Chapter 3 Planning for Production

Objectives Product oriented manufacturing systems versus people oriented manufacturing systems. Manufacturing smaller lot sizes with less lead time. Push, pull, and Kanban manufacturing systems.

The unskilled factory system Fredrick Taylor ( ) believed that complicated jobs can be broken down into a series of simple tasks. An inexperienced person could quickly learn how to do a simple task, which eliminated the need for skilled workers. Once a process was defined and the worker was following the correct procedure, Taylor timed each task – time and motion study. Knowing the time it takes to do a task enabled managers to predict how many parts could be made in a time period and how many people would be needed to make the products at the rate required.

The Production Line Manufacturing System Henry Ford developed a manufacturing approach known as vertical integration, where Ford created the parts instead of relying on outside suppliers. The Ford Company made everything from the steel to the paint used in their automobiles. Ford’ engineers used Taylor’s approach to define an individual’s work. They also used a conveyor to move the car from task to task (supposedly Ford adapted this idea from a meat packing plant he visited). Ford’s production system produced the Model-T automobile – the first affordable mass produced automobile.

People Oriented versus Product Oriented Manufacturing Systems Keeping workers busy was the focus of management. This created a build up of materials on the factory floor – called Work in Progress (WIP). Incentive systems paid workers on the amount they produced (piece rate) or bonus proportional to amount over a base level – created excess WIP.

Product Flow Manufacturing Systems A manufacturing system that is operating just in time (JIT) will not have any work in progress. Increase in excess WIP is a symptom that a problem exists. Problems can be one or more of the following 5 categories: quality, machine breakdown, setup or change over downtime, operator problems or unplanned absenteeism, or materials availability. Quality problem – 5 % of the parts made by the stamping operation are defective. Symptom – 105 parts are made for every 100 parts needed. Solution – institute a quality improvement process to eliminate quality problem. Machine breakdown – establish a preventive or predictive maintenance program to eliminate the breakdown problem. Setup or changeover downtime – establish a single minute changeover of dies (SMED) program. This is a team approach to reduce die changeover times. Operator Problem – Provide the operator with knowledge, support, authority, and responsibility to produce good parts. Delivery of required materials is late – choose suppliers on their ability to respond on time and provide quality materials.

The Basis for Lean Manufacturing 1. Quality Quality programs in lean manufacturing eliminate and prevent waste (non value added activities) in the production of a product. Inspection of parts and products is a non value added activity. Three steps used to ensure replication of characteristics in Statistical Process Control (SPC): a. Establish Control: make the process or activity capable of replicating a product or task. b. Monitor the Activity: visual method to track performance of activity to recognize when the activity is not performing normally. Designers usually provide for some variation – tolerance. Process variation is normally considered to be 6 standard deviations. Run charts (fig 3-5, page 63) incorporate a centerline and control limits to enable the operator to monitor and interpret if the process is in control. c. Problem Solving: train personnel to be problem solvers to bring activity back in control. Cause and Effect Diagram: Breaks down main cause into smaller sub causes to discover the root cause and not just the symptoms of a problem or condition. The 5 Why’s: Ask the question “why” 5 times to get to the root cause of a problem. Pareto Analysis: A bar chart displaying in descending order the most frequent to the least frequent problems. 80 % of defects are produced by 20% of problems.

The Basis for Lean Manufacturing 2. Reliability Institute a maintenance program based on following the manufacturer’s recommendation about the care that should be given to production equipment known as preventive maintenance. It requires operators to be trained in maintaining their equipment. The objective of all maintenance programs is to reduce waste caused by interruptions to product flow.

The Basis for Lean Manufacturing 3. Setup Reduction The setup time should be small enough to enable the manufacturing lot size to equal the quantity the customer wants shipped as an order. Successful companies approach setup reduction time the same way a NASCAR team views the time it takes to do a pit stop. Involve a setup reduction team in developing an innovative solution to achieve the target setup time.

The Basis for Lean Manufacturing 4. Operator Ability To carry out the tasks assigned each person must possess the knowledge/skill to: do the task correctly, obtain help to solve the problem if they are not able to do it, and never let a problem/defect move on in the manufacturing process.

Manufacturing System Materials Requirement Planning (MRP) is computer based scheduling that minimizes raw material inventory and excess WIP. For critical orders production control managers, manufacturing department supervisors, and sales managers rely on a group of people (expeditors) to track, confirm, and work out problems. Delays due to breakdowns, absences, and unforeseen setups cannot be forecast by the computer system.

Push and Pull Systems Push system: When an order is received a push system begins by ordering materials and then establishes a start date to begin production based on when the materials will be available. Push systems push the product through the factory. Pull systems: try to respond immediately by shipping the order when it is received. Shipping the order then creates a demand that moves up the production line to replace what has just been shipped. Pull systems are considered to be more responsive to customers than a push system.

Kanbans The triggers used to start production in a pull system are called Kanbans. The Kanban signal to initiate production consists of a card and a container (tote pan). The Toyota system used a specific size container for each part. This container cycles back and forth between the producing department and the using department. Producing departments may not make parts unless there is an empty Kanban container and a card (Kanban) authorizing production. The number of containers is controlled by manufacturing management and is kept to the smallest possible quantity.

Bringing Vendors into the Manufacturing System Typically, the date that a company said it would ship an order had to include the time it took to procure needed materials from a supplier. Buffer stocks allow lean manufacturing systems to deal effectively with distant vendors, complex product mixes, and fluctuating demand loads.

Summary Fredrick Taylor ( ) believed that complicated jobs can be broken down into a series of simple tasks. An inexperienced person could quickly learn how to do a simple task, which eliminated the need for skilled workers. Once a process was defined and the worker was following the correct procedure, Taylor timed each task – time and motion study. Knowing the time it takes to do a task enabled managers to predict how many parts could be made in a time period and how many people would be needed to make the products at the rate required. Problems can be one or more of the following 5 categories: quality, machine breakdown, setup or change over downtime, operator problems or unplanned absenteeism, or materials availability. Process variation is normally considered to be 6 standard deviations. Run charts incorporate a centerline and control limits to enable the operator to monitor and interpret if the process is in control. Cause and Effect Diagram: Breaks down main cause into smaller sub causes to discover the root cause and not just the symptoms of a problem or condition. The 5 Why’s: Ask the question “why” 5 times to get to the root cause of a problem. Pareto Analysis: A bar chart displaying in descending order the most frequent to the least frequent problems. 80 % of defects are produced by 20% of problems.

Home Work 1. What is Taylor’s time and motion study, and what is its advantage? 2. Name the 5 categories of product flow problems in a manufacturing system? 3. What is the acceptable normal process variation? 4. What are run charts?