9.1 Material Handling
9.1.6 Designing MH Systems
Design is the most important step in operating an MH system that will accomplish its objectives. From a variety of possible alternatives, the designer selects one set that will result in an efficient and economic system.
The design process is not a well-defined algorithm that the designer can follow through to a successful outcome. It is both a procedure and an art based on empiri-cal experience, engineering knowledge, and ingenuity.
The MH systems design process involves the following six-step engineering design process[5]:
1. Define the problem and identify the system scope and objectives of the MH system.
2. Identify the requirements and analyze them for moving, protecting, and controlling materials.
3. Generate alternative designs for satisfying the MH system requirements.
4. Evaluate alternative MH system designs.
5. Select the preferred design for moving, protecting, and controlling materials.
6. Implement the selected design, including selecting suppliers and equipment, training per-sonnel, installing equipment, and periodically auditing system performance.
Problem Definition
MH problems must be first identified clearly so that a solution can be achieved.
Existing operations should be reviewed, beginning with receiving activities and continuing all the way to final shipment.
The problem may arise from a critical incident, management’s perception that improvement is needed, competitive pressures, or even other parts of company such as warehouses.
The objectives of MH systems are the end results that the system is expected to accomplish. As Stock and Lambert mentioned in their research, a typical objective is cost reduction. Others may be better customer service, greater space productivity, increased efficiency, or decreased accidents and damages. Those criteria which measure the extent to which the systems design is expected to meet the objectives[6].
Analyzing the Requirements
The next step is to analyze the problem and related information gathered so far based on the problem definition. The designer reviews what has been learned and what there is to work with. A major result of this analysis is limiting the number of alternatives to be investigated based on the objectives that are identified in the pre-vious step. Careful selection of the most promising choices to investigate is the key to efficient use of engineering resources and to a successful design outcome.
Another outcome is determining any additional data that must be collected and any additional changes that must be made in the problem statement, objectives, and constraints[6].
Analytical techniques can provide valuable information for the design and deci-sion-making process in this step. Some of these techniques are as follows[1].
Fromto chart: A fromto chart is a matrix used to summarize information regarding material movement between related predefined nodes. It can be used to prepare material
flow patterns, compare alternative, identify bottlenecks, and determine candidates for mechanization and automation.
Flow-process chart: The flow-process chart is a step-by-step record of activities per-formed to accomplish a task. The flow-process chart is useful for analysis and for deter-mining improvements, such as combining operations, eliminating unnecessary handling, simplifying a method, or changing a sequence or routing.
Flow diagram: The flow diagram is a graphical outline of the steps in a process similar to a flow-process chart. It is valuable for obtaining a macroperspective on the entire activity.
Product quantity (PQ) chart: The PQ chart is a graphical record of various products, parts, or materials produced or used for a particular time period. Quantities should be related to standard unit loads.
Simulation and waiting line analysis: These two analytical techniques help designers to simplify the problem analysis.
Developing Alternatives
To help develop alternative MH system designs, the MH system equation may be useful. The equation gives the key for identifying solutions to MH problems. It determines three important system components: What defines the type of materials moved, where and when identify the place and time requirements, and how and who point to the MH methods. These questions all lead us to the system.
The MH system equation is given by[7]:
Materials1 Moves 1 Methods 5 System
Evaluating Alternatives
The objective of this step is to determine the value of alternative MH systems so that the designer can find the optimum solution. Economic analysis is an obligation for determining the best solution to a problem. It is also important in preparing a justification of capital expenditures for consideration and approval by upper man-agement. Basic methods of cost comparison are discussed below.
Payback period: The most commonly used method for economic analysis—payback period—is the easiest method to compute and understand. It computes the time period required for estimated project savings to equal the investment. A serious shortcoming is the assumption that one alternative is better than another because it pays for itself more rapidly.
Return on investment (ROI): Unlike the payback period method, the ROI method takes into consideration the equipment’s useful life. Normally, it relates net profit after taxes and depreciation to the total investment, thus indicating what each alternative will earn with respect to the investment.
Discounted cash flow (DCF): DCF computes the total present worth of cash flow over the project’s life, using an interest rate equal to the company’s minimum required rate of ROI. This method considers the present value of money after interest payments have been added to it over a period of time. Basically, it finds the interest rate that discounts future earning of the project alternative down to a present value equal to the project cost.
Some noneconomic factors can help the designer evaluate alternatives:
G Capacity
G Ability to handle the product
G Maintainability
G Reliability
G Damage and safety
G Compatibility
G Installation and lead time
Selecting the Preferred Design
In this step, all of the design alternatives that were evaluated in the previous steps are compared with each other, and the one that satisfies the objective is selected. If the MH system follows more than one objective, then the multicriteria decision methods will help the designer select the right alternative that will satisfy the majority of objectives.
Implementing the System
Implementation means to give practical effect to and ensure actual fulfillment by concrete measures. In this step, the approved MH project is implemented into a physical operating system which moves materials. The effectiveness with which implementation is carried out will determine the degree of success attained by the MH system.
This step includes the following tasks.
Organize for implementation: The quality of the design, the smoothness of installation, and the efficiency of the resulting system all depend on good organization and competent personnel.
Determine roles in implementation: The MH system designer works with many other departments and individuals in the design and installation of an MH system. Some of these have the authority to require changes in design and operation. Others may be spe-cialists who can furnish valuable advice on some facets of the system design. The system designer must be able to work with all those involved to secure the best results.
Determine the implementation procedure: After the MH system design has been approved, the system designer has to coordinate carrying out the plan and installing the system. This requires considerable efforts, good technical abilities, and personnel skills.
Train personnel: It is not a necessary part of project implementation to train operating and maintenance personnel in new methods and equipment, but this may be a major effort as in a factory introducing new developed equipment for the first time. On the other hand, little new training may be required if the system is similar to existing ones[6].