Product Details Supplier Info More products

Kardex explains how to select a vertical storage and retrieval system for tool and die applications

Material handling in a typical machining or manufacturing operation can account for a large percentage of production time and the movement and storage of tooling and dies can represent a significant portion of the cost of production.

A solution to more efficient storing, handling and retrieval of materials is the installation of a vertical storage and retrieval system as an alternative to conventional drawer, shelving and rack systems.

Vertical systems, when properly planned and integrated into daily operations, can solve many of the problems associated with poor utilisation of floor space, throughput restrictions, centralised stockrooms, information and inventory management, lean manufacturing and quick response/JIT disciplines.

In the process, they can significantly reduce operating costs.

Vertical storage and retrieval systems consist of two primary devices.

One is called a vertical carousel that uses rotating carriers, or shelves, that move on a track (like a Ferris wheel) in response to operator commands.

The other vertical device is a VLM (Vertical Lift Module).

VLMs consist of a series of trays that are mounted on both sides of an inserter/extractor device.

With both the vertical carousel and VLM, items are automatically delivered to the operator at an ergonomically positioned work counter.

These systems come in a range of capacities and configurations and can be used for a number of storage and retrieval requirements.

There are vertical systems that can easily handle tools, dies and pallets, with each carrier able to accommodate up to 11,025lb.

Some of these units are available with up to 210 shelf levels for a total unit capacity of 2,315,250lb.

Other vertical storage and retrieval systems are designed specifically to store small tooling and consumable safety items.

Standard vertical storage and retrieval systems can hold items as large as heavy tooling and subassemblies and as small as screws and other fasteners.

Defining System Performance Requirements Installing a vertical system means first considering a specific set of factors, ranging from discrete performance to equipment-design-code requirements, to arrive at the best solution to meet financial and operating objectives.

A key consideration is the nature of the load to be stored.

Since vertical systems can be equipped with many variations of shelf configurations, load data are used to custom engineer the application to the need.

For example, are the products to be stored in odd-shaped or standard vendor carton sizes? Are they loose, requiring a container or a tote? With the help of a storage specialist, users should categorise storage load quantities into groups based on similar length, width and height characteristics.

This way, each group can be assigned the best shelf configuration to maximise storage density within the unit.

When defining system requirements, average weight-density information is calculated to determine shelf-loading requirements.

Once information on load configurations has been determined and grouped by size and weight, it can be used to determine optimum shelf vertical spacing, depth and width.

In most cases, the maximum load clearance needed above load heights for access need only be between 1/4 and 3/4in.

Therefore, the pitch, which is the point-to-point shelf distance for a given model, can be estimated by adding the load height plus load clearance and hardware level thickness – approximately 1in to 1.5in in industrial applications.

This estimate can then be confirmed against vendor data to determine exact pitch and clear load access distance between levels.

Vendor information is also available on clearances for multi-tier shelf configurations when intermediate shelves are needed to accommodate load-height variability.

Load data are then used to establish desired shelf width, depth and quantity.

Various accessories are also available, such as wire or solid dividers, component reel inserts, different front-lip heights, drawers and security locks to accommodate special needs.

Average weight-load data, either in the form of discrete load-weight ranges or density factors, can now be used to establish carrier-load-weight configurations.

System throughput is defined as the rate of transaction per period of time.

Calculation of system throughput should include not only the standard ‘receipt to’ and ‘pick from’ inventory usage transactions, but also those associated with returns to stock, cycle counts and ‘hot’ picks.

Statistical information such as the average number of orders per day per shift, average number of line items per order, average pieces per line pick, average receipt of line items per day, and average miscellaneous transactions per day are common ways of expressing this performance requirement.

The method of inventory movement to and from the vertical system can also affect throughput.

Load parameters may necessitate a conveyor interface, or heavy load demands may require a manipulator in front of the unit.

Double floor-level operations may require dual top and bottom access points on the unit.

The quantity of units also affects throughput.

Inside building height along with vendor information concerning the number of shelves per given height are used to establish the number of loads per a given vertical unit.

A simple division of total loads required to store by loads per unit results in the total quantity needed.

Future growth and expansion capacity can be factored into this quantity.

Another key consideration when configuring a system is the location of the access.

The access opening of an industrial vertical storage and retrieval system is normally configured for either a standing or seated operation.

Multiple access locations can also be provided.

Access openings located at the top and bottom and front and back are most common.

Consideration must also 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 at a given spacing allowed in each unit.

In most cases, the top clearance from the unit to the building’s lowest obstruction above the unit can be as little as 8/10in.

It is possible to estimate space savings in square feet and percentage using general formulas developed by automated storage and retrieval system manufacturers.

For example, in a facility with a ceiling height of 40 feet, a vertical storage and retrieval system eliminates up to 100 shelving sections with a resulting space savings of up to 929ft2, or 91 per cent.

With a ceiling height of 30ft, a vertical solution can eliminate 46 drawer-type cabinets for a space savings of 311ft2, or 80 per cent.

Individual fire insurer’s requirements regarding ceiling clearance can also be a determining factor in unit height.

Some insurers may require at least 18in clearance between the top of the unit and sprinkler heads.

Industrial buildings with at least 4-6in of reinforced concrete over a solid, compacted base will support most loaded vertical systems.

The controller, software and computer interface are elements that can be combined in a number of ways to meet overall storage and retrieval objectives.

Operator interface with the system is a critical consideration.

For functional effectiveness, transaction information must be transmitted between the operator and the control system.

A determination must be made concerning what data will be generated by the control system and how it will be displayed to the operator.

For example, in a strictly manual system the operator decides all location transactions and enters, via keypad, the shelf locations.

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 control computer and host system are accomplished transparently with no operator intervention.

Vertical storage and retrieval systems can be controlled using PC software or hardware controls.

The difference is in the graphic interface, or ease of use and the amount of information needed to track and manage materials in a specific application.

A system can be configured for standalone, single-user operation or multi-user network use.

The controls solution can be as simple as a piece of paper indicating the shelf level of each stored item.

The operator simply enters the shelf number using the controls and the shelf and its contents are delivered automatically.

A single PC can control from one to 99 units.

In this type of operation, bills of materials (BOM) could be generated on the host system.

The BOM is downloaded and sent to the storage and retrieval system control PC.

The operator can call up each order, or batch picks multiple orders, depending on the hardware configuration.

Pick lights can be installed to direct the operator to the proper pick location for added accuracy.

Inventory is tracked by the control software that processes all parts orders, adjusts inventory files based on transactions and monitors inventory reorder levels.

Operator logins allow managers to track and monitor usage patterns to reduce shrinkage.

A software system can be networked to manage multiple vertical units in high-throughput applications.

A multi-user system provides independent operation of each unit in the network while information accessed on workstations is shared on a common database and uploaded to a host WMS or ERP system.

With a multi-user configuration, operators can process multiple bills of material orders, print status reports or store receipts.

Conventional static-storage systems such as shelving require employees to spend up to 70 per cent of their time travelling aisles searching for items.

In typical industrial applications, productivity throughput can increase by more than 2.5 times.

One of the primary reasons for considering a vertical system is the improved space utilisation they offer.

Depending on useable building interior heights, a significant percentage of a conventional storage system’s occupied floor space can be recovered.

The small unit footprint makes vertical systems especially valuable for point-of-use storage and JIT manufacturing applications.

Recovered floor space can be re-allocated from cost-associated functions of inventory to value-increasing production operations.

Improved space utilisation can also extend the useful life of existing facilities, eliminating the need for expensive brick and mortar expansion to meet growth requirements.

Redundant or non-essential handling can be reduced with vertical systems, especially in applications’ frequent reuse of tools and dies.

The time saved results in less operating cost and usually improved customer service.

Labour costs are reduced due to the system’s quick retrieval times and the capability to meet varying throughput requirements while not being bound by thresholds imposed by limited-access systems.

Typically, an operator’s walk and search time is reversed from that of conventional systems to 70 per cent picking and only 30 per cent dwell time.

The access area of vertical systems is ergonomically designed to present stored items at an ideal height for picking – usually about waist high.

This location of the access area contributes to employee safety since this positioning design eliminates the bending, climbing and stretching associated with conventional shelving and rack systems.

Throughput generally improves as well.

Since vertical systems are totally enclosed and lockable to protect products from external hazards and reduce product damage and pilfering, inventories can be reduced in many operations.

Stock rotation can be improved by utilising computerised picking controls.

Vertical storage and retrieval systems also offer increased picking speed and accuracy using microprocessor controls with position indicators, information displays, PC-based software and overall system physical design.

These systems can also be easily expanded since they are literally modular units.

Re-programming of system controls is a simple matter of software-configuration updates.

Vertical storage and retrieval systems are an important investment and they produce a verifiable positive return if they are properly configured for specific applications.

Integrated vertical storage and retrieval systems often have a return on investment (ROI) of less than 18 months.

However, as with any major investment, a comparison of the costs of the new system versus the old system must be considered.

For vertical storage and retrieval systems, the operative data are the amount of floor space occupied by current equipment, cost per square foot, the number of employees handling daily transactions, number of transactions performed daily, average labour cost and other information that affects system costs.

Sitting down with an installation specialist and putting the numbers into a standard ROI/IRR (Return on Investment/Internal Rate of Return) formula is one way to do this.

Another is to log the Kardex website and use a ROI/IRR calculator that allows users to enter the appropriate data.

It automatically computes the daily cost of the current system and the daily cost of the new system.

The calculator also computes dollar savings from reduced space requirements, cost savings from improved employee productivity, depreciation savings and total annualised savings.

From this information, the calculator helps determine the payback schedule for the user’s specific installation.

There are a number of important factors to consider when planning the installation of a vertical storage and retrieval system.

A properly applied approach to planning and specifying can substantially enhance the benefits these systems offer.

View full profile