What's New » 3-LAYER CAST SHEET – Inner Layer Control

3-LAYER CAST SHEET – Inner Layer Control

3-LAYER CAST SHEET – Inner Layer Control
The specific benefits achieved by installing LineMaster™ will vary according to the type of extrusion or coextrusion process involved, but in all applications it can accelerate line startup, reduce waste generation during product changeovers, and provide precise reports on raw material consumption.
 
A multinational manufacturer of film and sheet products [which declined to be identified for competitive reasons] installed LineMaster™ on a three-layer cast sheet line to evaluate productivity gains afforded by the system. Consisting of a primary extruder and two satellites, the line produces 60 and 80 mil (0.015 to 0.020 mm) coextruded sheet with a 20/60/20 ratio of skin layers to core.
  
The flat extrusion die employed has automatic thickness control that works in conjunction with a nuclear gauging system to maintain a uniform transverse profile of the sheet, primarily to eliminate unacceptable gauge bands in finished rolls.  Each extruder was previously equipped with a Maguire Weigh Scale Blender.  Before LineMaster was deployed, the extruder r.p.m and downstream takeoff speed were slaved to the thickness gauging system.  It determined, in other words, when changes were to be made to screw speeds or hauloff rates to maintain consistent thickness measurements of the coextruded sheet.
  
  Even though this sheet line contained state-of-the-art extrusion die and nuclear gauging equipment, the sample sheet examined by company was found to be defective, not in terms of overall thickness specifications, but because of substantial variances in the thickness of discrete layers.
  
The system was capable of maintaining a constant transverse profile of the coextruded web but was unable to maintain uniform layers for two reasons: 1) thickness gauging systems cannot yet measure individual layers in coextrusion; and 2) the Maguire gravimetric blenders involved, which log actual throughput by weight for each extruder, were not linked to the system.
  
The blenders were the ‘missing link’ in stabilizing the process because they are the only equipment capable of measuring and controlling actual material flow to each extruder and its respective layer in the coextruded structure.  And this capability is unaffected by process fluctuations such as changes in melt viscosity, variation in the bulk density of virgin resin or regrind, and pressure losses caused by clogged screen packs.
  
After installing the LineMaster™ on the line and slaving extruder r.p.m. to the three gravimetric blenders, the customer was able to maintain a consistent flow of  material through the die for each extruder, resulting in higher-quality coextruded sheet products.  In effect, the gauging system now controls the automatic die to keep the overall thickness constant, while the blenders control material flow to ensure consistent layers.  Greater control over the process made possible faster startups and reductions in raw material usage.
  
As a result of the successful deployment of LineMaster, the company has now ordered additional systems for film and sheet lines.

The specific benefits achieved by installing LineMaster™ will vary according to the type of extrusion or coextrusion process involved, but in all applications it can accelerate line startup, reduce waste generation during product changeovers, and provide precise reports on raw material consumption.
 
A multinational manufacturer of film and sheet products [which declined to be identified for competitive reasons] installed LineMaster™ on a three-layer cast sheet line to evaluate productivity gains afforded by the system. Consisting of a primary extruder and two satellites, the line produces 60 and 80 mil (0.015 to 0.020 mm) coextruded sheet with a 20/60/20 ratio of skin layers to core.
  
The flat extrusion die employed has automatic thickness control that works in conjunction with a nuclear gauging system to maintain a uniform transverse profile of the sheet, primarily to eliminate unacceptable gauge bands in finished rolls.  Each extruder was previously equipped with a Maguire Weigh Scale Blender.  Before LineMaster was deployed, the extruder r.p.m and downstream takeoff speed were slaved to the thickness gauging system.  It determined, in other words, when changes were to be made to screw speeds or hauloff rates to maintain consistent thickness measurements of the coextruded sheet.
  
  Even though this sheet line contained state-of-the-art extrusion die and nuclear gauging equipment, the sample sheet examined by company was found to be defective, not in terms of overall thickness specifications, but because of substantial variances in the thickness of discrete layers.
  
The system was capable of maintaining a constant transverse profile of the coextruded web but was unable to maintain uniform layers for two reasons: 1) thickness gauging systems cannot yet measure individual layers in coextrusion; and 2) the Maguire gravimetric blenders involved, which log actual throughput by weight for each extruder, were not linked to the system.
  
The blenders were the 'missing link' in stabilizing the process because they are the only equipment capable of measuring and controlling actual material flow to each extruder and its respective layer in the coextruded structure.  And this capability is unaffected by process fluctuations such as changes in melt viscosity, variation in the bulk density of virgin resin or regrind, and pressure losses caused by clogged screen packs.
  
After installing the LineMaster™ on the line and slaving extruder r.p.m. to the three gravimetric blenders, the customer was able to maintain a consistent flow of  material through the die for each extruder, resulting in higher-quality coextruded sheet products.  In effect, the gauging system now controls the automatic die to keep the overall thickness constant, while the blenders control material flow to ensure consistent layers.  Greater control over the process made possible faster startups and reductions in raw material usage.
  
As a result of the successful deployment of LineMaster, the company has now ordered additional systems for film and sheet lines.