Thickness Tester for Plastic Film and Paper QT-FTH

Operating Principle of Mechanical Contact Displacement

Manual thickness gauges relying on operator finger pressure compress soft polymer layers and flatten the microscopic air spaces inside fibrous paper sheets, producing inconsistent, skewed data. The Qualitest QT-FTH Thickness Tester for Plastic Film and Paper (a core model in the Qualitest Film and Paper Thickness Gauges line) eliminates this variance by determining substrate thickness through vertical linear displacement under a calibrated gravitational dead weight:

Thickness (t) = z_specimen - z_zero

Where:

• z_zero is the baseline zero position recorded when the circular measuring head rests directly on the bare lower anvil.
• z_specimen is the vertical elevation registered when a test specimen is placed between the two flat contact surfaces.

          [ High-Resolution Linear Displacement Sensor (0.1 µm) ]
                                    │
                         ┌──────────┴──────────┐
                         │ Calibrated Gravity  │  <── Constant 0.4 N Test Force
                         │  Dead-Weight Load   │
                         └──────────┬──────────┘
                                    │
                              ┌─────┴─────┐
                              │Measuring  │ (Standard Foot: Φ6 mm / Area A)
                              │Head Tip   │
                              └─────┬─────┘
  ──────────────────────────────────┼──────────────────────────────────
  ═══════════ [ Specimen: Film, Paper, Foil, or Non-Woven ] ═══════════
  ──────────────────────────────────┬──────────────────────────────────
                              ┌─────┴─────┐
                              │Lower Anvil│ (Optically Flat Solid Base)
                              └───────────┘

Regulated Contact Pressure Mechanics

Because plastic packaging films, paperboard plies, silicon wafers, metal foils, and non-woven textiles exhibit springy, compressible behavior under mechanical loads, raw thickness readings drift whenever contact geometry shifts. Standardized testing protocols eliminate this distortion by enforcing a strictly regulated Contact Pressure (P):

P = F / A

Where:

• F is the gravitational dead-weight load (factory-calibrated to 0.4 N on the QT-FTH).
• A is the contact surface area of the circular measuring head (standard Φ6 mm flat face).

Lowering a constant dead-weight foot with a cushioned, motorized drop prevents crushing the microscopic air pockets inside paper fibers or stretching soft polyolefin films, delivering dead-on consistent caliper readings across every batch.

Testing Methodology and International Standards Compliance

The Qualitest QT-FTH executes standardized mechanical contact test methods in full alignment with international standard specifications across various industrial substrates:

Physical Variables Affecting Mechanical Thickness Accuracy

To secure clean, repeatable data complying with ASTM D6988 or TAPPI T411 requirements, testing routines must control for five mechanical and environmental factors:

               ┌──────────────────────────────────────────────┐
               │    FIVE CRITICAL ACCURACY CONTROLS           │
               └──────────────────────┬───────────────────────┘
         ┌──────────────┬─────────────┼─────────────┬──────────────┐
         ▼              ▼             ▼             ▼              ▼
  [Gentle Descent] [Settling Dwell] [Clean Anvils] [Climate State] [Cross-Web Steps]
  Pneumatic buffer Allows creep to  Wiping dust    Stable 23°C /   Automated multi-point
  prevents impact  stabilize        specks clear   50% RH balance  stepping (0-100 mm)

• Kinetic Descent Velocity: Dropping a weighted foot too fast onto thin polymer film generates an impact force that momentarily exceeds the nominal load rating, creating local indentation. The QT-FTH uses an external pneumatic supply to cushion the descent, lowering the foot smoothly at a controlled speed (under 3 mm/s).
• Viscoelastic Creep and Dwell Duration: Viscoelastic polymers and porous paper webs experience time-dependent compression under sustained load. Standardized testing incorporates a steady dwell interval (typically 2 to 5 seconds) to let the substrate stabilize before the sensor locks in the measurement.
• Anvil Parallelism and Surface Cleanliness: When operating at a 0.1 µm resolution, microscopic dust specks or surface angular deviations generate false peaks. The QT-FTH uses diamond-lapped, optically flat contact faces that must remain wiped clean of debris.
• Thermal and Hygroscopic Equilibrium: Paper webs absorb ambient moisture from surrounding air and swell, while polymer films expand with room temperature increases. Samples require climate pre-conditioning (23 ± 2°C, 50 ± 5% RH per ASTM D618 / ISO 187).
• Transversal Profile Variance: Single spot checks fail to detect cross-direction gauge bands caused by extrusion die adjustments or papermaking flow variations. The QT-FTH integrates automated specimen feeding to take sequential measurements across the entire cross-web profile.

Method Execution on the Qualitest QT-FTH

The Qualitest QT-FTH Thickness Tester for Plastic Film and Paper puts mechanical contact theory into practice through the following operational parameters:

• Measurement Span and Resolution: Measures sample thicknesses from 0 to 6 mm with a digital sensor resolution of 0.1 µm, accommodating ultra-thin plastic diaphragms, packaging sheets, paper, silicon wafers, metal foils, and corrugated board.
• Standardized Contact Configuration: Operates with a factory-set 0.4 N measuring force applied across a flat Φ6 mm measuring head, with custom anvils and dead-weight loads available for specialized paper and textile standards.
• Dual Operational Modes:
  • Manual Mode: For single-point spot checks on standalone sheets or irregular specimens.
  • Automatic Multi-Point Mode: Performs automated step testing across 1 to 30 measurement points with a user-adjustable injection feeding distance of 0 to 100 mm.
• Pneumatic Descent Control: Eliminates operator technique variation and mechanical shock through an automatic pneumatic lifting and lowering mechanism (requires user-supplied compressed air).
• Real-Time Data Display and Statistical Output: The integrated backlit LCD tracks live testing and automatically calculates maximum, minimum, and average thickness values. Results can be output via the onboard microcomputer thermal printer or linked to a laboratory PC for data logging.
• Physical Specifications: Compact benchtop unit measuring 410 mm × 310 mm × 340 mm at 19.5 kg, operating on an AC 220 V, 50 Hz (or 110 V) electrical supply with a low 100 W energy draw.