PT&P: On-Line Tour: Scheduling Network

JOB SCHEDULING

In this photo customers are looking at the computer screen and print-outs showing how the scheduling system tracks the status of jobs in manufacturing. All work is tracked by an internal JOB NUMBER. A cross-reference to our customer's purchase order number is maintained in our information system computer. Customers can call our internal expeditor to obtain the status of orders.

WORK BREAKDOWN STRUCTURE
Each job must be broken down into a set of tasks which can be done by a Work Group using a known Process. The Work Group knows the optimum Process and the alternatives which can be used. This includes craft skill levels, machines, materials and techniques. The Work Group knows the optimum crew assignments and the(cycle)time required.

All precedence relations are known, for example, Task A must be done before either Task B or Task C can begin, but B and C can go on at the same time. For example:

Task A: Review the P.O. we have received and accept it.(Perhaps with exceptions)

Task B: Order long lead-time materials.

Task C: Prepare drawings for customer approval.

SEQUENCES OF TASKS FOR A SINGLE JOB
Using the precedence relations the beginning task(s) and ending task(s) for each job can be determined and the duration of each PATH of tasks can be calculated. The longest path is called the CRITICAL PATH because any delay of a task on this path will delay completion of the project.

MULTIPLE JOBS SEQUENCED THROUGH WORK GROUPS WITH DUE DATES
When Work Groups have to complete tasks for a sequence of jobs and when precedence relations exist then scheduling is usually resource limited. One or more Work Groups may be unable to complete the task required to meet all due dates.

PRIORITY SCHEDULING WITH LIMITED RESOURCES
Priority scheduling techniques apply different "costs" to being tardy on jobs with different priorities. An optimum schedule for a set of jobs would sequence all the tasks so as to minimize the total cost of tardiness.

PRODUCTIVITY CONCEPTS WITH A DYNAMIC WORK LOAD
A dynamic work load means that jobs are being added and other jobs are being completed so the work load constantly changes. It is important to know the limiting resources(Work Groups)at all times and take steps to maximize the productivity of all limiting resources. This usually involves communication of the situation to the Work Groups that are limiting and encouragement to "stretch" their effort. This is where creative alternatives and involved employees can be of great value.

Different items require different processes (man-machine operations) to produce. Scheduling is a prioritized, due-date sequence with target completion times. Second and third shifts will always focus on situations where machine availability is limiting production. One advantage of doing business in Houston is that there are many companies who can do certain operations when it is necessary or more cost-effective.

Questions/Feedback

Piping Technology & Products, Inc.
Online Tour
P.O. Box 34506 / Houston, Texas 77234-4506 / U.S.A.
(713) 731-0030 / (713) 731-8640 (FAX)
www.pipingtech.com / info@pipingtech.com