How to Fix Prusa MK4 First Layer Printing Too Low

Are you caught in an endless cycle of cleaning beds, adjusting Z-offsets, and watching sensor readings, yet still getting inconsistent first layers on your MK4? During the development of our auto ejection system for Mk4, we encountered the exact same issues. After months of testing across dozens of machines, we discovered that it’s not one or two single things causing this issue, but a number of compounding factors. For that reason, it can feel impossible to fix, as many have noted online. In this blog we’ll go through everything that could be causing this issue on your printers and how you can fix it.

Contents:

The Problem: More Than Just Z-Offset

When your MK4 levels too low, you'll notice your prints will show these symptoms:

• First layers that are inconsistent across the bed - perfect in some spots while overly squished in others
• Transparent or rippled sections in your first layer
• Visible indents or scrapes in your print surface
• Parts that are extremely difficult to remove
• Progressive damage to your print surface
• Layer shifts during fast first layer printing

During our testing across multiple machines, we noticed that some MK4s would consistently produce overly squished first layers - a serious problem when developing automated part removal. Through extensive testing, we identified several root causes that many users miss, including issues that can develop even in factory-assembled machines due to shipping, thermal cycling, and normal wear and tear.

Solutions: From Simple to Structural

Follow these solutions in order - each step builds on the previous ones to ensure consistent results.

1. Start With The Basics

Before diving into mechanical fixes:

1. Check filament tension (see our article on fixing mid-air printing issues). If the filament is pulling back on the extruder, it will need to push harder into the bed to trigger the reading on the sensitive load cell.
2. If you are printing in a new material, make sure your extrusion multiplier is correct.
3. Make sure your bed is clean and completely free of dust and debris. If you are using the VAAPR™ print surface, make sure you use dish soap and water.

2. Check Bed Stability

An unstable bed can cause inconsistent measurements. Confirm the bed carriage is solid by pushing on the corners with your finger. If the bed can be pushed down when the nozzle comes in to home, it will detect the Z home point too low.

To fix this:

1. Tighten the Y axis assembly.
2. Check all the screws under the build plate are tight and not stripped. Loosen all the screws, then re-tighten them in the order recommended in the Prusa assembly guide.

3. Address Heat-Related Issues

Use a straight edge to check if your heated bed warps when hot.

For high-temp materials: Warm up the print bed to 60-80°C before re-tightening the screws. This allows the bed to expand before it gets fixed in place. If the bed was locked into place when cold, it will flex when it expands with heat.

4. Check Nozzle Assembly and Condition

Two critical but commonly overlooked factors have to do with the nozzle itself.

‍Loose Nozzle Mount: If the thumbscrews holding the nozzle in place are loose, the nozzle won’t get an accurate reading when probing. If the nozzle is loose, it can drop down toward the bed as filament is pushed into it during printing.

Worn Nozzles: Worn nozzles will result in overextrusion and bad hotend thermals, resulting in unexpected material extrusion and poor leveling performance. Check if your nozzles are worn and replace them before they become a problem.

Maintaining Consistent Performance

With a properly functioning MK4's load-cell bed levelling, you shouldn't need Z-offset adjustments in PrusaSlicer. While these issues can appear even on factory-assembled machines, implementing these fixes and maintaining them will keep your printer running perfectly.

For optimal results:

• Re-tighten bed and nozzle screws every few hundred print hours
• Replace nozzles at first signs of wear
• Regular maintenance prevents the first layer from becoming problematic

Have you experienced first layer issues with your MK4? We'd love to hear about your experiences or answer questions about these fixes.

Looking for more MK4 solutions? Check out our previous posts on fixing mid-air printing and nozzle oozing issues.

Forum posts about this issue:

• MK4 first layer rippling‍
• Issues with Waves/Wrinkles on First Layers on MK4
• Mk4 uneven first layer
• MK4 first layer issues‍
• First layer rippling / Z height
• Never perfect first layer + warping‍
• What would cause this ripply look in first layer?  ‍
• First Layer Z Height Issues