The planning of the small parts warehouse
A small parts warehouse, i.e. those in which loading units with small dimensions or low weight are stored, usually have two types of problems to solve. On the one hand, there are many items, so there is a large variety of unit loads to classify, and on the other hand, a high turnover rate is required.
With this in mind, all the considerations that should be discussed before analyzing the storage solutions that are on the market are first set out. The analysis of solutions will be discussed later.
This article attempts to define all of the small parts warehouse parameters that need to be considered when planning an almost perfect small parts warehouse. This small parts warehouse should firstly have sufficient storage capacity for current and future situations and secondly the highest possible turnover rate.
Automation offers the most efficient and rational solution for meeting these conditions. However, one must never forget that when planning a small parts warehouse – especially a robotised or automated small parts warehouse – the costs of the system are in line with the total costs of operation. In other words, a balance must be struck between costs and benefits.
In order to be able to achieve all these goals, it is advisable to analyze all relevant parameters, as explained below.
Importance of the small parts warehouse in the production chain
A small parts warehouse is not a passive element in a company’s production chain; on the contrary, it is one of the most active and strategic elements. It can be just as productive as an assembly or distribution chain,or even more productive. Because if the small parts store is not working, all other chains can come to a standstill due to missing parts. This supply can only be controlled appropriately if the small parts warehouse is also operated appropriately.
For these reasons, it is essential for companies that need a small parts warehouse for their operations to do some thinking in advance. Questions like: Should the parts with the highest rotation be stored where they are easily accessible? Have the most delicate items been stored in clean locations? What level of security should be specified, at least for certain products?
Achieving sufficient storage capacity for present and future situations
The small parts warehouse should be seen as a living element in the production chain, as it is directly affected by changes in demand.
In times of enormous economic growth, the warehouse has to become more flexible, improve its storage capacity, increase the number of items to be handled and, as a result, prepare for an initial decline followed by a sharp increase in the number of parts to be stored.
These fluctuations must inevitably be taken into account from the outset when planning the system. However, there are unforeseeable circumstances that force the project designer to use other systems. Therefore, it is important to know how to prepare for sudden growth when the small parts warehouse is already in place.
How do you achieve a higher storage capacity in an existing small parts warehouse?
Depending on the small parts storage facility, achieving a larger storage capacity for storing small parts can be relatively simple or extremely complex. There are two basic strategies for increasing storage capacity. In one, the small parts warehouse is being rebuilt using the latest technology, while in the other, a new facility with greater storage capacity is being built.
The first procedure can be more or less complicated since not all small parts stores can be removed. If the small parts warehouse really cannot be expanded, the second strategy must be used.
The market offers various alternatives for increasing the storage capacity in both an existing and a new small parts warehouse. On the one hand, super-compact storage can be used, which is characterized by its height and extremely narrow aisles. Conventional, semi- and fully automatic conveyors are used here.
A second option is horizontal carousel storage. These can even be combined with each other to achieve the required storage capacity in the small parts warehouse and to ensure future expansion. In the same way, vertical small parts storage can be used, which can also be combined and expanded with a view to the future.
Another alternative could be to modify part of the existing facility and construct a self-supporting warehouse.
With the help of these four solutions, the project manager can plan a suitable small parts store, tailored to the products to be handled in the system. In specific cases it can happen that none of the solutions mentioned is ideal. However, combining solutions can potentially result in a highly optimized small parts warehouse. However, in order to make the right decision between all these solutions, it is essential to also take into account the second condition, which we have already mentioned and which we will now explain in more detail.
How is the highest possible turnover rate in the small parts warehouse achieved?
The turnover rate measures the outgoing frequency of stocked goods by relating the amount of goods consumed to your average inventory levels. For example, if 100 units of a product were consumed over the course of a year, and the average inventory of that product over a year was 25 units, the turnover rate is 4. This number represents the number of times that product has been renewed.
The turnover rate in a small parts warehouse can vary considerably. A single turnover rate is only acceptable if the rate of the entirety of all products is also acceptable.
Thus, it is not enough to achieve an optimal turnover rate, which may be 12 in some cases, 20 in others, and as low as 3 in others. If there is only a single product with a turnover rate of, say, 0.01, this means that the facility has a serious fault, or at least something is wrong with that item, since a large quantity of product is being stored for which there are no exits. This entails a sacrifice of space and efficiency.
It is also unacceptable if good turnover rates can be achieved for all cheap products while this cannot be achieved for more expensive products.
Therefore, a balanced small parts inventory is almost more important than achieving a high average turnover rate.
Effects of rationalization in the small parts warehouse
Each additional rationalization in the small parts warehouse has a particularly favorable effect on the overall costs of storing small parts.
This factor is consolidated by the use of suitable means for handling and storing the materials, avoiding downtime and, above all, unnecessary movements.
At the same time, rationalization is improved through the use of faster and safer channels in the material flow. In this way, unmeasured, complicated and tortuous routes are avoided, which increase cycle times and consequently handling costs. At the same time, the rationalization is influenced by a correct planning of the distribution of the storage elements within the facility (layout), since an optimization of the entry and exit routes is achieved.
In addition, an effective system of control and management of all the individual resources contributes to greater efficiency and increased rationality of the plant.
The final point to consider in this section is to set up workplaces inside the small parts store that have a comfortable environment and allow for good task planning. This increases the efficiency of the system.
Important principles for installing a small parts warehouse
These preliminary considerations serve as a starting point for the analysis of goals and circumstances (both general and personal). We will now analyze the different options available when looking for the best planning for a small parts warehouse.
When planning a small parts warehouse of this type, there are two crucial basic strategies to choose from. Either you choose one of the two or you combine both. It is about the principles of “man to goods” (the warehouse worker moves) or “goods to man” (the goods move to the position of the warehouse worker).
When choosing one of these principles, there is no standard or ideal small parts storage solution. It may even be the case that there really is no optimal solution, or that the most suitable solution is a combination of the two principles. Since these strategies have to be adapted to each individual product and to each individual industry, they raise infinite doubts about a question that is difficult to answer.
The aim of this article is to collect information that is relatively scattered and constantly changing as new solutions and elements are developed.
In this way, the reader can get an overview of the options available, even if he has not yet been sufficiently trained in new small parts storage. With the indispensable help of specialists, further decision-making aids are available about alternatives for the system and possible improvements that can be implemented in it. Based on this, the solutions available in an industry are examined below.
The strategy “man to goods”
The “man to goods” principle is the typical and classic approach. The disadvantage of this principle is its high handling costs, while the main advantage is the low investment costs.
With this strategy, the products are stored on shelves that can be arranged in different ways, depending on the small parts storage system chosen. These elements are handled either manually – the product is placed piece by piece – or mechanically. The latter option handles whole unit loads, generally crates or containers.
The units are usually removed manually. To do this, the warehouse employee moves on foot or with a vehicle to the position in which the article that he has to pick up according to the order form is stored.
With this approach, single-storey racking systems, multi-storey racking systems (using walkways or mezzanines), mobile racking, warehouses with narrow aisles and piece goods flow racking are used.
The degree of automation is very low and depends on the characteristics of the respective small parts storage system. Only piece goods flow racks with pick-to-light devices and trolleys with put-to-light systems achieve a considerable degree of automation.
Not all systems that work according to the “man to goods” principle are the same. The various options can be rated on a scale from 0 to 10, applied to four parameters.
The four parameters are: the total cost of the investment, the manpower cost of handling (cost of handling per item, which is independent of the investment), the handling capacity in number of movements per unit of time and finally the area utilization rate in terms of effective use.
In the following, these solutions are classified individually and according to these four factors.
Single-level shelving systems
These racking systems, which generally have a low load capacity, are arranged in the warehouse in such a way that they leave a small aisle for the warehouse worker and the picking trolley.
There are very sophisticated small parts storage systems with drawers of different sizes and layouts that adapt to all product volumes and industry activities. The lower levels are usually intended for heavier products.
These shelving systems in the small parts warehouse are generally not very high, and the height depends on the specific needs of the industry and the small parts warehouse in question. It must be taken into account that very high structures make it difficult to quickly access the products on the upper level. Sometimes even ladders or carts are required (almost always manual) which slow down the process of picking and placing.
Other mechanical means can also be used in the small parts stores equipped with these small parts storage systems. These include the manual or self-propelled pallet trucks as well as the order pickers for low and medium levels.
Multi-storey shelving systems
This storage system for small parts storage actually works on the same principles as the previous system, since in practice it is two or more single-level small parts storage rack systems that are installed one above the other. This is intended to achieve a higher storage capacity or to set up high small-parts storage racks with walkways (ultimately the same effect is achieved with these as with a multi-storey rack).
With this small parts storage system, there is no need to use manual ladders or ladder trucks. In this way, the time spent picking up or dropping off each item can be reduced.
Mechanical conveyors cannot be used in small parts warehouses with multi-level racking systems. Exceptions are the lower floor or very resistant mezzanines (which, however, involve greater installation costs). However, forklifts or other means such as elevators or load lifters can be used to load the upper floors with full pallets.