Sum of the parts

5 mins read

The right storage equipment enables more material to be held more efficiently – but how do manufacturers justify a requirement for modern stockholding equipment with the need to be lean and minimise inventory? Laura Cork reports

There are some plants where materials or components arrive on site barely minutes before they are needed on the line. These sites may be few and far between, but reducing inventory - whether incoming materials or finished goods - is today's manufacturing mantra. Elimination, however, is nigh on impossible which means the right storage equipment is critical to ensure goods are held in the right place and are readily accessible. "Storage plays a key role in a company's efficiency by reducing lead times, lowering costs, managing inventory and positively affecting the bottom line," says Clive Woodward, group MD for Bott, the Bude-based manufacturer of workplace storage kit such as cabinets, shelving and racking. "The right storage increases performance by reducing downtime and tool loss. Tools and components that are readily at hand and easily identifiable contribute to workforce efficiency - a fundamental lean principle. Mobile storage is growing in popularity for this reason, as workers can take the tools with them as they move around the plant, reducing man miles." The more a product is handled - manually or otherwise - the less efficient is its route through production. This is a point picked up by Bito Storage Systems' managing director Ed Hutchison, who warns against the hidden costs of double handling. "It's not just about saving time, it's about saving money," he says. "One of the operations leading to double handling is the common practice of taking pallet loads of stock arriving at goods-in to a buffer storage area. Here, they are held in pallet racking until they are needed to replenish the lineside pick face." Traditional pallet racking or shelving can't accommodate all the stock at the pick location, he says. Instead, he advocates a system of 'live' storage where cartons or pallets are on flow systems. Pallet flow racks are useful for picking lots of fast-moving, single, small components, where the worker can pick from a whole pallet box load of the product. Carton flow racks require the pallets to be broken down into cartons, but the flow rack can hold several cartons in each lane. There are higher investment costs for a live system, he admits, but says payback comes with increased working efficiency. "A saving on floor space in the region of 15-20% is a reasonable assumption for a carton live storage system for small parts, and travel times for pickers can be improved by up to 66%," says Hutchison. "What's more, because the goods move unassisted into the picking position, you can rely on a constant availability of goods which means there are no hold ups for manufacturing operations." Richard Price, UK sales manager for Kardex - best known for its vertical storage systems, notably the Shuttle carousel - says the justification for installing new storage equipment varies from customer to customer: "ROI comes from a combination of the cost of space, the revenue potential of the space that is freed up, time efficiencies of moving stock from a central location to the point of use - many customers use Kardex vertical storage systems at the point of use - stock level accuracy and productivity. The one that is most significant is very dependent on the individual business." That said, stock accuracy often tops the list, he says. "When organisations have an open store policy and an open stocking environment they know that they are going to have stock level inaccuracies. I recently talked to a company that has a 65% accuracy level of stockholding, with an average stock holding value of £2 million: that's a lot of money to lose. So, if a company is running with a known 35% stock level inaccuracy, they will overstock by 35% to create a buffer to ensure that there will never be any production line downtime due to a shortage of stock." Kardex systems incorporate a device, a sort of automated box, that only opens when certain criteria are met - for example, when the main IT system tells the Kardex equipment to open and issue stock for a particular process, works order, or individual. "Stock accuracy increases quite significantly and it's that increase in accuracy which enables stock levels to be reduced by removing stock buffers and freeing up cash that was tied up in stock," says Price. "This is one of the ways that Kardex customers see immediate payback after purchasing a system." Bigger challenge Stock accuracy is certainly critical when it comes to smaller components or tools. It's unlikely, however, that you'll 'lose' heavyweight steel bars or tubes - but these present quite a different storage challenge. The largest manufacturer of mechanical seals in the UK, AESSEAL, has installed an automated, double tower system at its Rotherham factory to store stainless steel and superalloy bar, tube and billet. The storage systems, Unitowers from Kasto, are used to house 5-tonne- and 3-tonne-capacity cassettes. They are positioned side by side and have a compact footprint, occupying just 30 sq m - a three-fold saving on floor space previously needed to accommodate 60 tonnes of material in conventional racking. Capacity of the new storage system is 126 tonnes. At the touch of a button on one of the control screens, raw material from any of the cassettes is retrieved in less than a minute. Better still, the material is presented at the optimum height for the operators which, as well as speeding delivery to machine tools for maximum productivity, reduces risk of injury. AESSEAL's production director Richard Cook says that health and safety was the primary reason for installing this storage system, rather than minimising inventory. Indeed, there's a strategic need for stock at this site: the company is enjoying significant growth, recently 20% year on year, and the factory has been working at full tilt. Quality, service and short lead times have been critical to its success, he says. The Unitowers are located in a new extension where they feed two machines in the newly-formed hydrocarbon processing cell. The towers also serve other machines in AESSEAL's standard-plus division which, like the hydrocarbon processing cell, produces bespoke, highly complex seals which would be impracticable to make for stock. These seals are often needed for critical processes in chemical, pharmaceutical or paper plants, so fast production of one-offs and quick turnaround are essential. AESSEAL already has a Unitower in another area of the plant, storing stainless steel tube and bar for batch production of standard seals. Cook says that Kasto was the only supplier which seemed capable of tailoring such a system and it was the automatic choice to supply the new tower. Kasto analysed AESSSEAL's material specifications to calculate the different stock items that would fit into each cassette without exceeding the 5-tonne and 3-tonne capacity limits. The height of each cassette also had to be determined to make best use of the overall height limitation of just over 6m. The result is the 5-tonne capacity Unitower has eight cassettes at 285mm high and seven cassettes at 200mm, while the smaller unit houses 17 cassettes which are 200mm high. All are 840mm deep by 4.2m long. Kasto's service throughout the design and installation was impressive, says Cook: "The factory incorporated design modifications on the fly as the project progressed, even when the towers were in build. Kasto also worked with us on the best method of handling stock that is too heavy to lift out by hand. Special slings were procured so that long, heavy items could be picked using either an electric hand pallet truck or a counterbalance handling trolley." A special system was designed for short billets that are difficult to sling: a hydraulic lifting mechanism means certain cassettes with loose bases can be pushed upwards for removal at the optimum height by a pallet truck with a handling attachment (see picture). The right material in the right place at the right time, with improved safety for the workforce. What better investment case?