Today, I'll discuss the topic of backlash. I'll start with an explanation of what backlash is and why it's a problem. After that, I'll discuss strategies for mitigating backlash. Finally, I'll give a demonstration of our MRJ 5 servo's integrated backlash estimation function. Let's get started.
What is Backlash? In mechanical engineering, backlash (sometimes called lash, play, or slop) is a clearance or lost motion in a mechanism caused by gaps between parts. It can also be defined as an angle or distance through which any part of a mechanical system may move in one direction without applying force or motion to the next part.
Example: When cutting gears, it's impossible to make all the gear teeth perfectly. Gears will always be slightly too small, too big, or not quite the right shape. To compensate, gear designers intentionally make gears slightly undersized, adding clearance to the design. This clearance keeps the gears from binding and allows smooth spinning. However, when the gearbox changes direction, the output shaft remains stationary for a brief moment, causing an offset equal to the clearance.
Sources of Backlash: Backlash can be introduced by gears, reducers, indexers, ball screws, and couplings, leading to positioning errors that can hurt machine performance.
Mitigation Strategies: One way to mitigate backlash is by attaching a load-side encoder to your application. The encoder provides real-time feedback to the servo amplifier, allowing the motor to compensate for the backlash by operating off the machine's position instead of the motor's position. However, this solution increases the cost and complexity of the machine.
Another solution is to use the built-in backlash compensation function of the motion controller. This function allows the user to tell the controller the amount of backlash present in the machine. When the motor changes direction, it offsets the motion by the backlash amount, eliminating positioning errors. The drawback is that accurately measuring backlash requires special tooling and can be difficult or impossible.
Mitsubishi Electric’s Solution: Our MRJ 5 servo amplifiers feature a backlash estimation function. The function rotates the servo motor back and forth at four points along the machine's travel. By measuring motor feedback, the amplifier approximates the machine's backlash in about two minutes with just a few clicks.
Demonstration:
- Power on the amplifier and connect it to your PC with a USB cable.
- Open MR Configurator 2 and switch to online mode.
- Under the Diagnosis tab, select Gear Failure Diagnosis to open the estimation function.
- Adjust the parameters to fit your application and write them to the drive. Cycle the power.
- Click Start, and the drive will begin moving. In less than two minutes, the function will complete and show the estimated backlash.
To summarize, backlash results from clearances in a mechanical system due to manufacturing limitations, causing positioning errors. Our MRJ 5 servo amplifiers have a built-in function to quickly and easily estimate the backlash of your machine.
Lastly, thank you for watching this video. I hope you found it helpful.
Thank you for watching and please call (855) 737-4716 or fill out our online form you have any questions.