Belt Frequency And Tensioning

What is the proper frequency to tune the belts? 

There are many opinions on the proper belt tension of a 3d printer belt system. The belt frequency may differ from one machine to another. Maintaining optimal tension is important for overall performance and frequency can effect speed and print quality. Mechanical and 3d printing issues can appear when belt tension is either too high, too low, or unbalanced. Common problems in print quality can be annoying but easily solved. Belt Frequency is based on belt tension and other things like:

• Belt Material
• Density
• Wear
• Temperature
• Belt Length

How tight should a 3D printer belt be?

Tighten the belt system until there is some resistance when pushed. Any slack should be removed. Belt tension should be similar to a rubber band stretching but over tensioning can increased belt wear.

CoreXY printers are known for their “belt stretch” issue that results in increased belt length and continuous maintenance. Repeated use may bring up issues such as:

• Inconsistent layers
• jagged or low quality prints
• Belt Ripple
• Decreased Quality

What to look For?

Loose belts are a common problem for users and cause a variety of issues. It may or may not be obvious that your 3d printer is experiencing issues. Belt tensioning defects can occur in finished prints as:

• Misaligned Layers
• Leaning or Lopsided Prints
• Holes And Misprinted Segments

Measuring Belt Frequency

A loose belt can result in layer shifts and other issues but measuring belt frequency and tuning can be done phone apps like Smart Tension or Gates. Gates is a popular belt manufacture of the GT2 belts. They also offer an app for measuring frequency. Other apps such as “Smart Tension.” calculate proper tension for your belt based on the design and length of the belt.

Calibrating Belt Frequency

Calibrating the frequency of a timing belt is similar to tuning a guitar. Pluck the belts as you would strum a guitar string until you match the tone to an appropriate frequency. It may not be the most accurate but It’s worth the time. Due to the range of belt materials and temperature it may be challenging to find that “sweet spot” frequency. 

While quality belts like Gates can be pricey. Most people use the most common and available belts they can find on Amazon or Aliexpress. These belts may not have any specs on material, tolerances and tensile strength. Although it may be challenging to find the proper frequency to tune to, it can be a good starting point to document a measurement.

Belt position and location may make different sounds and tones. The top belt may ring out more that the bottom side or vice versa. It may be better to move the carriage and gantry to the middle of the printer when taking measurements. Pluck each belt one at a time as you tighten your belts until they resonate to a desired frequency.

Misaligned Layers

Outer wall layers  look slightly uneven and slight irregularities across the surface. Loose or unevenly tightened belt. It may not be immediately visible but becomes apparent once completed. Watch closely as the print progresses through different stages.

Misprinted Segments

Loose belts can result in misprinted segments or holes in in printed parts. Check your machines bolts and screws to make sure that pulley’s are tight and unobstructed. As they loosen over time they can cause the belt to lose tension. Print layers may not be uniform which results in misprinted areas and holes in a section.

Mechanical Belt Tension Causes

A variety of reasons why belts become misaligned or lopsided. The belt is connected to other components that could contribute to defects and faulty prints 

• Belt Friction
• Damaged Belt Drive Teeth
• Belt Slip
• Belt Rub
• Debris

Belt Friction

An improperly tightened belt can rub against the side of the belt track causing friction which leads to increased wear over time. Misalignment can result in terrible print quality.

Belt Slip

3D printers operate along X and Y axes that allow them to print in multiple dimensions. Each axis has a belt that moves along. Over time nuts and bolts loosen and  causing belt slack. If the tension on the belt is not tight enough it will slip out of position misaligning layers.

Pulley Teeth

Loose or missing pulley teeth can cause the jerky movements.  You’ll find misprinted segments or incomplete features in the finished print. Belt Rub belt misaligned or tightened it can rub against the track. The friction caused by repeated rubbing will wear the belt out quickly and result in defects. The friction can snap the belt over time.

Debris 

Dirt and debris can build up in the track of the pulley and belt itself. Extreme build up could even interfere with the motion. Check the belt system and pulleys to eliminate any debris.

Belt Slip

Belts loop around pulleys and one side could slip off out of place, causing it to tighten more on one side. This will result in misaligned layers and your print will likely come out lopsided.

Measuring Deflection

You can measure deflection from the resting position of your printers belt with a ruler or scale. Check the exact length of the deflection distance to get a measured number tension.

• By Feel
• By Sound 
• Use a Ruler to measure Tension and Deflection
• Phone app
• By prints

Adjusting Belt Tension

Adjusting belt tension may be different on every machine. Methods may vary depending on size and mechanical configuration. This may be as simple as tightening a few screws or minor adjustments. A common method is to press down on the belt and tighten until you feel the slop decrease. The belt should vibrate back and forth when plucked. It’s not fool proof but a decent starting point.  Experience will get you closer to that “sweet spot” over time.

• Press the belt until you feel resistance.
• Measure the distance between the belt’s resting height and the pressed down position.
• Adjust the tension as needed.
• Re-test the deflection number to find a repeatable distance.

Belt Material

Most belts are made from rubber or neoprene and reinforced with fiberglass. the rubber will stretch over time so you’ll have to adjust tension. steel core polyurethane, which will resist stretching but not quite as flexible as rubber belts making them more likely to snap.

Belt Pitch

Belt designs can vary in style and pitch. Pitch is the distance between the teeth. Most 3d printer belts have a 2mm pitch. Any distance above 2mm or 3mm could result in jerky movement and decrease precision. More high end belts are designed with curved teeth to minimize noise and resonance while reducing backlash to get smoother and accurate motion.

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