FAQ: Is it possible to prevent the momentum of a linear motion system from carrying the table (or carriage) past a limit switch?
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The Sigma II amplifier is very robust and protects the motor from harming itself. The Sigma II has overtravel functions built-in to the amplifier, but it is important to understand the settings to use the overtravel feature.
The Sigma II offers three options which are set in Pn001.1:
1 & 2) Pn001.1=0, will stop the travel the same way a servo OFF or alarm stop mode (Pn001.0) is handled. This may be a coast or a Dynamic Brake.
3)Pn001.1=1, will stop the travel by using the Emergency Stop Torque (Pn406) to stop the motor.
The Dynamic Brake and the Emergency Stop Torque are the fastest ways to stop the motor. The "dog" or pickup for the overtravel switches, especially on fast moving machines, should be sufficiently long enough so as not to over shoot the switch and end up in a dead zone. If an overtravel occurs (input goes low) the drive will automatically begin to stop the motor. If the momentum moves the table beyond the switch while stopping, the overtravel will be reset and the motor will try to continue to the move. This may cause damage to the system mechanics.
An overtravel can be latched in the controller through programming. When programming a controller like the MP940, caution must be taken to set up the overtravel detection handling within the supervisory program. The program needs to prevent any movement in the direction of the overtravel, but must also allow the operator to jog back off the switch in the opposite direction.
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Please read and understand the product instruction manual before installing, servicing or operating Yaskawa products. FAQ content and illustrations are provided as technical advice to augment the information in manual, not supersede it. It is not possible to give detailed instructions for all types of installation or support activities. The information described in the FAQs are subject to change without notice to improve the product or FAQ. Yaskawa assumes no responsibility for errors or omissions or damages resulting from the use of the information contained in any FAQ. All warnings, cautions and product instruction for product use must be followed. Installation, operation and maintenance should be carried out by qualified personnel. Failure to observe these and other precautions highlighted in the product manuals will expose the user to high voltages resulting in, serious injury or death. Qualified personnel are defined as individuals who are familiar with the installation, starting, operation and maintenance of Yaskawa products of the type described and have proper qualifications to perform the work.
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