Edward Hutchison, managing director of BITO Storage Systems explains why order picking is an essential element of lean supply chain practice.
Keeping goods flowing with the fewest possible interventions and wasted movement should be continued inside the warehouse, from goods in, to order picking, through packing and on to dispatch. Paradoxically, how you store items will determine how well product flow can be maintained while the goods are in the warehouse.
Order picking is the most labour-intensive and costly activity in most warehouses – accounting for as much as 55% of the total warehouse operating cost. This alone is a good reason to choose a mode of storage that gives maximum efficiency; add the demands of optimum availability of goods, fast access and on-time delivery within the shortest possible lead time and it becomes imperative.
Space constraints are another factor. Lean practice may require consolidating all stock into a single site. Alternatively, it may require space for picking growing numbers of product lines and SKUs without acquiring a new building. Either way it means devising a way of holding the maximum number of products within the minimum footprint.
Yet this system must also be flexible enough to adapt to changing circumstances, as stock profiles are increasingly prone to change due to shorter product line life cycles and more fickle markets. Many companies will also experience big swings in picking activity during seasonal peaks.
Will conventional pallet rack-based storage systems support an order picking system that can meet all of these demands? Increasingly companies are finding that they can’t and are instead opting for live storage.
For small item picks in particular, the trend is moving away from traditional static shelving and longspan racking, towards dynamic carton live storage. This is because carton live provides a dense storage system that allows faster picking and reduced manpower, as well as improved space saving and organisation.
Storage density comes from concentrating cartons into flow lanes. With carton live, goods are fed into the system at the rear to flow down roller tracks in an inclined lane to be presented at the front on the pick face. Once a carton at the pick face is empty it is simply taken away to allow a full carton sitting right behind it in the lane to flow down on the roller tracks and take its place, therefore ensuring products are constantly available at the pick face. Being a First in, First Out (FIFO) system, carton live storage enables easy control of time critical products ensuring stock is not sitting around longer than it should be.
Carton live storage system not only maximises the number of products that can be held on a given footprint, it also gives a compact pick face. This is because sufficient quantities of fast moving products can be lined up in the flow lanes rather than, with conventional racking systems, occupying locations on the pick face. A greater number of fast moving SKUs can, therefore, be located within a shorter distance, thus picking zones can be smaller to reduce picker travel times and increase productivity. This means carton live is particularly suitable for applications with a wide range of SKUs and product lines.
For fast moving items in particular, conventional pallet rack based order picking, with its single, or even double deep, bays cannot provide enough locations at the pick face to hold sufficient stock without resorting to multiple replenishment runs from a bulk store. The alternative would be a very long pick face to accommodate sufficient numbers of locations for the fast mover. This of course means increasing travel distances for the picker. As with replenishment this incurs time and cost.
The live storage principle applies not just with cartons, of course, but with pallets also and solutions will often combine a mix of carton and pallet live. Pallets in a live system are ideal for holding large quantities of small items or extremely fast moving items. Picking straight from a pallet load not only saves time decanting these products into cartons, but also a single product line might need to occupy a whole level of flow lanes.
Where you have combined carton and pallet live systems, the pallet lanes – for faster moving goods – are located on the bottom level with the carton lanes above, creating a balanced work load in each pick zone.
The improvements in working efficiency made possible by a carton live storage system will more than compensate for its higher initial investment costs. For example, by providing within a short distance a greater density of pick locations for products, a saving on floor space in the region of 15-20 per cent, when compared to conventional storage, is a reasonable assumption. Products can be located far more quickly in small pick zones than they could by traveling round conventional racking. Depending on the application, travel times for order pickers can be improved by up to 66 per cent. Furthermore, because the goods move unassisted into the picking position, order pickers can rely on a constant availability of goods and are not left waiting for replenishment.
Operations also find they can eliminate double handling for an entire order arriving at Goods In by accommodating it directly within a carton live system, without it first having to go to bulk store and then managing numerous replenishment runs. This is particularly useful where carton live storage is being used itself as a buffer store to support, for example, an automated A-frame picker, which needs to be kept consistently full of product. Where buffer stock for the carton live system is required, pallets can be placed in racking directly above the carton lanes.
Picking performance is greatly influenced by pick face layout. With a carton live system, cartons can be stored for picking according to sales velocity and even ergonomic factors: fast movers can be located between a picker’s thighs and shoulders to minimise the picking effort. In fact ergonomic principal can be applied throughout a carton live system design to allow efficient picking irrespective of the picker’s size. Often these are quite simple things such as incorporating a fully adjustable step into the system’s flow shelves that would give shorter pickers easy access without interfering in the operation. Anti-fatigue matting will further help the pickers carry out their work comfortably and therefore more efficiently.
You can speed picking activity simply by designing the pick face around an operative’s natural picking curve. The flow shelves can be angled to provide the easiest access to the cartons. With BITO’s carton live systems, for example, roller tracks and dividers can be easily adjusted in 8.25 mm increments; levels can be repositioned in height in 12.5 mm increments.
The cartons themselves can further improve picking ergonomics: adding front face openings, for example, will not only improve access to the product but will also improve visibility for the picker, helping them to gain the correct item.
Another important design factor for carton live systems will be integrating conveyors. Picking conveyors need to be at the correct working height with a step-up rail to facilitate access to the working levels above natural reach height. A gravity picking conveyor allows picking totes to be rolled along the pick face, while a powered conveyor can run behind it to transport totes to the next pick zone or on to dispatch.
Lean and speedier supply chains should not compromise on health and safety. A further advantage of carton live storage is that while it can increase productivity its design also minimises accident risk: with replenishment taking place in the aisle at the back of the system while picking takes place at the same time in the aisle in front, pedestrian pickers are separated from lift trucks traveling up and down the replenishment aisles.
With all of these advantages, a lot of companies are converting their traditional racking installations into carton live at the bottom level by retro fitting flow shelves and introducing push back racks for pallet buffer storage to help ensure replenishment is separated from picking.
Flow shelves equipped with the right adapter sections will allow the integration of carton live storage into a standard racking construction of any brand. The adapter sections are bolted directly to the uprights of the existing installation. Support clips, which safely locate into the perforations of the adapter sections, serve as a seat for the self-supporting flow shelves.
It is important when installing any carton live system to test it. A good supplier will be able to provide a test facility or install a test lane on site where the customer can experiment with angles and containers to ensure as smooth flow and maximum efficiency. It is also helpful if the supplier can provide both the flow lanes and the plastic cartons to ensure they work together seamlessly. The racking or shelving structure combines with the dynamic flow racks for carton live solutions in different weight ranges. For example, light duty, would be based on boltless upright shelving; medium duty based on wide span heavy-load shelving and heavy-duty would be built upon a pallet racking structure.
Boltless construction will enhance flexibility for the customer. Because these systems use a safety clip rather than a bolt it is easier to lower a beam level, making the system simple to configure – not just during installation but also throughout its use – and allows the user to simply change the height of the shelf to suit. Everything will simply clip into place to create an ergonomic order picking environment tailored to the requirements of each order picker and to be adapted as required.
Quality is essential for successful dynamic storage – a carton live system that is not fully functional will restrict order picking operations. Seek a 5 year warranty on dynamic systems. The key to this warranty is the quality and strength of the roller, the most popular being plastic. They are quieter than steel, which is important for growing numbers of facilities trying to minimise noise in their order picking operations. A plastic roller will also have a lower coefficient of friction, which means it rolls better than steel to ensure cartons move smoothly down the flow lane.
Plastic rollers are tough also. BITO’s Carton Live Storage warranty, for example, is based on continuous use of a plastic roller with a 4 kg load. That might not sound much at first, but consider 4 kg of constant load over 5 years and you will start to get an impression of the plastic roller’s durability. That’s 140 kg per linear metre on one roller and because roller tracks utilise rollers in pairs that’s 280 kg per linear metre per pair of rollers. Systems can also handle an impressive downward force of 12.5 kg.
Customers should seek further value from suppliers during design and installation of a system. A ‘concept-to-completion’ consultancy service will see a project through from design to handover. It should offer the customer the opportunity to carry out a full technical appraisal of the storage equipment by providing a facility where the customer can come and assess the quality of the products in the metal and even bring along their own containers to try out. For a more thorough evaluation of a system a supplier should be able to provide a trial lane of dynamic racking, that will allow the customer to physically try it out different configurations within their own environment. To see a system working in full scale, ask to visit the supplier’s client sites.
Because carton live storage solutions will often involve multiple products such as pallet racking, dynamic storage, pallets, bins, containers, etc, seeking a supplier that can offer – and, especially, manufacture itself – all of these elements will make it easier when it comes to designing a complete solution that fits together precisely.
Furthermore, a customer need only have one port of call, which not only makes the initial procurement and design easier but also means the customer need only deal with one company when it comes to servicing the system throughout its life.