Some printed applications are padded into tablets or booklets with the use of an adhesive applied to one edge of a group of sheets. Padding techniques are actually a form of binding, but the resulting pad or booklet is not intended to remain permanently bound - the padded edge serves only to keep the sheets together until a sheet is used and then detached from the padded edge.
Most of the padded products begin as single sheet items, which are then gathered and padded
into various quantities to create note and memo pads, prescription pads, coupon pads,
and many other similar applications. The padding compound is usually a type of glue, which dries to a soft or semi-hard consistency. There are various types of glue used, such as varieties applied manually as a cold application and other varieties applied by machine as a hot melt application.
Cold Glue Application
The following steps are common for most padded applications using cold glue:
- A large quantity of single sheets is stacked into a pile.
- Chipboard or some type of heavy paper is inserted at designated intervals, which serves as a backer material
and gives the pads stability.
- The pile of sheets and pad backers are carefully jogged and precisely stacked to create a smooth edge for the application of the glue. The entire stack is jogged toward the side where
the padding compound is to be applied.
- A standard
paintbrush is used to apply the glue to the stack of sheets.
- After the glue is applied to the smooth edge of the stack, weight is applied to the top of the stack
or the entire stack is clamped into a device called a padding press.
- When the glue
has dried, the weight or clamp is removed.
- A knife is inserted into the large
stack along the bottom of each piece of backer material in order to cut the glue and
create the individual pads.
Hot Melt Application
For padded applications using hot melt adhesive, automated equipment speeds up the process. The circular or carousel padder is one of the most popular padding machines used for this type of application. The following steps are typical for hot melt applications using the circular or carousel padding machine:
These steps represent one revolution of the carousel machine. The speed of
the carousel can be increased or reduced to accommodate the skill level of the operator in their ability to insert the pads into each clamping unit.
- The single sheets are placed into stacks of 25, 50, 100 or an amount representing the quantity
of sheets required per pad. Automated equipment is often used to count the sheets
into the correct quantity per pad.
- Each stack of sheets is combined with a backer
sheet of chipboard or heavy paper.
- The carousel padder has several identical clamping units, which pass by a staging area as the machine rotates. From the staging area, the operator inserts a stack of sheets, with a backer, into each clamping unit.
- The clamping units have mechanisms that jog the
single sheets and backer material into an even pile before the pad is clamped together.
- The clamping units pass over a drum that applies the hot glue to the edge of the clamped pad. The hot
melt glue dries very quickly after it is applied.
- After a short interval, the clamping unit releases
the pad, which falls onto a conveyor belt where it is retrieved and packaged.
Products padded with a hot melt glue and exposed to high temperatures
in storerooms or car trunks, may develop a cracking or degumming of the adhesive
causing the padded sheets to separate from the padding adhesive. Cracking or
degumming of the adhesive will not occur with cold glue adhesives.
Your vendor may have limitations on
the number of sheets that can be padded as well as the minimum and
maximum paper weights that can be manufactured into pads.
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