Changing filament mid-print on your Ender 3 (Pro/V2) is easy if you’re using Cura 4.8 or higher.
The slicer gives you the possibility to change filament at any given point after the start of the printing process manually or by modifying the G-code.
To change filament with Cura mid-print manually, all you have to do is stop the print when you’re ready to make the switch. Purge the old filament and unload the spool. Load the new spool, adjust printing parameters, and let the printer reach the temperature. You can then resume printing with the new filament.
Performing a filament switch in Cura is easier if you choose the manual method.
However, if you don’t want to keep an eye on the screen the whole time, modifying the G-code can automate the process up to an extent.
Preparing To Change Filament In Cura
Changing the filament in Cura starts with a proper preparation of the file.
For a manual switch, you should determine after which layer you want to swap the spool and stop the printer after that row is extruded. You must also input the correct temperature for both filament types if you wish to change the material rather than the color.
Here’s what to do.
1. Slice the Model
The first pre-switch step starts with slicing the model in Cura. You can do this in the usual way, by preparing the file in CAD software. Save the file as STL and export it to your slicer – or download it on your computer, then load it into Cura.
Open the file and slick the Slice button. You don’t have to alter any settings at this stage – you’ll have to slice the model again before you start.
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Wait for the program to slice your model, then open the preview mode.
2. Decide When to Switch
With the object sliced and visible in preview mode, you can decide after which layer to make the switch.
If the model has multiple colors, you can use the sidebar to see at what layer a color finishes and another begins. If you want to swap materials completely – for instance, if you want to print PLA on top of ABS or TPU, you can use the slide bar on the right side of the screen to select the layer.
You’ll have to remember the layer number for the next step, so write it down.
3. Enable Layer Tracking
Deciding at which layer to make the switch won’t do much good if you can’t keep the printing process under control. That is, unless you want to count each individual layer during printing.
Luckily, there is a much easier way to monitor the process. All you have to do is enable layer tracking from G-code.
To do this, open Extensions in Cura and select Post Processing from the drop-down menu. In the new drop-down menu, you’ll find the option Modify G-Code.
Click on this option and select Add a Script. In the new window, select Display File Name and Layer on LCD. When enabled, this option displays the file name and current printed layer on your Ender 3’s screen.
That’s it, but before you go, make sure the initial layer is set to zero.
4. Re-Slice The Model
When you’re done, it’s a good idea to slice the model again to reflect the changes.
If you haven’t done so already, make sure all printing parameters (such as nozzle temperature, print speed, cooling fan, etc.) match the material you’re using.
How To Change Filament Mid Print On Cura
After the initial preparation, all you have to do is to keep an eye on the printing process to see when it’s time to pause it.
Here’s how to change the filament – the steps below refer to switching it on Ender 3, but the process is similar on any other printer.
1. Pause Printing
Following the steps mentioned above, monitor the printing process once it starts. You can see the layer number on the printer’s LCD (if you enabled layer tracking from G-Code).
All you have to do is to hit pause after the printer extrudes the last layer before the one you selected.
2. Unload the Filament
At this stage, you have to unload the first filament and load the new one. How you should do that depends on the type of filament you want to use next.
If it’s the same filament type but a different color, you don’t have to change any settings in Cura.
If the new material requires a lower printing temperature, let the settings unaltered for now. However, if the new material requires a higher printing temperature, change the settings before unloading the old filament.
In this way, the nozzle has enough time to reach the temperature while you perform all necessary operations.
- Move the extruder arm to home position
- Squeeze the extruder lever which keeps the filament in place and pull the filament strand out
- Enable extrusion to purge old filament from the nozzle
3. Load New Filament
Place the new spool on the printer and push the filament through the Bowden tube until you feel resistance. At this stage, the filament has reached the hot end.
It is essential to do this step after the nozzle has reached the temperature for the material you’re using, to avoid altering its quality.
If the nozzle is heated at the right temperature, keep pushing until you see the filament coming out of it.
Remove the purged portion of filament with a pair of tweezers.
4. Resume Printing
You can now hit start on the printer to resume the process. Monitor the printer carefully during the extrusion of the first layer of new material.
The greatest risk when switching filament mid-print is that of altering the calibration of the arm. If this happens, the new layer might not be printed right on top of the last layer, but slightly offset.
It goes without saying that this can alter your print quality.
If the layers are not aligned, stop the process right away and start again from square one.
5 Tips For Successful Filament Replacement
Changing filament mid-print with Cura can be tricky, but these tips could help you prevent most issues.
1. Clean Nozzle Properly
The most important thing to do before loading new filament is making sure the nozzle is clean.
Otherwise, the new filament could build-up on top of filament residues and clog the nozzle – the risk is higher if the new filament requires a lower extrusion temperature, as the old material can solidify inside the hot end.
You don’t have to cool down the nozzle to clean it. Simply wipe it with a damp cloth.
If you suspect there are clogs inside it, use the needle provided with your Ender 3 printer to dislodge and break up any material, then remove it.
2. Only Print with Quality Filament
Preventing clogs and obstructions isn’t always easy, but you can minimize the risk by using high-quality filament only. This rule should also apply for prototypes or when learning.
Beyond filament quality, you should also make sure that the filament you’re using is dry. Keep in mind that wet filament can behave like poor-quality material, and material quality can change over time, especially if stored incorrectly.
3. Check Nozzle Temperature
When changing filament mid-print, it is easy to forget the nozzle temperature. However, different materials require different extrusion temps.
Filament loading can easily fail if you switch a lower-temperature filament with a higher-temperature one, but you forget to heat the nozzle before loading the new strand.
To prevent issues, let the nozzle heat up and only remove old filament and load the new one when it has the temperature of the second material.
Things change if the new filament requires a lower extrusion temperature. In this case, only reduce the nozzle temp after loading the new filament – or the old strand could cool down and block the nozzle.
4. Purge Nozzle Properly
When unloading the filament mid-print, you technically pull out the old strand from the hot end. However, residues may remain blocked in the nozzle.
This is why purging after loading the new filament is crucial. The process is not complicated.
You only have to extrude a length of new filament until it comes out clean. Use a pair of tweezers to remove the purged strand, and you’re good to go.
5. Prevent X-Axis Movements
The greatest risk when changing filament mid-print – with Cura or otherwise – is to move the X-axis. If this happens, the new layer will be printed slightly offset, ruining the entire print.
On the Ender 3, you can prevent this issue by moving the extruder off X-gantry completely and using an upgraded top mount extruder and spool holder that you can print yourself.
Alternatively, you can use the printer’s menu to change the filament (skipping the Cura change). This option will keep the axis motor locked, preventing you from changing the X-axis position accidentally.
Common Issues With Mid Print Filament Changes
Beyond everything above, there are other potential problems that can occur. Here’s how to fix the most common ones.
Filament Not Sticking to the Print Bed
A common issue is new filament not sticking to the printed part. This is often caused by filament incompatibility. For instance, PLA might not stick to PETG, but it sticks to ABS or TPU.
For this reason, you should check material compatibility before designing your model.
Incorrect Filament Loading
Regardless of the printer you’re using, you may also fail to load filament correctly without realizing it.
A common mistake is loading filament that gets stuck in the extruder path. This issue is common on Ender 3 printers, as the filament might bend and break as you’re pushing it through the Bowden tube.
Filament slipping is another common problem, caused by the incorrect temperature of the hot end.
Incorrect temperature point is a common problem on printers like Prusa i3, too. Mechanical problems can also prevent filament from loading correctly regardless of the printer you have.
Layer Shift
As explained above, layer shifts happen when you accidentally move the X-axis.
This problem is very frequent when changing filament mid-print with Cura, because the software doesn’t block the arm motor when you’re pausing the print.
To prevent this, you can pause the printer and unload the spool from the printer’s screen. The methods detailed above can also solve the problem.
Bumps and Zits
When pausing the process mid-print, the nozzle might extrude extra filament before you manage to home the X-axis. This could leave an unsightly defect on the surface of your object, commonly known as a zit.
A way to prevent this is by enabling Wiping in Cura. This setting “wipes” the nozzle before a non-extrusion movement is performed, spreading excess material in a uniform layer on top of the last printed row.
Enabling retraction as soon as you pause the printer is another way to solve this issue.
Delamination
Poor layer adhesion can happen when switching from one material to another, but also if you’re only changing colors.
If the nozzle temperature drops for one reason or another and you start printing before the hot end reaches the correct extrusion temperature, the material won’t adhere properly.
Filament incompatibility is also a cause of delamination. There is nothing you can do to solve this, except printing with another material.
Warping
Warping, especially in the first layer, can happen if the bed temperature drops during the filament change. New layers can also warp due to poor adhesion or incorrect temperature.
These issues are easy to correct by keeping the bed and nozzle temperature under control.
Height Changes
This problem is similar to the layer shift, but results from altering the Z rather than X-axis. This could mean anything from extruding a too thick layer to squeezing the material too much to under-extrusion.
To fix the layer height, adjust the Z-offset mid-print with Cura.
Conclusion
Changing filament mid-print with Cura is a relatively easy process. Don’t forget to check material compatibility before starting and to keep the parameters under control as you do the switch. Hopefully, this guide can help fulfill these tasks like a pro.
