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3D Printer Belt Tension: Everything That You Need to Know

3D Printer Belt Tension: Everything That You Need to Know | 3D Printing Spot

Updated by

William Stone

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September 16, 2021

3D printer belts may be small, but they are the main movers of the major parts of a 3D printer. They are also responsible for allowing the printing elements to run smoothly as they produce the requested design. What you may not know is that the amount of tension on the belt during the printing process also plays a major role in the quality of the printed item.  

Achieving proper tension on a 3D printer belt is essential for getting high-quality prints. Loose tension on a printer belt throws off the accuracy of the print head, which will result in incomplete or inaccurate prints.

If you’re new to 3D printing or you have been having issues with outcomes of your prints that you cannot find the cause of, you may find that achieving proper tension on your printer belt will resolve these problems. The article below will give you the basic information you need to understand how to test for and achieve proper tension on your printer belt. You’ll also learn how to identify and diagnose belt tension issues and their potential causes.

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Table of contents:

How do I Know if My Printer Belt Has the Proper Amount of Tension?

Unfortunately, there is no “magic” number for achieving the proper amount of printer belt tension. Every printer and belt are going to be different, so finding the proper amount of tension for your particular set-up will require a certain amount of trial and error. However, there are plenty of relatively easy and straightforward methods that you can use to start testing and narrowing down the proper amount of tension for your printer belt. Listed below are some of the commonly-used methods for testing and finding proper belt tension for your printer.

  • Test the Tension of the Printer Belt by Feel
  • Listen to the Sound of the Printer Belt
  • Use a Ruler to Determine Proper Tension and Deflection
  • Test the Tension with an iPhone App
  • Let Your Printer Tell You What Tension is Best

Test the Tension of the Printer Belt by Feel

One of the easiest ways to test your printer belt’s tension is to use your fingers to feel for the proper amount of tension. Users of this method state that if you press down on the belt with your finger, it should be taught enough that it moves very little and vibrates back and forth quickly. While this certainly isn’t a foolproof method, it is a good starting point to start narrowing down where the “sweet spot” is. With experience, you may eventually be able to use this method without having to rely on any other measurements.

Listen to the Sound of the Printer Belt

If you’re concerned that using one sense isn’t enough, don’t worry – let your ears give you a helping hand. Finding the proper belt tension is essentially the same as tuning a string instrument – you should be able to hear a specific tone or note once you have tightened the string enough. 3D printer users claim that for printer belts, you should be able to hear a “deep, cello-like tone” to know that you’ve achieved the proper amount of tension.

Use a Ruler to Determine Proper Tension and Deflection

If you’re looking for a more numerically accurate method of achieving proper tension, you can use a ruler to determine the exact measurement of deflection that the belt has from its resting position. In the 3D printing world, there are various rules of thumb as to the exact length of deflection that is appropriate to achieve proper tension. This particular method may require some testing to figure out which one works best for your printer.

Despite the discrepancies in opinions on deflection distance, this testing method will allow you to come up with a specific numerical formula that you can follow every time. This will allow you to achieve ideal tension with very little variance. If you choose to use this method, follow these simple steps to determine the right amount of tension and deflection for your printer belt.

  • Press down gently on the printer belt with your finger 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 of the belt as needed to achieve a quality print
  • Once you have determined the proper belt tension, re-test the deflection number to ensure that it’s accurate

Let Your Printer Tell You What Tension is Best

If you’re lucky, your 3D printer might do all of the dirty work for you. Certain newer 3D printer models arrive with their printer belts pre-calibrated to a certain tension that is specific to that printer. For example, the PRUSA Mk3/S printer comes with a pre-measured number that your printer belt must fall between to achieve proper tension. All you have to do is run a self-test on the printer’s LCD screen to make sure your belt tension falls within the proper number range, and you’re ready to start printing.

Test the Tension with a Phone App

You’d better believe there’s an app for that! If you have an iPhone, you can simply download an app called “Smart Tension.” If you’re an Android user, download “Carbon Drive.” These apps calculate the proper amount of tension for your printer belt based on the design and length of the belt. They then calibrate the sound that the belt makes when plucked and allows you to match it with the appropriate frequency, similar to a guitar tuner. While this is likely the most fun way to test proper belt tension, it may not be the most accurate, so consider another testing method to back your results.

No matter which method you choose to use to find the right tension for your 3D printer belt, it’s going to take some time and patience. You’ll most likely go through a handful of imperfect prints before you narrow down your method. However, it will be worth the time and energy once you’re able to regularly print off perfect-looking designs without fear of a belt issue.

What is Causing the Printer Belt Tension to be Off?

There are a variety of reasons as to why your printer belt may be causing your prints to come out misaligned or lopsided. The belt is connected to many other parts of the printer that can contribute to its defectiveness and it’s important to know what part might be causing the issue before taking action to fix or replace it. Below is a list of the most common ways printer belts cause faulty prints and how to identify them.

  • The Belt is Sliding Along the X or Y-Axis
  • The Belt Pulley is Missing Gears
  • The Belt Has Slipped off a Pulley
  • The Belt is Rubbing Against the Belt Track
  • An Object is Caught in the Belt or the Track

The Belt is Sliding Along the X or Y-Axis

3D printers operate along X and Y axes that allow them to print in multiple dimensions. Each axis has a belt that allows the printhead and print bed to move along it. Over time, the nuts and bolts that secure the axes will loosen, causing the tension on the belt to begin to slack. If the tension on the belt is not uniform or tight enough, it will slide out of place on its axis and misalign your print.

This is one of the most common issues that people encounter when dealing with belt tension issues, especially on older or frequently-used printers. It’s important to regularly test the tension on your printer belt to make sure that it’s uniform throughout and to tighten any nuts or bolts that have become loose.

The Belt Pulley is Missing Gears

If the pulley that is feeding your printer belt has a loose or missing gear, your belt won’t run as smoothly and will cause the jerky movements as your print is being created. If this is the case, you will most likely notice that your design has misprinted segments or even complete holes once you have printed it.

The Belt Has Slipped off a Pulley

Most printer belts are fashioned in a big loop that is hooked around two pulleys. Occasionally, one side of the belt can slip off of its pulley, causing it to tighten more on one side. This will result in misaligned layers and your print will likely come out lopsided.

The Belt is Rubbing Against the Belt Track

If your printer belt is misaligned or wasn’t tightened correctly, it can rub against the belt track. The friction caused by the repeated rubbing will wear the belt out far more quickly and can result in an incomplete or misprinted design. If this situation is not addressed, the friction over time can be enough to completely snap the belt.

An Object is Caught in the Belt or the Track

Even very small amounts of dirt or debris that get stuck in the belt or the belt track can be enough to derail the belt and potentially manipulate the tension. Always check the belt and track to make sure that it is clear of debris before you start printing.

How do I Know if my Printer Belt Tension isn’t Correct?

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.

  • The Print Layers are Misaligned
  • Your Print Comes Out Leaning or Lopsided
  • There are Holes or Misprinted Segments in the Design

The Print Layers are Misaligned

You may notice that the layers on the outer wall of your design look slightly uneven and are causing slight irregularities across the surface. If this is the case, you are most likely dealing with a loose or unevenly tightened printer belt. While this deformity may not be immediately visible as the object is being printed, it will become very apparent once it has been completed. Make sure you take a close look while the print is forming to make sure this isn’t an issue.

Your Print Comes Out Leaning or Lopsided

If your printed replica of the Empire State Building comes out looking more like the Leaning Tower of Pisa, your printer belt is most likely to blame. If the printer belt is rubbing against something, it could be blocking the full travel of the printer head. If the head can’t travel the appropriate distance, once side of your design will be printed at an angle. To avoid this issue, make sure that the printer belt isn’t rubbing against anything before you get started on your print.

There are Holes or Misprinted Segments in the Design

A small hole or misprinted segment in an otherwise perfect design is going to be a source of serious frustration. You can avoid this problem by making sure that any bolts or screws attaching the printer’s pulley to the printer belt are tight and unobstructed. As these loosen over time, they can cause the print belt to lose uniform tautness. If the belt isn’t holding the same tension throughout, the print layers will not be uniform, causing misprinted areas and potentially even holes in a certain section.

How do I Adjust my 3D Printer Belt Tension?

The technique for adjusting the tension belt on your 3D printer will vary significantly depending on the style and brand of printer you have. If will also depend on whether or not you’re dealing with an X-Axis belt or a Y-Axis belt, as each belt is attached to its axis differently. You should always refer to your printer’s instruction manual to find exact instructions. However, the guidelines below will give you a basic outline of how to adjust belt tension on most common models of 3D printers.

How do I Adjust Printer Belt Tension Along the X-Axis?

The printer 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. The extruder is attached to a motor which allows it to move back and forth across the X-Axis belt. Because the majority of printing activity is occurring along the X-Axis, it is far more likely that any tension issue you will be dealing with will be related to this belt.

Adjusting the printer belt along the X-Axis may be as simple as tightening a few screws, or it may require disassembling parts of the extruder. Outlined below are the different methods you may need to utilize to re-establish tension on your X-Axis printer belt.

  • Tighten Screws on X-Axis Motor Shaft
  • Adjust the Belt-Holder Behind the Extruder
  • Increase Tension Directly on the Belt Using a Belt Tensioner

Tighten Screws on X-Axis Motor Shaft

Some printer belts are attached to their X-axis with a pulley that is screwed into a motor shaft to maintain maximum tension. If these screws have come loose and the belt is beginning to slide along the X-axis, you’ll simply need to get a small pair of pliers or a hex wrench to tighten them.

Adjust the Belt-Holder Behind the Extruder

If the slack in tension isn’t due to a sliding axis, the issue may lie within the printer belt holder itself. This belt holder is located behind the extruder and may require a little disassembly to re-establish proper tension. Follow these basic steps to disassemble the belt from the extruder and give it the proper amount of tension:

  • Remove any top-screws on the motor holder to give the belt additional slack
  • Remove zip ties on the back of the extruder
  • Unscrew the screws holding the backplate of the extruder and remove the plate. Be careful to avoid touching any exposed wires.
  • Access the area where the belt is mounted onto the extruder
  • Remove the belt from the mount and move it in as many teeth as you need to re-establish tension. Use a pen or marker to mark the desired distance.
  • Cut off any remaining teeth on the belt if necessary
  • Replace the backplate on and put the screws back on tightly
  • Replace the zip ties and secure tightly
  • Put the screws back on the motor and secure tightly

Some 3D printer brands come pre-packaged with the required hex wrench and tools to adjust both the X and Y axis belts. Make sure you check your printer’s packaging to see if the items you need to adjust the belt are already included with the printer.

Increase Tension Directly on the Belt Using a Belt Tensioner

One of the most common “quick-fix” ways to re-establish tension on a slack belt is to attach a device called a “belt tensioner” directly to the belt. This device pinches and holds the extra slack on the belt so that proper tension can be restored without having to disassemble any part of the printer.

Belt tensioners are created in a variety of different designs and some people even create their own with their 3D printer. Below are some of the most common belt tensioner designs available and how they work to increase the tension on the printer belt.

  • Spring Loaded Belt Tensioner This small tensioner uses a metal coiled spring to compress the extra slack on both sides of the belt. These tensioners are budget-friendly and can be purchased in bulk but may not be as strong or provide as much longevity as some other models of tensioners.
  • Screw-On Belt TensionerThis type of X-axis tensioner is attached to the belt with screws as opposed to with a spring. This makes for easier installation and adjustment of the belt if changes need to be made. These are slightly more expensive than the spring-loaded tensioners, but the ease of use will make up for the difference.
  • 3-D Printed Belt Tensioner – Many 3-D Printer aficionados prefer to create their own tensioner using their printer. There are a variety of different design templates available on 3D printing forums and YouTube videos. Or if you’re up for the challenge, turn on your printer and attempt to design your own!

How do I Adjust Printer Belt Tension Along the Y-Axis?

The printer belt that runs along the Y-Axis of the printer passes through a small stepper motor that is responsible for creating the 3-dimensionality of your design. It’s not as heavy or complex as the Extruder motor that runs along the X-Axis belt, so it won’t put the Y-Axis belt through as much wear and tear. However, that doesn’t mean that you won’t encounter a tension issue along the Y-Axis.

Since the Y-Axis belt doesn’t take as much of the printing brunt as the X-Axis belt, you’ll most likely be dealing with rubbing or slipping issues that can be easily fixed by tightening a few screws with pliers or a Hex wrench. Nonetheless, you should always give your Y-Axis belt a thorough inspection before you begin printing to make sure that it is uniformly taut, and that nothing is rubbing or catching on the belt.

How do I Make Sure the Printer Belt Tension Stays Secure?

Just because you finally found the proper tension doesn’t mean that it will stay that way without a little maintenance and upkeep. Before you start printing, you should always check your pulleys and gears to make sure nothing is loose or missing and that no dust or debris is caught in them. The better the rest of the printer works, the easier it will be to find the correct printer belt tension for your next print.

Once you’ve established proper tension and fixed any issues with the printer that may have been contributing to tension issues, you should immediately know the answers to the following:

  • What does the printer belt tension feel like when it’s properly set up?
  • What sound does the printer belt make when it’s at the right tension?
  • How much deflection should my printer belt have when it’s properly set up?
  • What other pieces of my printer (pulleys, extruders) contributed to the tension issue, and how did I adjust them?

It can be exciting once you’ve found the proper tension to jump right into the printing process without recording or remember the exact specifications for your belt tension. If you’re going to continue 3D printing regularly, you’ll save yourself a considerable amount of time and frustration by knowing exactly where you need your tension to be and what type of maintenance it needs to stay working at its best.

What Happens if my Printer Belt Snaps?

In the unfortunate scenario in which your belt completely snaps, there’s not much else you can do besides purchase a new one. Many printers come with specifications about which type of belt you’ll need, or If you are unsatisfied with the quality of your previous belt, you can start the search for a new one. When looking for a new printer belt, make sure you pay special attention to the following specifications:

  • What Material is the Printer Belt Made Out of?
  • What is the Pitch Level on the Printer Belt?
  • What Shape are the Teeth on the Printer Belt?

What Material is the Printer Belt Made Out of?

Most printer belts on the market are made of rubber or neoprene and reinforced with fiberglass to ensure that they won’t slip off a gear or pulley. However, the rubber will stretch over time, so you’ll eventually have to adjust the tension. Another common material is steel core polyurethane, which will resist stretching but are not quite as flexible as rubber belts, making them more likely to snap.

What is the Pitch Level on the Printer Belt?

The term “Pitch” refers to the distance between each of the teeth on the surface of the belt. For 3D printing, you should look for a belt that has either a 2mm or 3mm pitch to ensure that the belt moves smoothly along its gears. Any greater distance between the teeth will result in jerky movements that will throw off the preciseness of your print.

What Shape are the Teeth on the Printer Belt?

Some newer printer belts are being made with curved teeth as opposed to the traditional trapezoidal shape. Curved teeth are meant to be both stronger and quieter than the latter. Also, the cylindrical shape is supposed to reduce “backlash,” which refers to a loose connection between the teeth of the belt and the teeth of its pulley. The less backlash between the belt teeth and the pulley teeth, the more smoothly and accurately your printer will run.

How do I Know Which Belt Will Work Best for my Printer?

It may take many prints and many different styles of printer belts to determine which one works best with your printer and what level of tension allows it to function at its best. Once you’ve discovered the proper belt tension and can recognize and resolve issues that may prevent it from functioning at its best, you’ll be ready to print flawless designs with confidence and ease.

About THE AUTHOR

William Stone

William Stone

William has spent 20 plus years in the custom manufacturing industry as a COO, CEO and Owner of various custom product businesses. His experience has exposed him to all types of manufacturing from die cast, die struck, injection molding, CNC machining, laser etching, engraving and of course 3D printing.

Learn more about William Stone

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3D Printer Belt Tension: Everything That You Need to Know

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