Definition
A cardboard thickness tester is a specialized inspection device used to measure the thickness dimensions of cardboard, paper, and their related materials under specific pressures. The instrument is designed according to international and domestic standards, such as ISO 534, GB/T 451.3, etc., to ensure the accuracy and comparability of measurement results. Its core function is to quantify the thickness uniformity of materials, providing critical data support for product quality control, process adjustments, and compliance verification.
Measurement principle
The measurement principle of the instrument is based on contact displacement sensing. When measuring, the specimen is placed on a flat datum, and a circular foot gauge with a specified area and pressure is slowly lowered under standard conditions to make contact with the specimen surface. The sensor (usually inductive or grating) accurately detects the vertical displacement of the foot measurement, which is the thickness value of the corresponding specimen. The measurement process ensures that the pressure is constant and evenly distributed to avoid errors introducing compression deformation of the specimen. The basic relationship can be expressed as: T = D - Z, where T is the thickness of the specimen, D is the foot displacement reading, and Z is the zero point calibration value of the system.
Measurement method
Standard measurement methods typically follow these steps: First, calibrate the instrument according to standard requirements to ensure that the datum is parallel to the foot measurement and that the pressure is accurate. Secondly, a representative sample should be cut from the sample, and the specimen size should be larger than the foot contact area. The specimen is placed flat on the datum without tension, and the measurement program is started to make the foot measurement contact the specimen smoothly. After the specified holding time, the thickness reading is recorded. Repeated measurements are often performed at multiple different locations on the same specimen, with the final result expressed as an average and a coefficient of variation calculated to assess thickness uniformity.
Influencing factors
The accuracy of the measurement results is influenced by several factors. Instrumental factors include the magnitude and stability of the foot measurement pressure, foot measurement area, descent speed, calibration status, and the flatness of the datum. Environmental factors such as temperature and relative humidity can cause small changes in specimen size, and usually the test should be performed under standard temperature and humidity conditions. Operational factors include how the specimen is prepared, whether the placement is flat and wrinkle-free, and whether the selection of measurement points is representative. In addition, the properties of the specimen body, such as elastic recovery, surface roughness and material structure, will also have an impact on the measured values.
Applications
Cardboard thickness testers are widely used in papermaking, packaging, printing and quality inspection institutions. In the paper industry, it is used to monitor product thickness on production lines and optimize pressing and calendering processes. In the packaging industry, thickness is the fundamental parameter for evaluating the compressive strength, stiffness and calculating material costs of cartons. The printing industry relies on thickness data to adjust printing pressure and ensure post-processing accuracy. Third-party testing laboratories perform thickness tests against relevant standards and provide reports for trade and product quality certification.
Selection considerations
Choosing the right cardboard thickness gauge requires a comprehensive consideration of many aspects. The measurement range and resolution need to match the thickness specifications of the material to be measured. The foot measurement pressure and area must comply with the specific provisions of the implemented standards. The measurement accuracy and repeatability of the instrument are core performance indicators and should be confirmed by calibration certificates or verification data. The level of automation, such as automatic lifting, data statistics and computer software connectivity, can improve testing efficiency and data management capabilities. In addition, the structural rigidity of the instrument, ease of operation, maintenance costs, and the technical support and service of the supplier are also important considerations.