This guide will take you through the replacement of the heaterblock on the Original Prusa MINI and MINI+.
Allen key 1.5 mm (1x)
Allen key 2 mm (1x)
Torque wrench (1x)
Standard socket size 7mm (1x)
Needle-nose pliers for zip ties (1x)
Wrench sizes 16 mm / 10mm (1x)
Cloth or piece of fabric 15x15cm (1x)
The cloth will be used to protect the heatbed. You can use any similar material.
Plug in the printer and turn it on.
On the information screen navigate to the Settings.
Open the Temperature menu.
Set the nozzle temperature to 280 °C by turning the knob.
Make sure the filament is unloaded from the hotend!
WARNING: Avoid touching the HOT nozzle!!!
Set the torque wrench to 2.5 Nm.
With one hand, hold the heaterblock using the wrench size 16 mm. Place the wrench above the cables to avoid damage.
With the other hand, use a torque wrench, place it on the nozzle and slightly loosen it.
Navigate to the Preheat menu and at the end of the menu select Cooldown.
Wait 15 - 20 minutes to cool down completely before proceeding to the next step.
Turn the printer off and unplug it from the socket!
Before these steps, it is recommended to protect the heatbed!
Take off the flexible steel sheet.
Use any cloth or piece of fabric, which is thick enough and cover the heatbed. This will ensure you won't damage (scratch) the surface during the disassembly.
Loosen the upper fitting and remove the long PTFE tube from the hotend.
Release and remove the lower fitting from the heatsink.
Carefully pull out the PTFE tube from the heatsink using pliers or tweezers.
There are two designs of the textile sleeve mount on the print head:
The new design without a zip tie: Gently pull out the textile sleeve from the MINI-fan-spacer-clip. Do not pull on the cables!
The old design with a zip tie: Cut off the zip tie on the print head. Avoid cutting the print fan cable!
Remove the textile sleeve to the extruder.
There is no need to cut another zip ties!
Loosen the hotend cables for this step.Move the print head a few centimetres towards the center of the X-axis, see the picture.
Loosen three screws on the side of the heatsink with 1.5 mm Allen key.
Hold the heaterblock with the other hand.
Gently slide out the heaterblock with the heatbreak from the heatsink.
WARNING: Do not pull the thermistor or heater cables. Follow the instructions!
Release the heater screw and using the Allen key gently push the heater out.
Release the thermistor screw and using the Allen key gently push the thermistor out.
Clean the heatbreak from the old paste by using a paper towel.
Use the second cloth to protect the thread of the heatbreak.
Hold the heaterblock and using pliers release and remove the heatbreak.
We are done with removing the old heatbreak, let's move to the next step and install a new one ;)
If you are installing a new heatbreak, please skip this step.
For the following steps, please prepare:
New heaterblock (1x)
Thermal paste (1x)
If you are installing a new heaterblock, please skip this step.
For the following steps, please prepare:
New heatbreak (1x)
Thermal paste (1x)
This step is the same for assembly of the new heaterblock or the new heatbreak.
Screw the nozzle slightly in the heaterblock. Create a 0,5 mm gap, see the picture.
Secure the nozzle against movement with one hand.
With the other hand, screw the heatbreak into the heaterblock from the opposite side until it touches the nozzle inside. Do not tighten anything by torque wrench for now!!!.
Insert the thermistor to the heaterblock and secure by tightening the lock screw.
Insert the heater to the heaterblock and secure it by tightening the black screw. Make sure the heater goes through and sticks out slightly on the right side, see the picture.
Ensure both thermistor and the heater are properly inserted and tightened!
Apply 1/4 of the content of the thermal paste package on the heatbreak.
Spread the paste evenly over the surface. Do not spread to the ends. Leave at least 2 mm from each end of the heatbreak.
Do not apply the paste on the thread!
Insert and gently slide the hotend into the heatsink. Make sure the nozzle cables are on the left side.
Hold the heaterblock with the other hand.
Slightly tighten the three screws on the side. You will loosen them again later.
Remove excess paste with a paper towel or cotton bud.
If you have a version with the textile sleeve secured with a zip tie on the print head skip this step.
Wrap the cable bundle inside the textile sleeve.
Slide the textile sleeve into the MINI-fan-spacer-clip so that the sleeve sticks out on the other side about 2-5 mm.
Now skip to Hotend PTFE tube installation
This step is for the version with the textile sleeve secured with a zip tie on the print head.
Wrap the cable bundle with the textile sleeve.
WARNING: Don't overtighten the zip tie around cables, leave some slack or you might break some of them!
Secure the textile sleeve with a zip tie to the fan-spacer.
Double-check all cables aren't stretched, if so, please cut the zip tie, make them slightly more loose and tighten the zip tie again.
Use your phone LED flash or similar device to shine into the hole from the top of the print head. Take a look inside and check there is no filament. It must be clean and you should see only the metal surface inside. Open the full-size image if needed.
A clean print head is essential for successful prints. Double-check, there is no filament inside!!!
Insert and push the PTFE tube into the heatbreak all the way down.
Orientation of the PTFE tube installation does not matter. Both ends are symmetrical.
Loosen tree screws on the side of the heatsink with 1.5 Allen key.
Push the nozzle up. You must see the PTFE tube moving up a bit.
Mount the "lower" fitting to the top of the heatsink. Screw it all the way, but don't tighten it. As soon as you reach the end of the thread, release it by a full turn (360 °).
Push the heaterblock up against the fitting with a reasonable force. No need to bend the entire axis. This will pre-stress the PTFE tube inside. Now, it is important to keep the pressure.
Make sure the heaterblock is aligned with the heatsink. If not, realign it, but keep the pressure.
While holding the heaterblock from below (pressing the tube inside), tighten all three grub screws.
Now, you can release the heaterblock. Make sure it doesn't move. If so, the grub screws were not tightened properly. Release them and return to the beginning of this step.
It is crucial there is no gap between the PTFE tube and other parts of the hotend. This is why we are "pre-stressing" it.
Finish tightening of the "lower fitting", you should do a full turn to compensate for the turn we did in the previous step.
Mount and tighten the upper fitting with the long PTFE tube with a wrench. Do not use excessive force!
Plug in the printer and turn it on.
On the home screen, navigate to Control.
Open the Temperature menu.
Set the nozzle temperature to 280 °C by turning the knob.
WARNING: Avoid touching the HOT nozzle!!!
Set the torque wrench to 2.5Nm.
With one hand, hold the heaterblock using the wrench size 16 mm. Place the wrench above the cables to avoid damage.
With the other hand, use a torque wrench, place it on the nozzle and tighten it.
Navigate to the Preheat menu and at the end of the menu select Cooldown.
Great job!
Heat the printer up and try it out ;)
If you have a question about something that isn't covered here, check out our additional resources.
And if that doesn't do the trick, you can send an inquiry to [email protected] or through the button below.
