The calibration of the rebound testing machine needs to be carried out around four core modules: mechanical structure, measurement system, environmental control, and operation process. Combined with different industry application scenarios (such as rubber rebound, ball rebound, and building material testing), its technical requirements can be summarized as the following key points:
1、 Mechanical structure calibration
Positioning and clamping system
Positioning arm accuracy: Ensure that the distance between the sample's cutting point and the rebound plate is (1800 ± 2) mm (as per the standard GB/T14625.2-93 for measuring ball rebound height), and verify it with a laser rangefinder or high-precision ruler.
Symmetry of Fixture: The fixture needs to meet different sample sizes (such as rubber specimen diameter of 28.6829mm, iron rod diameter of 12.7mm), with adjustable distance up and down, and a left-right symmetry error of ≤ 0.5mm (refer to the configuration requirements of ball rebound testing machines).
Rebound board hardness and flatness:
Phenolic resin board hardness Shore HS80-HS90, thickness 25mm, or made of hardwood, rebound height error ± 2mm (ball testing machine standard).
In the rubber rebound test, the rebound plate must be a rigid metal plate with a surface roughness Ra ≤ 0.8 μ m (as required by ISO4662:2017).
Pendulum system (rubber rebound test)
The weight of the pendulum and pendulum: The total weight needs to be precisely controlled (such as a rubber testing machine pendulum with a total weight of 350g), and verified by an electronic balance.
Initial angle and release mechanism: The initial position angle deviation of the pendulum should be ≤± 0.5 °, and the release mechanism should have no frictional interference (ASTMD2632-15 standard).
2、 Measurement system calibration
Photocells and Sensors
Height measurement accuracy: Install photoelectric emission tubes and receiving tubes at positions such as 1000mm, 1200mm, 1500mm on the rebound plate, with a position error of ≤± 1mm (ball testing machine configuration).
Rebound height recording: high-precision displacement sensors (such as laser rangefinders) are used, with a resolution of ≤ 0.1mm and a sampling frequency of ≥ 1kHz (required for rubber rebound testing).
Polarization tube measurement: Install a photoelectric tube at the edge of the testing area to detect sample deviation (such as 370mm × 370mm in the ball test area), and automatically sound an alarm if the deviation exceeds the limit.
Force and angle measurement
Calibration of pendulum impact force: Use a standard force measuring instrument (range 20-200N, accuracy level 0.1) to verify the impact force, with an indication error of ≤± 0.5% (rubber rebound test).
Angle sensor calibration: The measurement error of the pendulum angle is ≤± 0.1 °, which is verified by a standard angle block or electronic level.
3、 Environmental control requirements
Temperature and humidity conditions
Rubber rebound test: temperature (23 ± 2) ℃, relative humidity (50 ± 5)% (GB/T1681-2009).
Ball rebound test: temperature 20-30 ℃, humidity 50% -70% (GB/T14625.2-93).
Building material rebound test: temperature (23 ± 5) ℃, relative humidity ≤ 80% (JJF (Shaanxi) 075-2021).
Barometric pressure and altitude
The accuracy of the pressure gauge is level 1.5, with a range of 0-0.16MPa and a minimum scale of 0.0025MPa (for ball testing machine configuration).
Altitude<2000m (required for rubber rebound test environment).
4、 Operation process and data processing calibration
Zero point and initial position calibration
Rubber rebound test: manually move the rebound hammer to the low point, confirm that the "zero position" LED is on, and press and hold the "reset" button for 2 seconds to complete the calibration (operating steps in the Zhihu column).
Digital display rebound instrument: when the steel anvil or concrete structure is hit, input the deviation between the mechanical value and the digital display value to complete the correction (Tiktok calibration method).
Repeatability and indication error verification
Repeatability: Measure continuously 10 times at the same position, with a standard deviation of rebound height ≤ 0.1mm (rubber rebound test).
Indication error: Compared with standard measuring blocks or force gauges, the error is ≤± 1% (JJF (Shaanxi) 075-2021).
Data recording and reporting
Automatically record the number of rebounds, height, and environmental parameters, and generate tamper proof blockchain reports (required by the intelligent system of Chemical Instrument Network).
Compliant with ISO/IEC 17025 standard, including measurement uncertainty assessment (e.g. extended uncertainty U=0.01mm, k=2).
5、 Industry specific calibration requirements
Rubber industry (ISO4662:2017)
The sample needs to be adjusted for 24 hours in a standard environment, with a hardness range of 30-85 IRHD.
The rebound height measurement needs to deduct the energy loss when the pendulum comes into contact with the sample (corrected by the standard curve).
Sports equipment (GB/T14625.2-93)
Balls need to be inflated to the specified pressure (such as 0.06MPa for adult basketballs) and tested after being left for 30 minutes.
A rebound height below 1000mm or above 1500mm is considered invalid testing.
Building Materials (JJF (Shaanxi) 075-2021)
The rebound tester calibration device needs to calibrate parameters such as the stretching length of the spring and the jumping position of the hammer.
The hardness of the steel anvil is 55-60HRC, and the surface flatness is ≤ 0.01mm.