We have developped an automatic loading machine for vacuum metallization painting line system considerring its great improvement to reduce labor works. When it’s well programmed and everything well tested for live production, suddenly some day we found the automatic loader can not put objects properly to chain spindle. After inspection on each unit carefully we finally found its due to the chain pitch elongated during operation.
Technically speaking, the painting line system is a high precision setup which should be always accurate in mechanical structure. Among all the components, conveyor chain is the most crutial part as it will carry all spindles and products to pass through various treatment stations. Elongated chains in painting lines will directly trigger a series of cascading failures in terms of machinery, processes, and safety. Specific consequences include:
Loss of Transmission Accuracy and Positioning Deviation
Increased chain pitch due to wear on the pins and bushings leads to inaccurate meshing of the sprocket teeth, causing inching, lag, or displacement deviations in the workpiece during transport. In high-precision painting lines, this deviation will directly cause misalignment between the spray nozzle and the workpiece surface, resulting in uneven coating thickness, runs, missed areas, or re-spraying, severely reducing product appearance quality and yield.
Especially if we install the automatic loading machine for a paint line, the loader can not put the pieces properly if the chain pitches are vary on every spindle. The reason chain pitch changes mostly is because the heat in dryer after long time operation. This happens more frequently if the dryer has a high temperature inside. Especially when the chain does not have properly heat treatment, the elongation or any other phenomenon will come out much earlier and more frequently.
To fix this, we firstly need to select a suitable chain for our paint line. Secondly need to ensure the chains for this paint line construction meets the operation requirements and well tested from supplier. Thirdly, we must have a good maintenance plan for our conveyor to make sure it’s smooth running.
If we do not have sufficient understanding of chain conveyor, the problem will be produced at the very start of paint line construction. Following is a list of chain issures we collected:
Increased Risk of Chain Derailment and Tooth Skipping
Elongated chains result in insufficient meshing depth between chain links and sprocket teeth, easily leading to tooth skipping, tooth climbing, or even chain derailment. In continuously operating painting lines, chain derailment can cause workpieces to suddenly stop, overturn, or fall, damaging not only the workpiece but also potentially injuring equipment or personnel, causing unplanned downtime.
Abnormal Equipment Load and Increased Energy Consumption
As the chain lengthens, frictional resistance increases, requiring the transmission system to output additional torque to maintain speed. This leads to drive motor overload, abnormal reducer temperature rise, and accelerated bearing wear. Long-term operation results in increased energy consumption, shortened equipment lifespan, and significantly increased maintenance costs.
Deteriorating Noise and Vibration
Poor chain-sprocket meshing generates high-frequency impacts, accompanied by metallic clanging noises and structural resonance, affecting the workshop environment. Simultaneously, vibrations are transmitted to precision components such as the painting robot and spray gun holder, interfering with the stability of the spraying trajectory and further reducing coating consistency.
Additional Risks of Rust and Contamination
In pre-treatment stages (such as phosphating and electrophoresis), if the chain lengthens due to poor lubrication, its exposed metal surface is susceptible to acid and alkali corrosion, resulting in rust flakes. Rust particles mix with the paint or adhere to the workpiece surface, forming point defects, pitting, or adhering impurities, directly contributing to paint film failure.
Replacement Threshold and Maintenance Window
Based on industrial field experience, when the chain elongation exceeds 1000mm (based on the total line length), it is considered severely worn and must be replaced immediately. Routine maintenance should include quarterly preventative checks using a chain elongation meter or the pitch measurement method (measuring the deviation of 10 chain links from the theoretical value)
