There are 2 main functional areas of the polywrapping process.  These are the inserting and the wrapping processes and are detailed below.

Insert Stations

The primary document and any other inserts are set up on separate insert stations/feeders which are situated along the length of the polywrapper. This explains why some of the most sophisticated polywrappers can be up to 50 feet in length as this is required to be able to handle many inserts.

When the polywrapper first starts, the product from feeder #1 is pulled down from a stack of the inserts and is placed on to a conveyor track. This product is then pushed down the track to the next feeder at which point the insert from feeder #2 is placed on top of the first insert. This process continues adding any additional inserts until the mail-piece comes to the wrapping section.

Wrapping Section

Most polywrappers are fed by a single roll of polythene which is just over twice the width of the product to be wrapped.

The mail piece 'set' is fed from the insert station track and is placed on top of and in the centre of the polythene. The polywrapper then folds the polythene up and around the top of mail piece until the polythene is overlapping down the centre of the mail piece. A heated wire then melts the polythene together creating the centre seal along the length of the mail piece.

The mail piece continues along the polywrapper, where a heated seal bar comes down just in front of the mail piece. The pressure and heat from the seal bar creates, melts and separates the polythene creating a very strong seal at the leading top edge of the polywrap.

As the mail piece continues along the wrapping section, the seal bar comes down again, melting and separating the bottom trailing edge of the polywrap.

Quality Control

The polywrapping process seems quite straightforward, however if you turn the speed up then you can look to wrap up to 13,000 items per hour.

To ensure that each wrap is complete and perfectly wrapped, polywrappers are fitted with a range of sensors that monitor each station and check the quality and integrity of the wrapped product.   Any issues are relayed to the central computer that controls the polywrapper and either stops the machine or diverts the problem mail piece to enable this to be fixed offline.   Built in sensors check for

• Stations - as each product is pulled from the stack on to the conveyor, sensors check the thickness of the product.   Too thin and this either indicates a problem product or no product at all.   Too think and this would indicate a faulty product or more likely that more than 1 insert has been pulled.
• Wrap Quality - once the item has been wrapped, sensors check the length of the pack.  This enables the polywrapper to verify that the package has been sealed and cut properly, because if the length was too long, this would indicate that the cross seal has not split the polythene correctly.

Other Considerations

• There may be a requirement to include an insert within a brochure or magazine, rather than as an onsert which is placed on top.  This is achieved by using what is called a windmill page opener.   This works by lifting up the first page using suction.   Once the page has been opened, it is then possible to keep this page open all the way down the conveyor track.   This means that each additional insert will be inserted into this open page.