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Guidabolla per film estrusi a soffio Bubble cages for blown films Cestas de guía para film soplado |
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Bmec c/o Sanplast - Busto Arsizio / Italy T. +39 0331-340523 F. +39 0331-354588 email: ctc@bmec.eu web: www.bmec.eu |
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Terminology
l What means “Layflat” Dimension of a flattened bubble. In the blown film industry this measure is the most used to indicate film size. This is not the bubble diameter!
l Why should I care about “Film Shrinkage” The cage size is to be calculated on the hot bubble diameter. Do not base your calculations on the winder or you will not get the film size you need. The hot film, getting cool, will shrink in a percentage related to material, thickness, temperature, etc. Stay on the safe side when selecting a cage, a too small cage cannot be corrected. Keep a margin of 4% or more.
l What is the “Frost Line” The point of change from melted polymers to solid film. IBC systems check this line.
l What means I.B.C. Internal Bubble Cooling or a system to enhance bubble cooling by replacing the air trapped inside bubble with chilled air, thus making cooling faster and film output faster. This process will create bubble instability. With IBC technique, the presence of a cage is really necessary.
l What is “IBC control” Replacing bubble air in a constant and smooth flow is a difficult process. The secret is to do the job and keep the bubble stable. The most common solution to get information about bubble status is the use of one or more ultrasonic sensors to detect bubble inflation and governing air in.
The ultrasonic system can work on 2 basic principles:
Constant distance from the center: Using 3 or 4 sensors, mounted on a stationary position (usually on the lower cage ring) at the same distance from the bubble center. The echo reading, will determine the bubble position and diameter.
Constant distance from the bubble: One or more sensors (1-3-4) move in or out, keeping the same distance from the bubble wall. The system can calculate the bubble status with great precision and react fast.
l Why our guide does not have a “CURVED” shape Certainly a bubble is round ! However cages work on a polygonal principle. A curved shape is noticeable only when the cage is working at the maximum opening. On lower bubble sizes the polygonal form is evident, so at the end a curve is not so important. Anyway on request we offer also a curved guide for those customers that think this point is important but we still think that a “V” mounting is better. Note: on strait rods segmented beads turn more freely and do not pinch film. The reduced side friction, means a longer working life (see guiding systems).
l Why you offer a cage Stationary and a cage with Vertical Regulation
Stationary Cage Such cage can be a budget solution since the vertical positioning is complex and expensive and this way you buy just the cage or what matters. However the real use of this model is to keep bubble centered, like under the collapsing tent or just to keep bubble stable; eg. with very high towers, when film gauge verification is performed, etc. Only 2-3 levels required and mechanical frame can be very simple.
Vertical Regulation · The main cage used over die is equipped with IBC sensors to verify bubble status and the frost-line position. The precise positioning over die is important to keep frost line stable and so getting a better IBC control. · Vertical positioning needs a certain travel (stroke). In most cases 1 Mt. (3Ft.) is adequate when extruding same family of polymers. Stroke length can change up to double and more, if your line programs can extrude several polymer families like HD and LLD. |
|
Terminology
l What means “Layflat” Dimension of a flattened bubble. In the blown film industry this measure is the most used to indicate film size. This is not the bubble diameter!
l Why should I care about “Film Shrinkage” The cage size is to be calculated on the hot bubble diameter. Do not base your calculations on the winder or you will not get the film size you need. The hot film, getting cool, will shrink in a percentage related to material, thickness, temperature, etc. Stay on the safe side when selecting a cage, a too small cage cannot be corrected. Keep a margin of 4% or more.
l What is the “Frost Line” The point of change from melted polymers to solid film. IBC systems check this line.
l What means I.B.C. Internal Bubble Cooling or a system to enhance bubble cooling by replacing the air trapped inside bubble with chilled air, thus making cooling faster and film output faster. This process will create bubble instability. With IBC technique, the presence of a cage is really necessary.
l What is “IBC control” Replacing bubble air in a constant and smooth flow is a difficult process. The secret is to do the job and keep the bubble stable. The most common solution to get information about bubble status is the use of one or more ultrasonic sensors to detect bubble inflation and governing air inlet.
The ultrasonic system can work on 2 basic principles:
Constant distance from the center: Using 3 or 4 sensors, mounted on a stationary position (usually on the lower cage ring) at the same distance from the bubble center. The echo reading, will determine the bubble position and diameter.
Constant distance from the bubble: One or more sensors (1-3-4) move in or out, keeping the same distance from the bubble wall. The system can calculate the bubble status with great precision and react fast.
l Why our guide does not have a “CURVED” shape Certainly a bubble is round ! However cages work on a polygonal principle. A curved shape is noticeable only when the cage is working at the maximum opening. On lower bubble sizes the polygonal form is evident, so at the end a curve is not so important. Anyway on request we offer also a curved guide for those customers that think this point is important but we still think that a “V” mounting is better. Note: on strait rods segmented beads turn more freely and do not pinch film. The reduced side friction, means a longer working life (see guiding systems).
l Why you offer a cage Stationary and a cage with Vertical Regulation
Stationary Cage Such cage can be a budget solution since the vertical positioning is complex and expensive and this way you buy just the cage or what matters. However the real use of this model is to keep bubble centered, like under the collapsing tent or just to keep bubble stable; eg. with very high towers, when film gauge verification is performed, etc. Only 2-3 levels required and mechanical frame can be very simple.
Vertical Regulation · The main cage used over die is equipped with IBC sensors to verify bubble status and the frost-line position. The precise positioning over die is important to keep frost line stable and so getting a better IBC control. · Vertical positioning needs a certain travel (stroke). In most cases 1 Mt. (3Ft.) is adequate when extruding same family of polymers. Stroke length can change up to double and more, if your line programs can extrude several polymer families like HD and LLD. |