January 30, 2014
By Klaus-Dieter Wurm, VP and Managing Director of Materials Handling at SSI Schaefer

Learn when to apply semi-automatic/dynamic VLM storage technology [and when to use traditional static storage methods such as shelf-supported mezzanines with shelf totes and shelf dividers].

We all understand Vertical Lift Module (VLM) technology (vertically arranged storage trays in the front and back of the system, with an elevator and extractor in the middle allowing individual trays to be moved to the operator at an ergonomic pick height) and the advantage of being able to convert square feet storage (shelving in x/y coordinates) into cubic feet storage which takes advantage of the z-direction to fully utilize the building’s clear ceiling height.  As an example, a shelving area of 25,000 sqft can be reduced to about 700 sqft when using a VLM, allowing the same amount of items to be stored.  
We also understand that traditional storage methods - such as shelving and pallet racking - require more people, because pickers have to walk from location to location with pick tickets, placing the items on picking carts which are pushed from aisle-to-aisle until the order is complete.  Walking alone can consume 70% of the picker’s time: a modest 20% for searching and finding the ordered articles leaves just 10% of productive time for picking orders.  That is where goods-to-man technology such as Vertical Lift Modules comes into play.
Due to the product mix and constantly changing SKU count, automation is perceived to be inflexible and as a result often rejected. There is also the large upfront investment costs and longer ROI period required. As a result, the most common storage method is picking cases from pallets and pieces from shelving and totes. 

The optimal time to transition into vertical storage

But...when is the moment right to look at vertical storage?  There is no easy answer to that question, because most storage applications require a mix of storage solutions, not a ‘one-size-fits-all’ approach.  Every storage application is different and therefore requires a thorough ABC analysis (fast, medium and slow moving items) to design a perfect, custom storage solution.  We need to analyze what kind of goods need to be stored, for example: 
  • Are the items even suitable for vertical storage? [E.g., a basketball fits neither in a modular drawer cabinet nor on a tray/pan of a VLM]
  • What is the quantity of goods to be stored?
  • What are the characteristics of the goods to be stored? [E.g., perishable items, FIFO picking requirements, temperature criteria, etc.] 
  • Are there unique handling of goods issues? [E.g., weight and/or size]
  • What is the order frequency? [E.g., 5 items per hour or 250 items per hour?]  What is the perfect mix of storage solutions?  There are fully-automated solutions, static solutions, dynamic solutions and semi-automated solutions.
Fully-automated solutions typically do not require any human intervention, neither in the picking nor the replenishment processes.  Automation is used in high-throughput picking processes such as fast-moving distribution centers.  The Return-On-Investment (ROI) comes from labor savings, improved order accuracies, and faster throughput. 
Static solutions are mainly pallet racking for full pallet in-and-out handling (most commonly selective and drive-in), and shelving systems for case picking, split-case picking and bulky item handling.  Static solutions are typically used for medium-to-slow A-movers and fast B-movers.
Dynamic storage solutions utilize the flow principle. with titled flow-beds available for both pallet handling and carton/tote handling, allowing First-In-First-Out (FIFO) order fulfillment. Dynamic storage solutions are typically used for fast A-movers.
Semi-automatic solutions such as Mobile Racking systems for full pallet handling, and Vertical Lift Modules, which many industry experts including this author consider to be dynamic solutions, and are typically used for medium-to-slow B-movers and faster C-movers.

When do we choose which technology, and more specifically when do we want to employ Vertical Lift Module technology?

  • When horizontal space is at a premium
  • When due to space restrictions, expansions are not feasible [E.g., land-locked buildings]
  • When manufacturing requires additional floor space
  • When product mix and product throughput are established
As mentioned earlier in this article, there is no ‘one-size-fits-all’ solution.

Look at your Material Flow

When used in combination with other storage technologies - considering through-put (A, B and C movers), and considering the Pareto Principle – Vertical Lift Modules are a perfect solution for order fulfillment, parts consolidation, kitting operations, lean manufacturing operations, shipping buffers, inventory storage, and Work-In-Process manufacturing environments.  
However, the VLM is just one piece of a perfect storage and order picking operation solution designed to improve the performance of the picking process. With the VLM, the employee travel time can be reduced up to 70%, his picking performance can increase up to 20% due to the ergonomic features of a VLM, and space utilization can improve up to 80% compared to traditional storage methods.  It is up to you, the end user, to decide on the best storage mix of carton flow rack, static shelving, pallet rack replenishment and Vertical Lift Modules.  

Klaus-Dieter Wurm, Vice President & Managing Director of Materials Handling at SSI Schaefer, is a leading expert in Vertical Lift Module technology. He can be reached at Klaus.Wurm@ssi-schaefer.us