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.

Sizing Cage Components
Specifying a Sizing Cage - Size Range, Style, IBC

Size Range: identifies the mechanical range of bubble sizes the cage can support with the bubble lightly touching the rollers. Ranges can be specified with a minimum and maximum size or a maximum size with a size ratio. For instance a cage with that can handle a maximum layflat of 2000mm with a max:min size ratio of 4:1 will be able to run a 500mm bubble as well. There is layflat shrinkage between the bubble cage and the final roll. DRJ makes specifying a bubble size range simple; tell us the minimum and maximum layflat range you want to run and that’s all we need to know. We account for bubble shrinkage in our sizing calculations.

Cage Style and Levels: Each sizing Cage uses either a radial or iris style arrangement to move the arms in and out. Levels refer to the number of cage arms on each level. For IBC applications, between 5 and 6 levels are most popular; 8 levels is the maximum. For bubble stabilizing applications (nonIBC and tall tower applications 2-4 levels are adequate.

This is a 6 Level Cage with 12 Arms per Level This is a 5 Level Cage with 8 Arms Per Level

IBC Compatible: Most sizing cages can be fitted with IBC sensors. For DRJ IBC systems, the sizing cage must provide a means to move the IBC sensor with the sizing cage arm and maintain a constant distance between the bubble and the inside of the cage roller arm. Further the sensor should always point at the verticle centerline of the bubble (+/- 3°) for all bubble sizes. For IRIS style cages, the cage manufactuer needs to provide a special mounting system to accomplish this. For radial style cages, this is not an issue.

Cage Roller Arm Type
Silicone roller covers are the most common roller cover. They are a general purpose sleeve that provides a soft surface for bubble contact, that due to a reasonable low COF, are relatively low maintenance.
Wool Felt covers are used for hot, or tacky films. Wool does not easily transfer heat, which could negatively affect the film cooling process creating gauge variances. Tacky films also do not adhere easily to wool. However maintenance is higher as oil/residue is absorbed into the material more easily.
Silicone over Wool: Combing these two technologies, the aim is to achieve the low maintenance of silicone covers with the low thermal transfer of wool covers.

Teflon rollers maintain the benefits of the old segmented Teflon rollers without the pinching action of worn segmented rollers.  Instead, protected bearings ensure long life and low maintenance.  These are FDA approved for food contact films.  They however do require quite a bit of inertia to spin due to the weight, so may not be the best solution for thin films.

Carbon rollers have the main benefit of requiring very little inertia to spin.  As such, they are ideal for thin or delicate films.  With a low COF, buildup is uncommon.

Carbon No-Stick Rollers have an FDA approved coating for compliance with food grade applications.  Again low inertia is required to spin these lightweight rollers.  Additionally, the «no-stick» coating has an extremely low COF, whereby even the tackiest of films will not adhere.

Optional Air Exhaust System

An optional air exhaust system is available for applications that produce gas / residue as a byproduct of film production. The air exhaust package integrates suctioning exhaust vents around the sizing cage to extract extrusion fumes and contamination, which keeps the bubble and workspace free of residue and potentially harmful fumes.

The system is all inclusive, coming with self-positioning suction hoods, exhaust fan, tubing, ducting and an electrical cabinet with a speed drive to regulate the exhaust blower speed. A separate filtering unit can be also included, to treat the exhaust air, and trapping the pollution. Using the highest grade of filtering materials, efficiency upwards of 90% is available with the optional filtration unit.

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