Thermoforming is the process of heating huge plastic sheets into a very high temperature and cooling them in the required format. Vacuum forming is a sub process or a type of thermoforming where vacuum is applied in between the molds and the plastic to create various shapes. Thermoforming has several advantages and disadvantages compared to the other plastic molding methods like injection molding. In addition to vacuum forming, several other methods like drape forming, twin sheet forming and pressure forming can be incorporated along with thermoforming to produce different kind of products. Several types of plastic can be molded in the method.
Disadvantages of thermoforming
1. Thermoforming is quite costly. Compared to other methods like injection molding, this method can cost up to 50% more.
2. Large plastic sheets are used in the method. They have to be fed into the rollers again and again. This leads to lots of extrusion.
3. The plastic street is stretched in the under pressure in this method. Hence the products formed using thermoforming break at a certain temperature.
4. Thermoforming uses more plastic than other methods. Nearly 10 to 20% more plastic is used to make any product in this method. This adds to cost and creates extensive wastage too.
5. Vacuum forming process done along with thermoforming does not give the required shapes sometimes. The whole process has to be repeated which is expensive as well as time-consuming.
Advantages of thermoforming
There are several advantages in using this method in spite of all these disadvantages.
1. Thermoforming is the only method in which huge plastic sheets can be molded into huge objects. All other methods are used for making small objects only.
2. Though the process is costly, the tools required for the trade or quite cheap. Injection molding machinery is nearly 33% costlier than the Thermoforming machinery tools.
3. Several different products can be prepared in the thermoforming machines. Only certain products can be prepared in other machines. Nearly all types of plastic can be used for the plastic. Other methods use only specific plastic for production.
4. Skilled labor to operate the thermoforming machineries are available in abundant. But, laborers capable of operating machineries of injection molding or vacuum forming are quite less.
5. Superior quality products using more plastic are formed in the method. Hence, they are more durable than the objects created through other local methods.
There are many more advantages in the method. Though costly and a bit time-consuming thermoformed products are preferred by most of the packaging industries due to their high quality.
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.