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 machine for introduction of web materials (coated paper, fabric, scrims, and poly liners) into the process
• All unwinds feature tension control through brakes or AC drives and are normally load cell controlled through the PLC
• For operator safety and convenience, unwinds feature heavy-duty safety chucks and lightweight air shafts
• 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
• Turrets are controlled by 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 design concept uses driven s-wrap stands – no 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
• Metering roll sets are machined to TIR ranging from 0.0002” to 0.00005” depending on the application
• Special bearings and housings are used, and metering rolls are final ground in these 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
• Additional available features:  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 within 3 feet, class 1 division 2 requirements apply

• 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
• Ovens can be vertical or horizontal depending on the application and space available
• A proprietary Oven Sizing computer program is used with customer production requirements to determine correct oven length
• Vertical ovens are the most popular as it allows the prepreg to exit the metering rolls and enter the oven without touching any rolls
• When used, horizontal ovens feature a “spring” conveyor to support the web during drying and curing processes
• 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 and 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 incorporate 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 Rolls

• Some processes include compaction rolls for further smoothing and impregnation of the resin into the woven fiber
• Litzler compaction rolls feature exclusive designs including
  • Machined  to 0.0002” TIR
  • Large diameter to minimize deflection – typically 24” (600 mm) diameter for 50” (1270 mm) or wider web width
  • 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

• To meet end-user clean edge requirements, shear or score edge slitters are incorporated
• Center cuts and multiple-web slitting is also available
• Web-following (guiding) systems are available 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 accumulation
• The accumulator allows the operator to make the winder change safely by stopping the web and allowing the roll change to occur
• 30 seconds is typically enough time for most process requirements

Poly Unwinds/Poly Rewinds

• Unwinds and rewinds for poly liners, scrims and paper liners are provided to maximize flexible processing potential
• 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 the Litzler Automation –  Control Systems web page for additional details

Copper Clad Laminates

Litzler has built and delivered many CCL machines for the PCB industry, using several resin chemistries.  Our CCL machines feature integrated web and tension control, precision metering rolls, Opti-Flow convection ovens or our patented Perfect Radiant ovens, and Litzler Automation control systems.

• 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