Blown Film Extrusion Internal Bubble Cooling and Non-IBC

Sizing Cage Features

The primary features of a sizing cage are the size range, the arm material, and the compatibility with internal bubble cooling control sensors. Secondary features include the speed of diameter movement (particularly important for auto cage control applications), the height range of the cage, and the ability to easily realign the cage after installation.
Size, Style, IBC	Cage Arm Material
Size range: identifies the size of the bubble diameter or layflat that can run with the bubble touching the cage arms. Ranges can be specified with a minimum and a maximum size, or with a maximum and a size ratio. Many cages come with a 3:1 size ratio, but some are available with a 4:1 size ratio.		Segmented Rollers - Each arm is made up of many insulating rollers. Common materials are Teflon and PTFE. This style of roller arm is good for low and high density polyethylene (LDPE and HDPE). These style arms require periodic cleaning to ensure the rollers do not drag on the film.
Cage Style and Levels: Each sizing cage uses either a radial or iris style arrangement to move the cage arms in and out. Levels refer to the number of cage arm levels on the cage. Most IBC cages use between 6 and 8 levels.	.	Single Rotating Cylinder Arms - A special covering provides a soft, insulating contact with the film. No scratches, no markings, no film thickness variation. The covers can be easily cleaned or replaced. Tacky films, very soft and thin materials benefit (LLDPE and Metallocenes).
IBC Compatible: Most sizing cages can be fitted with IBC sensors. The sizing cage must provide a means to move the IBC sensor with the sizing cage so the sensor always points towards the vertical centerline of the bubble (+/- 6°) for all bubble sizes. For IRIS style cages, the cage manufacturer provides any special mounting arrangements for the sensor.
		Low COF Arms - This type of cage arm does not have a rotating surface. Instead the entire surface of the arm is specially treated to provide very low coefficient of friction (0.056) and are very good for tacky films. Liquid cooling can also be incorporated into the arm to remove heat. Very soft and thin materials benefit (LLDPE and Metallocenes).

Diameter, Height, and X-Y Axis Controls
	Diameter Control: All sizing cages have diameter control. The issue is whether the control is manual (via a turn-crank), or motorized. Further, some cages also can provide variable speed for the motorized control. The variable speed feature is useful when the IS-IBC1 is providing auto cage control. Contact us if you need help on deciding which level of control to specify.
	Height Control: Most blown film extrusion lines that run more than one size will require a height control mechanism. Similar to the diameter control, the choices are no control, manual control and motorized control. The motorized control is recommended for almost every application. This control allows the operator to set the cage properly above the frost line which gives the bubble optimum stability.
	X-Y Axis Controls: The X-Y Axis Control feature allows the cage to be moved in the X or Y axis after it is installed. This allows for alignment changes which may be necessary if the die is moved after cage installation. Some cage manufacturers offer a motorized version as well. The manual version is generally sufficient for most applications.