A major problem with the Prusa Mini is that you have to mess with the hotend so often.

This by itself is not so bad, but the three (3) grub screws you need to remove each time, are simply not made for it.

A known problem on the Prusa Mini is the heat break slips down. The only thing holding it in place are three (soft metal) grub screws. You can’t tighten the grub screws they tend to round off really easily if you’re not careful. If your heat break lowers even by a fraction of a mm it creates a gap between ptfe tube and heat break. This gap area can fill with retracted filament which then cools. The gap creates a plug. The filament can’t go forwards or backwards and the extruder drive gears just grind the filament to dust. So you end up having to get in there and pick filament out of the hob gear’s teeth as well as clearing and reseating the heat break and resetting the pinda probe.

Just remember don't try to screw them in flat against the heat sink, there should be a 1mm or so gap. Finger tight then a smidge more, I am sure you can snap that heatbreak, but don't. If you do, you are on your own.

I fit these cap heads bolts when the printer is warm so everything contracted when cooled. Follow the guide on prusa*. There are a lot of wrong YouTube videos out there that just push the heat break up and tighten and forget to unwind the connector at the top half a turn first. So after you pushed the heat break up and tightened it you can then screw down half a turn on top connector to remove any last gap and squish the ptfe tube a fraction of a mm.

* Link to Prusa guide

Ignore the dirty Heatblock! Remove these 3, cheap, soft grub screws.

Ignore the dirty Heatblock! See no crummy grub screws here!

Ignore the dirty heatblock! Screw in the three machine tool steel cap bolts. Gently!

Finger tight and a slight smidge more. Don’t gorilla it down! Should be a mm showing of thread!

This guide references the Prusa mini+ Z axis lead screw aligner that is located here.

This printed part snaps in place to keep the lead screw aligned in the middle of the Z-bottom hole on the Prusa Mini.

It takes care of the wobble in the Z-axis lead screw. (Check yours yourself, grab the z-axis leadscrew near the bottom and give it a wiggle, you’ll see what we mean). It improves your print quality.

Step 1

Raise your Z-axis up to give yourself some working room. Halfway is more than enough!

Step 2

Position the Z-Axis Lead Screw Aligner as shown on your Prusa Mini Lead Screw.

Step 3
Push down on the right hand side of the Z-Axis Lead Screw Aligner and firmly snap it into place. You will note that it is now parallel to your Z-Axis.

Step 4

There is no step 4, Print long and prosper! Wasn't that easy?

For references sake:

Front: Looking over your Prusa Mini Control screen.

Rear: If you were seeing it from the back of your Mini.

Ultimately terms like XZ skew and XY skew are confusing, and it's simpler to explain skew in terms of the problem it creates than in these terms.

• X axis - the horizontal arm where the print nozzle travels (left and right).
• Z axis - the vertical arm, that holds the horizontal arm (up and down).
• Y axis - the rods where the print bed travels along (forward and backward).

Skew Fixes

Squareness Skew

What is it?

This occurs when the horizontal arm of the printer is not perpendicular (at at 90 degree angle) to the Y axis below (which the print bed travels along). It is either pulling forward towards the front of the printer, or backwards towards the back of the printer.

Issue

This will affect if a print is square, specifically how a line of filament is printed from right to left (or left to right) on the bed. A line of filament printed from the front to back (or back to front) will be unaffected as this is reliant on the Y-axis.

What do you need?

• Calipers for the most accuracy OR a set square

Measuring

You can test this by printing something square and then either using a set square to check if all 4 corners are square, looking for any visible gaps. OR if you have calipers, you can measure corner to corner inside the square (both diagonals) and compare the values. If it is perfectly square, the values will be the same.

Fixes

• Refer Prusa Mini Shims, these are the screws you'll need to unscrew to install the shim.
• Refer Prusa Mini + _ Squaring X Y Axis Skew.
• Refer goskew, this will post process your gcodes and account for skew in your printer.

Bed Level Skew Left/Right

What is it?

This occurs when the horizontal arm of the printer is not parallel on the X axis with the print bed below. It is either tilting downward towards the print bed, or upwards towards the ceiling. As a result, your printers bed will be sloping from left to right or right to left.

Issue

This affects the first layer calibration, the left hand side of the x-axis will be either too close or too far away from the print bed causing a slant. The printer can only compensate for an uneven bed so much, so depending on how severe the slant is, it may or may not affect your prints.

What do you need?

If you follow the Prusa solution below, they suggest simply moving the print head from one side to the other and visually checking the height from the bed. In all honestly, I think that is a waste of time as it will never be anything close to accurate. I highly recommend setting up a Raspberry Pi with Octoprint and the Bed Visualiser plugin. I also highly recommend that you should have a mechanism to measure belt tension (for Solution 2 below). Without this, you will be completely in the dark as to how tight your x-axis belt is, and if you are messing with those screws, you would want to know. This is what I recommend, it's very good. I verified its accuracy on a MK3S(+), which can give you a belt tension reading which I then compared to the meter.

Measuring

As above, I suggest running the Bed Visualiser plugin on Octoprint. This makes it very clear to see if you have an issue or not. This is a good example of what to look for, in this case you'd need to lower the arm, by tightening the top screw. Once you have run the visualiser you will know whether the arm needs to move up or down. Ensure you turn on "Descending y axis" if you are looking at the "Current Mesh Data", this orientates the data as it would be if you are looking at your printer from the front. Do not worry about any dips or raised areas you see in the corners when running the visualiser, there is a separate fix required for this. The aim here is just to get it as level as possible from left to right.

Fixes

There are two potential causes for this...

1. The Z axis arm is not perpendicular to the bed
2. The X axis arm is not perpendicular to the Z axis arm (and therefore not parallel with the bed)
3. Both

Solution 1 - Z axis arm not perpendicular to the bed

You can loosen the three screws holding the Z axis arm and adjust it to ensure it is at a 90 degree angle from the print bed. I did this by placing a small set square on my print bed, adjusting the position of the arm, then retightening the screws in the order specified. Unfortunately if you have the print bed positioned such that you can place a set square on it and touch the arm, you won't be able to reach the main print arm, you'll just have to keep checking it until you get it right. Another option would be a digital level e.g. Klein Tools 935DAG Digital Electronic Level. You can hold the level against the Y axis while you are tightening the screws and try and align it at 90 degrees. One thing to consider though, is unless your print bed is perfectly level and it may not be, you may want to factor in any discrepancy into how you align the Z axis. Refer to Prusa's guide to see which screws need to be loosened source. There are also some mods that may help here, I have not tried these

• Prusa Mini XZ Support
• Prusa MINI Z-Axis Support Brace

Solution 2 - X axis arm is not perpendicular to the Z axis arm

Follow the steps as provided by Prusa. Remember, if you tighten the lower screw, this moves the arm upwards, towards the ceiling. If you tighten the upper screw, this moves the arm downwards, towards the bed. This is counterintuitive, so it's worth mentioning. Once you have made the adjustments, check that both of the horizontal bars are straight and not twisted. Look at your printer from the top and check the two bars are perfectly aligned. If you need to adjust turn the orange piece with the screws a little to correct. If they are not aligned your print nozzle will turn slightly as it moves along the x-axis. If you loosen the belt tension screws, you should push the orange piece that holds the screws inward towards the z-axis arm, while holding the other end with your other hand. This is not mentioned in the Prusa's, but is mentioned in a video I watched and you will feel the orange piece move inward when you do this. Otherwise loosening the screws may not have an effect. Once you have made an adjustment, you should check the belt tension! See "What do you need?" above.

Bed Level Skew Corners

What is it?

This is the skew that occurs when your print bed is not level. With the "Bed Level Skew" fixes above, you should be able to achieve a level bed from left to right in the very center of the print bed (or at any single point on the Y-axis). However the print bed itself may not be consistently level from front to back and as it moves backward and forward on the Y-axis, the level changes. In my particular case, my print bed actually droops in the front right and back left corners, and is elevated in the back right corner. As the bed moves forward or backwards the level will change since the leveling is not consistent.

Issue

Depending on the severity this may or may not cause you issues. The Prusa Mini (and MK3) both have auto bed leveling, which detects any variance in your print bed, and accomodates this by raising or lowering the nozzle height accordingly in those areas. However if the variance is too high, your printer may not be able to compensate for these differences. The other potential issue, is although the nozzle compensates for an uneven bed, the bottom surface of your print will follow the contours of your bed.

Measuring

Your only option here is Octoprint with the Bed Visualiser plugin, this makes it very clear how level your bed is. Before going any further you should decide if this is worth the effort. If your differences are small I honestly don't think you should worry about it. How small is acceptable? I'm not sure I can answer that. I feel like I read somewhere up to 0.5mm from corner to corner is acceptable, but don't quote me on that. In my case my front right corner was -0.16mm and my front right corner was +0.38mm, so just over a 0.5mm slope. I can't say I can definitively attribute any issues I've had to my print bed, but I decided I wanted it as level as possible as that's the kind of perfectionist I am.

Fixes

Solution 1 - Masking Tape Mod

Someone recommended to me to perhaps try the masking tape mod. This was actually an incredibly quick and easy way to level the print bed at a very low cost. Using octoprint each time I made an adjustment I focused on getting the front left and back left corners the same height, and likewise with the front right and rear right. I then leveled the bed almost completely using the XZ skew adjustments by Prusa. One caveat with this fix though, is this "may" affect your print bed temperature as the masking tape will insulate the heatbed from the steel sheet. If you are printing PLA that should not affect your first layer, as you can technically print on a cold bed (I believe), but it may cause warping if your bed is not evenly heated. It's hard to say if this is an issue and probably depends on how much masking tape you use and where you put it. You'll need to experiment for yourself. Solution 2 - Silicone Mod So what is the ultimate solution? It's this and while it is the perfect solution it's also pretty involved and requires a lot of care to execute.

Getting the Prusa MMU2 work is about removing friction and pinch points on the filament.

First – Watch this You tube Video:

Prusa MMU2 Multi Material Unit - Tips and Tricks - Chris's Basement
Link to Youtube Video

Two Primary items to review when working to get reliable prints for your MMU2.

1) Checking the filament paths to make sure there is as little friction as possible. From the spool to the extruder here are the steps to take.

a. Make sure you have the latest selector printed from Prusa.
i. Print the selector out at .15 with Quality layer height out of PETG.
ii. When you assemble make sure the filament path is clear, Use a drill to clean it up a bit. Also, when you set your finda height make sure the filament can pass through WITH MMU THE FORMED END. When changing filaments, the MMU forms an end that has a larger OD.

b. Updated M10 Pass Through connector to get filament tube all the way to the bond tech gears.
i. https://www.thingiverse.com/thing:3541897

c. Prusa MMU2 PTFE Holder M10 Passthrough Adapter.
i. Supports the PTFE tubes as they enter the MMU with much less resistance.
ii. https://www.thingiverse.com/thing:3233579

d. Gravity Auto – Rewinder
i. I have tried 4 types of buffers, 2 rewinders and this so far is the best I have found.
ii. https://www.prusaprinters.org/prints/3729-multiple- mechanism-auto-rewind-spool-holder

2) Tension on the MMU and Extruder can cause issues. There is a sweet spot for both that can cause miss feeds. Specifically, that the filament would index to the extruder. The extruder would grab it, pull it in and then retract. Not sure why it does this but sometimes it retracts too far and loses the filament.

3) Signal and Power cables between the MMU and Prusa. I kept having the MMU fail with both Red and Green flashing lights. After I separated power and signal cable, re-routed then along the frame to the MMU it solved the issue.

Leadscrew induced Z banding.

Leadscrew induced Z banding is primarily caused by lateral displacement of the bed arms by the radial movements of the lead screws. In a perfect situation the Z linear rails and the carriages fixed to the bed arms would be able to resist this lateral movement.

Many 3D printers describe their bed mounting system as being a Maxwell kinematic coupling. According to the Wikipedia definition, “Kinematic coupling describes fixtures designed to EXACTLY (my emphasis) constrain the part in question, providing precision and certainty of location”

At first glance these bed mounting systems look like perfect Maxwell Couplings…but they are not, because the fixtures (balls sitting in pins and arms bolted to linear rail carriages, mated to the linear rails) do not solidly and EXACTLY constrain the bed, simply because there is a very small amount of movement between components in this restraint chain.

Under good circumstances the weakest point in this restraint chain is the clearance tolerances between the carriages and the linear rail. The clearances could be reduced by using higher grade, but more expensive linear rails/carriages. The effects of these clearances could be reduced by using wider rails and/or longer carriages, again at some increased expense. Prusa for example uses two linear bearings stacked one above the other to increase their effective length as part of their solution to Z banding.

Money can help solve a lot of problems, but so can clever design with cheaper components, and the aim with a hobby/prosumer printer is to get the biggest bang for buck.

In practice, because the large cross section of these is able to withstand bending from the applied forces it is very unlikely that any flexibility in the printed bed arms contributes to Z banding. However, a small amount of movement between the bed arms and carriages is possible and does occur if one or more of the screws that hold them on to the carriages work loose due to plastic creep or vibrations backing off the screws. Checking the tightness of these cap crews should be part of periodic maintenance.

Other issues such as loose grub screws on both X and Y motors and the Z lead screw flexible couplings can also cause artefacts that look like lead screw Z banding. In addition, the beds are not fully constrained against the pins by more than the weight of the bed assembly and sometime with the added assistance of quite weak magnetic force.

When one arm moves laterally, the balls in the other two arms can either slide on their respective pins which allows the bed to rotate fractionally or climb up on one pin in the pair to accommodate this, which if/when achieved would/will fractionally lift the bed. Both these options cause imperfect layer stacking, which can be viewed as Z banding in the prints.

Contributing to the issue is that the length of the bed arms amplifies any lateral displacement caused by the lead screws.

Before trying to engineer a new solution it is best to ensure that your printer is as mechanically fine-tuned as possible. It may be after doing this tuning you deem you do not have a problem that needs solving.

What causes the lateral movement of the lead screws?

1. Radial misalignment of the stepper motor shaft and the lead screw. Radial misalignment is when the centre of these two rotating ‘axels’ is not perfectly aligned.

2. Angular misalignment. This is when an extension of a line drawn along the two axial centres of two shafts intersect each other.

3. Angular misalignment of the lead screw with the linear rail. I have published sturdy lead screw alignment tools on Thingiverse to assist with reducing this misalignment.

4. Bent lead screws. Lead screws may not be straight to start with, but are also likely to become bent over time.

All of the above cause lateral (sideways) forces to be present at your lead screw nuts which are attached rigidly to your bed arms.

The only thing constraining the lateral movement of the bed arms is the chain of restraint from the from the linear rails to the carriages to bed arms through to the lead screw nuts

In attempting to move the arms sideways the printers lead screws are a competing with this chain of restraint…and you definitely want the chain of restraint to win this argument.

You have seen it, and it is very frustrating as the solution is not an easy ziptie or cable. 

Simple fix by tightening these two screws.

Y_Axis

A lot of people have reported problems with the stepper motors from Aliexpress.

But before we start let me say this. Most of the problems are mechanical problems.
Make sure you're frame is perpendicular and all axes can move freely without any issues.
Also test if you only have problems in stealth mode or also in normal mode.

Tweaking the motor current setting can do damage to the Einsy board as well as create issues with prints like high TMC temp failures!

Be aware that the Einsy board is only capable of 980mA per stepper motor, while the TMC driver could peak up to 2A.

If you choose to tweak the settings, you do this on your own risk!

If you still having issues with the motors you can adjust the motor current. Some user reported that they had success by increasing the motor currents in the firmware. So I will show you now how to do it.

Before we start changing values in the firmware, we should figure out what the right values would be.
The easiest way to do this is to use the g-code command M907 which is supported in Prusa Firmware since Version 3.5.0.

Let me explain first how the command works, you can also find more details here.

You can set the motor current for all axis to 500mA with

         M907 S500

or for each axis individual, which I strongly recommend.

        M906 [E<mA>] [X<mA>] [Y<mA>] [Z<mA>]

The format in M907 command is is E,X,Y,Z !

But what would be good values to start with? Well lets have a look into the Prusa Firmware:

In the Configuration_prusa.h file the motor currents are defined in trinamic registers, not in mA!
The format in the Prusa firmware is X,Y,Z,E !

     #define TMC2130_CURRENTS_H {16, 20, 35, 30} // default holding currents for all axes
     #define TMC2130_CURRENTS_R {16, 20, 35, 30} // default running currents for all axes
     #define TMC2130_UNLOAD_CURRENT_R 12 // lowe current for M600 to protect filament sensor

So we need a table to compare the trinamic registers with mA settings.

So the default for the extruder is 535mA. For the z-Axis it is 580mA, for the x-Axis 300mA and for the y-Axis 370mA.

A G-code command for setting the motor current with default values it would look like this:

     M907 E535 X300 Y370 Z580

So now you have a baseline to work you way up, until you don't have any issues anymore.
If you just have a problem with one or two axis you can simply remove the other axis.

For example if you have only issues with the Y and the Z axis your command would look like this:

     M907 Y390 Z610

Now add this line to the top of your g-code file that you want to use for testing. Print and check if you still have any issues. You can slowly increase the values until your problem is solved.

Once you have verified the values for your printer, use the table again to calculate the register settings.

So in our example the g-code:

     M907 Y390 Z610

would translate into:

#define TMC2130_CURRENTS_R {16, 21, 37, 30} // default running currents for all axes

Now we change the Configuration_prusa.h file and compile our firmware and upload it to the printer. Look at my previous posts how to do that. We just change the running currents, the holding currents should not be a problem.

Then test again if everything is ok. If you still have issues try to figure our the proper values with the M907 command first, before you make changes to the firmware settings.

With the higher motor current you might run into some issues. Maybe you get the TCM diver temp failure for long prints or your stepper motors get really hot. This is why it is important to increase the current setting just to what you really need!

 Many people share their print settings online. Some are really good, like the ones from Chris Warkocki aka codiac2600 who publishes them in the Prusa Facebook group and on GitHub.

While for many those profiles work very well out of the box, to me there is always some room for improvements that lead me to have my own profiles per printer, not per type of printer.

There are no 2 identical MK3S in the world. From little variations in the used parts over the care that was put in to put it together to the variation of adjustments like the belt tension there is always a difference in 2 printers.

So for really good prints, you need to spent some effort to calibrate your printer. Also if you have multiple printers like myself, then you want the printed parts to come out the same quality and size on every printer.

In the beginning I spent hours to adjust model dimensions in CAD between my first two printer.

But before we start, just a reminder that this is very much depending on the material you print and the shrinkage is dependent on the material and might have huge effect on the size of an object. 

So one of the first things I start with is the extruder stepper. You can use Octoprint and the Terminal to send commands and receive the output.

With "M503" you get the current settings. Not just the steps per unit, but this is the part that is in focus here so I cut the rest out. I also assume that you have already some filament preferable PLA loaded.

Send: M503

Recv: echo:Steps per unit:

Recv: echo:  M92 X100.00 Y100.00 Z400.00 E415.00

As I have a BMG extruder clone installed I have 415 steps for the extruder motor per unit.With a standard extruder you might have less, roughly 1/3. 

Now we need to make accurate measurements or we will only make things worse. Take some calipers or a very precise ruler. A folding ruler like shown in some videos is not an appropriate tool for this job. The maximum my calipers can measure is 150mm. Now measure the 150mm from the top of the extruder body and mark the filament with a fine permanent marker.

Next we heat up the nozzle and maybe just give a 5°C more than usual to make sure the filament is properly molten in time. With the nozzle at temperature we go back to the terminal in Octoprint. And set the count for the extruder stepper to 0.

Send: G92 E0

Recv: ok

Again, make sure the nozzle is at temperature. Then send the command to extrude 100mm of filament. 100mm is just fine as it leaves you with plenty length to measure. If you would extrude 150mm the mark maybe already in the extruder body and not visible and/or reachable to measure.

Send: G1 E100 F30

Recv: ok

Then measure the distance from the extruder body to the mark you made with the permanent marker. In my case I there was 47mm of filament left. So the extruder extruded 103mm instead of 100mm.

We need a little bit of math now to calculate the new values based on the ratio. 

100/103 x 415 = 402.91

That is quite some difference. For the next stepp we need to terminal again to send the new value to the printer.

Send: M92 E402.91

Recv: ok

But we also need to save it to the eeprom.

Send: M500

Recv: echo:Settings Stored

We can now read it back from the eeprom and ask for the values.

Send: M501

Recv: echo:Hardcoded Default Settings Loaded

Send: M503

Recv: echo:Steps per unit:

Recv: echo:  M92 X100.00 Y100.00 Z400.00 E402.91

As next step I usually perform a first layer calibration. There are plenty of instructions about it that you can find with google or at the Prusa blog or forum. Important is that the surface is clean, so you don't have adhesion problems.

Then I print a 1 layer test rectangle of 40x40mm and let it cool down. Then I measure the thickness with my calipers. AS I use the cheaper powder coated steel sheets from China, they have a rougher surface as  the Original ones from Prusa. Because of the texture you will not be able to get a 0.2mm thickness with a 0.2mm layer height. Usually I end up with a thickness between 0.2 and 0.3 mm. 0.25 is what I try to archive. 

But be careful to not scratch the build surface with the tip of the nozzle. And keep in mind to you have to do this for every sheet. This is why Prusa added the feature to store values for multiple sheets.

When I am happy with my first layer, then I move onto the other dimensions. Usually I print a cube of 40x40x40mm. I often see people using cube with just 20mm edge length. That save some material, but as short the distance is as smaller the deviation will be that you can measure. The optimal size would be 200x200x200mm I guess, but that costs a lot of material as you might need to redo this step a few times.

Once the print is cooled down we start to measure. Make sure you mark the surface somehow so you know later which axis it is. There are cubes with marks, but they introduce irritation in the surface that might lead to false measurements.

So again in my example those where my measurements:

X 39,80mm  Y39,60mm  Z 40,70mm

Similar math as we did for the extruder needs to be done per axis now.

X = 40 / 39.8 x 100 = 100.50

Y = 40 / 39.6 x 100 = 101.01

Z = 40 / 40.7 x 400 = 393.12

So we have our new values now and need to program them into the eeprom of the printer.

Send: M92 X100.50 Y101.01 Z393.12

Recv: ok

Save them

Send: M500

Recv: echo:Settings Stored

Read back and check values

Send: M501

Recv: echo:Hardcoded Default Settings Loaded

Send: M503

Recv: echo:Steps per unit:

Recv: echo:  M92 X100.50 Y101.01 Z393.12 E402.91

So now all stepper motors are calibrated for now. You might want to revisit this calibration once in a while to check if everything is till ok with you favorite print profile. As you can see here I still have a little "elephant foot" on the bottom of my test cube. There is are also some vertical lines that you can barely see. 

I have noticed that the nozzle was scratching over the print while printing and making a squeaky noise sometimes. Could the steps for the z axis be wrong? Well, as the end result was exactly the 40mm the 0.2mm layer height seemed to be ok. Did it?

No, remember when I said above that you will never get an exact first layer height of 0.2mm with a textured print bed?  So if your measured first layer height is 0.25mm, then the cube height should be 40.05mm, not exactly 40mm as you have to add the difference from the first layer.

So I had to adjust the steps for the z-axis again. 

Last, but not least there is shrinking. Shrining is what makes objects warp on the drin surface. When the molten plastic cools down it shrinks a bit. Some plastics shrink a lot, like ABS, some less like PLA. so you might have a PLA cube that is exactly 40mm on all sides, but the same cube printed in PETG it is not.

Then I focused on the surface. So I just printed a rectangle with 10mm height. What you see in the photo is the pain top surface, no ironing. You can nearly see some marks from the infill.

But still I was not happy with the top surface. So the next area to improve the settings was the print profile in Prusa slicer. In the filament settings you find the extrusion multiplier. I used the pretty PLA profile from Chris as a base that had it set to 0.95 (95%). I ended up using 0.93(93%) in this case.

Keep in mind that this might also vary on the filament you use. Especially when you use cheap filament that varies in diameter over the length of a spool, the results might not be very good. 

You can also set the change the flow multiplier in firmware  with M221. But I prefer to do this in the slicer profile as this is very much different depending on the filament. 

Basically the math is Total flow rate = Flow multiplier in firmware (M221) x Extrusion multiplier in PrusaSlicer. So a flow multiplier in the printer of 1.05 and a multiplier of 0.95 in Prusa Sliver would be a total flow rate of 0.99 again.

Once you have dialed in your slicer profile, you might want to revisit the calibration again as those settings might affect the overall values of the size of the printed part. If you really need that precision.

https://youtu.be/n5AAarO-3J4

I’ll use the following diagram as a visual aid. Note that this image has it’s own problems, but I’ll explain those below.

The key point of this image is the fact that there is no gap between the top of the nozzle (yellow) and the bottom of the heat break tube (green). This is a critical requirement because it is the only way to prevent filament leaks that will find a way out and creep over the heat block and nozzle.

The way to ensure you have no gap is to assemble the nozzle, heat block, and heat break while cold, make sure the nozzle and heat break are tight against each other, then heat up the entire assembly to printing temperature (or a bit above actually), and re-tighten the nozzle against the heat break. The nozzle should make about a 1/8 – 1/4 turn when you do this. The reason is that when you heat up the hotend everything expands, so you have to re-tighten the nozzle to eliminate the expansion gap between it and the heat break.

The diagram shows that the PTFE channel is not the same diameter as the outside diameter of the heat break. In real life it should be the same because the PTFE channel is where you insert a PTFE or Capricorn tube to feed filament into the heat break and then into the nozzle. The PTFE or Capricorn tube, just like the nozzle, needs to have no gap between it and the heat break.

If you have a direct drive extruder it will sit right on top of the hotend, so the PTFE or Capricorn tube will be short – just long enough to reach from the top of the heat break to the bottom of the extruder. But if you have a Bowden tube and remote extruder, the PTFE or Capricorn tube will be a lot longer. In either case the tube feeding your filament to the hotend must not have any gap between it and the top of the heat break.

Setup Guide

Required for the setup:

Bondtech PTFE fittings set for Prusa Mini

8mm Wrench / Spanner (included with the mini)

Permanent marker (optional)

1: Heat up, Unload filament, cooldown.

2: Unscrew nut on extruder, unscrew nut on Hotend, remove long PTFE tube.

3: Remove stock pipe fitting in hotend and extruder.

4: Remove stock PTFE tube in hotend and extruder.

5: (optional) : Use removed PTFE tubes and a marker to make a validation marking for PTFE tube insert depth, to make sure it seats all the way down.

6: Install bowden fittings in the extruder and hotend.

7: Insert PTFE tube into the extruder, push all the way down, Insert Bowden clip.

8: Insert PTFE tube into the hotend side pipe fitting, push all the way down, Insert Bowden clip.

Done!