MLX100: Recovering from a Soft Limit Alarm

MLX100:  Recovering from a Soft Limit Alarm

* This solution may also apply to the MLX200 platform as well.

When a soft limit is violated, the most common solution is to use the [Bypass Limits] button or open the Software Travel Limits.     However, if the soft limit and the hard limit are close together, these methods probably won’t work.   This document will explain 4 methods to recover from a MLX100 Soft Limit Alarm.    

Alarm Message

The RLx Error # 305 shown below states that there is a Motion Planner Error in R0 due to a Soft Limit Violation in axis 2, which is A02 on the Teach screen.  

Note that some of the text is not displayed completely. 
     Ext.  Desc. 1:   “…In Manual (Teach) Mode….”
     Ext.  Desc. 2:   “…then clear the fault.”

OPTIONS TO RECOVER FROM A SOFT LIMIT VIOLATION

1. [Bypass Limits] button

Normally, the [Bypass Limits] button on the Teach screen can be used to release the limits so that the robot can be moved out of the alarm condition.   However, there are conditions where this bypass will not work.

2. Open Software Limits

If the [Bypass Limits] button doesn’t allow recovery, the Soft Travel Limits can be increased or decreased on the Robot Configuration screen.    These values are in degrees.   Verify the axis position value on the Teach Screen and increase or lower the limits shown below so the current position is within the range of the limits.    Press the [Set Soft Limits] button to make the modified limit valid.    After jogging the robot to a valid position in the robot workspace, reset the limit value to its original setting.

3. Change the Home Position

If the first two options don’t work, it’s probably because the axis soft limit is too close to the hard limit.    For this case, opening the software limits won’t help.   The next option would be to change the Home Offset data on the Robot Configuration screen.     Refer to the picture in Option 2.

1. Take a picture of the current Home Offset data.
2. Press the [Get Offsets at Current Position] button.    This will update the Home Offsets display with the current position of the robot.    This data is in pulses, not degrees.
3. Enter the original Home Offset numbers for all axes except for the axis that is past the limit.  
4. Press [Save Home Offsets].
5. Jog robot to a position in the workspace that’s inside the limits.
6. Reset the Home Offsets to the original values, and press [Save Home Offsets].

4. Release the Brakes

For smaller robots, the axis brakes can be released to manually move the robot back to an acceptable position.   This is not recommended for large robots, because the weight of the arm could cause it to crash into something or cause physical injury to a person moving it.

To release the brakes, perform this operation:

1. Turn servo power off and release all E-Stops.
2. Switch the controller to the Manual mode.
3. Press the [Reset Safety Relay] button.
4. Select which axis or axes you would like to release the brakes on.   The bubble next to the axis number will turn red. 
5. While holding the Pendant Enabling Switch, press and hold the button to release the selected brakes.