Aluminium profiles save cost and time compared with steel

Having developed the innovative and highly successful TwinBin fastener management system, which is greatly reducing wastage of fasteners and other small parts in the aerospace, defence and other industries, Hurst Green Plastics had one remaining problem: how to produce a versatile and cost-effective rack to accommodate the TwinBins.

The original arrangement, based on welded steel racks custom-fabricated for each order, had many limitations. These are, however, completely eliminated in a new design developed in conjunction with ADM Automation, which is based on aluminium extrusions and accessories from the extensive Bosch Rexroth MGE range of basic mechanical elements.

At the heart of the TwinBin system is a double bin with two compartments arranged vertically one above the other and separated by a slide. This allows the bin to be loaded with products that the operator accesses from the lower compartment until it is empty. Then, by simply withdrawing the slide, the lower compartment can be replenished. This ensures that the older stock is utilised first rather than mixed with newer items. The empty upper compartment clearly identifies the bin as requiring stock replenishment.

TwinBin benefits

The TwinBin is an element of a Kan Ban system that adheres to Six Sigma principles. It not only helps to eliminate stock-outs, which interrupt production, but also greatly reduces the risk of spilling or contaminating parts. These issues are particularly important in industries such as aerospace and defence.

TwinBins are housed in racks that, according to customer requirements, can be supplied to accommodate any number of bins. When the system was first launched, these racks were fabricated from sheet steel and were produced on an order-by-order basis.

Stephen Clarke, Managing Director of Hurst Green Plastics, says: "That gave us a problem. We could have the bins ready for delivery in just a few days, but it was taking six to eight weeks to get the frames made. We even tried putting frames into stock to get round this, but that did not help with specials, and we also had problems when customers wanted a particular colour of paint finish."

These were not the only shortcomings of the fabricated steel frames. They were also heavy and bulky, which made them difficult to stock and to transport to site, particularly for the export orders that form a significant part of Hurst Green Plastics' business. In addition, the frames were difficult and costly to modify if the end user's requirements changed.

Aluminium alternative

To find a solution to these problems, Hurst Green Plastics enlisted the aid of ADM Automation, a company with wide experience of designing and fabricating structures for industrial applications. After carefully analysing the requirements, ADM Automation proposed a design based on MGE aluminium extrusions from Bosch Rexroth.

There are many extrusion suppliers in the market today, but using the Bosch Rexroth product has a number of important advantages. First of all, there is an enormous range of extrusions to choose from, which makes it easy to find exactly the right product. Secondly, Bosch Rexroth offers a full range of accessories. Finally, as would be expected from a company with the reputation of Bosch Rexroth, quality is assured.

The new racking concept developed by ADM Automation incorporates three sizes of MGE extrusions together with coupling components from the MGE range. Where a specialist component required for the application has been designed by ADM, it has been secured to the structure with standard fasteners from the MGE range.

This arrangement means that the racking can be fabricated quickly and, as customers are invariably prepared to accept the natural aluminium finish without painting, the delivery bottleneck that had been so troublesome with the steel racks is eliminated completely. Furthermore, the new racks are much lighter than their steel predecessors and they have been designed by ADM so that they can be supplied as flat packs, which dramatically reduces shipping costs.

Configured to order

The new racking system also benefits from versatility, allowing customised racks in special configurations to be offered quickly and cost-effectively. Recent examples have included an L-shaped assembly and a rack in the form of a cube, both of which were configured to make best use of the limited space available at the end user's site.

Finally, the use of aluminium extrusion rather than welded construction for the racks makes them easy to extend and modify. In particular, because the bins are retained by slide nuts, drilled fixing holes are not necessary. As a result, when a bin is moved, no unsightly holes with potentially sharp edges are left behind.

All of these benefits are provided without any significant cost penalty. Although the basic materials used in the aluminium frames are more expensive than those used in the old steel frames, the cost of fabrication is reduced and the cost of painting is eliminated entirely. These savings easily compensate for the small extra expenditure on materials.

Stephen Clarke states: "Our TwinBin system was well received in the market from day one, but there is no doubt that the new racking system, based on Bosch Rexroth products, has made it even more attractive to our customers.

"And, of course, it has solved a lot of problems for us. We no longer have to worry about deliveries and paint colours. Aluminium extrusion may seem like a very simple product but, as we have discovered, it has got a lot to offer and it can provide really big benefits."