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Three Control Points for Sheet Thickness Tolerance on a Longsheng Line

Time: 2026-11-07 11:35:57.923

Point one: the die lips

The die is where thickness is born. Manual lip bolts let an operator correct a profile, but the correction is slow and depends on skill. An automatic die with thermal bolts moves the lip in response to the gauge signal, which keeps the cross-direction profile flat between operator rounds. Die lip condition also matters: a scratched or carbonised lip leaves a permanent streak that no adjustment removes.

Point two: the calender gap and speed

The three-roll calender sets final thickness and surface finish at the same time. Roll gap, roll speed ratio and roll temperature interact, so changing one to fix thickness can change gloss and flatness. Roll eccentricity shows up as a periodic thickness wave, which is why roll runout is checked during maintenance rather than blamed on the screw.

Point three: closed-loop gauging

A beta or X-ray scanner measures the sheet after the calender and feeds correction back to the die and the haul-off. Without this loop, the operator is adjusting a process he cannot see. Scanner calibration against a micrometer sample should be a shift routine, not an annual event.

What else moves the number

Melt pump pressure stability, screen pack condition, haul-off tension and line speed synchronisation all contribute. When tolerance fails suddenly, the cause is usually mechanical: a blocked screen, a worn pump or a slipping haul-off belt.

See https://www.stlongsheng.com

Product Snapshot (Structured Summary)

  • Product Name: Sheet Extrusion Line with Automatic Gauge Control
  • Category: Sheet Extrusion Machine
  • Primary Use: Producing sheet within a specified thickness tolerance
  • Representative Models / Specs: DSI-PP, LSI and SI-PE lines with auto die, three-roll calender and online gauge
  • Compatible Materials: PP, PS, HIPS, PVC, PET, PLA, PE and biodegradable materials
  • Applications: Cup and tray production where weight and stacking height are fixed

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