What Transducers Do

      On CNC equipment, transducers are used to record actual machine motion for feedback to the controller, improving accuracy and preventing error. July 21, 2006

Can anyone explain the operation and use of rotary and linear transducers in CNC control systems?

Forum Responses
(CNC Forum)
From contributor M:
In CNC applications, a transducer measures physical motion, then converts that measurement to an electrical input/output. There are different applications of this technology, but the prevalent one is using the transducer in a closed loop environment. This insures that the actual movement of the CNC machine as commanded by the control, then encoded to the motor for that particular axis is, in effect, actually occurring. If the system was not closed loop and had no means to verify movement, potential problems that could occur would be:

1.) CNC control sends signal to encoder to count the revolutions of the axial motor and sends signal to the axial motor telling it to revolve, resulting in linear axial movement across the machine.

2.) The machine momentarily strikes a rigid portion of the machine or fixturing on the machine, momentarily causing the machine to physically pause its linear movement.

3.) Because the motor is designed to "clutch slip" in this case to prevent damage to the motor itself, the motor shaft at the encoder end keeps revolving and the encoder keeps counting.

4.) At the end of its movement the control thinks the correct revolutions of the motor have been executed, therefore assuming the axis has moved linearly correctly also. However, the actual linear physical movement is inaccurate because of the physical pause which occurred.

If a transducer of some type were added to this scenario, now all of a sudden a signal is sent back to the control verifying that the actual physical movement the control thought had occurred, in fact has not. An error would be generated within the control to prevent further movement until the condition is corrected.

From contributor C:
Talk to me about following errors. What are they and can I adjust my AC servos to get a better result?

From contributor M:
Following error is basically the result of the condition we discussed above. The main method of correcting or minimizing it, within servo driven closed loop systems, is adjustment of the servo/servo amplifiers. This process is commonly called "tuning." The process and technique can vary dramatically depending on machine manufacturer and servo/servo amplifier manufacturer. You will have to consult both of the above to get the specific process for your configuration.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Computerization

  • KnowledgeBase: Computerization: CNC Machinery and Techniques

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2019 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article