One of the key considerations is whether to adopt a goods-to-man or man-to-goods strategy – the former involving automated equipment like carousels and mini-load systems, the latter based on more traditional methods like pedestrian picking from shelving or lift truck based picking in racking.
Automated solutions like carousels, vertical lifts and mini-load systems share a number of common benefits including high storage density, fast throughputs and enhanced product security. But they can be costly. You’ve also got to have the right volumes before the true benefits can be realised, stresses Richard Price, marketing services manager at carousel and vertical lift manufacturer Kardex Systems UK. “Using technologies like these, one person can easily pick 200 items or more an hour… but the flow has to be there to support that. If you only have 500 ad hoc picking requests a day being drip-fed to pickers in an uncontrolled way, you’ll obviously struggle to achieve these numbers.”
Automated solutions can handle a surprisingly wide range of goods, however – Kardex’s Shuttle vertical lift system for example, can hold “100kg a shelf up to metric tonnes per shelf”, says Price – and often also allow vertical space to be used that would otherwise be wasted. The Shuttle goes up to 25m high, for example, way beyond the capabilities of most lift trucks.
Compared to the most common alternative picking method – pedestrians picking from tote bins on a mezzanine floor – automated systems are hugely more efficient. In fact the productivity increases of automated technology are often in the order of 200-300 per cent, says Price. Payback can be quick, too – typically 12-18 months for the average user, says Price, depending on the cost of picking mistakes, the cost of space and the value of products.
Similar benefits for automation are mentioned by David Long, ASRS product manager at SSI Schaefer, whose Pickomat vertical lift can handle up to 250kg per 1220 x 820mm tray, goes up to 13m high and holds either 96 or 120 tonnes in all, depending on model. Trays can be delivered to each picker at a rate of 100 an hour, and two operators can be served at any one time. To help pickers pick the right product from each tray, meanwhile, the Pickomat comes with a laser-pointer pick-by-light system as standard, which is located above the picker’s head and points to individual containers on each tray as picking proceeds.
Like Price of Kardex, Long suggests the payback on automated technology can be very fast. “It’s mostly within two years, depending on labour savings, space and time,” he says. “But it can be much quicker – for example if you avoid the need to extend an existing building to accommodate more stock.”
Adopting a man-to-goods approach in place of such automated solutions may not provide the same kind of picking speeds, but there is still much you can do to speed up the process, says Paul Forster, sales and marketing director at Atlet. For example ensuring that your pick faces are at ground level wherever possible to reduce individual pick times and storing fast-movers at the near end of your racking to keep travel distances to a minimum.
It’s also important to use proper order picking trucks, says Forster. You can get away with a powered pallet truck for ground-level picks, he admits, but a real order picker is far more ergonomically suited to the job, because drivers are usually standing near the load which cuts down on the time taken to dismount and walk around the truck at every location. Order pickers are also better suited to fulfiling two orders simultaneously as they can usually carry two or more unit loads at once. And multiple order picking is almost always worth pursuing, says Forster – though there are exceptions. “It’s fine if all the orders are for one store, but if they’re for multiple stores you’ll need some degree of sorting afterwards, so do the calculation to find out how long it’s taking the goods to get to the right place and what has really been gained,” he advises.
What’s really key to speeding up picking, says Forster, is the initial design of the warehouse and the sophistication of the software that’s devising the pick sequence. “The lift trucks are just there to enhance the efficiency of the system,” he says. “Users should remember that and not get over-concerned with comparing the lift or travel speeds of individual trucks.”
It’s also important not to get too hung up on storage density, he says. “While narrow aisles make sense from the storage point of view, always remember that big lift trucks may need to pass smaller ones in the aisles to replenish the pick faces – and if they can’t, that’s going to have a big effect.”
Using onboard radio data terminals can also speed up lift truck picking by avoiding the need for pickers to return to a central point to get fresh instructions on a regular basis, says Forster. And there are also some situations in which picking can be speeded up by live storage systems, which effectively self-replenish. Users should, however, be wary of the effect of live storage on the ratio of pick lines to pallets stored, warns Forster – live stores usually involve holding five or more pallets deep of the same product which may not be practical in all warehouses or with all product lines.
Picking fast obviously means nothing if you’ve picked the wrong goods. So making sure your picking is accurate is another key issue in raising pick speeds.
Here again, automated systems are generally regarded as the best bet but there is a lot that can be done to improve the accuracy of manual picking, including the use of bar code scanning, pick-by-light systems and voice picking technology.
Voice picking, in particular, has been growing in popularity recently. Greg Tanner, MD of Vocollect, says the main benefit is that the operator’s hands and eyes are both left free to concentrate on the picking task itself, rather than fiddling with bar code scanners or handheld terminals.
Tanner suggests voice picking can lead to a 10-15 per cent improvement in productivity compared to paper picking list operations and a 20-35 per cent improvement compared to operations involving handheld terminals. Accuracy, too, is improved, even compared to bar code based operations, he says. “When people are bar code scanning and picking ten of the same items, they’ll often pick one, scan it ten times, then pick the rest without scanning them separately. But sometimes, they’ll pick only eight more. Or they might scan the item first, then turn to leave the scanner on the truck, turn back and pick the wrong item altogether. So there is still scope for error.”
Voice picking doesn’t prevent this kind of error but makes it less likely as there is no need for operators to turn away from the pick face at any point and operators have nothing to gain by short-cutting individual item confirmations.
Voice picking isn’t inexpensive – Tanner didn’t twitch at the suggestion that the hardware would cost around £3,500 per head – but if you’re running multiple shifts, each set of equipment can be shared, he points out, and whatever your shift patterns, the payback can be pretty swift from the reduced cost of errors, around six to nine months being typical.
Where to start?
With all the options facing those looking to refine their picking processes, it can be hard to know where to start working things out.
The perfect place, according to Simon Butcher, director of supply chain consultancy Crimson & Co, is with your customers. “Your starting point should be what your customers want. In a retail environment, for example, they might want goods in a certain way to fit the layout in the store, so although you might want to pick the heaviest items first, like jams or jars of coffee, with lighter ones like teabags or light bulbs on top, that might not be what suits them. So start by thinking about what happens to the output.”
The next step, says Butcher, is to consider the product itself, paying particular attention to picking methods and picking order for items that are crushable or have limited shelf life and working out what kind of technology and process will suit any products with particular requirements.
“After all that, you can look at the technologies themselves!” he says.
Before you get too excited about any given technology, however, check that you really can accommodate it, advises Butcher – for example, is your building tall enough for it and do you have enough floor space?
Techniques such as line picking (in which a single line is picked in volume to fulfil multiple orders at once) can be useful in some instances, says Butcher – typically for ‘overnight clearables’ – but bear in mind that if you’re filling lots of orders with one line at a time, you can’t send any one out until they’re all complete. Picking individually by store, on the other hand, means orders can be sent out independently but can make for longer pick times per order, especially if each one requires a lift truck to thread its way around the entire warehouse.
Zone picking (in which multiple pickers operate together to build up orders with each picker working in a defined zone), meanwhile, can be excellent in some applications, for example where pickers are picking to totes on conveyors, but can result in high labour costs.
Users should also think carefully about the replenishment issue, says Butcher. Some modern systems – sophisticated A-frame dispensers, for example – may be able to fulfil huge numbers of orders, spitting out three items a second until they’re empty, but if they take 20 hours to replenish afterwards, they may prove unsuitable for your particular operation.
Above all else, suggests Butcher, the best way for many firms to speed up their order picking and raise picking efficiency is to make sure there is a decent stock control system in place. “It’s all too easy to slow things down by having hopeless stock management, bad layout and bad housekeeping,” he says. “If your stock’s not in the right place, it’s bound to take you twice as long to find it!”
Voice technology may be increasingly popular in picking applications but the GMB trade union recently called on employers to end the use of such “dehumanising” technology – and warned that it may be prepared to take industrial action if firms don’t.
In a recent statement the union says that the use of technologies like voice picking systems and satellite tracking has led to “battery-farm” style workplaces in which workers are controlled down to the last minute by computer systems, rather than merely using computers as an aid.
The GMB’s concerns about voice picking largely boil down to two distinct areas. First, it is concerned about the wearable IT devices often used with voice picking systems, such as ring-style barcode scanners and wrist-mounted computer terminals, which it suggests may significantly raise the risk to workers of repetitive strain injury (RSI).
Its second concern is that such systems are sometimes used to track how long workers take to carry out particular tasks within distribution centres and from that to calculate bonus payments.
Workers also dislike being driven by the technology, claims the GMB – in one warehouse that uses voice systems, labour turnover leaped from over 100 per cent a year to over 300 per cent following the introduction of voice technology, it suggests.
Physiotherapists express some support for the GMB’s views – the Chartered Society of Physiotherapy, for example, says it’s concerned not just about the physical RSI risk but also about workers’ mental health, as studies have shown that stress goes up if workers know they are being monitored.
But the GMB’s concerns have been overwhelmingly rejected elsewhere, including by trade associations like the Chartered Institute of Logistics & Transport (UK) and the United Kingdom Warehousing Association, large users of voice picking technology including Exel, and voice technology suppliers themselves. The GMB’s calls for voice picking systems to be redesigned have even been labelled “hysterical” by the Forum of Private Business (FPB), whose chief executive, Nick Goulding, says there is no evidence of employers misusing the technology as the GMB suggests.
Arm-mounted data collection device manufacturer Symbol, meanwhile, says it does not believe its products pose any increased health risk to those using them and that there are no documented cases where wearable computers have led to RSI.
Even rival union the T&G doesn’t see eye to eye with the GMB about the issues it has raised. “Our warehouse people haven’t reported any major concerns about this,” says a T&G spokesman. “There’s bound to be the odd isolated case but by and large, it’s not come across to us as a big issue.”