Stretch Wrap Machine

Compare STRETCH WRAP MACHINES or STRETCH WRAPPERS. A stretch wap machine wraps layers of plastic film around a pallet load. A stretch wrap machine (stretch wrapper) applies the film by a travelling carriage. This is the critical part of the machine because it determines how the film is stretched and how it is to be deployed.

Stretch wrap machines come in two basic configurations. Overhead and turntable systems. The advantage of an overhead machine is that it takes up less floor space than turntable models. They are better for light loads which may fall apart when the load spins on a turntable. Loads are placed on the floor for wrapping so there is no need to move the load up and on to a turntable

Another model, the Horizontal wrapper is a custom designed machine. It is listed here with the basic parameters, but manufacturers require a lot more information before responding to any product inquiry The mfr will mail questionnaires to interested customers.

The carriage goes up and down on a mast (rotary arm machine) or on a metal track (ring wrapper machine) The film is placed in the carriage and fed through a series of rollers which stretch the film and pace how the film is coming off the roll. The machine will be set to at specific pre-stretch level usually between 175% to 300% with 250% being the most common. 250% pre-stretch means that for every inch of film that comes off the roll, 3.5 inches of film are going on your load. Higher pre-stretch means greater film savings and because the film wants to rebound, tighter loads are achieved. The pre-stretch is determined in the carriage by gears and a chain and can not be easily increased or decreased. Many machines have an adjustment called "force to load" which can be confused with pre-stretch. Force to load is the speed at which film is deployed from the carriage to the load. It can have about a 10% effect on pre-stretch but does not control overall pre-stretch levels.

Semi Automatic machines require an operator to attach the film to the load and then activate the machine to perform its wrapping function. When the load is finished the operator must tear the film from the roll before removing the load.

Automatic machines are usually placed over a conveyor. When a load moves into place the machine attaches the film to the load, wraps the load, tears the film off and wipes the film tail to the load. Now the load is ready to be removed by by the conveyor. The entire process is completed without any operator intervention.

Although all applications differ, automation of a stretch wrapping process begins to be cost effective at around 30 loads per hour.

There are two types of automatic overhead machines. Rotary arm and ring wrapper Rotary arm machines as the name implies have an arm that revolves around the load as the carriage moves up and down dispensing the film. Ring wrapper machines have a large round track that raises and lowers around the load. The carriage rides around the track and dispenses the film. Ring wrapper machines are more expensive and much faster than rotary machines. Rotary arm machines can wrap up to about 45 loads per hour while ring wrappers will wrap up to 120 loads per hour