Adjusting the Belt Tension on the Mark One for Optimal Performance
The print head on your Mark One 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 an iPhone 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.
- Install Cleartune app on iPhone.
- Within Cleartune settings, set Needle Damping to the II position and turn on the Frequency Display option.
- Manually place the print head in the far back left corner.
- Place your phone's microphone close to, but not touching the back belt. Pluck (as you would a guitar string) the back belt and adjust the rear belt tensioner (as shown below) until a frequency of 49Hz is read by the app.
- Do the same for the front belt and adjust the front belt tensioner until a reading of 62Hz is obtained.
A few hints for best results:
- Make measurements in quiet surroundings.
- Place your phone's microphone close to, but not touching the belt. The microphone on an iPhone 6 is located right next to the headphone jack.
- If you cannot count on a quiet environment, invest in a shotgun condenser microphone to plug into your iPhone such as the MightyMic S iPhone Shotgun Video Microphone.
- 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.