Speed adds flexibility

Citation

Loughlin, C. (2007), "Speed adds flexibility", Assembly Automation, Vol. 27 No. 2. https://doi.org/10.1108/aa.2007.03327baa.001

Speed adds flexibility

An assembly production line will normally be designed to be capable of producing a certain number of products per day. This will have been decided by analysis of market expectations with a bit of spare capacity to cope with down times and the hoped for increased demand.

If a production line is only capable of making one product (and perhaps a few minor variations) then this is probably a perfectly reasonable way of operating. However, these days assembly lines have to be designed so that they can handle a wide variety of products. This is partly because of the trend for just-in-time manufacturing and also the ever decreasing product lifetime brought on by constant global demand for the very latest of whatever is being produced.

In this environment, the speed with which an assembly line can manufacture a part becomes all important. If you need to manufacture 1,000 each of seven different products in the course of a week then in theory the line needs to be able to produce each part at the rate of 1,000 a day. To paraphrase Mr Micawber in Charles Dicken's David Copperfield – “Daily production 1,000 units, daily demand 999 units, result happiness. Daily production 1,000 unit, daily demand 1,001 units, result misery”.

If you can make products significantly faster than you need them, then this not only allows you to cope with occasional downtime but also allows you to consider putting additional products down the same line. It also allows you to recover from difficulties such as late component supply or last minute changes to order quantities, that much sooner and with a lot less hassle.

Basically – time is as important for flexibility as the ability to assemble a variety of parts.

The speed with which something can be assembled is influenced by many factors. The number of components is clearly important – especially if they can only be added one at a time. The mass of the parts is also a key limiting factor. Lightweight electronic components can be assembled at ridiculously high rates (tens per second); try doing this with a six cylinder engine block and something will soon break. Some processes, such as the curing of adhesives, also introduce delays.

Flexible assembly systems can be quite tricky to design and there is always a trade-off between overall system complexity and the time needed to changeover from making product A to making product B. An assembly system that can changeover instantaneously may well have cost double that of an alternative that requires an hour of manual intervention to swap between products. The fast changeover system will inevitably be more complex and equally inevitably will have taken longer to design in the first place. Also this very complexity will limit the possibilities for future changes.

If we can design our assembly systems to operate at high speed then we buy ourselves the time necessary to make changes between production runs and this in turn allows us to achieve greater flexibility both for the assembly of products we already have and for those we will want in the future.

Clive Loughlin