Cast-sheet variation is hidden later
The final film is wider and thinner, so an upstream die pattern no longer aligns one-to-one with downstream positions.
Measure the cast sheet. Understand the stretch. Control the final profile. Scantech combines online, cross-web low-energy X-ray measurement, one- or two-station scanner architectures, TDO stretch-profile logic, automatic mapping and optional BC3 die control for BOPP, BOPET, BOPE, BOPA and other oriented films.
Application-specific architecture: Not every biax line requires the same scanner count, measurement output or control strategy. Final scope depends on film structure, stretch sequence, measured width, passline, edge objective and available actuator authority.
A biax line changes the sheet in both machine and transverse directions. A final profile can show the result without proving whether the variation began at casting, developed through orientation or came from unstable edge behavior.
The final film is wider and thinner, so an upstream die pattern no longer aligns one-to-one with downstream positions.
MDO and TDO behavior can amplify, redistribute or introduce variation that a film-end scanner sees only after orientation.
The edge must remain thick and correctly shaped enough for the clips to grip without turning the trim region into an unmonitored blind spot.
Automatic control needs registered process positions, transport delay, stretch ratios, valid edge rules and qualified actuator influence.
Scantech strongly recommends two scanners on many biax lines: one at the cast section and one at the film section. Relating the two profiles improves die mapping, control stability and insight into how the orientation process is performing.
The cast sheet begins with the current die-lip and actuator profile.
Scanner one measures the incoming pre-stretch sheet profile.
Machine-direction stretching changes thickness and material coordinates.
Transverse stretching expands the web and forms the final edge geometry.
Scanner two measures the post-stretch final-film and edge profiles.
Stretch-aware logic supports diagnosis, operator guidance or qualified upstream control.
The relationship is not simple point-to-point matching. The project must account for scanner registration, machine- and transverse-direction stretch, width change, trim and clip-zone exclusions, line delay and the accepted measurement model before a final-film deviation is assigned to an upstream die zone.
Scantech links its X-ray measurement footprint and sensor speed to high-fidelity edge measurement. This is especially relevant where tenter clips require a thicker, correctly shaped region of film or sheet for reliable clamping.
On BOPET and other demanding biax processes, the edge profile can influence clip engagement, clip-outs, film breaks and usable width. A well-resolved edge signal gives operators and control logic a clearer view of the transition between the product profile, tenter-grip region and excluded trim.
Important boundary: Edge performance comes from the complete low-energy X-ray measurement architecture, including footprint, sensor response, scanner positioning, sampling and configured edge processing. It should not be reduced to an unconditional claim that X-ray physics alone solves every edge problem.
Define whether production accepts an X-ray mass response, a calibrated thickness result or another qualified output.
Density, fillers, cavitation, layers and formulation changes still belong in the calibration review.Agree which edge regions are measured, trended, controlled, alarmed or excluded.
One universal edge cutoff can hide the condition the line is trying to manage.Effective resolution depends on the full measurement and motion system, not sample spacing alone.
Review line speed, scan time, web flutter and the smallest profile feature that must remain visible.Use Scantech low-energy X-ray where total-film profile, edge fidelity and non-isotope operation match the production objective.
If a specific layer or constituent is the true target, define that requirement before selecting the measurement model.Need the physics-level comparison? Review X-Ray Transmission Web Gauging for measurement boundaries before treating any sensor label as the complete specification.
The published ranges overlap. Width screens the portfolio, but final selection also depends on passline, foundation, opening, service access, environment, sensor count and the mechanical demands at each measurement station.
Ultra-light O-frame starting point for cast or film sections where a compact full-pass-through frame fits the line.
Heavy-frame architecture for wider biax stations requiring greater span, stiffness and structural capacity.
Super-heavy frame for very wide measurement stations. The image shows the SHF3 platform with optional integrated visual inspection; dimensional gauging does not require the VI package.
The two stations do not need identical frames. A narrower cast section may fit ULO3 or HF3 while the expanded final film requires HF3 or SHF3. Select each station independently around its measured width, passline, opening, access and structural requirements.
FlexScan/APC can relate the measured profiles to the upstream automatic die, apply the qualified control model and coordinate corrections through Scantech Bolt Controller 3 or another approved actuator interface. Scantech publishes TDO stretch profile, mass conservation, melt-flow modeling and cascade control as biax capabilities; the exact model and loop architecture are application-engineered.
Die coordination: Gauge Advisor has worked with projects involving Cloeren, MAAG, Nordson EDI, maku, JCTIMES and other equipment suppliers. Final compatibility is confirmed from the exact die, actuators, electrical architecture, controls and drawings.
Operators need the cast profile, final-film profile, stretch behavior, edge rules and control status to remain distinguishable. Production and quality teams then need a configured history that can be retrieved after the roll is complete.
Configure the operator view around profiles, targets, edge exclusions, mapped zones, trends, alarms, control mode and the response following each qualified correction.
When TREX is included, it can retrieve, sort, categorize and collate archived production reports using configured tags. Report contents, identifiers, retention, user access and plant-interface requirements are defined in the project scope.
Plant connectivity: Scantech publishes OPC UA as standard for the biax system architecture. Final tag ownership, PLC logic, cybersecurity, retention, remote access and higher-level interfaces remain project-specific.
A two-scanner project succeeds when the line drawing, stretch sequence, accepted result, edge objective, die authority and data workflow are reviewed together.
Define what the system must measure and what production releases.
Describe how material coordinates change through the line.
Confirm each web can be measured safely and repeatably.
Separate the regions instead of applying one generic edge cutoff.
Document what hardware can make the correction.
Agree how operators and quality teams will use the result.
Scantech reports that two-scanner biax systems can support more reliable mapping, faster and more stable control and better process insight. Actual results depend on the starting line, film recipe, measurement model, die condition and commissioning.
Relate the expanded final-film profile to the correct upstream material and control zones.
Use qualified mapping and cascade feedback instead of repeated manual interpretation.
Monitor the grip-band shape and edge behavior associated with clip stability and usable width.
Connect live profiles and control behavior with configured TREX history and roll reporting.
Basis weight and physical thickness are not always interchangeableDensity, filler, foam, cavitation and layer changes can change the relationship. Specify the accepted measurement result.
Edge data needs a declared purposeGrip band, edge bead, trim and saleable width may need different trend, alarm, mapping and exclusion rules.
Measurement does not create actuator authorityAutomatic correction still requires a compatible die, sufficient response, safe modes and commissioned control limits.
Use the equipment hub for the complete Scantech platform, the APC page for detailed die-control scope and the film and sheet pillar when the broader process path is still open.
Review scanners, measurement technologies, FlexScan, TREX, plant integration and optional control as one production system.
Explore web gauging → Automatic die-control pageGo deeper into mapping, process delay, BC3, die compatibility, retrofit inputs and control acceptance.
Explore automatic control → Extrusion process pillarConnect biax measurement with cast film, sheet, blown film, web handling and the wider Gauge Advisor offering.
Explore film and sheet solutions →Gauge Advisor can organize the product, scanner stations, edge objective, measurement model, die, controls, data and acceptance inputs; coordinate Scantech application review; and turn the project into a clear, reviewable project scope.