EQUIPMENTS FOR HOT STAMPING

There are basically two types of machine used in the process viz.: The Reciprocating Press and The Rotary machine.
The Reciprocating press:
It is used when the surface of the substrate is flat, concave, or convex. It is also used to mark the cylindrical shape. It is difficult to eliminate air pockets trapped between the die, roll leaf and the part with this type of press. Usually it is squeezed out by doming the die. The press basically consists of: a head ram--- moving up and down; a table ram--- which can be adjusted up and down according to the height of the plastic part and a frame--- containing the drive mechanism and it supports the pressure development and maintains alignment between the two rams. A heating head is attached to the head ram to supply and maintain heat to the die. An automatic roll feed is also attached to the head ram to advance the roll leaf or transfer. The head ram is driven by direct air cylinder, or a hydraulic or an air-hydraulic system.
Rotary type machine:
Here the rolling action of the rotating silicone coated roller pushes the entrapped air and gases ahead of it as it passes across a broad area. It also eliminates the need of extremely high pressure on broad area coverage because only a line contact is made between the roller and the plastic surface. The die can be cylindrical or flat. The item is placed on a support mandrel, to back up the impression. The mandrel, which accurately fits the item, is driven mechanically at the same speed as the rotating die, when designs or lettering are applied, but when smooth silicone pad is used to release the solid foil coating or a transfer design, the mandrel is not mechanically driven but is designed to turn as freely as possible. When the part with a flat surface is to be decorated, the part is mounted on a fixture and is transported, by a hydro-check table, beneath the roller. The speed of rotation of the roller is equal to the speed of movement of the table because tremendous heat is removed from the roller, it is usually heated both internally and externally and hence the roller is constantly rotated even if the object (substrate) is not in contact, otherwise the external heater can cause overheating and rapid decomposition of the rubber coating. On some rotaries, several rollers are used to assure complete transfer of the coating. Low tooling cost in short runs can be obtained because flat die is cheaper than a cylindrical shaped die.