As a consumer, nearly every physical object you use on a day-to-day basis was, at some point, loaded on a pallet, from boxes, to jugs, to bottles. Pallets are the simple, structural foundations used to ship loads of product all over the world. They are the commodities on which other commodities are shipped. Because pallets occupy such an integral part of our modern lives, they are among the most engineered and re-engineered products in existence.
Pallets are manufactured in various sizes for various applications. Many pallet standards exist, as do many organizations which set these standards. Some organizations are concerned with strength of materials, some with pallet dimensions, some within specific industries, and so on. ISO sanctions six pallets, the most common of which in North America has dimensions of 40” x 48” (typically 5-6” in height). These pallets fit well in a standard ISO 40’ shipping container. In other parts of the world, like Europe, one will come across metrics pallets with similar, but different, dimensions as those in North America. Different shipping containers are sometimes used to maximize the load capacity with matric pallets.
Most commonly manufactured from wood, these pallets typically use industrial grade lumber in contrast to high grade (commonly known as ‘grade’) lumber like that used in construction, flooring, and furniture. (The industrial lumber comes from the parts of the tree which cannot be used as grade lumber.) Plastic pallets are the second most common type. In general, plastic pallets can be reused more times than wood pallets and are well-suited for applications requiring a high degree of sanitization. For these benefits, among others, plastic pallets often come at a premium over wood pallets.
The two most common designs for wood pallets are called stringer pallets and block pallets. Stringer pallets use boards (or ‘stringers’) to support the top deck boards. Block pallets, as the name implies, commonly use nine blocks to support the top deck boards. In many cases, stringer pallets are ‘two-way’ pallets which can be accessed by fork trucks and pallet jacks from two sides; whereas block pallets are ‘four-way’ pallets which can be accessed from all four sides. There are exceptions to this rule, however, and one could find hundreds of detailed articles evaluating the two types.
As factory automation has become more widespread, so has the automatic loading of product on pallets. The most typical object automatically loaded on a pallet is some sort of secondary package like a box, bag, or drum. Within the consumer goods industry, the most common secondary package is a corrugate shipping case or tray. Most automatic pallet loaders (‘palletizers’) in this industry are designed to handle corrugate cases or corrugate trays.
Conventional palletizers typically use a series of conveyors, guides, and pneumatic actuators to position and orient cases in the desired array which is equal to one layer in the unit load. The layer is then placed onto the pallet by a combination of a tray to support the layer and an elevator (sometimes the layer is elevated and sometimes the pallet is elevated). These types of palletizers can reach high speeds and have the flexibility to be changed from one product/load configuration to another. The reverse of this process can sometimes be used to de-palletize cases at the point of destination.
Robotic palletizers typically consist of a four or six-axis robotic arm integrated into a cell which picks individual cases, or a row of cases, and places them onto the pallet. The cases, pallets, and tier/slip sheets are often picked by the same end-of-arm tool installed on the robot arm. Robotic palletizers are well suited for medium and low speed applications, and applications where multiple products must be palletized at the same time, in the same cell. Robotic palletizers also have the capability of palletizing bulk product (not in cases) like empty bottles shipping to a fill line. Again, the reverse process of the robotic palletizing process can be used to depalletize loads.
When selecting a palletizer, one must consider the speed of the incoming product, the type of pallet, the load configuration, tier sheet/slip sheet requirements, the available floor space, the number of different product types (SKUs), and the size/shape of the products. There are many other factors to consider, but these are the basics used to select the type of palletizer. Automatic palletizers are often combined with an automatic stretch wrapper or automatic bander downstream in the product flow.
Every application is unique and requires a thorough review to ensure the best performing and most cost-effective palletizer is selected/designed. Please reach out to Brenton to discuss a specific application. Brenton has completed over 2,000 robotic and conventional palletizer installations, and our team is happy to use our experience to provide a trustworthy consultation. Learn more at https://www.brentonengineering.com/products/palletizing-systems/