Use of mechanical transfer devices Low WIP and throughput times Capacity is fixed by the line

Flow Manufacturing Production Activity Control Plans the flow of work Planned schedule of materials to the line Implementation and control are relatively simple

Intermittent Manufacturing Many variations in: product design process requirements order quantities

Intermittent Manufacturing Flow of work is varied - work flow not balanced Machinery and workers must be flexible Usually grouped according to function Throughput times are generally long Capacity required depends on product mix

Intermittent Manufacturing Production Activity Control is complex: number of products made variety of routings scheduling problems PAC is a major activity Controlled through shop orders for each batch

Project Manufacturing One or a small number of units Usually in one place Close coordination between: Manufacturing, Marketing, Purchasing, Engineering Examples: Shipbuilding House construction

Data Requirements Need to know: Organized into databases: What and how much to produce When parts are needed What operations and times are required Work center capacities Organized into databases: Planning or Control

Planning Files Item master file Product structure file Routing file Work center master file

Item Master File Part number Part description Manufacturing lead time Lot size quantity Quantity on hand Quantity available Allocated quantity already assigned to other work orders On-order quantities

Product Structure File Bill of material file A listing of single-level components to make an assembly Forms a basis for a ‘pick list’

Routing File Step-by-step instructions on how to make the product Operations and their sequence Operation descriptions (brief) Equipment tools and accessories Operation setup times Operation run times Lead times for each operation

Work Center Master File Details on each work center Work center number Capacity Shifts, machine hours and labor hours per week Efficiency Utilization Average queue time Alternative work centers

Control Files Shop order master file Shop order detail file Summarized data on each shop order Shop order detail file Current record of each operation

Shop Order Master File Shop order number Order quantity Quantity completed Quantity scrapped Quantity of material issued to the order Due date Priority Balance due Cost information

Shop Order Detail File Operation number Setup hours planned and actual Run hours planned and actual Quantity complete (at this operation) Quantity scrapped (at this operation) Lead time remaining

Order Preparation A check for available: Tooling Materials Capacity - when it is needed

Scheduling To meet delivery dates Make the best use of resources Need information on: Routing Capacity Competing jobs manufacturing lead times

Manufacturing Lead Time Queue - time spent waiting before operation Setup - time to prepare the work center Run - time to make the product Wait - time spent after the operation Move - transit time between work centers

Manufacturing Lead Time Queue Setup Run Wait Need a lift truck here Move Queue Setup Run Wait Move

Cycle Time “The length of time from when material enters a production facility until it exits” APICS Dictionary 11th Edition Synonym - throughput time

Example Problem

Scheduling Techniques Forward Scheduling Start when the order is received May finish early Used to determine the earliest completion date Determine promise dates Builds inventory Backward Scheduling Uses MRP logic Schedule last operation to be complete on the due date Schedule previous operations back from the last operation Reduces inventory

Forward and Backward Scheduling: Infinite Load Order Recieved Due Date 1 2 3 4 5 6 7 8 9 Forward Scheduling Material Ordered 3rd Operation 1st 2nd Backward Scheduling Material Ordered 3rd Operation 1st 2nd Figire 6.4 Infinite load profile

Infinite Load Profile Capacity Overload Capacity Capacity Underload Figure 6.5 Infinite load profile

Forward and Backward Scheduling: Finite Load Order Recieved Due Date 1 2 3 4 5 6 7 8 9 Forward Scheduling Material Ordered 1st Operation 2nd Operation 3rd Operation Backward Scheduling Material Ordered 1st Operation 2nd Operation 3rd Operation Figure 6.6 Forward and Backward scheduling: finite load

Finite Load Profile Capacity Smoothed Load Figure 6.7 Finite load profile

Example Problem Backward Scheduling A company has an order for 50 brand X to be delivered on day 100 Only one machine is available for each operation The factory works one 8 hour shift 5 days a week The parts move in one lot of 50 X A B

Example Problem Answer Part A OP 10 OP 20 X Assembly Part B OP 10 85 90 95 100 Working Days

Operation Overlapping The next operation is allowed to begin before the entire lot is completed Reduces the manufacturing lead time Order is divided into at least two transfer lots SU Lot 1 Lot 2 Operartion A T T Transfer Time SU Lot 1 Lot 2 Operation B

Operation Overlapping Costs involved: Handling costs between work centers May increase queue and wait for other orders Idle time if the second batch doesn’t arrive in time

Size of the Transfer Batch SUA = Set up time operation A SUB = Set up time operation B RTA = Run time per piece operation A RTB = Run time per piece operation B QT = Total order size T1 = size of the first transfer batch T1 = QT x RTA - SUB T2 = QT - T1 RTA + RTB

Size of the Transfer Batch If the second operation is slower than the first make the first transfer batch small i.e. get the slower machine started early If the second machine is faster than the first make the first transfer batch large i.e. the second machine will be able to catch up

Example Problem Operation A 70 x 10 = 700 30 x 10 = 300 70 x 5 = 350 30 730 1,000 (Minutes) 30 70 x 10 = 700 30 x 10 = 300 T Transfer Time 1,010 50 70 x 5 = 350 30x5 = 150 740 790 1140 1290 Operation B Stores 1305

Operation Splitting Reduces manufacturing lead time The order is split into at least two lots Similar machines are run simultaneously Setup time is low compared to run time Operators can run more than one machine

Operation Splitting Run Run Run Figure 6.9 Operation splitting One Machine SU Run Two Machine Operation Splitting SU Run Reduction in Lead Time SU Run Figure 6.9 Operation splitting

Load Leveling Load Report Tells PAC the current and upcoming load on a work center Based on standard hours of operation for each order

Load Report Figure 6.10 Work centre load report

Scheduling Bottlenecks Some workstations are overloaded and some are underloaded Bottlenecks “a facility, function, department, or resource whose capacityis equal to or less than the demand put upon it.” APICs Dictionary 11th Edition

Throughput The total volume of product passing through a facility Bottlenecks control the throughput If Work centers feeding bottlenecks produce more than the bottleneck can process, excess WIP inventory is built up. Therefore, work should be scheduled through the bottleneck at the rate it can process the work Work Centers fed by bottlenecks have their throughput controlled by the bottleneck, and their schedules should be determined by that of bottleneck

Example Problem - Bottlenecks Wagon Wheel Assembly - 1200 sets (2) per week Handle Assembly - 450 per week Final Assembly - 550 wagons per week a. What is the capacity of the factory? b. What limits the throughput of the factory? c. How many wheel assemblies should be made each week? d. What is the utilization of the wheel assembly? e. What happens if utilization is 100%

Example Problem - Bottlenecks a. 450 units per week b. Throughput is limited by the handle assembly operation c. 900 wheel assemblies per week d. Utilization of the wheel assemblies = 900 ÷ 1200 = 75% e. Excess inventory of wheel assemblies

Bottleneck Principles (7) 1. Utilization of a non-bottleneck resource is not determined by its potential, but by another constraint in the system. 2. Utilization of a non-bottleneck 100% of the time does not produce 100% utilization. 3. The capacity of the system depends on the capacity of the bottleneck. 4. Time saved at a non-bottleneck saves the system nothing. 5. Capacity and priority must be considered together. 6. Loads can and should be split. 7. Focus should be on balancing the flow in the shop.

Managing Bottlenecks 1. Establish a time buffer before each bottleneck. 2. Control the rate of material feeding the bottleneck. 3. Do everything to provide the bottleneck with capacity. 4. Adjust loads. 5. Change the schedule. Back schedule before the bottleneck; forward schedule after the bottleneck.

Theory of Constraints 1. Identify the constraint Figure 6.11 Process 1 5 per hour Process 2 7 per hour Process 3 4 per hour Process 4 9 per hour Marketing sells 5 per hour? Figure 6.11

Theory of Constraints continued 2. Exploit the constraint. (idle time?) 3. Subordinate everything to the constraint. 4. Elevate the constraint. 5. Once the constraint is a constraint no-longer, find the new one and repeat the steps.

Drum-Buffer-Rope Drum - pace of production set by the constraint Buffer - inventory established before the constraint Rope - coordinated release of material

Example Problem Work Center 20: Capacity = 40 hours per week Z Work Center 20: Capacity = 40 hours per week Y: Setup = 1 hour, Run Time = .3 hours per piece Z: Setup = 2 hours, Run Time = .2 hours per piece Let x = the number of Y’s and Z’s to produce 1 + 0.3x + 2 + .2x = 40 hours 0.5x = 37 hours x = 74 (you can produce 74 Y’s and 74 Z’s)

Implementation Issuing shop orders to manufacturing Which have a good chance of being completed on time Orders which have the: tooling material capacity

Shop Order Information Order number, description Engineering Drawings Bills of Material Route Sheets Material Issue Tickets Tool Requisitions Job Tickets Move Tickets

Review Order Figure 6.12 Order Release Process Check Tooling and Material Availability Okay? No Resolve Yes Check Capacity Requirements and Availability Okay? No Resolve or Reschedule Yes Release Order

Control Control the work going into and out of a work center: Input/output control Set the priority of orders to run at each work center

Input / Output Control Input Rate Control Queue (Load, WIP) Output Rate Control Figure 6.13 Input/output control

Figure 6.14 Input/output report

Cumulative Variance The difference between the total planned for a given period and the actual total for that period Cumulative variance = previous cumulative variance + actual - planned

Cumulative variance week 2 = -4 + 32 -32 = -4 Figure 6.14 Input/output report

Example Problem: Input/Output

Operations Sequencing “a technique for short term planning of actual jobs to be run in each work center based on capacities and priorities.” APICS Dictionary 11th Edition Priority: The sequence in which jobs should run at a work center

Dispatching Selecting and sequencing jobs to be run at a work center Dispatch list Plant, department, work center Part number, shop order number, operation number and description Standard hours Priority information Jobs coming to the work center

Dispatching Rules FCFS - First come, first served EDD - Earliest job due date ODD - Earliest operation due date SPT - Shortest processing time CR - Critical ratio

Critical Ratio CR= due date - present date lead time remaining = actual time remaining CR<1 Behind Schedule CR=1 On Schedule CR>1 Ahead of CR<0 Already late

Sequencing Rules Figure 6.16 Application of sequencing rules

Production Reporting Feedback of what is actually happening on the shop floor Needed for management decisions on-hand on-order job status shortages scrap material shortages

Production Activity Control Summary Converting MRP plans into action Reporting results Revising plans Need: detailed and current schedules and priorities Results: on-time deliveries, well utilized labor, and equipment, minimum inventory levels