TOTAL CONTROL OF SHEET EXTRUSION WITH HARREL SHEETROL^(R) SYSTEMS

The Harrel SHEETROL systems are a family of automation and control systems for total automated control of the sheet extrusion process. They range all the way from simple machine direction thickness controls up to systems which control the thickness of the sheet in both the longitudinal, or machine, direction and the profile of thickness across the sheet. The more sophisticated systems also include the controls for temperatures, pressures, RPM's, etc., for the line itself, so that the SHEETROL controller is the only ontroller required for the sheet extrusion system. All forms of SHEETROL controls also include full SQC capabilities.

SHEETROL systems are designed on a building block basis, so the user can install just the degree of control which he needs and can afford. Additional functions can be added later by simply adding additionsl upgrade modules.

The range of control functions available in standard modules is as follows: For full details on any module, click on the underlined statement in each listing.

• Basic, economical systems for monitoring and control of sheet thickness in machine direction only.
  • Uses basic TG-601 gama backscatter type measuring head, mounted in a fixed position over the sheet.
    
    
  • Indicaaates average thickness of sheet in the machine direction.
    
    
  • Ideal for monitoring and control of thickness of narrow sheet.
    
    
  • Click here for full details, pricing, and ordering directions for the BASIC SYSTEM FOR MEASUREMENT AND CONTROL IN MACHINE DIRECTION ONLY. ORDER ON LINE.

• SHEETROL I -- Control of sheet thickness in the longitudinal, or machine direction, plus measurement and display of the cross machine profile:
  • A backscatter thickness gauge measures the thickness of whatever portion of the sheet is in front of the gauge at any time.
  • The movement of the sheet under the gauge allows measurement of the thickness variations in the longitudinal, or machine direction.
  • A rugged Harrel TM-600 sheet traverse moves the gauge head back and forth across the sheet and allows measurement and display of the thickness profile across the sheet.
  • The thickness profile is displayed on the 14" full-color display of the very talented TG-873 SHEETROL I controller. In particular, the thickness at each die bolt position is shown, with out-of-tolerance values in red. It thus is a simple matter for the operator to adjust each die bolt to eliminate the red portion and hence bring the sheet into specification.
  • Thickness variations in the longitudinal, or machine, direction are eliminated by the TG-873, by adjustment of the ratio of the pull roll RPM and the RPM of the melt pump, or the extruder screw, if no melt pump is used.
  • An optional "repeater" 14" full-color display can be mounted over the die position, making it extra easy for the operator to see the results as he adjusts each die bolt.
  • Click here for full details on SHEETROL I -- FOR CONTROL OF SHEET THICKNESS IN THE LONGITUDINAL OR MACHINE DIRECTION, PLUS MEASUREMENT AND DISPLAY OF THE CROSS-MACHINE PROFILE.
  
  
  
• SHEETROL II: AUTOMATIC SHEET PROFILE CONTROL. Adds an important dimension to sheet control by providing automated, closed loop control not only of the sheet in the longitudinal, or machine, direction but also by totally automated control of the profile in the cross machine direction.
  
  
  • Harrel offers two different systems for automated control of sheet profile:
    
    
    • HEATED DIE BOLTS: Several die manufacturers offer automated dies where heaters are installed around each die bolt to allow the temperature of each to be individually controlled. As the temperature of an individual die bolt rises, it expands, just as if it were being manually adjusted. The Harrel SC-973 SHEETROL II controller measures the thickness of the sheet opposite each die bolt, compares the value with the target, and adjusts the temperature of each die bolt to bring the thickness at that bolt position to the target value.
    • ULTRATHERM: The exclusive Harrel ULTRATHERM system, accomplishes the control of profile by controlling the temperature of the bottom die lip through temperature controlled heated zones opposite each die bolt. Changing the temperature of the die lip varies the friction characteristics between the plastic stream and the die lip and allows adjustment of the profile.
    • COMPARISON: The Harrel ULTRATHERM system is 3 times or more faster in response than the heated die bolt system, and it has the tremendous advantage that it can be retrofitted onto existing dies. The heated die bolt system, on the other hand, can handle somewhat thicker sheet.
    • The SC-973 SHEETROL II control system can handle either profile control system with equal ease.
    • Click here for full information, pricing, and ordering directions for SHEETROL II: AUTOMATED, SHEET PROFILE CONTROL.
      
      
• SHEETROL III: Stabilization of exruder throughput
  • Provides a considerable improvement in the quality of the sheet produced by stabilizing the throughput of the extruder to within 0.1% through addition of a precision Harrel melt pump.
  • Harrel has been making melt pumps since 1978, and we strongly recommend that one be added to any sheet line which is intended for really high quality sheet.
  • Click here for full information, pricing, and ordering directions for STABILIZATION OF EXTRUDER THROUGHPUT WITH SHEETROL III AND A HARREL PRECISION MELT PUMP

• Total DIGIPANEL control of the entire sheet extrusion system
  • Harrel has a longer experience in the precision control of extrusion systems than anyone else anywhere. We introduced the industry's first PID temperature controls in 1967, the industry's first plant-wide control in 1968, the first microprocessor control for total control of the extrusion line in 1975, and the first all-digital nuclear gauge in 1978.
  • Harrel offers a complete line of DIGIPANEL control systems for total control of the extrusion process. It is a simple matter to combine this control capability with the thickness control of the sheet, to achieve a control system that provides truly total, automated control of the entire sheet extrusion system.
  
  
  
• STATISTICAL QUALITY CONTROL
  • SQC should be a way of life for any plant making quality sheet. Harrel has been offering SQC systems since the earliest days of the Deming revolution. Two forms are supplied:
    • CP-603 Single line SQC module. Recipe storge for all parameters of the line, including sheet dimension parameters. SQC calculation, display, and print-out of X-bar and sigma of any pertinent characteristic, plus Cpk, etc., as desired.
    • CC-620 Plant-Wide Control and Management System. Full SQC data for all the lines in the plant, plus TIME MACHINE recording of everything that happened in the plant for the past 7 days, unlimited recipe storage, read-out in any of four languages, etc., etc., etc.
    • Click here for full information, pricing, and ordering directions for STATISTICAL QUALITY CONTROL FOR SHEET SYSTEMS. ORDER ON LINE

• BUILT-IN COMPOUNDING CAPABILITY - The Harrel SINGLEPASS extrusion system:
  • Such additives as colorants, radio-opaque materials, etc., are conventionally added in a separate compounding operation, usually using an expensive twin screw extruder. This is not only costly but also it subjects the polymer to a second high-temperature processing operation.
  • Use of a Harrel SINGLEPASS system, with the CRD mixer developed by Dr. Chris Rauwendaal, eliminates this extra step.
    • The CRD mixing screw gives mixing in a single screw extruder that is fully equivalent to that obtained in a twin screw extruder.
    • Both mixing of additives and regular extrusion are performed in a single operation.
    • The extra capital cost is purely nominal, but the savings in operational costs can be enormous.
    • The SINGLEPASS system is particularly valuable for heat sensitive polymers, such as PVC, for the polymer is only heated and extruded once instead of twice.