Getting goods from A to B is hard enough. Finding the right way to carry those goods is another headache. Once, we loaded and unloaded goods item by item - those were the days when labour was cheap. Then the Second World War came. This mother of many inventions brought us the wooden pallet. This, combined with a fork lift truck, enabled goods to be moved quickly and with less labour.
The wooden pallet was a great idea. So good was the idea that it is still going strong to this day. However, things have changed. Pallet pooling can be an expensive business. Rental and purchase costs have risen to reflect the increase in timber costs and the extra burden of fumigation and quality control.
Escalating fuel costs have taken their toll on the inevitable dedicated trips that are made to repatriate empty pallets when imbalances occur in the supply chain. These fuel costs - and driver shortages - have also forced an examination of the space and weight taken up by the ubiquitous pallet.
The pallet is a bit like the air that we breathe. It is all around us yet we don't see it. It is easy to forget the extra cost that the pallet adds to the value chain. Perhaps now the time has come when, in some eyes, the pallet has outstayed its welcome. Rather than being the carrier, is the pallet itself being carried by the value chain? Rather than wait for another world war, a ready solution has been found and is tried and tested. That is the Slip Sheet.
Enter the Slip Sheet
Slip sheets have been around for some time, especially in the
U.S. where the free market has always had the knack of taking the path of least resistance. European countries tend to prefer centrally planned systems and standardization. Slip sheets lack firmly agreed international standards and this may be one of the reasons why they have not been popular in Europe. The greatest reason is ignorance. Many simply have no understanding of slip sheets and how they work - so they don't bother.
So perhaps it's time to right this wrong here and now.
How Slip Sheets Work
1. Slip sheets are durable sheets of material that are designed to carry a uniform load of goods with plan dimensions (or "footprint") of roughly 1 metre square/40 inches square (typically they may be designed to carry a footprint of 40 inches x 48 inches - 1m x 1.2m). The slip sheet is made to these dimensions plus a pull tab - an extension to the sheet - of up to 6 inches/15cm. There may be just one pull tab sticking out from under the load on one side. There could, however be pull tabs on 2, 3 or all 4 sides. Slip sheets can be made of
fibreboard or plastic.
2. Goods are loaded directly onto the slip sheet within the creases that border any pull tabs. A push-pull attachment on a forklift truck is used to drag the load onto the truck by gripping (one of) the pull tab(s). The push-pull attachment has very flat ground-level forks that are designed to go under the
slip sheet whilst it is under load
3. To unload, the forklift truck pushes the load, complete with slip sheet off of itself and withdraws
Pros and Cons
Slip sheets are not the panacea to all distribution needs. For one thing, all parties in any supply chain will need to invest in the push-pull attachments, which are not cheap. The staff training that will be required, especially for forklift truck operators, can also be expensive. Perhaps the greatest factor, though, is the uniformity of the load itself. This exposes the slip sheet's greatest advantage - and greatest disadvantage. Slip sheets may not be able to cope when boxes are awkwardly shaped or where there is a mixed load of different shapes. Conversely, if a company is shipping out large quantities of the same sized box, then slip sheets are ideal. As such, slip sheets lend themselves to operations further upstream of the supply chain. As loads are broken down further downstream, then pallets may be more appropriate. The good thing is that loads of slip sheets can be easily transferred to pallets. A good example of the advantages of using slip sheets is where parts for goods are manufactured and shipped through a long distance sea route. The space and weight saving can result in a significant financial boost for the value chain.
Co-operative Value Chains
Another great factor in all this is uniformity of slip sheet systems. All parties in the supply chain need to be using the same specification of slip sheet and ensure that all staff are fully trained to ensure delivered loads are configured correctly for the receiving party. This requires value chains that are highly co-operative, or, to be realistic, it requires a value chain that has one dominant party who will simply dictate their requirements. The U.S. has pioneered slip sheets and has used them for many years. However, the dominance of the supermarket sector in some European countries may be forcing the change there also. The ability of large supermarkets to influence their supply chains means that they are in a position to take a strategic view of the benefits that slip sheets can bring. They are in a position to arrange for both senders and receivers to be ready to handle products on slip sheets. Things are changing. Perhaps the pallet industry is about to get a jolt.
Watch this space. There are tremendous savings to be made and significant environmental benefits to be gained. Full conversion to slip sheets for any supply chain is not going to happen, but a partial conversion for particular product lines is not only desirable, but inevitable - even in Europe.
In vacuum forming or thermoforming fabrication, the material is just as important as the mold. If a lower-quality plastic sheet is used, the end product could be compromised. The color of the sheet could be uneven and inconsistent. Unpredictable melting could occur, causing irregular gauge thickness. Longer curing and drying could add operation time and cost to the fabrication process. In other words, having the best vacuum formable plastic sheet will always yield the best-finished product.
In short, vacuum forming is a stripped down, simpler adaptation of thermoforming. With vacuum forming, a heated, pliant plastic sheet is stretched on top or inside of a mold. The formable sheet then conforms to the shape of the mold with the application of a vacuum to ensure the plastic fills the mold, tightly and neatly. Once the sheet is formed, the vacuum is released, along with the now-formed plastic sheet.
Vacuum forming is ideal for prototyping and manufacturing parts with a shorter-run production output due to being an easy and economical operation. It is also an outstanding way to fabricate more shallow molds without the higher operational costs associated with thermoforming. Newer, technological advances have allowed vacuum forming with deeper molds, as long as the formable sheet is of higher quality and is mechanically stretched before application to the mold.
When selecting the material for your project, forming plastic is an ideal option. Vacuum formable plastic sheets, usually made of PVC (Polyvinyl Chloride) are designed especially for the vacuum forming or thermoforming process. They can withstand heat application without melting or breaking down. They are also highly regarded for their ease of processing and are inexpensive in comparison to other sheets. Be sure to choose a plastic or PVC sheet that meets your specific requirements, such as thickness, color, surface texture, and overall size. Look for a product that offers precise gauge control and consistent color with lot-to-lot traceability. This way, there will be no differences between manufacturing runs.
There are a variety of applications that benefit from both vacuum/thermoforming and formable plastic sheets. The production of kiosks and automated teller machines include external plastic structures that accommodate delicate, internal mechanisms securely and with branded aesthetics. Since the formable sheets are highly customizable, medical device housing and electronic equipment cases can be properly fitted for a precise fit and appropriate protection. On a smaller scale, electrical components are a perfect application because of the inherent flame retardance of the formable plastic sheet material.
If you are considering your options for a small run of manufactured molded parts or experimenting with a prototype, vacuum forming/thermoforming with vacuum formable plastic sheets is an excellent choice. While the manufacturing process itself is straightforward, the selection of an industry-proven formable sheet will provide high-performance durability without cutting into your bottom line. Be sure to choose a high-quality formable plastic sheet that will hold up to the demands of your next project; you will have a consistent, reliable end product every time.