Solution Prepreg Machine Features

Creels for UD machines
  • Creels are available in various levels of tension control – from basic friction tension holdback up to servo driven and load cell controlled positions
  • Creels are designed to present the fiber sheet in a stable condition to the impregnation process
Fabric/Paper/Poly Unwinds
  • Unwinds (or Let offs) are used throughout the process in order to introduce a web into the machine
  • Unwinds are used for coated paper, fabric, scrims, and poly liners throughout the machine
  • All unwinds feature tension control through brakes or AC drives and are normally load cell controlled through the PLC
  • Unwinds feature heavy duty safety chucks and lightweight air shafts – for operator convenience and safety
  • Fixed, turret and guided versions are available
  • Turrets are available in two, three, four, and six position designs
  • Cantilevered unwinds are available on narrow machines
  • Controlled via Litzler Automation control system
Splice Press
  • All fabric lines require a splice press for continuous operation
  • Splice presses feature heated platens to join the fabric using heat, pressure and splicing tapes
Accumulator
  • In conjunction with the splice press, an accumulator allows a fabric prepreg machine to operate in a continuous fashion
  • When a fabric roll is almost empty, the accumulator automatically fills with fabric, when the accumulator is full, the operator has several minutes to change to a new roll and make the splice
  • The impregnation process continues as the accumulator empties
  • Litzler accumulators feature low drag idler rolls, and specific controls to maintain tension control and are usually designed for 2-6 minutes of storage
Tension Control
  • Tension control and tension isolation are critical for high quality operations
  • Litzler machines isolate the unwind and rewind tension from the coating and drying tension for more flexibility and process control
  • Our philosophy includes the use of driven s-wrap stands and never any running nips which can damage delicate materials
  • The s-wrap rolls are either load cell or dancer controlled depending on the application
Impregnation (Metering Rolls)
  • Prepreg requires precise application of resin in order to control weight and / or thickness
  • The impregnation starts with submerging (dipping) the fabric in a tank with 2-5 stainless steel rollers
  • The tank features recirculation controls and overflow weirs to maintain a constant level
  • Tanks are available with heating or cooling options
  • The metering rolls include two precision rollers with TIR ranging from 0.0002” down to 0.00005”
  • The rolls include special bearings/ housings and the rolls include a final grind in the bearings
  • Gap control is precise and repetitive using our proven gap setting design. Manual or Servo controls are available
  • The rolls are driven by individual servo drives to give precision RPM control
  • The complete system is designed to typically operate within the Class 1, Division 1 regulations (or CE/ATEX) for solvents and includes explosion proof designs and an enclosure with supply and exhaust fans, and LEL monitoring
  • Features can include special tungsten carbide roll coatings, custom resin delivery pans, servo driven rolls and servo controlled gap setting
Resin Recirculation System
Metering Enclosure

Solvent coating operations require a metering roll enclosure system to contain and exhaust the solvents. The area inside the enclosure requires special electrical classification (Class 1/ Division 1) for explosion proof components and wiring.

Outside the enclosure is class 1, division 2 up to 3 feet away from the product slot

  • The enclosure is normally assembled with an aluminum and glass structure
  • Inlet and outlet ports for the supply and exhaust fans
  • Includes an area LEL monitor to monitor the solvent levels in the enclosure
  • Multiple doors and access panels for machine access and cleaning
Oven
  • Litzler ovens all feature our unique Opti-flow design for uniform temperature and airflow
  • Prepreg ovens can be vertical or horizontal depending on the application and space available
  • Litzler uses a proprietary Oven Sizing Computer Program to work with customer to determine the correct oven length to meet your production requirements
  • Vertical ovens are the most popular as it allows the prepreg to exit the metering rolls and enter the oven without touching any rolls
  • Horizontal ovens are used on occasion and feature a “spring” conveyor to support the prepreg during the drying and curing process
  • Ovens feature multiple zones and variable speed drives for good process control and flexibility
  • Most ovens for solvents feature stainless steel interiors for easy cleaning and long life
  • Removable nozzle for cleaning
  • Makeup air and recirculation air filters are available
  • Heating can utilize waste heat from the pollution control or standalone direct or indirect heating with gas, electric, steam or oil coils depending on the utilities available at site
  • Vertical ovens feature driven turn around rolls that are water cooled to prevent pickoff
  • Turn around zone also features our exclusive Perfect Float flotation air bars for improved cooling heat transfer and increased web stability
  • Pollution control is integrated into the system as required to ensure clean air standards and operator safety
Web Cooling
  • The prepreg requires cooling after the oven and this is accomplished two ways – convection or conduction
  • A Perfect Float convection system is available after the oven for cold air impingement on the prepreg – this also helps to stabilize the prepreg after the long down pass in the oven
  • Cooling rolls are also used featuring conduction technology – cooling rolls also act as the lead drive and are part of the tension control system
  • UD machines utilize a curved aluminum heat transfer plate for cooling. The convex curved plate keeps the UD material flat and in full contact with the cooling plate for a high heat transfer (cooling) effect
Web Guiding
  • After the prepreg leaves the oven, typically an edge guider is provided to ensure that the web is properly aligned prior to winding
  • Guiders feature electro mechanical or pneumatic actuators to keep the web aligned
Compaction Roll
  • Some processes include compaction rolls for further smoothing and impregnation of the resin into the woven fiber
  • Litzler compaction rolls feature exclusive designs including
    • 0002” TIR rolls
    • Large diameter rolls to minimize deflection — typically 24” (600 mm) diameter for 50” (1270 mm) and wider
    • Precision gap setting mechanism

Heat and pressure are used to heat the resin from the carrier paper/film and transfer it to the fiber. The “flow” of the resin is dependent on the heat of the rollers.

The combination of heat, precision TIR of the rolls, precision of the deflection of the rolls, and the pressure (Pounds per Linear inch – PLI) all contribute to the proper impregnation. The prepreg manufacturer needs a precise final thickness, a precise final areal weight, and a tape with little or no voids in the prepreg.

To achieve these results, multiple sets of compaction rolls are implemented. Because the resins are viscoelastic, the prepreg tends to spring back after compaction. To avoid this, multiple roll sets are used with progressively smaller gap settings.

Edge Trim
  • End-users require clean slit edges and Litzler provides shear or score slitters on the machine
  • Center cuts and slitting multiple webs is also available
  • Web following systems are available (guiding system) to ensure consistent web width
Edge Trim Collection
Windup accumulator
  • A windup accumulator is a smaller version of the unwind accumulator – 30 seconds to 2 minutes
  • The accumulator allows the operator to safely make the winder change by stopping the web and allowing the roll change to happen
  • 30 seconds is typically enough time for most process requirements
Poly unwinds/Poly Rewinds
  • Poly liners, scrims, and paper liners are all part of the potential flexible processing requirements
  • Each unwind features safety chucks and tension control using load cell or diameter sensor closed loop feedback
  • Some positions feature removable carts for loading and unloading
  • Drop splice designs are available
  • Web guiding is available for scrims
Winders
  • The winder is a critical part of the process and Litzler features multiple designs
    • Turret winders – 2-6 positions available – cantilever and safety chuck styles
    • Fixed winders
  • All winders feature AC drives and either load cell or slip clutch control for natural taper or constant tension winding
  • Lay on or press rollers available
Controls and Machine Integration
  • The control system provided by Litzler Automation operates the complete machine via an LHMI interface and a sophisticated PLC system and drive system
  • See Litzler automation control systems for additional details

Copper Clad Laminates

A printed circuit board consists of layers of impregnated fiberglass and copper foil. Litzler CCL machines impregnate the fiberglass prepreg with resin. The CCL machines feature integrated web and tension control, precision metering rolls, Opti-flow convection oven or patented Perfect Radiant oven, and Litzler Automation control system.

  • Traditional treaters with 6-12 meter tall ovens
  • Lightweight glass treaters with 3-9 meter tall ovens
  • PTFE treaters with high temperature drying and sintering zones

A complete system includes some or all of the following components:

  • Unwinds with precise tension control
  • Splice press for continuous operation
  • Accumulator for continuous operation
  • Tension isolation and control via load cells, brakes, tension stands (s-wrap) and AC drives
  • Impregnation with precision Metering Rolls
  • Resin mixing and recirculation
  • Drying
  • Pollution control if necessary with solvent applications
  • Web guiding
  • Web cooling
  • Compaction Rolls
  • Poly liner unwinds and rewinds
  • Edge trim or slitting along with trim collection
  • Windup accumulator for safe continuous operation
  • Winding
  • Controls integration (drives, safety, temperature control, LHMI, data acquisition)
  • Solvent safety management