Material handling: Optimizing for flow-through [from the May-June 2012 print edition]

by Dave Luton
From the MM&D MAY/JUNE 2012 print edition

A flow-through centre is very similar to a cross-docking centre, but it usually allows more order selection and it may have a longer goods-holding period than the classic 48-hour window for a cross-docking operation.

The first consideration when looking at a building’s suitability for flow-through is to consider the needs of the truck driver, who is often the most forgotten element in flow-through design.

Simple and inexpensive aids can often provide drivers with great assistance easily and inexpensively. For larger sites, a map and simple instructions (ideally ones that can be downloaded in advance) are a great help. Use the Internet to facilitate scheduling of receipts and giving instructions on the information you want truck drivers to have available in advance.

From the transport drivers’ viewpoint, how they enter a site is important, so include an area where they can safely park their vehicles while they receive their instructions before proceeding to the designated offloading dock. Too many times a driver has to park his rig on a city street and walk to a shipping office or guard house before he can get access to the site.

After reporting in, the driver needs to have sufficient yard space to back and turn his rig so that it can be properly placed in the dock for offloading. One pet peeve I have with building designers is that, for some reason, they think that we don’t have winter in Canada. In most winters we get snow, sometimes lots of it. We need a place to put the snow out of the way of the main truck working areas.

Another key consideration is the basic size of the facility, as facilities that have 100 truck docks have different needs than those with five truck docks, but all flow-through facilities have some fundamental requirements, whether large or small.

Initially, the distribution centre’s design should incorporate the basic business requirements. You need to analyze what you receive during both average and peak periods, and then ensure that there are sufficient resources—both facilities and equipment—devoted to serve the demand. The design should be able to address the fundamental question of whether there is sufficient loading dock capacity to meet your receiving delivery volumes.

If you handle a large volume of light-density products that cube out a truck’s capacity before reaching maximum weight limits, there is a strong cost incentive to floor-load the vehicle. Manually offloading these shipments can tie up your docks, unless mechanization, like an extensible conveyor system is employed.

The design analysis should also consider the volume of the various types of transport equipment, such as containers or straight trucks, as the optimal loading dock design for each is somewhat different. The best dock design for a large volume of ocean containers, for example, uses a higher than normal dock height (or alternatively, a longer leveler) to compensate for the higher transport vehicle bed height often encountered with ocean containers.

Proper equipment for the loading docks is also key to facility design. There is a wide variety of dock leveler designs including those for non-standard equipment like couriers (scissor lift levelers). Dock safety needs (such as vehicle restraint systems) should also be part of the package.

Inside, staging requirements are often overlooked when flow-through facilities are designed. In the need to conserve space, they are often sacrificed, resulting in bottlenecks even when there is sufficient loading dock capacity. Particular attention should be paid to sortation and unpacking tasks which require more space to lay out shipments.
Exterior site needs are another often-neglected area, as designers are pressured to minimize land use due to high real estate costs.

Next, no matter what size the facility, you need to ask: is it organized for efficient operations of each size of receipt? For simplicity, assume your facility has three types of receipts: truckload, LTL (less than truckload) and courier or small shipments.

Truckload shipments should always be scheduled so dedicated unloading manpower and equipment can efficiently service them when they arrive. Owing to the large volume they carry, there is a need to get them off-loaded quickly and get the loading dock and staging space freed up for other receipts.

If the flow-through system is to work, it should be co-ordinated with outbound shipping so time in the facility is minimized. The objective is to prevent the products from being put into storage and to keep them moving to their final destination.

My personal experience is that LTL shipments are almost impossible to schedule in big cities. The solution to this can be a combination of facilities and operations. From the facility perspective, designating one or a few (depending on volume) docks as LTL docks greatly helps the situation.

Operationally, taking control of inbound LTL shipments and having a designated carrier pick them up, cross-dock them so they form a truckload, and ship them in as a truckload of LTL, helps. This is widely practiced in the automotive industry where it is called “sweep” and works by consolidating multiple LTL shipments into a truckload.

For smaller-volume courier shipments, having a dedicated loading dock is an advantage.
Of course consolidating all of these shipments with one carrier also will also help.

Dave Luton is a consultant in the greater Toronto area.