Adjust Belt Tension


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Adjusting the Belt Tension on the Mark Two for Optimal Performance

The print head on your Mark Two printer is moved using a system of motors, pulleys, and belts.  For optimal operation, it is important that belt tension is maintained at the correct level.  High belt tension will contribute to premature bearing wear.  Low belt tension can lead to reduced printing accuracy and/or dislocation.

Belt tension is adjusted at the factory using an expensive meter to measure the audio frequency of the belt when it is plucked.  There is a direct relationship of belt tension to frequency and this is a well established method.

Since belts may stretch over time, it is recommended that users occasionally (every 100 prints) measure belt tension and adjust as necessary. This can be done with any device that allows you to measure audible frequencies. One inexpensive option is to use a mobile device equipped with the $4 Cleartune app.  This application is designed to tune musical instruments but it can also be used as a very capable and accurate frequency meter.

To adjust the belt tension on your Mark Two Printer:

  1. Install and open the Cleartune app on your mobile device.
  2. Within Cleartune settings, set the "Needle Damping" field to the "II" position and turn on the "Frequency Display" option.
  3. Manually place the print head in the far back left corner.



  4. Place your phone's microphone close to, but not touching the back belt.  Pluck the front stretch of the back belt, as if it were a guitar string. Adjust the rear belt tensioner until a frequency of 49Hz is read by the app.



  5. Manually place the print head in the front left corner.
  6. Place your phone's microphone close to, but not touching the front belt.  Pluck the back stretch of the front belt, as if it were a guitar string. Adjust the front belt tensioner until a reading of 62Hz is obtained.

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Learn More About Adjusting Belt Tension

A few hints for best results:

  • Make measurements in quiet surroundings.
  • Place your phone's microphone close to, but not touching the belt.
  • If you cannot count on a quiet environment, consider investing in a shotgun condenser microphone to plug into your mobile device.
  • Do not over pluck the belt such that it vibrates against the gantry plate. When you initially pluck the belt, it will produce harmonics at multiples of the fundamental frequency. These quickly die off and you are left with only the fundamental frequency. For this reason, ignore early readings that appear to be a multiple of your target. With a little practice you will obtain highly repeatable and accurate results in less than two minutes.

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