Vertical storage and retrieval systems help shops reach for lean
August 8, 2007
Using conventional rack and shelving systems to store and retrieve dies is inefficient and can cause damage to dies. Five critical areas of concern are space utilization, worker productivity, potential for die damage, ergonomics and cost justification. Shops can reach new lean levels by improvements in these areas.
Conventional rack, shelving, and drawer systems used in many stamping facilities are a less-than-lean method of storing dies. They consume a lot of floor space, and locating and retrieving dies encroaches on production time. In addition, these conventional methods expose dies to damage.
The focus of lean manufacturing initiatives is to eliminate waste that occurs during manufacturing operations and to optimize process flow to improve overall efficiency. Vertical automated storage and retrieval systems address five lean manufacturing goals for stamping die storage options: maximizing space utilization, increasing employee productivity, ensuring safety, optimizing equipment efficiency, and reducing tooling costs.
Recovered floor space can be re-allocated from cost-associated inventory functions to value-increasing production operations. Improved space utilization also can extend the useful life of existing facilities, eliminating the need for expensive brick and mortar expansion to meet growth requirements.
The small unit footprint makes vertical systems especially valuable for point-of-use storage. Storing dies and other tooling at point-of-use reduces unnecessary processing and transportation common with central storage.
The systems can be configured to store various sizes of items, from dies to tooling to fasteners to safety products, and can be easily reconfigured to accommodate physical changes in stored items, such as finished goods. This will allow shops to keep on hand only what they need.
Vertical storage and retrieval systems can be equipped with microprocessor controls, position indicators, information displays, and PC-based software to further increase the speed at which specific tooling is located and retrieved in the system.
Vertical storage and retrieval systems can be controlled using PC software or hardware controls. A system can be configured for stand-alone, single-user operation or a multiuser network. The operator enters the shelf number using the controls, and the shelf and its contents are delivered automatically.
For functional effectiveness, transaction information must be communicated between the operator and the control system. The level of the system's sophistication will help determine how the information will be displayed to the operator.
For example, in a strictly manual system, the operator decides all location transactions and enters the shelf or tray locations via keypad. This activity is followed by manual inventory adjustments.
In a fully automated environment, all information requests—from location selection, container type, inventory adjustment, activity analysis, and data—transfers between the vertical system's software and the facility's host system, such as a shop's MRP system. This can be accomplished transparently, with no operator intervention.
Because they help shops meet the requirements for lean manufacturing, vertical storage and retrieval systems can have a verifiable positive return in terms of improved operating efficiency if they are properly configured for specific applications.
However, as with any major investment, a comparison of the costs of a new system versus the old system must be considered. Sitting down with an installation specialist and putting the numbers into a standard return on investment/internal rate of return (ROI / IRR) formula is one way to do this. Another way is to use an ROI/IRR calculator that allows users to enter the appropriate data that automatically computes the daily costs of the current system and the new system. The calculator also computes dollar savings from reduced space requirements, cost savings from improved employee productivity, depreciation savings, and total annualized savings. From this information, the shop can determine the payback schedule for a specific installation.
Because vertical systems can be configured with many shelf and tray variations, load data is used to design the application to the need. For the storage of stamping dies, weight is a primary consideration. To define system requirements, you must calculate average weight density to determine shelf or tray loading capacity. Once load data has been determined and grouped by size and weight, it can be used to determine optimum vertical spacing, depth, and width.
Consideration also must be given to the physical layout of the installation site. The clear height of the building interior will determine the height of the units and the total number of shelves or trays allowed in each unit. It is possible to estimate space savings in square feet and percentages using general formulas developed by automated storage and retrieval system manufacturers (see Figures 3 and 4).
For example, in a facility with a ceiling height of 40 feet, a vertical storage and retrieval system can eliminate up to 100 shelving sections with a resulting space savings of up to 929 square feet, or 91 percent. For a ceiling height of 30 ft., a vertical system can eliminate 46 drawer-type cabinets for a space savings of 311 sq. ft., or 80 percent.
Industrial buildings with at least 4 to 6 in. of reinforced concrete over a solid, compacted base will support most loaded vertical systems.