Troubleshooting bed adhesion and first-layer problems¶
Bed adhesion and first-layer calibration are the first great mystery that new users encounter with the Prusa Mk3 printer. They are two different topics, but both must work well together for consistent good printing reuslts. If you can’t get both working properly, you’re likely to suffer from a variety of problems.
- Prints pop off mid-print, resulting in a tangled mess of filament spaghetti.
- Walls and vertical surfaces are uneven as the print wobbles on upper layers.
- The print warps away from the print surface in corners, resulting in wobbly bottom surfaces and uneven veritical surfaces.
- Lower surfaces are compressed, resulting in the “elephant’ss foot” effect.
- Bottom surfaces appear uneven.
Simply put, if your print doesn’t adhere well to the bed on the first layer, your print is very likely to fail. They first layer is key to good bed adhesions.
These notes are based on my experiences with the Prusa i3 Mk3 printer. If you are using a different printer, please verify the hardware details are same. These pages may be a bit rough as I revise them and add new material. Please check back regularly for updates.
Causes of poor bed adhesion and first-layer problems¶
Assuming you have no fundamentsl hardware problems, there are common challenges that you need to master. These are:
A dirty print surface. The PEI print surface works amazingly well, but must be kept clean. Very clean. Once your printer is initially calibrated, most print shifting and adhesion issues can be resolved with regular cleaning. It doesn’t take much to foul a PEI print surface. A few stray fingerprints, grease or hand lotion can cause havoc with adhesion.
Poor “Live-Z” initial nozzle height adjustment of the gap between nozzle and print surface. If you’ve never been able to get a good first layer, have changed nozzles or done hardware adjustments, your “Live-Z” (the initial gap between the nozzle and print bed) needs to be calibrated.
- Too high and molten filament won’t “squish” sufficiently to get a good grip on the surface, resulting in stringy, loose 1st layers. This leads to shifts and the resulting “spaghetti” results when a part pops loose and gets dragged around by the nozzle.
- Too low and the nozzle digs into the freshly-laid down filament, causing distorted surfaces and nozzle snags. In additoin to a stringy mess, this can result in the dreaded “Blob of Doom” that encases the nozzle, hotend, fan and other parts in a moltend mass of melted filament.
Let’s take a look at these two topics in more detail.
Understanding the PEI sheet and adhesion¶
The first thing to understand is that PEI is very different than most other print surfaces. Do some searching on the internet and you’ll find hundreds of articles on using glue stick, hair spray, glass sheets, blue painter’s tape, sugar syrup, and a host of other solutions. Ignore these. They’re usually written for printers that require manual bed leveling, ship with warped parts, lack removable print surfaces, use rudimentary print surfaces, or suffer other shortcomings.
The one and only trick to PEI is to keep it clean. How do to this depends on just how contaminated the surface is. The biggest enemy is grease, and the biggest source of that grease is your fingers as you handle the sheet. No matter how you clean your sheet, try to avoid touching the PEI surface as much as possible. The PEI sheet used on the Mk3 is a wonder. When properly cleaned and cared for, printed parts will stick firmly enough to get a solid print, yet pop off easily when cooled.
There’s no magic to getting good 1st layer results and excellent bed adhesion with this surface. The only requirement is proper maintainenance of the PEI surface and first layer (Live-Z) calibration to get the best results.
- Refer to the print bed cleaning procedure for details on properly cleaning and maintaining the PEI print surface.
When you adjust Live-Z, you’re adding or subtracting a small amount of height from the 0 position of your Z axis to adjust the initial gap between the nozzle and the print surface at the start of a print. This is essential to get a good 1st layer.
Unfortunatley, the on-board 1st layer calibration routine is difficult to use and understand. If your 1st layer isn’t good, there’s no sense trying to print anything more ambitious.
When you start a print, the sequence is:
- Startup g-code homes the printer to establish the X=0, Y=0 & Z=0 position of the extruder. (In reality, Z won’t be moved below 0.15mm.)
- G-code that your slicer generated moves the extruder up to the layer height you specify for your 1st layer and starts extruding.
Unfortunately, the Z=0 position may be sub-optimal for a number of reasons:
- We want a bit more or less squish for some filaments for adhesion purposes.
- We have a hard time gauging the thickness (but thanks to Jeff Jordan’s amazing “Life Adjust” procedure, this is much easier.)
- Your print surface may not be perfectly flat.
Live-Z lets us add or subtract a small increment from that 0 position to make these adjustments.
A few notes:
- On other printers, 1st layer calibration is a manual process that involves adjusting screws and using a sheet of paper to gauge the distance between the nozzle and bed. Disregard bed leveling or 1st layer calibration measures for other printers. The Prusa i3 Mk3 handles most of the details for us.
- Ideally, setting a 0.2mm 1st layer height in your slicer will result in a 0.2mm layer height being printed, but it can vary. We may wind up squishing the 1st layer for better adhesion or backing off a bit to avoid dragging the nozzle.
- Mesh bed leveling further complicates all this (for our benefit) by making yet further adjustments at various spots on the bed to compensate for an uneven print surface. At the start of the print job, the printer will make measurements using the PINDA probe to make sub-millimeter adjustments to compensate for minor deviations in the print surface.
- Refer to the Live Z calibration procedure for details on adjusting your Live-Z 1st layer nozzle settings.
Testing bed adhesion¶
If you’ve not seen the Prusa PEI surface in action, here’s a quick test showing just how good the Prusa PEI flex surface is. Let’s start matteeee’s bed adhesion test model to test the limits of adhesion.
This is an ideal model for testing the limits of adhesion.
- The print is attached to the bed with only a small surface area. No brim, raft, or other adhesion aids should be used.
- The severe, unsupported, tall print angle applies downward force to pull poorly-attached surfaces away from the print surface.
- The tall print will come under maximum pressure and bumping from the nozzle as it moves throughout the print.
Here’s the same model ready for slicing in PrusaSlicer.
Here are the results of slicing, verifying the lack of bridge, raft, supports or infill.
Here’s the model printed on a 9 month old cleaned PEI surface using PLA with 0.20mm layer heights with a 0.40mm nozzle.
Finally, here’s the process involved in removing the print without damaging the PEI surface or injury.
The same prints that are used for Live-Z calibration can be useful for testing bed adhesion. Here are the STLS for the 75x75, 210x205mm, 3x3 grid, and 20mm cube prints:
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Last updated on 20190729