Accumulation is a process in which products are gathered before being passed on in the production line. This is done in order to make the most use of the machines involved. For example, if the input of a production line exceeds its output, an accumulation buffer can be used to even out these peaks. With these buffers, an evener flow throughout the system can help prevent both the overloading and the underutilization of your machinery and improve OEE in the production process. In this blog article, I will describe the process of accumulation, what makes it useful, and what to consider before implementing it.
Avoid production gaps by making your production more balanced
Accumulation can be applied in virtually any kind of manufacturing industry. It is a process that allows production to continue even if one of its machines is temporarily not operating. And although everything may be up and running as it should, the production rates of different machines may not match. Moreover, some of them take a longer time to turn on or off than others. These kinds of potential production gaps, due to delays or stops, can be avoided through the use of accumulation. Harmonizing the flow through accumulation can ultimately make the entire production process smoother, more balanced, and less vulnerable.
Pressure-less solutions for sensitive products
Temporarily gathering products in a designated area during the production process is the most common form of accumulation. This is usually done by stopping the flow, using a device preventing products from moving while the conveyor is still running. Sometimes, the line is divided into multiple sections which can be slowed down or stopped sequentially in order to achieve a more gentle accumulation. The products will be released to the next segment of the production line when the downstream machine is able to process them.
Another option is to use so-called pressure-less accumulation, which means that the products maintain a certain gap between one another while being accumulated. This can be done by using expandable conveyors which either allow products to temporarily leave the normal production flow or redistribute them onto other conveyors and carriers. This can be done horizontally or vertically, by devices such as diverters, mergers, elevators and/or pushers. Pressure-less accumulation is especially useful when the products are sensitive to pressure, such as food industry products.
Before you decide on what accumulation method to use, it is important to consider which kind of accumulation your production process requires: FIFO (first in, first out) or LIFO (last in, first out).
Anti-starve and anti-block accumulation keep your machines engaged to their full capacity
In order for accumulation to work as intended, or as optimally as possible, one should have concrete knowledge of both the limits and the actual production rates of the individual machines – upstream as well as downstream. This maintaining of the flow is one of the more challenging aspects of accumulation, and essential if one is to avoid micro stops or the overloading of critical machines.
Without any kind of accumulation, the production line becomes very vulnerable to all kinds of disturbances in the process. If a machine stops or slows down, all the machines have to stop or be slowed down. Ideally, upstream machines should always be engaged to their full capacity, regardless of the downstream machines, and downstream machines should in turn continually be provided with new items even when an upstream machine is not working, due to it being provided with material for example. This is known as anti-starve and anti-block accumulation, respectively.
Utilize the production intervals of your machinery by means of accumulation
The most significant benefit of accumulation is that it can streamline production by making your machinery co-operate more smoothly. If not planned or implemented properly, however, accumulation might instead cause damage to your products and your machinery. It is tempting to think that increasing the pace at which something is produced in turn makes the production more efficient. Thus, if the downstream machines do not have enough overcapacity at reasonable time intervals, accumulation may not be the best solution.
With accumulation, the key to its success lies in utilizing the production intervals of the machines involved, making sure that they are always put to use without becoming overloaded or starved. Should they become overloaded or starved, the purpose of the accumulation is lost.
Furthermore, when using accumulation correctly, the line speed can be decreased but with a retained production rate. This will reduce energy consumption and wear of equipment, as well as making the process more stable and improve product quality.