Orientation Principle:Material Handling Principles
Orientation Principle:
Study the problem
Identify:
Establish goals
Planning Principle:
Establish a plan to include:
Systems Principle:
Integrate the material handling system of operations and storage activities into a coordinated system of operations. (Integration should include receiving, inspection, storage, production, assembly, packaging, warehousing, shipping, and transportation activities)
Unit Load Principle:
Handle product in as large a unit load as practical.
Space Utilization Principle:
Optimize the space utilization. Make effective use of the available space.
Standardization Principle:
Standardize the handling methods and equipment.
Ergonomics Principle:
Recognize human capabilities and limitations by designing material handling equipment and procedures for effective interaction with people using the system.
Energy Principle:
Minimize the energy consumption when selecting material handling equipment.
Ecology Principle:
Use material handling equipment and procedures that minimize adverse effects on the environment.
Mechanization Principle:
Increase the efficiency by mechanizing and automating a material handling system.
Flexibility Principle:
Use methods and systems that can perform a variety of tasks.
Simplification Principle:
Simplify material handling operations by eliminating, reducing, or combining unnecessary movements and/or equipment.
Gravity Principle:
Utilize gravity to move materials (keep in mind the issues of safety, product damage, and loss before applying this principle)
Safety Principle:
Provide safe material handling equipment and methods that follow safety codes and regulations such as OSHA .
Computerization Principle:
For improved material and information control, consider computerization in material handling and storage systems.
System Flow Principle:
Integrate data flow with physical material flow in handling and storage.
Layout Principle:
Optimize the layout which provides the most efficient and effective material handling and storage system.
Cost principle:
Compare the economic justification of alternate solutions.
Maintenance Principle:
Prepare a plan for preventive maintenance and scheduled repairs on all material handling equipment.
Obsolescence Principle:
Prepare a long-range and economically sound policy for replacement of obsolete equipment.
Capacity of a Material Handling System
When selecting a certain material handling system, the main goal is to maximize the utilization of the equipment.
Machine utilization can be analyzed by the following formula:
% utilization = (Actual number of pieces handled ) / (machine capacity /hour)
The following example explains how equipment utilization is calculated.
Example:
A punch press can cycle every 0.03 min. (33 times /min). The standard time for manually loading and unloading the press is only 300 pieces /hour. What is the percent utilization of the punch press ?
Solution: The number of pieces that can be punched in one hour:
Machine capacity/hr = (33 pieces/min) x (60 min)/hr = 1980 pieces /hour
% utilization = ( actual number of pieces loaded /hr) / (machine capacity/hr)
% utilization = 300 pieces / 1980 pieces = 15.2 %
This is a low rate of utilization. Purchase an automatic feeding system to utilize the punch press at full capacity.
Performance of a Material Handling System
Prior to the design of an improved material handling system, estimate the cost of material handling in the present system. Since the cost of material handling is proportional to the time it takes to handle the material, maximize the performance of the system by eliminating bottlenecking and backtracking operations.
Performance of a material handling system can be calculated from:
% of Material Handling (MH) = MH time / Total time
Total time includes the time spent for material handling and production and inspection of a part.
Note: As can be seen from the formula, the goal is to reduce the MH time. However, it is not always necessary to select the highest speed of handling. Primary goal is to eliminate bottlenecking and backtracking.
Example:
We are asked to analyze the performance of a MH system between a machining center and exit which are connected by conveyors A and B as shown below. (assuming that the machining center is used at full capacity) Calculate:
(a) the percent utilization of the inspection center.
(b) percent MH of the process between points X and Y.
Figure 1
(a) The capacity of Conveyor A:
5 parts/min = 5 parts/ min x 60 min/hr =300 parts/hr.
The capacity of the Inspection Center:
400 parts/hr (given )
At inspection center 6.67 parts can be inspected in one minute. (400 parts/hr x 1 hr/60 min = 6.67 parts/min)
Each part takes 0.15 min. to inspect. (1/6.67 =0.15 min.)
We can see from here that Conveyor A can only bring 300 parts/hr .Thus, we will not
be allowed to utilize the inspection center at full capacity.
% utilization of inspection center = 300 /400 = 0.75
Unless we increase the capacity of the conveyor A, we can only utilize the inspection center at 75 % capacity.
(b) Now we look at the time it takes for each part to move from conveyor A to the Exit.
|
MH System Component |
Capacity (parts / min) |
Time required for each part (minutes) |
|
|
Conveyor A |
5 |
0.20 |
|
|
Inspection Center |
6.67 |
0.15 |
|
|
Conveyor |
5 |
0.20 |
|
|
|
Total time it takes to move each part from X to Y |
0.55 |
|
Using the data from the table above, we can find the % time spent for material handling (% MH) as follows:
% MH = MH time/Total Time = 0.40 / 0.55 = 0.73
which means that 73 % of the processing time is spent for material handling.
Unit Loads
The concept of unit load is derived from the unit size principle and is defined as the unit to be moved or handled at one time. In some cases a unit load is one item of production; in other situations the unit load is several cartons, each containing numerous items of production.
Components of a Unit Load
:Container (cartons, boxes, bins, crates, baskets, bags)
Carrier or support (pallet, skid, cardboard, plywood, polyethylene slip sheet)
Product
Advantages of using Unit Load
:Handles more items at a time
Reduces the number of trips
Reduces the handling costs
Reduces the loading and unloading times
Reduces the product damage
Types of Unit Loads:
The following factors affect the unit load size and the dimensions of the Material Handling device:
Pallet sizes are determined by the storage volume to be utilized.
Pallet pattern is determined by volume to be utilized and weight of the products to be stored.
Unit load dimensions influence the conveyor dimensions.
A popular method of building a unit load is to place one or more items on a pallet. Figure 2a through 2e show pallets that are designed in a variety of shapes and sizes.
Figure 2 a. Standard single-deck wooden pallet.
Figure 2 b. Double-faced nonreversible pallet for pallet truck handling.
Figure 2 c. Four-way block -leg pallet.
Figure 2 d. Double wing type pallet.
Figure 2e. Three board single deck expendable shipping pallet.
Figure 3. Various pallet stacking patterns
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(a) Block pattern (b) Row pattern (c) Pinwheel pattern (d) Honeycomb pattern |
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(e) Split-row pattern (f) Split-pinwheel pattern (g) Split-pinwheel pattern for narrow boxes (h) Brick pattern |
Figure 4. Other pallet stacking patterns.
Volume and weight of the items to be stored determine the size of a pallet and the stacking pattern. When the items to be stored are heavy, weight considerations may be more important than volume considerations. Weight considerations also influence the structural design of the pallet and the capacity of the handling equipment and storage racks. Pallet dimensions influence the size of the space to be used for storing loaded and unloaded pallets.
Among the most popular pallet sizes are the following:
|
32 x 40 in. |
40 x 48 in. |
48 x 40 in. |
|
36 x 48 in. |
42 x 42 in. |
48 x 48 in. |
Other sizes that are considered by American National Standards Institute (ANSI) are:
|
24 x 32 in. |
36 x 36 in. |
48 x 60 in. |
|
32 x 48 in. |
36 x 42 in. |
48 x 72 in. |
When the material handling system in an existing building is to be changed, the door width, column spacing, turning radius of material handling vehicles, clear stacking height are among the other factors that affect the unit load specifications. Numerous examples can be found in existing buildings where an equipment purchased could not be installed on schedule because it was too large to pass through the doors. Similar examples are common for unit loads that were not sized for stacking in material handling vehicle or too large to handle by an existing conveyor system.
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Last Update: November 11, 1999 |
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Prepared by : Serdar Z. Elgun |
