Feeding frenzy

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 in a compact footprint.

The Kasto Unitowers, housing five tonne and three tonne capacity cassettes respectively, are positioned side by side and occupy just 30m². This represents a threefold saving compared with the 90²m of floor area previously needed to accommodate approximately 60 tonnes of material in conventional racking.

Capacity of the entire storage system is 126 tonnes, so there is ample opportunity to hold more stock as growth dictates. At the touch of a button on one of the control screens, retrieval of raw material from any of the cassettes is achieved in less than a minute. Presentation of material at an ergonomic height in front of the towers, in addition to speeding delivery to machine tools for maximum productivity, reduces risk of injury to operators.

Housed in a new, purpose-built, 30,000ft² extension at Aesseal's Mill Close site, the fully clad stores feed, amongst other machines, two Mori Seiki NT 4300 DCG 9-axis mill/turn centres in the manufacturer's recently formed Hydrocarbon Processing Cell (HPC). The power generation, minerals/mining and particularly the oil and gas sectors are seen as major strategic growth areas for Aesseal. On average, floor to floor times on the NT 4300 DCGs are less than two hours, giving an indication of the highly integrated process infrastructure and slickness of materials handling within the factory.

Served also by the store are machine tools dedicated to the manufacturer's Standard-Plus Division (SPD), which like the HPC produces specially designed, complex seals which would be impracticable to make for stock. Often, such seals are needed to replace a faulty one in, for example, a critical chemical, pharmaceutical or paper plant process. So fast, reliable production of one-offs and quick turnaround are essential to support the customer, which could be located anywhere in the world.

Tailor made

Since the mid 2000s, Aesseal has successfully used a similar Kasto Unitower to house mainly 316 stainless steel tube and bar in an area where higher volume, standard seals are manufactured in larger batches. Before the tower was installed, recalls Aesseal's production director, Richard Cook, Kasto was unique in being receptive to tailoring a system to suit the application.

The company is described by Mr Cook as one of the most flexible of all major suppliers to Aesseal and was the automatic choice to supply the new tower store. First came the time intensive job of analysing Aesseal's 160 different material specifications, encompassing stainless steel, superalloys of nickel, titanium and zirconium, plus some, phosphor bronze and investment castings. Solid bar is from 25mm to 150mm diameter up to 1,000mm long and from 150mm to 254mm up to 500mm long. Billet can be anywhere between 254mm and 406mm in diameter and of 250mm maximum height. Tube is held in the range 90mm to 250mm diameter by up to 1,200mm long.

Complex calculations

There is no algorithm that currently exists to calculate how a mix of material like this can be best stocked in the available space, so the entire job was completed manually and took several days. The number of different types of stock items that would fit into each cassette had to be worked out, without going over the five tonne and three tonne weight capacity limits.

The task was made more complex by having to determine the height of each cassette so that best use could be made of each storage volume, which was constrained by the stores' overall height limitation of 6.13m.
In the end, the optimum solution was found to be eight cassettes, 285mm high, and seven cassettes, 200mm high in the five tonne store, while the three tonne store accommodates seventeen 200mm high cassettes. All are 840mm deep by 4,200mm long.

Comments Mr Cook: “As always, Kasto's service was impressive. Not only did the UK staff carry out the stock analysis meticulously, but the German engineers were equally helpful in taking on board our changing requirements. The factory incorporated design modifications on the fly as the project progressed, even when the towers were in build.

“Kasto also worked in unison with us on the best method of handling stock that is too heavy to lift out by hand,” he elaborates. “Special slings were procured so that long, heavy items could be picked using either an electric hand pallet truck or a counterbalance handling trolley.”

Ingenious solutions

A particularly thorny problem was how to access heavy, short billets that are difficult to sling. The solution that Kasto devised was to make the base of several cassettes loose in the five tonne store and build a hydraulic lifting mechanism into the output station.

When a cassette emerges from the store, the lift pushes the base upwards until it reaches the top. It is then a simple matter to remove the billets using a pallet truck equipped with a special handling attachment. It is believed that this arrangement is a world first – it certainly is for Kasto.

Several different material types and sizes are held in any given cassette, so it is not possible to use the computer controlled tower's stock control capability. It is performed manually instead, using intelligent layout of material in the cassettes to assist both stock control and picking.

Important also in a fast turnaround production environment is efficient cutting of stock to speed supply of material to machine tools. Three Kasto bandsaws at Mill Close assist in this activity, one of which is devoted to SPD work, while another, smaller machine serves the HPC.

Kasto
www.kasto.uk.com Aesseal
www.aesseal.com