How to Fix MK4 First Layer Too High
December 5, 2024
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If you've ever started a print on your MK4 only to find your first layer is being printed too high off the bed, you're not alone. This frustrating issue has been widely reported in the community, and we encountered it ourselves while developing automated part removal for the MK4. After extensive testing and experimentation, we've not only identified the root cause but developed a reliable solution that doesn't require constant manual intervention.
Contents:
The Real Culprit: Oozing During Bed Levelling
The MK4's bed levelling system relies on the nozzle physically tapping the bed to create an accurate mesh. While this is generally an excellent approach for precise first layers, there's a catch: any material on the nozzle tip can throw off these measurements.
As we attempted to pinpoint the issue, we observed that printers which consistently produced high first layers typically had residual filament buildup from previous prints. As the nozzle moves around taking measurements, more material leaks out, so the nozzle essentially gets "taller" with each measurement, progressively throwing off the calibration. It's like trying to measure with a ruler that keeps getting longer!
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This becomes particularly problematic when:
- Printing with larger nozzle sizes
- Using materials that tend to ooze (like PETG)
- Running back-to-back prints
- The printer heats up for the next print
We first noticed something was wrong when some printers would repeatedly trigger their automatic nozzle cleaning routine - a feature designed to handle small amounts of residue. However, with larger buildups of material, this built-in cleaning system would often fail, leaving us back at square one.
Our Journey to a Solution
Prusa's recommended approaches include:
- Sticking to smaller nozzle sizes (0.4mm or 0.6mm)
- Manually cleaning the nozzle before each print
- Using a silicone sock on the nozzle
While these work, they either limit your printing capabilities or require constant attention. When you're running hundreds of prints, stopping to clean the nozzle before each one isn't just inconvenient—it's a significant time sink.
A New Approach
We noticed that Bambu Lab printers, which use a similar bed-tapping system, handle this issue with a built-in nozzle cleaning mechanism. While the MK4 doesn't have this hardware, it gave us an idea: what if we could create our own cleaning mechanism using the printer itself?
Our solution is elegant in its simplicity. Here's exactly how it works:
1. Before each print starts, we print a thin block of material that serves two purposes:
- It properly primes the nozzle for the upcoming print
- More importantly, it creates a disposable "cleaning area" for the nozzle
2. Instead of wiping the nozzle directly on the bed (which is standard practice), we wipe it against this freshly printed material. This seemingly small change offers several significant benefits:
- Fresh plastic naturally wants to stick to other fresh plastic, so any material on your nozzle preferentially sticks to the purge line
- Wiping against plastic instead of the hard bed surface significantly reduces nozzle wear over time, helping maintain print quality
- Every print gets its own fresh cleaning surface - no worn-out brushes to replace
3. During the cleaning process, we cool down the nozzle. This critical step:
- Makes excess material stick more readily to the purge line
- Allows any remaining material in the nozzle to solidify, preventing further leakage during homing
4. After cleaning, we:
- Home again to get an accurate bed reading (now with a clean nozzle)
- Keep the nozzle firmly pressed against the print surface during cooling
- This prevents any additional material from leaking out and interfering with bed levelling
The Result
This solution has transformed our MK4 printing experience:
- No more manual cleaning between prints
- Reliable first layers regardless of nozzle size
- Compatible with "oozy" materials like PETG
- Reduced nozzle wear over time
While you'll still need to do occasional hotend maintenance every few days with particularly sticky materials, it's far better than cleaning between every print.
Make It Work For You
Want to implement this solution on your own MK4? We've built this into our AutoFarm3D software, but we believe in sharing solutions with the community. You can use our tested start gcode sequence, which we've made freely available here:
Important Note: The provided gcode includes temperature and extrusion settings that work well with standard configurations. However, you may need to adjust these based on your setup:
- Larger nozzle sizes may require more material for the purge line
- Different materials may need adjusted cooling temperatures
- The heating and cooling durations might need tweaking based on your specific filament
Join the Conversation
Have you experienced first layer issues with your MK4? We'd love to hear about your experiences or answer any questions about implementing this fix.
Looking for more MK4 solutions? Check out our previous post on fixing mid-air printing issues, and stay tuned for more proven fixes for common MK4 challenges.
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