Types of packs

The primary pack is the moistureproof unit which is usually the type offered for sale to the consumer. Secondary packaging into groups of up to about 6 units may be made for multipacks of individually wrapped biscuits. The main type of secondary packaging is in boxes or cases for ease of storage and transportation. Primary packages are of only a few basic types. The wrapper may be rigid in the form of a tin or plastic box, but much more commonly it is some form of flexible material. If flexible it may be a preformed bag which is sealed after the biscuits have been placed in it, or it may be formed round one or a group of biscuits and heat sealed automatically. Some biscuits are collated and placed into preformed bags which are hand sealed, but by far the most common form of biscuit packaging is with sophisticated machines which carry groups of biscuits through wrapper forming and sealing arrangements at high speeds. The group of biscuits may be a column, a set of piles, or jumbled.

The biscuits in the pile packs are usually determined by number, those in column packs by thickness and those in jumble packs usually by weight. Individually wrapped biscuits are also referred to as "countlines". The pack sealing may be by fin seals or lap seals.

Types of pack seals

Fin seals require only one surface of the wrapper to be heat sealable, but lap seals require both surfaces to be heat sealable and pressure must be applied against the pack contents.

4cbPackSeals-thumbTypes of flexible wrapper seals

Sometimes there is a combination of seal types to utilise the greater efficiency that fin sealing allows in respect of moisture protection combined with the neatness that lap sealing gives to pack appearance.

Printed or unprinted wrapping materials are usually fed from reels and the action of the wrapping machine may be intermittent or continuous. Continuous fin sealing involves the formation of a tube around the product which is crimped and cut at appropriate pitch after the pack is completely formed. The tube may be formed horizontally or vertically. The horizontal type allows the introduction of a group of biscuits in a preformed arrangement, but the vertical type is used for preweighed biscuits in a jumbled arrangement. Product overwrapped and sealed with fold seals, particularly on the pack ends, permits the simultaneous feeding of more than one wrapper (for example, paper within a moistureproof heat sealable film) and card or corrugated materials for additional protection and rigidity (for example, corrugated folds or base cards). Wrapping material for packs with fold seals is cut before the pack is formed so transportation of the materials through the wrapping machine is much more critical. Within these generalised methods of pack construction there are many sophistications of engineering design which give particular advantages and characters to meet different requirements.

Where printed wrapper is used it is necessary to control the feed against register marks to ensure that the design remains central on each consecutive pack.

It is extremely unusual to print the wrapper at the same time as it is used for wrapping, but there is an almost universal demand for every-package coding to communicate the age or shelf life of the biscuits to the consumer. This necessitates in-line printing with a few characters. To overcome smudging problems as the film is drawn past folding and driving devices on the wrapping machine special dry printing techniques must be used. Obviously the film cannot be perforated as this would spoil the moisture barrier properties and the most commonly used method is by heat/pressure transfer from a coated ribbon. The technique is known as hot foil printing and the method is similar to that used on carbon ribbon typewriters.

Another demand from customers is ease of opening for the pack. On certain lap seal type wrapping machines it is possible to incorporate tear strips which hopefully initiate the splitting of the tough moistureproof film. Unfortunately the most common criticism by consumers of biscuits is of the difficulty of opening packets without damaging the biscuits. To use a knife or scissors cannot be regarded as convenient! Fin sealed packs are best opened by pulling the seal apart.

Having opened the pack there is then the problem of continued protection against moisture until the biscuits are eaten. Simple resealable packs are not common and are usually not very successful. Transfer of biscuits from an opened pack to a tin or plastic box in the home is still the best solution. As this is not universally convenient, sales of biscuits in relatively small packs, allowing all the contents to be eaten soon after opening, has increased despite significant increase in total packaging costs that this involves.

Biscuits fully coated with chocolate do not require the same degree of moisture protection and packaging is often different. Using film with good dead fold characters, where the sheet remains in the position after bending without springing back, such as aluminium foil or a laminate including aluminium foil, a seal may not required. These packs are not only easier to open but also can be re-closed.

Tins and rigid plastic boxes are now rarely used for packaging small units of biscuits. Although these containers offer many advantages, they are expensive and difficult to fill. Machines have been developed which will collate and drop biscuits into the tins, but the mechanism is so elaborate that the cost is only justified for expensive types of biscuits made on dedicated plants. Assortments of Danish Butter Cookies may be packed in this way, but in most cases even these are still packed into the tins by hand. Another disadvantage of tins is the enormous amount of space needed to store them while still empty! Tins and boxes, therefore, are now used only for relatively large packs or for expensive types and assortments in presentation packs.

Horizontal flow packs

These machines are by far the most popular type for biscuit packaging. A continuously moving infeed chain is loaded with groups of biscuits and flexible film is drawn around the biscuits as a tube. The edges of the tube are sealed as a fin with rotating sealers and at this point the biscuits leave the conveying chain and are transported in the tube to the end crimping, sealing and cutting station. The end seals are thus also fins so there is an excellent chance of having very complete seals all around the pack.

Normally the sealing is with heat and pressure but contact sealing is also available which requires only pressure. The heat and pressure conditions are very critical for correct sealing and this means that thermostats within the sealing jaws and wheels must be very accurate. If the wrapping machine is running fast the dwell time of the wrapper between the sealers is very short so the temperature must be higher than if the machine is running slowly. If the temperatures are too high the film may either melt (plastic based films) and then stick to the sealers or burn (cellulose based films) leaving residues on the sealer jaws. Even if the films are not overheated there is a tendency for the film to stick to the sealers so they must be kept clean and correctly spaced to suit the film being used. It is not possible to vary the speed of a wrapping machine where the sealing is with heat, thus the machine is either running or stopped. If there is a "jog" setting which allows the machine to be run slowly before moving into normal speed, this must be used sparingly otherwise overheating and difficulties with the sealing jaws may result.

The feeding of biscuits to these machines may be either manual or automatic. For manual feeding flat plates beside the conveyor allow biscuits to be slid into place and the locations on the conveyor are relatively easy to use as the operator's eye soon registers with a continuously moving chain with pins to catch the groups of biscuits. The groups or "slugs" of biscuits can be fed in either as a series of small piles or as columns on their side.

There is a photoelectric eye that allows automatic registration of the film to packs ensuring that the cut off at the end sealers is always in the correct place. Flow pack machines can run fast but the number of packs per minute is related to the length of each pack; if the packs are short, for example individual biscuits, the number of packs made per minute may be as high as 300 or more per minute but for typical 200g packs speeds of up to 130 per minute are more usual.

4cbTypesOfPacks-thumbTypes of biscuit pack

Vertical form fill seal packs

Like the flow pack machine, vertical form fill machines form packs by making a tube from the reel of film and cutting off lengths after the biscuits have been introduced. The machine runs intermittently and preweighed groups of biscuit are dropped into the tube of film. These machines are also known as bag packers and the packs, jumble packs.

The long seal is always a lap seal but sealing is good because the heater bar presses against the smooth wall of the tube former. The end sealers are reciprocating in motion and, as for the flow pack machines, incorporate the cutting device.

Speeds are limited to about 60 packs per minute and because the biscuits are dropped into the bag they are in a jumbled form and there is often a little damage.

Weighing heads above the machine allow automatic feeding and biscuits are typically fed to the weighers on inclined conveyors.

Roll packs

The name roll wrap suggests only round biscuits packed to form a cylinder but these machines can also handle rectangular and square biscuits.

The most basic machines carry columns of biscuits sideways to a wrapping station where they are pushed into cut lengths of film. The film is firstly sealed along the length of the pack and then the film is folded at each end before being sealed by heat and pressure. The feed of the biscuits is continuous but the wrapping is intermittent in action.

The first, long, seal may be a lap seal which is made by pressing against the edges of the biscuit (in which case it may be difficult to achieve a complete seal) or fin seal that is later laid flat. The latter is preferable as it secures a more complete seal.

The intermittent action of the wrapping station limits the speed of the machines to about 40 packs per minute for manually fed machines to about 100 packs per minute for those with automatic feeds.

There is much sophistication available in this range of machines. It is possible to feed more than one wrapper, for example a sheet of greaseproof paper or corrugated paper within the outer film, or to form a protective "box" with two U's of cut corrugated paper within the film overwrap. It is also possible to incorporate a tear tape with the overwrap to facilitate opening of the pack by the consumer. Some machines allow the gluing of paper seals over the end seals to make them look tidier.

Block bottom bags

Totally manual wrapping systems usually involve the placing of biscuits into preformed bags. These bags have folded and sealed bases which allow them to stand. When the biscuits have been placed in them the tops are heat-sealed with or without being folded over first.

These square based bags are known as block bottom bags. Fully automatic machines are available to form the bags, fill with biscuits and fold and seal the tops. They are a relatively expensive way of packaging and the machine is typically slow. They are used to fulfil a particular marketing image and are most suitable for relatively large packs.

Cartoning machines

Machines are now available for both placing individual biscuit packs into chipboard cartons and for collating biscuit packs and placing them into storage cases (fiberites).

These machines erect the cartons and cases from flat stocks and fold and secure the ends after they have been filled. The successful and smooth operation depends very largely on the quality and strength of the flat stocks provided. One of the commonest causes of problems is board that has become soft and weak due to storage in a damp place.

Setting up machines for changes in pack type and sizes

All wrapping machines, except vertical form-fill-seal types, are designed to accept biscuits that vary slightly in dimensions. However, in all cases the change parts and the settings for adjustable parts must be closely matched to the biscuits in question. The machine should be designed to suit the biscuits and it is much less satisfactory to try to make biscuits to suit a machine. This is a point that should be remembered at the product design stage.

Most biscuit manufacturers make more than one type of biscuit on a production plant. This means that either more than one set of wrapping machines must be provided to pack the biscuits or, more usually, changes are made to the wrapping machines to make them accept different products.

There are two aspects that affect the efficiency of any wrapping operation, one is the accurate setting of the machine to the size of the biscuits to be wrapped and the other is the uniformity of the biscuit feeding arrangements. Many wrapping machines are manually fed and it can be shown that operators vary in the way that they place and squeeze biscuits into the machine inflights. This affects the wrapping operation. In the case of automatic feeding systems they are normally adjustable to cope with different biscuits. Making these adjustments requires either skill or excellent calibration facilities (or both!). Many lower cost wrapping machines have inadequately calibrated adjustable parts and these can cause much start up trouble after the settings have been changed to suit a different biscuit type.

Settings for the adjustable parts of wrapping machines should form an essential part of data recorded on the Process Standards Document.

Every packet coding

Legislation and consumer pressure have resulted in very widespread application of every packet coding in the biscuit industry. All packaged food products should be coded to ensure that they are likely to be in satisfactory and safe condition when they are bought and consumed. For perishable foods where there is a potential for food poisoning "Sell by" coding is used but for other foods, like biscuits, where deterioration is not dangerous "Best before" marking is usually adopted. In some countries it is also necessary to show the date of manufacture of the product. In this way consumers are protected from the possibility of purchasing packets that contain substandard biscuits.

Most biscuits are wrapped in plastic films that are formed into packs from reels. It is normally impossible to include a "Best before" coding onto the film at the time that it is printed because the time when it will be used is uncertain. Thus techniques have to be used that print the code as the pack is made and this can mean very high speed movement of the film on the wrapping machine. Of all the possible methods the only practical one for biscuits is hot foil printing. This involves the setting of a small die assembly with the desired information, and placing it in an apparatus that heats it and presses it against a film with transferable material, usually plastic "ink", which is pressed against the wrapping film at the correct place. In the early days of this technique more problems arose from this printing device than for all other adjustable points on the wrapping machine. Thankfully the hot foil printers are now much more reliable. Their good performance needs constant vigilance as it may be an offence to supply biscuits with no coding or illegible coding.