Pallets are a critical component in workpiece pallet-handling conveyor systems. The size and weight of the product to be conveyed will dictate many of the parameters of not only the pallet but also the conveyors. The processes and flow of the pallets will also affect the design of the pallet. In this article, we will explore various design styles and features of workpiece pallets.
Workpiece pallets can be broken down into two distinct groups: framed and unframed. Both pallets consist of a baseplate (see below). With a framed pallet the baseplate is “framed” – like a picture. This frame can be made up of engineered plastic segments or a t-slotted aluminum extrusion. The size of the pallet and the load it is carrying can be a determining factor in deciding if a pallet is to be framed or unframed. Generally speaking, the larger the pallet and the heavier the load, the less likely it is that the pallet will be framed. Unframed pallets are often referred to as “single-piece pallets”.
Pallet Feature: Baseplates
As mentioned above, all pallets include some sort of baseplate. The baseplate is the load carrying component for the product and is what distributes the product (and pallet load) between conveyor strands.
Baseplates come in a variety of materials and finishing – which as you guessed are often dictated by the size and weight of the product. Smaller products or applications that require less precision can utilize baseplates constructed out of any variety of hard engineered plastics. Metal baseplates come in a nearly endless selection. These materials include aluminum, in a variety of alloys, as well as steel and stainless steel. Aluminum cast plate is a popular option. Which material, its type, and thickness are dictated by the conveyor manufacturer. Many conveyor manufacturers including mk North America’s VersaMove line offer custom baseplate options.
Pallet Feature: Wear Surfaces
Wear surfaces are the part of the pallet that is in contact with the conveyor chain or belt. With framed pallets, the frame acts as a wear surface. For single-piece or unframed pallets wear surfaces are added to the underside of the pallet, and they provide another avenue for customizing the pallet based on specific application needs. On this type of pallet, the wear surface can be tool-steel or even an anti-static composite plastic. The wear surfaces are designed to be wear items and should be stocked as a replacement part.
Pallet Features: Bumpers, Strike Plates, Locating Features and More
While the frame (if there is one), the baseplate and wear surfaces make-up the minimum recommended components for a pallet. Additional features such as bumpers, strike plates and locating features are necessary for the pallet to perform on the conveyor system as expected.
Bumpers can be integrated into the conveyor frame or they can be added to the baseplate. Bumpers are necessary to prevent hard impacts between pallets in accumulation applications. They can also help provide application specific spacing between pallet edges.
All pallets need a feature which can engage with the stops on the conveyor system. With framed pallets the stop often engages with the frame. On single-piece pallets there is often a notch or cut-out machined into the pallet which engages with the stop. Often times this area is reinforced with a strike plate, this strike plate can be replaced when wear occurs.
Lift and locate devices are mounted onto the conveyor frame and are used to positively locate the pallet. These devices typically consist of a pair of locating pins. These pins then mate up with matching bushings which are mounted into the pallet. Without this critical feature, the precision in which the pallet can be located is greatly reduced.
Other accessories that pallets may contain are RFID tags and/or tag locations. Sensing features can also be added to the pallets.
Pallet Features: Tooling and Machining
No pallet is complete without a way to hold the product in place. It is rare for the product to be set down on the pallet without any type of holder (tooling) or nest. Because of the way the pallets intact with the stops, locating and rotating devices it is paramount to ensure that the product is properly retrained on the pallet. Tooling is most often provided by an integrator or the end-user, and the conveyor manufacturer will machine the pallet’s baseplate in order to accommodate the tooling. Additionally, the baseplate may be machined to reduce the overall weight of the pallet or for mounting additional equipment or accessories. Because the center of gravity on the pallet is critical, pallets (and tooling) should never be altered after-sale.
Ultimately the design of the pallet will depend on the product and the total weight on the pallet. But regardless of these factors, the pallet will consist of the components reviewed in this article. And since pallet size often dictates the conveyor platform it is important to work with a conveyor manufacturer that will assess your product and tooling and recommend the best possible pallet design and thus conveyor for your specific application.
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