Hello, it’s Morio here!

Today on our deep dive blog, we’re going to discuss the critical issue of failures in rotary encoders within machine tools and the pivotal role they play in maintaining precision. Understanding the common causes and phenomena of failures is crucial for effective maintenance and troubleshooting. Let’s explore these causes and their effects comprehensively.

Common Causes and Symptoms of Failures:

1. Mechanical Damage
   • Cause: Impacts and excessive vibration can damage internal components of the encoder, notably the disk or code wheel. In environments like spring machining, the shock from cutting can impact the encoder. Rough handling during assembly, such as hammering, is also a known cause of failure.
   • Phenomenon: This can result in intermittent errors or complete loss of signal.
2. Wiring Issues
   • Cause: Loose connections, severed wires, or corrosion can occur.
   • Phenomenon: This leads to unstable signals or a total loss of output from the encoder.
   • Preventive Measure: Ensuring wires are securely fastened is a recommended approach to prevent such issues.
3. Electrical Failures
   • Cause: Overvoltage or power quality issues can lead to malfunctions.
   • Phenomenon: Damage to internal electronic components, frequent errors, or complete encoder failure.
4. Contamination
   • Cause: Entry of dust, oil, or other contaminants inside the encoder.
   • Phenomenon: Reduced accuracy in readings and generation of inaccurate data.
   • Note: Encoders are typically shielded by parts such as servo motor covers, making actual incidents rare.
5. Wear and Tear
   • Cause: Natural wear from prolonged use.
   • Phenomenon: Gradual decline in encoder performance, eventually leading to failure in delivering accurate positional information.
6. Thermal Effects
   • Cause: Excessive heat can affect the encoder.
   • Phenomenon: Deformation of internal materials and overheating of electronic components.
   • Preventive Measure: Implementing fan cooling in areas prone to thermal effects, particularly around motor feeds, is advisable.

Setting the Home Position: Encoders, being critical in position management, require home position (origin) setting when replaced. Two common methods are employed:

1. Magnet Contact Switch Method:
   • Process: A magnet placed on a specific encoder position triggers a contact switch as it passes, automatically setting this position as the home position. This setup auto-detects the zero point upon each startup, designed to react at specific mechanical positions (like the bottom dead center in eccentric shafts).
   • Advantages: Automation saves operator time, and the magnet-switch combination offers high precision and consistent home position setting. It also enhances system reliability due to clear physical feedback.
   • Disadvantages: Potential for mechanical wear or displacement errors due to physical contact. Environmental factors like strong magnetic fields or metal debris can affect switch operations.
2. Teaching Method:
   • Process: This manual method involves moving the encoder to the desired home position and ‘teaching’ the controller by pressing a ‘set zero’ button.
   • Advantages: Flexible adjustment as any position can be designated as the home position.
   • Disadvantages: More labor-intensive and time-consuming, requiring fixtures and potentially difficult to replicate the same home position consistently. Due to these complexities, home position setting is often handled by manufacturer technicians rather than machine operators.

This detailed exploration helps us understand the meticulous care required in handling rotary encoders and ensuring their optimum functionality in machine tools. Stay tuned for more insights into the intricate world of manufacturing technology!