Line storage – an obstacle for production development

The factories in Finland finally receive so many orders that the production capacity needs to be increased. Often, there is a situation where one line needs to be more efficient, its flexibility and capability produce quality need to be improved (RFT). At the same time, the demands for material handling increase.

According to VTT, “In a typical factory, 25 per cent of employees participate in the transport of parts and components, 55 per cent of the factory’s floor space is in use and the process takes up 87 per cent of the production time.” The processing and moving of the materials takes up a huge part of the production time. This time is usually hiding inside other work and detecting it requires effort. Walking up to the line storage even looks industrious.

In an earlier article, I have pondered, what is to be done about the material flows when establishing a super flexible factory. This article tackles the foundations of the matter. In the following list, there are five reasons why you should consider giving up on line storages.

1. Maximizing the assembler’s productive work. Especially in a line-based production, shortening the phase time directly increases the overall productivity. It is much quicker for the assembler to take the parts from a set platform than fetch them from a shelf. This can easily be examined with spaghetti diagrams.
2. The Ikea quality (in a positive sense). The right parts are brought to the assembler. Once the set has been used, the assembler can be happy with their work. This is the exact same phenomenon as when assembling Ikea furniture: once all the parts have been used, the assembler can be happy. With the modern digital methods, the 99.9% level of picking accuracy can be achieved fairly easily.
3. Picking efficiency. With the modern automatic and group picking methods, the picking efficiency is 10–20s per row. In production facilities, the same efficiency is achieved in only very little parts.
4. Balance errors and material shortage. It is always fun to check, whether the supplier is late or has the order been sent late due to a balance error. The fact is, that as the assemblers are picking, the storage balances become distorted. When no one notices the adjustment notification, wrong parts might end up going to the assembling. Additionally, as the assemblers are collecting, the error proofing cannot usually be used. Thus the picking quality is poorer.
5. Use of space as part of the production. 55% of the production space is used to store materials. Lower line storages especially take up a lot of space. In Leanware projects, the materials are often stored more compactly, which frees up more space for the production.

The explanation for line storages that is the most likely to shoot you in the leg, is that the product structure is so weak that collecting cannot be used. But, if the deviations are not caught, the product structures will never improve. The wrong kind of product structure can influence the purchasing, the wearing of parts and the funds calculations, at least.

Is set collecting always the way to go? Well, no. For example, the separate lines made for mass production of small products can be implemented with efficiency and quality with line storages and, for example, with kanban.

If you have any questions, we here at Leanware can help you. We do different kinds of analyses and consultations about materials logistics. In a year, we help over twenty companies with the challenges of materials processing.