Configure WMS in a warehouse with narrow-pass technology

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    Implementation of a warehouse management system is a difficult but interesting task. The most common end-user mistake is usually that he is confident in the omnipotence of the software product, and the novice implementer - in his confidence in "best practices" and "industry solutions." Warehouses are more similar not from the point of view of industry, but from the point of view of the technology of storage and processing of goods, and "best practices" require the addition of real experience. In this article I will try to cover the main differences between the two most commonly used storage technologies, as well as the nuances that must be taken into account for a truly high-quality implementation. It’s much better to know this in advance than to face during go-live, when every minute of downtime will be incredibly expensive.


    Wide-pass and narrow-pass technology: introduction


    The most common storage equipment that is used to organize the storage system is the front shelving for pallets. They look as follows:

    image

    Their installation is made - for stability - in double rows. And stability is definitely needed, since the weight of one pallet with a pallet area of ​​1200x800 mm can be 1000 kg (the illustration above shows, by the way, the storage of 2 pallets in one section, which is more typical for pallets with an area of ​​1200x1000 mm, or 1200x1200 mm, and their weight may be even more). In order to place or remove pallets in such a rack, access to a row for handling equipment is required: a loader, a stacker, and the like. The type of equipment is selected depending on the required carrying capacity and cargo handling height (the loader, for example, works up to about the height of the 3rd tier, and there may be 7 in the warehouse), and also - which is also very important - depending on the radius of the turn:

    image

    However, there are some nuances here: the wider the passage, the more we can simultaneously place employees and / or pieces of equipment in it when performing the required operations. Accordingly, in narrow aisles we are deprived of such an opportunity: there can only be one piece of equipment that enters it either along mechanical guides (“rails”) or using induction tracking (“induction”). Due to the very significant difference in the methods of performing various operations, the concepts of “wide-pass technology” and “narrow-pass technology” appeared. Actually, here we are faced with one of the main tasks of warehouse logistics: the search for the optimal balance between the efficient use of volume and the productivity of cargo handling.

    From the point of view of warehouse automation with the help of a centralized operation management system (WMS - Warehouse Management System), control algorithms, on the basis of which tasks are given to final executors, also have cardinal differences, the main of which are “parallel” and “sequential” task processing. As mentioned, a wide aisle allows several performers to perform tasks in parallel, and a narrow aisle requires only one performer in the aisle, which is why it is necessary to manage the task execution queue and ensure the correct distribution of the execution resource. The main emphasis - as the name of the article implies - I will do specifically on the specifics of narrow-pass technology, the opinion of which is very different: some experts say that it is absolutely ineffective, others - that with its help you can do real miracles. Be that as it may, it is possible to increase the storage capacity quite significantly with its help - there are living examples when 1200 pallet places turned into 1800. However, narrow passages impose an incredible amount of restrictions: if there is no experience in setting up or developing an automation system specifically for such warehouses, then there is a chance that "take off" does not work.

    Why the “through” warehouse is not always good, and why to place products in a “transverse” way


    One of our first projects (and more than 100 have already been implemented in 11 years) was implemented just in the classic narrow-aisle warehouse. The management tasked the logistics director with increasing the warehouse capacity, and he emphasized the installation of new racks and the purchase of specialized equipment. In terms of storage volume, he solved the problem, but in terms of the number of operations he received an unexpectedly bad result. An analysis of the situation showed that the stackers make a large number of “pendulum” movements, for the reduction of which it is necessary to develop and implement an effective cargo placement strategy.

    Moving for loads to the beginning of the row


    The problem was decided to close due to the implementation of WMS. At that time, a self-written address storage system and even a “paper-based” technology for task distribution had already been introduced, so automation at the “push a button and performed a miracle” level was completely excluded. In addition, there was a problem of determining normative productivity: some employees performed as many tasks in one shift as their colleagues did in one and a half or two shifts. There was clearly a need for centralized dispatch of tasks to ensure uniform workload and the operator and contractor not being able to create the most “winning” list of tasks for the “chosen ones”.

    The first step that has been taken is the implementation of the “transverse storage" strategy. A non-automated warehouse where employees have to independently search for the required goods, they try to place goods of one group, or of one item, as close to each other as possible, as a rule - longitudinally in one pass. If the consignment of goods that we need to place consists of several pallets of the same name, then a much greater effect can be obtained by placing them not in one passage, but across the aisles, that is, put the first pallet in the first passage, the second - in the 2nd, and so on. Thus, if our shipment is made in pallets, and in the order you can find not 1, but 2 or 3 pallets, then they will be removed not by one unit of equipment, but several at once, since several passes are involved.

    The second step is to change the placement strategy over time. The output from production (it is also the entrance to the warehouse) was from one part of the warehouse, and the docks for shipment of products (exit from the warehouse) from the other. Such a warehouse is usually called “through”, because the products seem to pass through it. On the one hand, such a structure seems to correspond to certain mythical “principles of building an ideal warehouse”, and on the other hand, in fact, it greatly complicates any optimization. For example, if we decided to use optimization of cargo distribution by frequency of calls, then the most popular cargo would have to be transported along the longest path to the cells located closer to the docks. In connection with such a dilemma, we decided to try to place the goods in the most intensive hours for production - closer to the exit point from production (so as not to overfill the buffer areas between the production and storage racks), and to send the goods to the least intensive ones to the farthest cells. At the level of the operational production plan, the most popular positions were issued just at the time of the largest “unloading” of the warehouse. The result is a 20% increase in productivity.

    The third step is to prioritize tasks from the current stacker location and take into account the position of the forks. That is, until the stacker completes all the tasks in the current passage, he does not go into another passage. This approach requires care when sending orders to work, but - on the other hand - reduces one of the most resource-intensive operations to move to another mall or turn the pitchfork. Result - it was possible to increase productivity by almost 10%.

    The last step in optimizing warehouse processes was to modernize the current incentive scheme for employees, but here - after much debate - it was decided to leave the existing option when the employee received a certain amount for each operation. Since the employee could not choose what operations he should perform (in contrast to the previously existing paper technology), the distribution of remuneration became more equitable. The project was recognized as successful and continued as part of the solution of the following tasks.

    Two-stage deployment, batching and task rotation


    Already in the somewhat distant future, on a completely different project, we took another approach that would allow us to solve many problems in the aforementioned warehouse. We are talking about a two-stage arrangement of goods in narrow aisle racks. In a separate buffer, a number of pallets are collected, which must be placed on shelves. They are grouped by alleys (not necessarily physically, the main thing is at the level of task fulfillment), and pedestrian employees with hydraulic trolleys receive tasks on rolling pallets into the alleys, starting from the most remote place where the control system carried out the placement of cargo, to the nearest one. Each pallet is placed directly in the aisle, under the cell where the WMS “aimed”. The work of the stacker is only to drive in a row, drive up to each pallet and lift it to the desired place.

    2-stage accommodation


    If the truck has a restriction on the rotation of the forks in the aisle, this approach will not work. But if there is no such restriction, then due to this approach, constant movement to the beginning of the row is excluded, and the operation of heavy equipment becomes much more rational. This approach is consistent with the concept of “batching”, when before we begin to complete tasks, we are waiting for their accumulation. Thus, together with all the advantages of this approach, we will also get disadvantages (the need for a clear separation of the packages of operations in time, for example).

    Some WMSs have “task rotation” functionality, when a technician can perform tasks of various types in parallel mode, depending on the current picture of priorities and location. For simplicity's sake, let's first look at how such a technology should ideally work in a warehouse where wide-pass technology is used, and the truck can go onto the dock. Then, the employee on the stacker on the assignment drives up to the pallet standing on the dock, takes it to the forks and places it on the rack. Immediately after that, he receives the task of taking another nearby pallet, and lowering it to the first tier (replenishing), and - since he again needs to go to the dock in order to place the next pallet, he receives one more task to take out another a nearby pallet to a neighboring dock, after which it takes the next load. Let’s now consider how to apply this to narrow aisles. To begin with, the stacker will not be able to go to the dock. Theoretically, yes, but in practice, he will spend a lot of time stabilizing in the aisle, and not always the ceiling height above the dock allows the high-altitude narrow-aisle stacker to go there. We also note that if we decided to place goods in two stages, as discussed above, then when placing any alternation of tasks, we clearly cannot realize it. However, imagine that we do the placement through transit cells in the end of the rack. This means that to place the pallet in the target place, it is first placed in a cell to which the stacker has access to the stacker without the need for repeated stabilization. The stacker drives out, picks up the desired pallet, and then puts it in the target place. If, when moving in the opposite direction, he needs to complete an assignment for the removal of a pallet, then it must be understood that the buffer cell where he will put it must be empty. Thus, in such a technology there should be separate (physically separated) buffer cells for both the incoming stream into the given alley and the outgoing one. At a minimum, there can be two of them (one at the entrance, the second at the exit), but each can have a capacity corresponding to the physical possibilities of using the available area. I can not resist the convincing request not to engage in amateur activity, and not to enter and exit through the same cells: the same input and output buffer must have a double capacity, and increases the likelihood of making an error, so there are no miracles. that the buffer cell where he puts it should be empty. Thus, in such a technology there should be separate (physically separated) buffer cells for both the incoming stream into the given alley and the outgoing one. At a minimum, there can be two of them (one at the entrance, the second at the exit), but each can have a capacity corresponding to the physical possibilities of using the available area. I can not resist the convincing request not to engage in amateur activity, and not to enter and exit through the same cells: the same input and output buffer must have a double capacity, and increases the likelihood of making an error, so there are no miracles. that the buffer cell where he puts it should be empty. Thus, in such a technology there should be separate (physically separated) buffer cells for both the incoming stream into the given alley and the outgoing one. At a minimum, there can be two of them (one at the entrance, the second at the exit), but each can have a capacity corresponding to the physical possibilities of using the available area. I can not resist the convincing request not to engage in amateur activity, and not to enter and exit through the same cells: the same input and output buffer must have a double capacity, and increases the likelihood of making an error, so there are no miracles. so for outgoing. At a minimum, there can be two of them (one at the entrance, the second at the exit), but each can have a capacity corresponding to the physical possibilities of using the available area. I can not resist the convincing request not to engage in amateur activity, and not to enter and exit through the same cells: the same input and output buffer must have a double capacity, and increases the likelihood of making an error, so there are no miracles. so for outgoing. At a minimum, there can be two of them (one at the entrance, the second at the exit), but each can have a capacity corresponding to the physical possibilities of using the available area. I can not resist the convincing request not to engage in amateur activity, and not to enter and exit through the same cells: the same input and output buffer must have a double capacity, and increases the likelihood of making an error, so there are no miracles.

    “Altitude selection?” What is there to automate? Any cell for storage and selection! ”


    A separate discussion deserves recruitment using the so-called High-Level Order Pickers (HLOP). For narrow aisles, this equipment is very similar to standard narrow aisle stackers, but due to some features it allows you to work not only with pallets, but also perform dialing operations. In front of the employee, a pallet is located at a certain height, which, upon the fact of increasing its height during recruitment, can be lowered lower, making it possible to carry out cargo handling without the need to bend or pull up.

    High altitude picker


    At first glance, a warehouse with such equipment works on the principle of “the entire warehouse is a set area”. Whatever it seems, this is completely wrong. Firstly, only in a very, very low-intensity warehouse, employees in narrow-aisle high-level commission agents will calmly move from row to row, waiting for their colleagues to complete their tasks. Recall that a lot of time is spent on stabilization in a row. Secondly, there are a number of cargoes that are extremely difficult to collect on the upper tiers: for example, 25 kg bags. Whatever the ergonomics, it’s better to place such positions in wide aisles on the first tiers. Thirdly, there is another problem - fragmentation of orders. Since each piece of equipment has its own area of ​​responsibility, one order may fall to several performers. Thus, after dialing, you will also have to consolidate the parts received. Alternatively, you can use the so-called “dial with transfer”, when after dialing by one employee, the pallet is transferred to another employee to continue the operation. If this is not possible, then it is necessary to provide for a sufficiently capacious section where additional cargo transshipment will be carried out: fragments of the same order collected by different contractors will be combined into one package and placed on one carrier.

    When placing goods, it is necessary to ensure extremely uniform load on the warehouse so that none of the units of technology with the above technology becomes a "bottleneck". And - since this technology is very close to sequential assembly line, - professional WMS have special strategies for sending orders to work, allowing within the current package (for example, a flight) to calculate the optimal next order for processing, based on the already calculated load for each contractor. If a simple product is installed in the warehouse that does not have such functionality, then with a high intensity of operations, the dispatcher simply may not be able to cope with its functionality, which will lead to a significant decrease in productivity.

    Finally


    I would like to emphasize this fact separately: the average manager who works at an enterprise not involved in the implementation of software products takes part in about 3-4 projects over his entire career. Those who are professionally engaged only in such projects can take part in more than a hundred during their careers. It is quite clear who will have more chances for successful implementation, but very often you have to see how the internal employees of the enterprise try to implement their own systems, based only on personal experience. We decided to save on the product and implementation - do not save on setting the task, and order at least professional consulting.

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