SolidCore CoreXY
Belt Tensioning
What is the proper frequency to tune the belts? Belt tensioning is essential when it comes to tuning your corexy 3d printer build. Printing issues may appear when belt tension is either too high, too low, or even unbalanced?
CoreXY printers are known for their “belt stretch” issue that results in continuous maintenance. Repeated use may bring up issues such as:
- Inconsistent layers
- jagged or low quality prints
- Belt Ripple
Decreased Quality
But what is the science behind belt tensioning? Assuming there is ‘no one size fits all’ frequency and that it most likely depends on machine design and other factors that may affect speed and print quality. Common problem in print quality may be annoying but easily solvable
Belt Frequency is based not just on belt tension but also other things like belt material density/wear/temperature.
A loose belt can result in layer shifts and other issues. There are many opinions on belt tensions. An ideal belt frequency. Some say an audio spectrum analyzer phone app can be used to measure belt frequency in the tuning process. Gates, the name brand of GT2 belts, has 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. Calibrate the sound of the belt by plucking the belts to match it to the appropriate frequency. Just like a guitar tuner tuning the strings of a guitar. 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.
Quality belts like Gates can be pricey. Most people use whatever belts they can find from Amazon or Aliexpress. Without any specs on the belt tensile strength, you’ll never know what frequency to tune to. All you can do is match the belts to each other and hope the tension is within their tolerances. Frequencies measured from apps may result in false results
Your top of the belt may make a different sound than the bottom One side, is attached to a carriage or the other is 'longer' and makes a deeper sound. Which part should produce which frequency when plucked? Measured during calibration, I assume using some sort of calculation with stepper current/position.
Frequency is based not just on belt tension but also other things like belt material density/wear/temperature. Move the carriage and gantry to the middle of the printer and pluck each belt one at a time. Similar to tuning a guitar you need to tighten your belts until they resonate at a desired frequency. Mechanical issues can cause a more than allowable deviation and still produce great prints. Belt frequency is affected by belt tension other things such as:
- belt material
- density
- wear
- temperature
What to look For?
If your printer belt tension is off, it’s going to be very obvious in your completed print. You may even notice that something doesn’t look quite right as your design is being printed. Listed below are the print defects that are most likely to occur if your belt tension isn’t what it’s supposed to be.
- Misaligned Layers
- Leaning or Lopsided Prints
- Holes or Misprinted Segments
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.
Leaning or Lopsided Prints
The printer belt could be rubbing or blocking travel of the print head. If the head can’t travel the full range or one side of your print will be at an angle. Make sure the printer belt isn’t rubbing against anything before you get started on your print.
Holes or Misprinted Segments
Small holes or misprinted segments. make sure all bolts or screws and printer’s pulley are tight and unobstructed. As they loosen over time they can cause the belt to lose tension. Print layers will not be uniform, causing misprinted areas and holes in a section.
Decreased Quality
Layer lines become increasingly more visible with use. Loose belts are a common problem for users and cause a variety of issues.
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.
Misprinted Segments
Loose belts can result in misprinted segments and holes in the print
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 cause belt slack. If the tension on the belt is not tight enough it will slip out of position misaligning layers.
Pulley Teeth
If the pulley has a loose or missing gear will cause the jerky movements you will notice misprinted segments or incomplete in the printBelt Rub
A misaligned belt or 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 trapped in the belt or track can be enough to interrupt smooth motion. Check the belt and track to make sure it’s clear from debris.
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
- Mechanical
- Missing Teeth
- Belt Slip
- Belt Rub
- Debris
The Belt Has Slipped off a Pulley
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.
Belt Tensioning Methods
- By Feel
- By Sound
- Use a Ruler to measure Tension and Deflection
- Phone app
- By prints
Belt Tension By Feel
The most common method is pressing down on the belt with your fingers until it moves very little and vibrates back and forth quickly. It’s not foolproof but a decent starting point. Experience will get you closer to that“sweet spot” over time.
Measuring Deflection
You can use a ruler to measure deflection from a resting position. exact length of deflection. Deflection distance gives you a number to put on belt tension.
- Press down on the belt until you feel resistance.
- Use a ruler to 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
Test Prints
Most printers ship pre-calibrated to specific tension. run a test to make sure your belt tension falls within the proper range.
Adjusting Belt Tension
Methods may vary depending on the style and location of the printer.belt is attached to its axis differently. The belt that runs along the X-Axis of the printer runs directly through the Extruder, which releases the material that your print will eventually be made out of. move back and forth across the X-Axis belt. Most printing is along X-Axis travel, so tension issues will appear. This may be as simple as tightening a few screws, or disassembly.
Belt tensioners are a “quick-fix” way for belt slack. Mounting directly to the belt. It holds the excess slack on the belt so that it can be tightened without disassembly of any parts. Different Belt tensioners such as 3d printed or even spring Loaded Screw-On designs are available to increase the tension on the printer belt for adjustment.
Y-Axis belts typically don't take as much of the wear as X-Axis belts. You’ll most likely notice rubbing or slipping issues that can be easily fixed by tightening a few screws. Check the machines pulleys and gears to ensure nothing is loose or missing and that there is no dust or debris. Established proper tension and fixed any issues with the printer that may have been contributing to tension issues, you should immediately know.
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 Pitch” or the distance between teeth is either a 2mm or 3mm pitch .Any greater distance will result in jerky movements throwing off precision .
Teeth shape
Some newer belts are made with curved teeth opposed to the standard trapezoidal teeth. Curved teeth are designed to be stronger and more quiet. The cylindrical shape reduces backlash in the system. Less backlash results in smoother and more accurate motion.
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