Jasch develops and manufactures non-contact and non-destructive measurement and control systems to improve the quality of fast running webs and bring cost reduction and productivity increase to sheet, film, foil, textile or coating operations.
Our control systems continuously monitor and control the quality parameters such as Basis weight, Caliper, Coating thickness, Moisture, Ash contents, plastic thickness etc. The deviations from preset target values are instantly detected allowing immediate corrections to the production process to maintain constant product quality. All relevant measuring results are evaluated and displayed graphically on a monitor and documented by hard copy.
More than 100 systems installed worldwide are impressive evidence of the market acceptance and capability of our products and services.
The measuring principle of plastic thickness gauge is based on the attenuation of Beta radiation emitted by a nuclear source as it passes through a material. The thickness/basis weight is determined by sensing variations in the energy radiated by the source of known intensity. The measurement is continuous On-line and therefore useful as feedback for automatic control.
DESIGN AND CONSTRUCTION
The nuclear sensor is designed on a large volume pressurized ionization chamber coupled with a highly stable electrometer amplifier. The sensor performs automatic calibration after predefined intervals to guarantee stable measurements. For measurement on hot webs where basis weight of air in the measuring gap changes with temperature, fast temperature sensors are provided for compensation. The scanner is built on rugged steel structure free from deflection and misalignment to ensure precise sensor positioning. All linear motion system components are CNC machined to precise Alignment for long service life. The frame is an enclosed construction to shield all mechanical and electronic components from ingress of dust and corrosion. Where ever possible standard parts have been used which are available off the shelf in most locations.
The scanner is linked with the operator station through a high speed serial link. The single two wire link saves on cabling costs and also makes the installation easier. The operator station has a PC (Personal Computer) architecture with industry-standard hardware and software which allows for easy upgrades and local support throughout the world. The operation is through touch screen for easy and efficient operator interaction. The operator station is available either in a NEMA 4/12 enclosure for harsh out door operation or as a desktop workstation for control room installation.
The standard displays provided are cross web, machine direction profiles, trends, product recipe and roll reports. SPC charts are available as an option
Cast or extruded film and sheet
IGS ensures uniformity in machine and cross-web directions of the extruded webs. The machine direction uniformity is achieved by controlling the line or extruder screw speed through average thickness in every scan. For cross-web direction control the scanned profile is divided into zones equal to number of die bolts as per APC (Automatic Profile Control algorithm) The set point deviation for each zone is determined based on which corrective signals are applied to the corresponding die bolts by adjusting their heating power. The set point for each zone is taken equal to the last scan average thickness. This decouples the control in the two directions and avoids interference in die bolt control loop from machine direction control. Both the control loops have PID characteristics and equipped to detect sheet breakage to avoid excess line/screw speed in that event. The effect of adjacent bolts interaction can also be incorporated in control loop.
To ensure that each die bolt adjustment affects the right zone on the film the measured profile is precisely mapped to the die bolts. For this purpose IGS uses the primary sensor to find the sheet edges automatically every scan to with in 2mm. This means that dynamic changes of film shrinkage and die deckling are exactly accounted for in every scan.
The thickness and profile control of calendared plastic films is achieved by dividing the scanned profile into the three zones. The averages of the zones at the edges are used to control right/left nip adjustment of the last roll. The average of the centre zone in synchronism with those at the edges is used to influence either roll bending of the last roll or the cross axis adjustment of the penultimate calendar roll.
IGS can be used in production lines like spread coating lines impregnation
lines, extrusion coating lines where a base material is coated with one or more layers, by addition of one extra scanning or fixed gauge. The additional gauge is required to measure the base material before the coating is applied. The differential measurement is then used to control coating profile and the total final coated product thickness The advantage of nuclear gauge is that it can measure the coating in wet state i.e. just after the coating is applied and therefore corrections can be immediately applied.
AUTO CONTROL BENEFIT
The raw material is the single largest manufacturing cost in any production set. up. The automatic process control through IGS plastic gauge reduces the spread in thickness/basis weight variation and consequently the safety margins are lowered. A resulting set point reduction of even a few percent point can save a lot of precious raw material. Therefore the system repay quickly. Normal repayment is less than a year.
Plastic Thickness Gauge and QCS.