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Here’s What To Do When a 3D Printer Runs Out of Filament

In 3D printing, the filament is your ink. So, it’s essential to have a sufficient supply of it in your printer for a smooth printing process. But what happens if your printer runs out of filament mid-print?

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In 3D printing, the filament is your ink. So, it’s essential to have a sufficient supply of it in your printer for a smooth printing process. But what happens if your printer runs out of filament mid-print?  

When a 3D printer runs out of filament, and it has a runout sensor, it’ll automatically pause so you can load a new roll and it can resume printing. If it doesn’t have a sensor, you’ll have to pause manually and load more filament, start all over again, or print the unfinished part separately. 

Running out of filament while printing a 3D object is a common problem considering that the process takes many hours to complete. In this article, I’ll talk about what you can do when your printer runs out of filament mid-print. You’ll also learn how to deal with it depending on whether your printer has a sensor or not and at which stage of the process this happens.

How Likely Are You To Run Out of Filament While Printing?

Filaments usually come in one-kilogram (2.2-pound) spools. Of course, there are smaller and bigger ones available, too. However, considering that a spool needs to unwind to feed the plastic filament into the extruder, a bigger spool could have difficulty moving. That’s because your printer will require a greater pull force with a bigger spool.

If your 3D printer has a small build area that can only print a small object, you aren’t likely to run out of a single regular spool of filament. However, it’s a different story if you bulk-print small 3D objects or your spool has already been used for previous prints. 

You can also quickly consume a regular spool of filament if you’re using a large 3D printer and printing bigger objects.

If you want a better estimate of how long your filament will last or how much filament your print will use up, you need to check your slicer software. It’ll show you the exact number of grams or ounces of filament your 3D print will need, as well as the total number of hours it’ll take to complete the project.

As such, you’ll have an idea whether the spool you’re using is enough and whether you’ll need to load a new spool before your 3D object is done printing.

What Does a Filament Runout Sensor Do?

Filament 3D printers, also known as fused deposition modeling (FDM) printers, come in various models with a wide range of features. One of these features is the filament runout sensor, and while some printers have it, there are also those models that don’t. 

The filament runout sensor tells the 3D printer that a spool is empty and that no filament is feeding anymore. Without this sensor, the 3d printer doesn’t have any other way of knowing that all the filament has been used up. 

The printer simply pulls in filament through a programmed mechanism, where it feeds, melts, and extrudes the filament. This mechanism doesn’t report back to the printer. 

If your 3D printer doesn’t come with a filament runout sensor, the good news is you can usually add one. 

What To Do if Your Printer Runs Out of Filament

With a sensor reporting to the internal processor that the filament is running out, your printer will automatically move its print head up and away from the 3D print. This way, the printer lets its nozzle and the unfinished print cool down until it gets more filament. 

So all you have to do is load a new roll, and that’s it.

Once you’ve replenished the filament and threaded it through the extruder, you can tell your printer to pick up where it left off.

Check out this video demonstrating what to do when filament runs out, and your 3D printer has a sensor:

What To Do if Your Printer Doesn’t Have a Filament Sensor

A 3D object can take many hours to finish printing. Some projects can even take the entire night or half a day. So, it’s expected that you won’t be able to watch over the process from start to finish. And it’s perfectly understandable if your filament runs out mid-print without you even noticing it.

Now, if your 3D printer doesn’t have a filament sensor and it runs out of filament, here are some of the things that you can do, depending on certain factors:

  1. Print the Unfinished Portion Separately

When your printer runs out of filament and it doesn’t have a sensor, its nozzle will continue moving around, and its print head will keep on moving up with each supposedly added layer of your print. At this point, it’s too late to pause your printer for you to load a new spool. You also cannot continue printing using the same G-code file.

The only option you have left is to print the rest of the piece as a new, separate project. Here’s how to do that:

  1. Get the height of your unfinished print using a ruler. 
  2. Open your 3D project on your slicer software and, using the measurements you’ve taken, bury the portion of the object that was already printed. 
  3. Generate a new G-code for the unprinted section of the 3D object and start printing it.
  4. When the second part of your 3D object is done printing, you can join the two sections and glue them together. 

However, there’s a good chance that the layers of the two portions won’t perfectly align. If this happens, you can fix it by sanding and filling the gaps with glue.

Here’s a video showing how printing two 3D portions separately works:

  1. Print From the Beginning

If it turns out that your filament was only enough to print a few layers and you’re okay with throwing that object away for the sake of convenience, you can print a new one from the top. Just be sure to load enough filament to finish the print this time around.

  1. Pause the Printer Manually and Load New Filament

If you happen to be around right before the filament runs out, you have time to intervene and hit pause. 

Most 3D printers allow you to swap in new filament by pausing the current print. The print head will go back to its home position, allowing you to remove the leftover filament and replace it with a fresh new spool.

Once you’re done loading the new filament, you can now feed the new filament to the extruder and resume printing.

Watch this video to see how you can load a new roll of filament before the current one runs out entirely:

Final Thoughts

Running out of filament is common when printing 3D objects. It’s also common for you not to notice that your filament has already run out since the printing process takes many hours. Fortunately, dealing with this problem is easy if your 3D printer has a filament runout sensor because it’ll automatically pause and wait for you to load a new spool.

However, without a sensor, things could get inconvenient for you. Your best bet to save your 3D model in this instance is to print the rest of it as a new and separate project and glue the two portions together.

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About Ben

I started 3D printing since 2013 and have learned a lot since then. Because of this I want to share my knowledge of what I have learned in the past years with the community. Currently I own 2 Bambulab X1 Carbon, Prusa SL1S and a Prusa MK3S+. Hope you learn something from my blog after my years of experience in 3D printing.