Why Stepper Motors Lock & How to Disable?
Posted by Joey Weng on
Background
Stepper motors are commonly used as the power source in NEJE series devices. They can be in a "free" state (where the axis can be manually moved) or a "locked" state (where the axis is difficult to move manually) when not powered or not running. In GRBL mode, NEJE devices lock the stepper motors by default to maintain position information and prevent position loss during repeated engraving tasks. This design enhances the device's precision and stability, especially in scenarios requiring multiple processes or precise positioning.
Why Stepper Motors Are Locked by Default?
The primary reason for locking stepper motors by default is to ensure that the X and Y axis positions are accurately recorded and maintained when the device starts in GRBL mode. This locking mechanism provides:
**Prevention of Position Drift**: During engraving or cutting, locking the motor prevents position deviation due to external interference (e.g., manual movement).
**Support for Repeated Processing**: For tasks requiring multiple processes on the same workpiece, locking ensures the device returns to the original position, maintaining processing consistency.
The default locking is achieved through the GRBL configuration parameter `$1=255`, which means the motor remains locked indefinitely when idle (in milliseconds). If you are not comfortable with this setting, refer to the instructions below on how to disable it.
How to Disable Stepper Motor Default Locking?
If users find the motor locking inconvenient (e.g., preferring manual axis movement or finding the locking noise disruptive), the locking time can be adjusted or disabled by modifying the GRBL configuration. Here are the steps:
1. **Using Lightburn/LaserGRBL Software**:
- Ensure the device is in GRBL mode.
- After connecting the device, access the parameter settings via:
- **Lightburn**: Edit -> Machine Settings
- **LaserGRBL**: Menu -> Grbl -> Grbl Configuration
2. **Modify the $1 Parameter**:
- Locate the `$1` parameter, which is set to 255 by default (indicating indefinite locking).
- Change it to a smaller value, such as `$1=20` (releasing the motor lock after 20 milliseconds of idling), or set it to `0` to completely disable locking.
3. **Save the Settings**:
- After modifying, click the **Write** button to save the configuration. (Alternatively, you can enter the command `$1=20` in the Console and press Enter to confirm.)
4. **Reset GRBL Configuration** (Optional):
- If incorrect settings cause device malfunctions, you can restore the default configuration by updating the GRBL firmware or selecting “GRBL Setting Reset” in the NEJE control software.
**Note**: Modifying GRBL settings requires caution, as incorrect configurations may cause abnormal device behavior (e.g., axis inversion or mirrored operations). It is recommended to keep default values if you are unsure of parameter meanings or to back up the current configuration before making changes. If the device behaves abnormally (e.g., the motor fails to lock or release properly), you can reset the settings by updating the firmware via the NEJE Win software like below:
Common Concerns About Stepper Motors
**1. What to Do If the Stepper Motor Gets Very Hot?**
Stepper motors generate some heat during locking, which is normal because the motor driver continues to supply current to maintain torque. Here’s an explanation regarding temperature:
- **Reason for Temperature Increase**: When locked, the motor’s coils remain energized by the driver current, producing heat. The temperature typically rises gradually and stabilizes after a certain period (e.g., 30 minutes). If you touch the stepper motor and find it hot but can still hold it for more than 5 seconds, it indicates that the drive current is very close to 80% of the motor’s maximum drive current, which is the optimal setting.
**2. Should You Be Concerned About Temperature?**
It is normal for the motor to heat up when locked, and there’s no need to worry. If the motor becomes too hot to touch for more than 5 seconds, it may indicate excessive drive current, which could lead to overheating and damage. In this case, reduce the drive current by referring to the motor’s user manual or contacting the NEJE support team.
**3. How to Deal with Stepper Motor Noise?**
First, you have to learn that stepper motors have two states when stationary:
- **Free**: The axis can be easily moved by hand.
- **Locked**: The axis is difficult to move by hand.
In the free state, the stepper motor consumes no power. In the locked state, the motor has maximum torque and consumes the most power.
Modern stepper motor drivers typically use microstepping technology, which makes motor movements more precise. However, when locked at a specific position, the motor may produce noise, with the volume varying depending on the microstep position. This noise does not affect the device’s functionality. If the noise is bothersome, you can turn off the device’s power when not in use.
Conclusion
By following the above methods, users can adjust the stepper motor locking settings based on their needs while ensuring the device operates within a safe temperature range.
For further issues, it is recommended to contact the NEJE forum for support and provide screenshots of the device’s status for assistance.