Dead time is an unproductive but unavoidable so-called secondary time that arises during picking due to preparatory and follow-up activities (e.g. search and identification of the storage location). It can be optimized by simple measures.

 

The following applies: The activities that occur for each order item at the staging location and that cannot be directly assigned to the actual picking process belong to the dead time. On average, it takes up 10-25 percent of the total picking time (1). By way of comparison:

Calculating picking time and dead time processes

Apart from the base time, all the picking time segments listed above depend on the number of items in a single picking order. The Technical University of Munich has therefore come up with the following formula for calculating the total picking time. n describes the number of individual orders.

In addition to the search and identification of the stored goods, the following process steps are included in the dead time

  • Checking the picked items
  • Reading processes
  • Reacting to picking errors
  • Confirming

Optimization of dead time

As described above, reading processes, checking items and entering information can cost the picker valuable time. This unproductive time can be longer than the productive picking time if storage locations are insufficiently labeled, the input technology is unsuitable, inventory comparison is done in real-time and an excessive amount of information is provided. It is therefore not uncommon for uncoordinated warehouse processes to cause warehouse management systems (WMS) to generate system-related waiting times of up to five seconds. In the age of e-commerce, modern distribution centers should therefore use self-sufficient picking systems or controls (2). This means that order picking is initially decoupled from the actual inventory management. When an order is placed via the web shop, the item is immediately reserved for the customer via the ERP system. The picker starts his tour, removes the items relevant to the order without forcing an online synchronization with the system above. The removal is only synchronized online at the end of the tour. The advantage of this is that the order picker can complete his tour smoothly without having to wait for feedback from other systems (e.g. from the ERP). The system-related waiting times described above are thus bridged.

The dead time can also be easily optimized using the following methods

  • Unique labeling of the shelves (see storage location management)
  • Pre-packaging or pre-picking in different quantities
  • Electronic counting processes (e.g. using RFID)
  • Digital navigation via data glasses and smartwatch
  • No delivery of so-called partial quantities. Only pre-packaged quantities are sent to the customer.

Important: Dead time is not the same as distribution time, which also does not record productive work, but this is usually due to personal influences.

There are various factors that influence dead time. These include the presentation and processing of information, the quality of employees and the ergonomics of the workplace.

Summary of dead time

Dead time consists of work steps that inevitably occur during the processing of a picking order or batch, but do not belong to the actual productive process. These include, among other things:

  • Searching for the storage location
  • Opening packaging (see “Optimization of dead time”)
  • Counting, weighing, measuring the items
  • Checking the item to be picked
  • Noting the removal (confirming)

(1) Jens Wisser, The process of warehousing and picking in the context of the Distribution Center Reference Model.

(2) Tim Gudehus, Logistics – Fundamentals, Strategies, Applications, 4th updated edition, page 693. 17.4, Picking quality

For more information on picking, see also person-to-goods picking and goods-to-person picking.

Teaser image: Author: KBS Industrieelektronik GmbH / License: CC BY-SA 3.0