The variable frequency feeder is the "precise feeding valve" of the quartz
sand production line, which achieves stepless control of the feeding amount
through variable frequency adjustment (requiring feeding accuracy error ≤ 5%).
If the feeding accuracy is low (with an error of over 10%) and there is a large
start stop impact (material spraying during startup and accumulation during
shutdown), it will cause downstream equipment load fluctuations and uneven
product quality. Based on practical experience, summarize the three-step
troubleshooting method to quickly restore accurate and stable feeding.
Step 1: Calibrate the frequency conversion control system - the electronic
core determines the accuracy
Abnormal parameters of the frequency converter and sensor feedback are the
main reasons for low accuracy.
Improper setting of frequency converter parameters: acceleration time is too
short (<3 seconds), sudden increase in motor speed leads to material
spraying; Insufficient deceleration time (<2 seconds), accumulation caused by
inertia pushing during shutdown; The V/F curve does not match the motor,
resulting in insufficient torque at low speeds and intermittent feeding. Reset
parameters: set acceleration time to 5-8 seconds, deceleration time to 4-6
seconds, select "constant torque V/F curve" to ensure sufficient torque at low
speeds (below 10Hz); Activate the "slip compensation" function to reduce the
impact of speed fluctuations on the feeding amount.
Sensor feedback delay or malfunction: The response time of weight sensors
(such as belt scales) exceeds 0.5 seconds and cannot provide real-time feedback
on the feeding amount; The zero drift of the sensor (displaying over ± 2kg when
empty) leads to measurement deviation. Calibrate the sensor with standard
weights and adjust the zero offset to within ± 0.5kg; Replace high-precision
sensors with a response time of ≤ 0.2 seconds, form a closed-loop control with
the frequency converter, and adjust the feeding speed in real time.
Step 2: Check the mechanical transmission and feeding structure - Mechanical
adaptation to prevent impact
Abnormal structures of conveyor belts, drive rollers, and material troughs
can exacerbate impact and deviation.
Belt slippage or uneven tension: Insufficient tension in the conveyor belt,
insufficient friction between the drive roller and the belt, and delayed speed
transmission; Uneven tension leads to material deviation and excessive feeding
in certain areas. Adjust the tensioning device to achieve a tension of 15-20N/cm
on the conveyor belt, and use a tension meter to measure it; Install
wear-resistant rubber sleeves on the surface of the driving roller to increase
friction and avoid slipping; Install a belt correction device to ensure that the
deviation of the conveyor belt operation is ≤ 5mm.
Problem with the material blocking plate or lining plate in the material
trough: If the height of the blocking plate is too low (<10cm), the material
is prone to overflow; If it is too high (>20cm), the material will instantly
pour and cause impact when turned on; The lining plate is worn
(thickness<3mm), the material slides too quickly, and the feeding is
unstable. Adjust the height of the blocking plate to 12-15cm, and install rubber
buffer strips on the inside of the blocking plate to reduce material impact
during start stop; Replace the polyurethane lining board (thickness 8-10mm),
increase the friction between the material and the lining board, and make the
feeding uniform and smooth.
Step 3: Adapt materials and adjust operations - dynamically optimize to
improve stability
Improper material characteristics and operating modes can affect feeding
accuracy.
High moisture content or large particle size fluctuation of materials: when
the moisture content exceeds 10%, the material adheres to the material trough
and the feeding amount gradually decreases; The particle size fluctuates between
coarse and fine (such as 0.5-5mm mixed), the bulk density changes, and there is
a large deviation in the feeding amount at the same speed. Before feeding, add a
drying process (reducing moisture to below 6%) and install a screening machine
for grading treatment to ensure uniform particle size of the material entering
the feeder (deviation ≤ 1mm); If grading is not possible, activate the "adaptive
adjustment" function of the frequency converter and adjust the speed in real
time based on the feed amount feedback from the sensor.
Long term full load start stop or frequent switching: frequent start stop
(more than 5 times per hour), intensified mechanical impact, accelerated
component wear; Long term full load operation caused the motor to overheat,
resulting in the protection shutdown of the frequency converter. Optimize the
operating mode by adopting the process of "low load start (20% rated speed) →
gradual speed increase → stable operation → gradual speed decrease → shutdown";
To avoid frequent switching, if it is necessary to adjust the feeding amount,
use a frequency converter to gently adjust the speed (with each adjustment
amplitude ≤ 5Hz) to reduce impact.
Daily maintenance should pay attention to: clean the residual materials in
the conveyor belt and material trough every week, and check the connection
circuit between the sensor and the frequency converter; Monthly calibration of
frequency converter parameters and sensor accuracy, tightening of drive roller
and tensioning device bolts; Replace the wear-resistant rubber sleeve and lining
plate of the conveyor belt every quarter. By taking the above measures, the
feeding accuracy error can be reduced to within 3%, the start stop impact
amplitude can be reduced by 70%, and the stable operation of the quartz sand
production line can be ensured. If there are still problems, it is recommended
to contact the manufacturer to test the mechanical and electrical compatibility
and optimize the control program.