Copyright, CSC Publishing, Powder and Bulk Engineering International If you choose a One -wrapping ill you store the pallet loads W he most common mistake in he most common choosing a method for wrapping is to focus on only two factors: the cost of packaging material and the cost of the machine. These are important factors, of course, but they show you only half the picture. Other important factors to consider are labor requirements, storage, energy customer acceptance, and cost, capacity, service. after-sale Labor requirements. less-expensive semi-automatic machine instead of a fully automatic one, will the savings be consumed by the extra labor needed to operate the machine? Storage. outside? For how long? How durable is your pallet wrap and how well can it protect your product from moisture and ultraviolet (UV) radiation? By choosing a pallet wrap that eliminates the need for protective tarps, you may free up inside storage space for other uses. Another pal- advantage of outside storage: Your from the need to be shipped lets don’t loading dock. Instead, you can load at an outside storage facility and thus save (Covering loaded pal- time and money. lets with tarps during storage and again during transport can be quite costly.) Energy cost. method, called thermal shrink-wrap- ping, requires heat from natural gas, Be sure to factor propane, or electricity. as in the on-going cost of this energy, well as the one-time cost of installing a The other pal- gas hook-up, if necessary. let-wrapping methods discussed in this T erpackung, Schrumpffolien- erpackung und Folienhauben- Choisir la bonne méthode pour l’enveloppage des palettes Le choix de la meilleure méth- ode pour la consolidation de chargements de palette tient compte de plusieurs facteurs, pas seulement du coût de la ma- chinerie ou du matériel d’em- ballage. Cet article énumère ces facteurs et examine trois options d’enveloppage de palette : ban- derolage conventionnel, embal- lage sous film rétractable et l’utilisation d’un couvercle coif- fant extensible. Auswahl der richtigen Methode von Paletten zum Verpacken Die Auswahl der besten Methode zum Sichern von beladenen Palet- ten ist von mehreren Faktoren ab- hängig, nicht allein von den Kosten der Maschinen und dem Verpack- ungsmaterial. Diese Faktoren wer- den in diesem Artikel aufgezählt, und es werden drei Optionen für von Paletten ver- die Verpackung glichen: konventionelle Spann- V V Stretching. ple costo de la maquinaria y el ple costo de la maquinaria material de empaque. Este artículo enumera los factores y examina tres opciones para empacar pale- tas: envoltura por elástico, en- voltura con elástico termosensible y estirado de forro.

Escogiendo el método correcto para envolver paletas Seleccionar el mejor método para asegurar paletas cargadas depende de varios factores más allá del sim- Selecting the best method for secur- Selecting the best method ing loaded pallets depends on sev- eral factors, not just the cost of the machinery and the packaging material. This article lists these fac- tors and examines three pallet- wrapping options: conventional stretch-wrapping, thermal shrink- wrapping, and hood-stretching.

Uffe S. KristiansenUffe Lachenmeier A/S Choosing the right method for wrapping pallets the right method Choosing C o p y r i article, stretch-wrapping and hood- that equipment vendors be ready to pro- The turntable type is the least expensive g h t stretching, do not use heat. vide instant technical assistance. Some machine. It places the pallet on a spin- ,

C

vendors offer an around-the-clock ning table (turntable), and as the table S help-line, as well as a modem hook-up spins, a worker or a film-dispensing de- C

Capacity. Can the pallet-wrapping ma- P

for communicating electronically with vice covers the pallet load with stretch- u

chine that you choose keep up with pro- b l

the vendor. film. With the swing-arm and the i duction? Does the machine have s satellite types, a film dispenser spins h i reserve capacity that can handle a pro- n around a stationary pallet. You can pro- g

With these factors in mind, let’s look at ,

duction increase? gram them to wrap the pallet loads in P

three methods of wrapping pallet loads. o different patterns. Stretch-wrapping w

The methods discussed are stretch- d

Customer acceptance. In today’s cus- machines may include a pre-stretch de- e

wrapping, thermal shrink-wrapping, and r tomer-driven market, it is very impor- vice and a top-sheet dispenser. a hood-stretching. Table I summarizes n tant to investigate how the customer will d

many of the factors for comparison. B react to a different kind of pallet wrap A pallet wrapped by conventional u l before you select it. Some home-im- k

Stretch-wrapping stretch-wrapping is generally stable, but E provement centers, for example, prefer n

not as stable as pallet loads secured by g hood-stretching. It not only stabilizes i Conventional stretch-wrapping ma- shrink-wrapping or hood-stretching. n e and protects the pallet load, it gives the chines use the natural tension of plastic e

This is because the pro- r i product a high-value image. stretch-film to keep pallet loads to- n vides only a small amount of vertical g

I

gether. They come in different types and holding force. Essentially, the wrap con- n t After-sale service. Every plant man- with different levels of automation. The sists of multiple narrow, horizontal e r n ager knows that downtime is costly and three main stretch-wrapping machines strips of film, one overlapping the other. a t i leads to dissatisfied customers. It is are the turntable type, the swing-arm The wrap does not form a complete film o n therefore imperative, in today’s market, type, and the satellite type. over the pallet load. a l

Table 1

Comparison of pellet-wrapping methodsa

Factor Stretch-wrapping Shrink-wrapping Hood-stretching Capacity Up to 120 pallet loads per hour, depending on Up to ≈ 350 pallet loads per hour in two-station ma- Up to 180 pallet loads per hour, depending on load dimensions and wrapping pattern. chine. Up to ≈ 120 pallets per hour in combined-sta- load dimensions. tion machine. Energy cost Low. (No heat required.) High. (Heat required.) Low. (No heat required.) € Film price Stretch-film ≈€1.50 per kilogram. ≈ 1.30 per kilogram. ≈€1.60 per kilogram. Top-sheet film ≈€1.30 per kilogram. € Film cost per load based on pallet load of 1,200 by ≈ €.60 based on 100-micron-thick cover and ≈ .60 at a film thickness of 60 microns. ≈€.52 based on a film thickness of 60 microns. € 1,000 by 1,100 millimeters three bottom layers, two general layers, and ≈ .96 at a film thickness of 95 microns. ≈€.80 based on a film thickness of 95 microns. three top layers of stretch film. Pre-stretch is 150%. Pallets per film roll based on pallet load of 1,200 ≈80 to 150 pallets. 700+ pallets based on a film thickness of 700+ pallets based on a film thickness of by 1,000 by 1,100 millimeters 95 microns. 95 microns. Transport stability Adequate for light, stable loads. Good for all non-settling loads. Very good for heavy, unstable loads, especially bagged products. Load protection Stretch-wrapped loads are not suited for outdoor Excellent protection against dust and moisture. Well Excellent protection against dust and moisture. storage without tarps. Not 100% moisture suited for outside storage and truck transport without Well suited for outside storage and truck proof. Film attracts dust. using tarps. transport without using tarps. on film Not possible. Possible. Possible. Film transparency Not very transparent due to overlapping and a Very transparent. Very transparent. cling additive. Suitable for heat-sensitive goods? Yes. Yes, but not recommended for flammable goods. Yes. UV stability Poor. Very good. Very good.

Note:aThe cost calculations in this table are based on price information available to the author as of August 2002. Use the cost calculations as a guideline only. The author assumes no responsibility for their correctness. C o p y r i g h t ,

Figure 1 C S C

Hood stretching operation P u b l i s h i n g ,

P o w d e r

a n d

B u l k

E n g i n e e a. A sensor detects the incoming pallet load. b. Sealing devices close the opening of the tubular film to form a hood. r i n g

I n t e r n a t i o n a l

c. Rollers gather enough film to cover the pallet load. d. Stretching units enlarge the hood to fit over the pallet load.

e. The machine places the hood over the pallet load. f. The machine raises the pallet and releases the hood.

g. The stretching units return to position to handle the next pallet. h. The operation repeats. C o p y r i For this reason, it is virtually impossible with mixed pallet loads. Shrink-wrap- g Figure 2 h t

to make the stretch wrap watertight. As ping these types of loads works well be- ,

C discussed earlier, this is a great draw- cause the heat forces the film to conform Pallet load of bagged products after S back if the pallets are to be stored out- tightly to the contours of the load and C

hood-stretching P

side. The pallets will need tarps to gives a very snug fit. u b

protect them from the elements during l i s storage and truck transport. h

The two main drawbacks to thermal i n

shrink-wrapping are the need for heat g ,

and the high cost per pallet. Furthermore, P

Thermal shrink-wrapping o machine maintenance costs are higher w Shrink-wrapping machines apply a d than those of either stretch-wrappers or e r or bag of heat-shrink film over pallet loads hood-stretchers. The use of fire in gas- a then apply heat to shrink the film and se- n d

heated shrink-wrappers deters producers cure the pallet load. Before the introduc- B

of flammable goods from using them. u l tion of hood-stretching, thermal k shrink-wrapping was the most common E n method of wrapping pallets in cases where Hood-stretching g i n stability and protection were the primary e The latest method of pallet wrapping, Figure 3 e r objectives. In such cases, the cost of wrap- i called hood-stretching (Figure 1), uses n ping the pallets was usually secondary. g low-density (LDPE) film Hood-stretching machines also secure I n t

in the shape of a tube. In operation, the pallets loaded with bulk (FIBCs) e r

Like stretch-wrapping machines, ther- hood-stretcher senses the incoming pal- n a t mal shrink-wrapping machines come in let load (Figure 1a) and seals the open- i o various types and levels of automation. ing of the tubular film into a bag, or n a Some use a hand-held torch to shrink the hood (Figure 1b), just as a fully auto- l wrap. Others automatically shrink-wrap matic thermal shrink-wrapper does. hundreds of pallets per hour using mul- Rollers then gather enough film to cover tiple sizes of film. A fully automatic the pallet (Figure 1c). thermal shrink-wrapping machine may include two separate stations: a film-bag The hood, however, initially has a applicator and a film-shrinking station smaller circumference than the pallet (such as an oven- or frame-type). Or, the over which it will fit. To make the hood machine may combine the film-bag ap- fit over the pallet, four stretching units plicator and film-shrinking station into grab the film and pull it open until it is one unit. large enough to fit over the pallet load shrink-wrapper. Some hood-stretching (Figure 1d). The machine then raises the machines can wrap different pallet sizes In recent years, frame-type shrink- pallet and pulls the hood over the load and load heights fully automatically at wrapping machines have gained market and pallet (Figure 1e). Finally, the up to 180 pallet loads per hour. share over the conventional oven-type stretching units release the bag, allow- machines because they use less energy ing the film to snap back underneath the Hood-stretching has increased world- pallet (Figure 1f). The tight-fitting hood and they control the shrinking process. wide at the expense of conventional makes the pallet and the load one unit By controlling the shrinking process, stretch-wrapping and thermal shrink- (Figure 1g and Figure 2). these machines enable you to use a thin- wrapping. Part of this growth is because ner film without sacrificing stability. the number of qualified film suppliers Hood-stretching combines the best has increased. In addition, the hood- Film thickness, however, is not the most qualities of other pallet-wrapping meth- stretch film has improved in recent important stability factor when shrink- ods. The cost to wrap pallets is low, as it years, allowing you to wrap not only wrapping. More important is the so- is with stretch-wrapping, and the pallets palletized bags, but also rigid and flexi- called “bottom shrink.” Bottom shrink are as stable as those made by thermal ble bulk . See Figure 3. describes the step in which the machine shrink-wrapping. Hood-stretch film costs more than shrink-wrap film, but raises the pallet from the conveyor and Another advantage of hood-stretching is the hood-stretcher operates at a lower sucks the film underneath the pallet be- the film’s enduring flexibility. It con- cost per pallet load because it uses less fore shrinking it. A correct bottom forms to the load even when the load film. Furthermore, hood-stretchers are shrink unifies the pallet and load and is settles during transport, a common oc- simple to operate, reliable, and robust. essential to good stability. currence with bagged products. The price of a hood-stretching machine Thermal shrink-wrapping is the best op- lies somewhere between that of a fully Conclusion tion if the pallet load to be wrapped has a automatic stretch-wrapper and that of a If maximum stability and protection are non-standard shape, which is common comparable fully automatic thermal secondary and if your output simply C o p y r i does not justify an investment in state- g h t

of-the-art , the ,

C

conventional stretch-wrapper remains S the best choice. It is fairly simple to op- C

P

erate, comes in many different types and u b

price ranges, and is fairly reliable. Also, l i s you will always find a qualified film h i n supplier nearby. g ,

P o

However, if minimal downtime, high w d stability, and superior protection are your e r primary objectives, opt for either the a n d

shrink-wrapping or the hood-stretching B method. Both methods allow you to u l k store pallets outside without tarps. E n g i If you are handling pallets of bagged n e e

product, the choice between shrink- r i n

wrapping and hood-stretching is easier g

I to make now than it was a few years ago. n t e

Today, there are numerous qualified sup- r n pliers of hood-stretch film around the a t i world. o n a l Using today’s hood-stretch film, you can reduce your cost of film per pallet and increase load stability, even when the products settle during transport. In addition, the price of a hood-stretching machine is the same or lower than that of a comparable shrink-wrapping ma- chine. As an added bonus, you do not need to install a gas hook-up in your plant. PBE International

Uffe S. Kristiansen, US sales manager, Lachenmeier A/S, Sønderborg, Denmark. Tel: +45 73 42 22 00 Fax: +45 73 42 22 10 Website: www.lachenmeier.com