How to Fix 3D Printer Nozzle Hitting Prints or Bed (Collision)

You’ve leveled out your 3D printer correctly and done the normal process of 3D printing, but for some reason your nozzle is hitting or dragging into your prints or scraping and digging into your bed surface. Even worse when it’s a print lasting several hours.

These aren’t ideal scenarios, I’ve experienced these before but it’s definitely fixable.

The best way to fix your nozzle hitting your prints or bed is to slightly raise your Z-endstop on the side of your 3D printer. This is what tells your 3D printer to stop moving down so much. You can also use a Z adjustment in your slicer settings to account for a higher bed surface.

This is the basic answer but there is more important information to understand to make sure you avoid this problem in the future. Read on to find out about specific issues such as printer settings, how to adjust your Z-endstop and so on.

Why Does Your Extruder Knock Over Models Randomly?

There are a few reasons that we can get into behind why your extruder randomly knocks over your models.

• Poor Layer Adhesion
• Warped Print Bed
• Over-Extrusion
• Extruder Too Low
• Incorrectly Calibrated X-Axis
• Extruder Not Calibrated

Let’s go through each of these bullet points and explain how it can contribute to knocking over your prints or even having your nozzle dig into the bed.

Poor Layer Adhesion

When you experience poor layer adhesion in your 3D prints, you can definitely struggle from your prints getting knocked over during the process. We can see the reason for this being that if each layer isn’t extruded correctly, it can affect the layer above.

After a few poor layers, we can start to have material going in the wrong places, to a point where your extruding pathing gets in the way.

A little bit of contact with the print head and nozzle in this instance is likely to knock over your 3D print, regardless whether you are hours into a print.

How to Fix Poor Layer Adhesion

The solution here is to ensure you have the correct speed, temperature, acceleration and jerk settings so you can ensure a smooth printing process.

It can take some trial and error to figure these values out, but once you do, poor layer adhesion should stop plaguing your prints to get knocked over. The fans on your 3D printer can also have a part to play in this, depending on what material you are using.

Some materials don’t work very well with fans on such as PETG, but we definitely recommend using a good fan for PLA, especially at a fast speed.

Warped Print Bed

A warped print bed is never a good thing for many reasons, one of which being how it can contribute to knocking your prints over, or causing the nozzle to dig into the print bed.

When you think about a warped print bed, it means that the bed level is uneven so a nozzle movement from one side to the other will have the print bed in lower and higher locations.

Your bed may be relatively flat when it’s cool, but after it heats up it can warp even more which can result in your nozzle bumping into your models.

How to Fix a Warped 3D Print Bed

I’ve written an article on How to Fix a Warped 3D Print Bed so definitely check that out for more details if this may be your cause, but the short answer here is to use sticky notes and place them underneath the print surface to slightly raise the level.

Although it doesn’t sound like much, this solution has actually worked for several 3D printer users out there, so I would recommend it. It’s not hard to try either!

Over-Extrusion

If your 3D printer is suffering from over-extrusion then it means some layers are being built up slightly higher than it should be. That increased amount of extruded filament on a model can be high enough to have your nozzle knock into it.

The over-extrusion can also make this happen because the extra material that is extruded can block up the extrusion pathway, building up pressure and causing the X and Y axis to jump steps.

There are several causes of over-extrusion, meaning it can be a challenge to fix this issue but I’ll give you some of the most common fixes that help solve the problem.

How to Fix Over-Extrusion

The usual fixes for over-extrusion tend to be either with temperature or flow changes in settings.

Try the following fixes:

• Decrease printing temperature
• Lower extrusion multiple
• Use a higher quality filament with good dimensional accuracy

If your printing temperature is on the higher end for your material, it means that it is in a more liquid state, or less viscous. Now the filament is too melted and flows easily, leading to increased flow rates.

The extrusion multiplier is related, where the flow rates can be decreased to account for too much material being extruded. This should decrease how much filament is coming out and result in fixing over-extrusion.

Sometimes its just what type of filament you are using or the quality of your filament. Using cheap, unreliable filament is going to be more likely to give you issues even if you have successfully printed with it before. If this has started happening after changing your filament, this could be the issue.

Extruder Too Low

The level of your extruder shouldn’t be too low, which can be the case if the assembly isn’t precise. It’s not out of the ordinary to assemble your 3D printer quickly and end up not placing things how they should be.

How to Fix an Extruder That’s Too Low

If your extruder is too low, you’ll have to take your extruder apart, then reseat it properly. The case here is that the extruder might not be securely fitted inside how it should be. I would search a video tutorial on your specific 3D printer and follow how the extruder was put in.

Even if you have been printing just fine for some time, it’s still possible that you temporarily fixed the symptom without fixing the problem.

Incorrectly Calibrated X-Axis

This isn’t a common issue but one user described how an incorrectly leveled X-axis after a certain Z-height caused prints to start catching on prints and get knocked over. It would be pretty difficult to notice such a thing, especially since it happens so far into a print.

If you realize that your prints fail at the same point every time, this could be the cause of why your prints are failing and models getting knocked over.

How to Fix an Incorrectly Calibrated X-Axis

The simple way to calibrate your X-axis is to turn the eccentric nuts of the wheels and tighten them.

Extruder Not Calibrated

Many printing issues are actually caused by the extruder itself rather than all these other factors that you are coming across. It’s easy to underestimate the ability of your extruder settings and calibration to have a negative effect on prints.

Follow the video guide below to correctly calibrate your extruder.

I would advise doing it twice just to make sure you have the extruder calibrated perfectly.

Other Solutions to Fix Nozzle Knocking into Prints

• Try using a Z-hop setting in your slicer to raise the nozzle while it moves (0.2mm should be fine)
• Decrease printing temperature if you see the material curling is the cause

How to Fix Nozzle Scraping or Digging into Print Bed

Z-Offset Settings & Endstop Problems

Put simply, the Z-offset settings are a slicer setting which moves an extra distance between your nozzle and bed.

Before you get into your Z-offset settings, you want to check that your endstop limit switch is in a good place. This endstop tells your 3D printer where to stop your print head from moving past so it doesn’t overextend.

At times, simply lifting this endstop up will solve issues with your nozzle hitting or digging into your bed.

You should also run some other checks:

• Is your endstop switched wired up properly?
• Is the switch working?
• Have you firmly mounted the switch to the frame and adjusted it correctly?

Another thing you shouldn’t overlook is having your bed level. A bed that is uneven can easily be the downfall of your 3D printing success, so it needs to be parallel to the X axis and the same distance away from bed to nozzle throughout the platform.

Make sure you set your Z endstop so that the nozzle is close to your build platform, while your bed leveling screws are screwed in for a decent amount.

After doing this, do your normal leveling process with each corner, using a piece of paper to get the correct distance throughout your bed.

Keep in mind that your leveling procedure varies whether your print bed is hot or cool, but a hot bed is most preferred.

Double check your slicer settings and make sure you aren’t using a Z-offset unless its for a specific reason such as printing ontop of another object or doing more complicated prints.

M120 enables endstop detection, and some slicers don’t actually enable this before a print starts. If your printer doesn’t detect the endstop, that’s where you can run into your nozzle hitting your print bed. You definitely want this to be detected before starting a print or doing auto-home.

How Far Should The Nozzle Be From The Bed?

This really depends on your nozzle diameter and layer height, but generally, your printer’s nozzle should be around 0.2mm away from your print bed, while your bed leveling screws are fairly tightened.

The most common method to determine the distance between the nozzle and the bed is using a piece of paper or thin card between the nozzle.

It shouldn’t be overly tight on the nozzle and piece of paper though because it can get squashed down and actually be lower than you need. There should be a good amount of wiggle of the paper or card.

What this does is allow for enough space for your nozzle to extrude material out onto your bed and actually make enough contact for proper bed adhesion, creating a perfect first layer.

If you have a layer thickness of 0.6mm compared to the average 0.2mm layer thickness, then your printer nozzle being 0.2mm away from your print bed won’t work as well, so you want to take layer thickness into account when determining this.

You definitely want to go around each corner of the bed, as well as the center twice so you can get a good gauge of the level.

I also like to try a test print with a few skirts so I can actually see how well material is being extruded from the nozzle.

Ender 3, Prusa, Anet & Other 3D Printer Nozzles Hitting Prints

Whether you have an Ender 3, Ender 5, Prusa Mini or Anet A8, these all have the same type of causes and solutions to stop your nozzle hitting your prints. Unless there are large design different, you can follow the steps above.

I would make sure to check your nozzle and extruder are in good order. There have been cases where there’s a missing screw that holds the hotend in place, which can lead to uneven sagging to one side.

Before a 3D printer is sent to you, they are put together in a factory so you can get loose screws in certain parts of your 3D printer which can lead to some printing failures.

I would go around your 3D printer and tighten up the screws as it can easily translate to better print quality.

You can adjust the filament diameter if you are extruding too much plastic or check for large changes in direction, which can cause your print head to bump into your model.

How to Fix 3D Printer Hitting Supports

There are some cases where rather than hit your actual model, your nozzle decides to only hit the supports. This can be a frustrating issue, but there are definitely ways to fix this problem.

Some people will just increase settings to make their supports stronger but this isn’t always going to be practical.

Look towards adding a raft or a brim to your model if your supports are printed from the bed since the support itself doesn’t always have a good foundation.

Check your X-axis and make sure there isn’t any looseness or wobble in there. If your hotend has the chance to sag a little due to vibrations and quick movement, it can go low enough to hit support layers or previous layers.

If there is an off-set on your motor and the X-axis carriage, you can print a Z-axis motor spacer to correct it.

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