Lead screw transmission inevitably has lead errors. However, cumulative errors and sectional errors bring totally different dynamic impacts to the system. Cumulative errors expand positioning deviations gradually along the travel stroke, while sectional errors sharply break motion stability in local areas. Most engineers only focus on the overall tolerance of the whole screw, yet overlook that sectional fluctuation is the main cause of vibration and noise.
Cumulative lead error refers to the total deviation of lead across the entire screw length, representing a long-term trend that total displacement error accumulates as the stroke increases. Sectional error only measures the maximum fluctuation of local lead against the theoretical value, without error transmission or accumulation over the full length.
1. Different Impacts on Positioning Accuracy
Cumulative error makes the actual position of the worktable drift further away from the commanded value as the stroke extends, resulting in systematic positioning drift. Sectional error causes periodic or random position jitter within a local stroke, leading to instant instability of repeat positioning accuracy in short travel ranges.
2. Disturbance to Speed and Acceleration
Cumulative error changes gently and barely affects instantaneous speed, but it causes a fixed deviation between the actual average speed and the set speed. Sudden lead changes from sectional error trigger frequent speed fluctuation and instantaneous acceleration impact, which easily arouse mechanical vibration and noise in the transmission system.
3. Different Compensation Methods
Cumulative errors are generally corrected point by point via lead error compensation tables or full-stroke linear calibration. Sectional errors cannot be eliminated by global linear compensation. They need to be suppressed by improving local grinding craftsmanship, optimizing raceway uniformity or adopting closed-loop control to reduce short-cycle fluctuations.
4. Long-term Effects on System Stability and Service Life
Cumulative error forces the servo system to continuously output static correction torque, increasing the thermal load of motors and drivers, while mechanical wear remains relatively even. Sectional error subjects local balls and nuts to repeated impact loads, accelerating contact fatigue and pitting, and eventually causing premature component failure.
