Making The Best Pick for Picking

The term “walking papers” generally means “you’re fired.” In the area of picking product, these are the sheets that send pickers along a long aisle of bins looking for a list of products to be pulled for a customer order. Unproductive, tending towards inaccuracies, and short on accountability, paper picking is gradually being replaced in distribution centers and manufacturing plants by pick-to-light (PTL) systems.

PTL is a technology featuring lights fixed to picking bins. When a light for that bin is lit, a display tells the picker to pull an item or items out of the bin for an order. The picker then pushes a button, indicating to the system that the pick was made. But before tossing out the order sheets, an operation has to ask itself a couple of questions. The first is typical when bringing on all equipment— is it cost-justifiable?

The Case For PTL
Like all equipment, PTL systems make sense for the right operation. RF terminals, RF carts and voice picking systems handle full cases or slower moving products. Bring on PTL for partial case shipments of one item on up, which are relatively fast moving. to 5,000 SKUs, where 20 percent of the SKUs represents 80 percent of the shipments and where three or more people are picking. In rare cases, PTL can be used for up to 20,000 SKUs.

As for a typical payback on PTL, the aim is to move 50 percent of the picking crew onto other jobs. Benefits versus paper picking include:
• Greater accuracy.
• Traceability— Software can answer the question of whether an item is in the queue, if it is being picked, or if it is in shipment.
• Workload planning— Is the picking crew the right size, who is keeping up with the work and what can be done to help them do a better job?
• Replenishment— PTL enables the operation to stay on top of the inventory and respond quickly. PTL is generally married to gravity flow racking, with a push-along conveyor traversing all racks. Bins run along both sides of the conveyor while the gravity flow conveyors supply cases to the bins.

Pick-to-Light aims at increasing efficiency by eliminating errors with fixed bin lights that alert pickers of when to pull items for an order.

A person assigned to the back end of the system makes sure the gravity fed conveyors have cartons. In some cases, this system of continual replenishment can be two to five times faster than paper picking.

Improving On History
As with all technological changeovers, part of the old procedure hangs on with the new way of doing things. In the case of PTL, as with paper, picking was originally based on zones. In paper picking the idea was to avoid a picker inefficiently walking the entire 160 feet or so of conveyors that are present in a typical operation.

So, to reduce body movements— the key to all industrial efficiency studies— pickers are confined to zones. Once the items from the zone are picked, the tote gets passed to the next picker via the bucket brigade method.

Over time, PTL systems replaced sequential picking with cluster picking. In sequential, the pick light goes on for an item and the next light does not go on until that item is picked and the light is extinguished. This process involves acquisition time, which reduces picking time. In cluster picking all the items that need picking light up and catch the peripheral vision of the picker. The picker can work along the area snatching the items within proximity to one another. Zone picking has a built-in inefficiency of its own. Based on the order flow, one picker along the line may have many items to pick while the next one has just a few, and waits for the tote to roll past.

Go Zoneless
In zoneless picking, with the help of hardware and software, pickers can be positioned so everyone is busy all of the time and totes move down the line at an even pace. Planning software aids in minimizing motions in several ways. First is the ability to set-up a ski-hill configuration for the SKUs – the bulk of the picks are clustered more at the beginning of the line and then the picks diminish as the tote moves down the conveyor, requiring people to move the shortest distance.

Second is the “golden zone” set-up, in which the majority of the high volume SKUs are along the mid-level ergonomic bins. The result is faster picking and a more ergonomic operation with reduced bending and reaching. These positions are dynamic based on historical information accumulated by the picking system.

The lights and buttons on each bin are on what is referred to as the pick face. That unit has a snap-in bus enabling easy installation. Once in place, the pick face is connected into a three-wire circuit – power, ground and data – that runs along the racking. The product at each pick face is immaterial to the system, as all it is looking for is the address at each pick face when an order is in the process of fulfillment. The microprocessor receives its commands from the central system and reports back when the pick is made.

Order flow is a moving target, with SKUs that were popular one month falling out of favor the next. Whenever management determines necessary to optimize the ski hill/golden zone set-up, the system can re-shuffle product positions along the conveyor line.

Track Your Picking
Accountability can still be a problem with zoneless picking. Say, one of the pickers is on not so friendly terms with one of their co-workers and decides to punch several pick face buttons while the other picker is away. The order comes up short and the picker’s accuracy suffers.

For this and other reasons, IPTI has developed the Watch-Me Zoneless Picking System. Rather than punching buttons at the pick face, the picker has a device worn on the wrist that signals the system when an item is picked. This system is capable of capturing the picker’s ID as they complete picks, greatly improving productivity by eliminating efficiency-robbing zones.

The Watch-Me device provides a hands free interface that does not require pickers to push a button to complete a pick, and keeps them out of trouble in case someone else does.