3D Printer Belt Tension (How to Find the Right Tension)

Marcello De Lio

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Close up of a 3D printer making a small print

Belts are a very important component for all FDM 3D Printers. Belts are the main drive unit, moving the print head along the X and Y axis. When you have the correct 3D printer belt tension, they ensure a smooth, consistent movement of the print head.

When the belts are worn out, too loose, or too tight, they can result in print defects and failed prints.

So what is the proper 3D Printer belt tension?

The belts on a 3D printer should be tight enough so that there’s no slack, and there should be some resistance when you push down. But, they shouldn’t be so tight that they are rigid as it will increase wear and tear on the belt.

This article will discuss some inspection and maintenance tips to keep your belts running smoothly and help you better understand the proper tension and how to adjust the tension by yourself.

What is the Right 3D Printer Belt Tension?

A finger pointing to a 3D printer belt on an Ender 3 V2

The belts on your 3D printer should be quite tight. When properly tensioned, there shouldn’t be any slack in the belt, and they should resist being pushed on but still be able to flex slightly. A properly tightened belt should have the same tension as a stretched-out rubber band.

When you push on the belt, they should feel springy, pushing back on your finger.

You need to take care that you don’t overtighten the belts. If your belt tension is too high, it’ll increase wear and tear on the belts. Additionally, overtightening your belts can cause print defects and failed prints.

My general rule of thumb is that you should be able to flex the belt when pushing down on it, but it shouldn’t have any slack in it when it returns to its normal position.

How To Tighten Belt Tension on a 3D Printer

Allen Key Belt tensioner on an Ender 5 3D printer

Understanding why we need to ensure we have proper belt tension is equally as important as understanding how to adjust the tension.

Not all 3D printers are the same. And some printers may have different methods for tightening the belts. But the general principle applies.

We’ll first look at how to tighten belt tension on 3D printers with an Allen key or screw setup:

  1. Take a look at your 3D printer and locate the belt tensioner for the axis you want to adjust. Usually, the belt tensioner is positioned opposite the stepper motor.
  2. Determine the appropriate tool to adjust the tension. Usually, you’ll need an Allen key or screwdriver. If your tensioner features a knob, you can simply rotate the know clockwise to tighten the belt or counterclockwise to release tension. 
  3. Loosen the belt tensioner using the Allen key or screwdriver. (Note: You don’t need to remove the screws completely. Simply loosen the screws so that you can move the belt tensioner.)3d printer belt tensioner on an Ender 5
  4. Hold the frame with one hand, and pull the belt tensioner until you achieve the correct belt tension. Moving the tensioner away from the frame tightens the belts while moving it toward the frame loosens them.
  5. Tighten the screws to re-attach the belt tensioner to the frame. (Pay careful attention that the belt is level with the frame. If the belt is not level, it can rub on the frame, increasing wear and tear on the belt.)

That’s it! It’s a good idea to adjust the belt tension on every axis to ensure smooth and consistent 3D printing. 

Ender 3 Belt Tensioner

Knob belt tensioner on an ender 3 v2

Built-in belt tensioners are the easiest and most reliable way to tighten the belts on a 3D printer. Newer Ender 3 models, like Creality’s Ender 3 V2, have built-in knobs to easily tension the belts.

But older Ender 3’s require an Allen key.

If you’re using a 3D printer without a belt tensioner, you can print one and add it to the frame.

You can find belt tensioners for almost every 3D printer. Below are some of our favorites:

Additionally, there are knob tensioners you can purchase to upgrade your Ender 3 or Ender 3 Pro.

When Should You Check Belt Tension?

We recommend checking your belt tension every few prints.

Issues With Loose Belt Tension

3d printer printing a small yellow model

Layer shifting is one of the common side effects of improper belt tension. If you have layer shifts in your prints, your belts may be too loose or too tight.

A very loose belt could result in the belt slipping on the pulley cog, making the belt move while the print head stays stationary.

Slipping causes a slight pause during normal movement and offsets the printer nozzle. Once the belt regains grip on the pulley cog, the print will continue as normal.

Proper belt tension is essential for geometric accuracy. If the nozzle changes directions along the same axis really quickly, a loose belt may experience a condition called backlash.

Backlash is when the pulley cog takes some time to catch up to the belt’s change in direction, resulting in poor geometric accuracy. The backlash isn’t noticeable on properly calibrated belts.

Issues With Belts That are Too Tight

Close up of the belt on a 3D printer while printing a small model

Belts that are too tight often don’t cause print defects. But the increased tension results in more wear and tear, reducing the belt’s life.

Most belts are made of rubber mixed with chords for reinforcement (usually steel). The cords improve tensile strength and create more reliable parts.

If you over-tighten the belt, you could stretch the belt. A stretched belt is not fixable. Once the belt stretches, there is no way for it to go back to its original shape.

Any stretching forces the belt out of alignment with the cog, which could lead to slipping.

In extreme cases, an overtightened belt can snap like an elastic band. Not only does this damage the printer, but it could lead to injury.

Maintenance Tips for Your Belts

Close up of a 3D printer making a small print

Printer belts are relatively low maintenance, especially compared to other components of 3D printers.

However, it doesn’t mean they should be neglected. Belts should be regularly inspected to ensure they are working properly, properly tensioned, and free from tears.

Here’s a list of what you should look for when inspecting your belts.

  • Check the tension of your belts periodically. It’s especially important to check belt tension if you plan to undertake a long print (nothing is worse than coming back from a 3-day print just to find a pile of spaghetti).
  • Dust off the belts and aluminum extrusions using a vacuum and a small painter’s brush to ensure contaminants don’t interfere with the belt’s normal motion.
  • Flip over each belt to get a good look at the teeth and underside. Ensure the belt isn’t beginning to fray and all the teeth look good (no chips or cracks). If you notice some damage, replace all the belts ASAP. Damaged belts can snap, causing injury.
Belt tensioner on the x axis of an Ender 3 V2

Some people online talk about lubricating the belts or applying conditioner, so they run smoothly.

Not only is it not necessary, but lubricating the belts may negatively impact your prints.

Printer belts are not flat like automotive belts. 3D printer belts have teeth to grip the cogs. Applying lubricant to the belt may make the belts slip which causes layer shift.

Additionally, If you were to use the wrong lubricant that isn’t compatible with the belt material, you may degrade the rubber, which will cause a premature failure.

Article by

Marcello De Lio

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