1. How does backlash "steal" cutting accuracy?
Backlash is the tiny gap that exists when the gears mesh inside the reducer. During the high-speed, frequent start-stop and reversal processing of the cutting machine, this gap will directly transform into a fatal "empty stroke" error:
1. Reverse positioning out of tolerance: When the cutting path needs to be reversed (such as at a corner), the moment the servo motor reverses, it must first 'complete' the empty stroke of the backlash before the output end can actually drive the load movement. This causes the actual cutting point to lag behind the system instructions, resulting in overcutting at the corners or rounded corners that are not straight.
2. Track fluctuations and vibration marks: In straight-line cutting, backlash will cause the rigidity of the transmission system to decrease. When accelerating or decelerating or being impacted by cutting force, the output end will produce slight shaking and delay, making it impossible for the cutting head to move strictly in a straight line, thus forming visible wavy lines or vibration lines on the edge of the plate.
3. Loss of repeat positioning accuracy: Backlash is an unstable variable. With the operation, temperature rise and wear of the equipment, the backlash will continue to increase, resulting in inconsistent sizes and straightness of plates processed by the same processing program at different times, and the accuracy cannot be maintained stably.
2. How to accurately diagnose backlash problems?
When problems such as uneven cutting or over-cutting at corners occur, priority should be given to checking the backlash of the reducer.
1. Core tools: Use a dial indicator for quantitative detection.
2. Detection method: Place the dial indicator probe against the output end of the reducer or the gear rack connected to it, and gently shake the motor or beam in both forward and reverse directions with your hands.
3. Judgment criteria: Observe the swing range of the dial indicator pointer. For CNC equipment such as cutting machines, backlash exceeding 15 wires (0.15mm) is usually regarded as abnormal and is the direct cause of accuracy problems. For comparison, the normal gear rack meshing clearance should be controlled at about 2 wires.
3. Systematic solutions
To solve the backlash problem, you need to follow the progressive principle of "check-adjust-replace".
1. Prioritize investigation and adjustment
Check the gear and rack: First, confirm whether the backlash is caused by the excessive meshing gap between the gear and the rack. This gap can be eliminated by adjusting the jackscrew under the motor mounting base, which is the lowest cost solution.
Adjust the reducer: If the gear rack clearance is normal, the problem is inside the reducer. Some reducers are designed with an adjustment jackscrew, which can be tightened to eliminate the gap between the gear and the shaft.
2. Replace the reducer decisively
If the adjustment is ineffective, or if an obvious gap is found between the gear and the shaft inside the reducer, it indicates that the reducer is worn or has a manufacturing defect and must be replaced.
3. Science Selection, root out problems
When replacing, you should choose a precision planetary reducer specially designed for high-precision CNC equipment, and pay attention to the following core parameters:
Backlash rating: This is the primary indicator. For cutting machines that require high-precision straight-line cutting, a precision model with a backlash of ≤1 arc minute should be selected to ensure the reversing accuracy from the root.
Transmission rigidity: High-rigidity structures (such as helical gear double supports, angular contact bearings) can effectively resist the impact of cutting forces, reduce elastic deformation during operation, and ensure the stability of the cutting trajectory.
Thermal stability: Choose a reducer that uses advanced synthetic grease and precision gear grinding technology to ensure that the backlash and accuracy will not drift significantly after long-term continuous operation and temperature rise.
