Servo Motor Repair
Servo motors offer excellent power and efficiency in a small package. While they have some similar elements to AC/DC motors, they also have a positioning device that provides feedback for enhanced control in a closed-loop system. For these reasons, they are integrated into equipment across a wide range of industries, especially where precise control over speed, rotation, speed, and torque is required (e.g., CNC machining units).
Repair Process for Servo Motors
Given the important role servo motors play in many industrial devices and systems, it is vital to keep them in proper working order and, if they do break down, get them up and running quickly. Generally, repair operations proceed as follows: evaluation, disassembly, cleaning, bearing change, and final testing. During the initial evaluation stage, the repair technician conducts a thorough inspection of the system to pinpoint any problems. The unit is disassembled, cleaned, and the necessary components replaced. The final steps are reassembly and testing.
Common Servo Motor Problems
Servo motors are often subjected to harsh operating or environmental conditions, which can lead to a variety of issues that cause a breakdown, such as:
- Dusty brakes
- Bearing failures
- Winding issues
- Damaged cables
- Component failures
- Positioning errors due to encoder issues
Circuit Board Repair
Circuit boards serve many functions in CNC machinery. For example, they are used for control, communication, motion, input/output (I/O), and programmable logic controller (PLC) applications.
Repair Process for Circuit Boards
If and when a circuit board stops working in a CNC machining unit, repairing it is usually more cost-effective than replacing it. The first step in the repair/replacement process is evaluating the unit; the technician thoroughly analyzes the unit to diagnose the issue.
- If the issue is fixable, then the technician provides a quote to the customer. If the client accepts the quote and approves work, they complete it as indicated.
- If the issue is not fixable, then the technician may recommend replacing the unit.
Common Circuit Board Problems
Circuit boards can experience a number of problems that affect the operation and performance of CNC systems, such as:
- Memory loss
- Data corruption
- Servo control or I/O functionality interruptions
- Power supply issues
Encoders are electromechanical devices used to monitor motion within a system. They are critical for operations that require users to closely observe the direction, speed, and location of objects and equipment. Types available include linear, rotary, angled, absolute, and incremental.
Repair Process for Encoders
Any encoder repair operation begins with an evaluation of the equipment. The technician inspects the unit to determine the source of the issue. Then, they detach the encoder from the motor, repair, clean, and realign the optics (if needed), replace the bearings (if needed), and reattach the encoder to the motor. Finally, they test the unit to ensure it runs to OEM specs.
Common Encoder Problems
While users commonly assume incorrect encoder signals stem from encoder problems, they are often caused by mechanical or environmental factors. Typical encoder signal issues include:
- Extended pulses
- Signal jitter
- Stepped pulses
- Very low amplitude signals
- Delayed signal rise time
- Signal flicker jump
Power Supply Repair
CNC machining equipment needs continuous and consistent power to perform precise and accurate operations and achieve maximum productivity. Any issues with the power supply can negatively affect the quality of products and the efficiency of processes.
Preventative Maintenance for Power Supplies
Preventative maintenance is key to ensuring the power supply for a CNC machining unit runs without problems. Typical preventative maintenance operations may include:
- Cleaning and replacing fans
- Removing buildup (e.g., dust) from heat sinks
- Inspecting and replacing pin connections
- Checking the integrity of cold solder joints
- Evaluating the condition of wear components
Considerations When Selecting a Power Supply
In addition to keeping a power supply well-maintained, it is important to use the right power supply for the particular CNC machining unit. Otherwise, it may not operate or perform as expected. Some of the factors to consider when selecting a power supply include:
- Peak power requirements
- Load and line regulation
- Physical volume and weight
- Installation and maintenance cost
- Regen control capability
Spindle Drive Repair
Spindle drives are designed to convert the power created by the motor into feed velocity and force. They have an integrated axial bearing that allows them to handle high axial loads. They are available in AC and DC variations.
Repair Process for Spindle Drives
The repair process for spindle drive can vary depending on the issue and how far it has progressed. For example, if the problem is small, reversible, and caught early, it may be possible to resolve it in-house. However, if the problem is significant, it most likely needs to be addressed by a spindle technician.
Common Spindle Drive Problems
Below, we highlight common problems with spindle drives, some of which can be fixed in-house and some of which need professional repair or parts replacement.
- Incorrect parameter settings
- Main power disconnect
- Oversized transformer
- Poor drive input power connections
- Broken resistor
- Defective spindle encoder
- Loose motor or electrical junction box connections
Resolvers are electromagnetic transducers commonly used in position and velocity feedback applications. They offer good performance in high-temperature conditions, which makes them well-suited for use in servo motors.
Troubleshooting Resolver Problems
Troubleshooting tips to follow if a resolver is experiencing problems include:
- Check the resistance measurement. Check across the white cable for the resistance of primary windings, the yellow and blue cables for the resistance of the sine coil windings, and the red and black cables for the resistance of the cosine windings. The sine and cosine coil resistance values should be the same. The excitation coil resistance should be different.
- Check the input voltage. If the resistance measurements are correct, check the input voltage. If it is low, the issue is the resolver interface card.
- Check for cabling loss. If there is a voltage drop at the resolver interface but not at the output cables, there is cabling loss.
- Check axial and radial offsets. Use a dual-channel oscilloscope to test for axial or radial shifts. These can be caused by improper resolver installation, system tolerance buildup, or hardware defects.
Monitors allow users to keep track of the performance, production efficiency, and resource analysis within CNC equipment. As such, they help ensure the units are working as intended.
Common Monitor Problems
Typical problems that may occur in monitors include:
- Dim or burned CRT screen
- No picture
- Monitor won’t power up
- Broken controls
- Garbled data
- Failed components
Controllers act as the links between the computer system and industrial equipment. CNC units cannot operate without them, which is why it is necessary to keep them properly maintained. Well-known manufacturers of controllers include Fanuc, Siemens, Landis, Allen Bradley, Okuma, Mazak, and Yaskawa.
Common Controller Problems
Problems that often arise in controllers include:
- Damage to workpiece edges when cutting
- Vibration or chattering
In CNC equipment, transducers track machine motion and convert the measurements to electrical input/output for submission to the controller. This information helps improve machine accuracy and prevent errors.
Considerations When Selecting a Transducer
Due to the vital role transducers play in CNC equipment, selecting the right ones for the particular application is important. Factors to consider when choosing transducers include:
- Index channel
- Desired resolution
- Cable length
Common Transducer Problems
Even if the right transducer is integrated into CNC equipment, it may still experience some problems that affect its operation and/or performance, such as:
- Incorrect output
- No output
- Worn ball bearings
- Particle contamination
- Moisture intrusion
- Heat damage
While the keypad may seem like a minor component, it is essential to the operation of CNC equipment; it allows users to input information that alters the operation and/or performance of the unit to better suit current requirements and restrictions. For this reason, it is critical to take steps to keep it in working order.
Common Keypad Problems
Some common keypad problems include:
- Sticking buttons
- Buttons not actuating
- Keyboard buffer overflow
- Outdated firmware
- Loose or damaged cable connections
Contact Us for Your CNC Electronics Service & Repair Needs Today
If you need assistance repairing and servicing your CNC electronics, Rubin Engineering & Sales is the ideal partner. We offer repair capabilities for servo motors, circuit boards, encoders, power supplies, spindle drives, resolvers, monitors, motor controllers, transducers, and keypads from a range of brands and manufacturers. Request a quote to get started on your solution today.