Author: Jonathan van Heijzen

I saw a user in a forum asking for help with bridging. They were trying to create a large print that had many bridging features that were intended to be straight across and ended up being droopy.

When someone asked what they had done already, they responded with “I slowed down my speed to help the bridging out.” In most cases, this is the opposite of what needs to happen. If my print has a lot of bridging features I typically speed it up. If you think about the mechanics of what is happening here, heat is being applied the entire time that your nozzle is extruding. So, the longer something takes with heat being applied to it, the more it will sag as a result.

I’ve printed parts in the past that end up looking like something was dragged across the surface while it was printing. In reality, something may have been dragging across the surface. The first thing that I check when this happens is to make sure that the nozzle is clear. This is a typical sign that the nozzle may be clogged.

If it does turn out to be clogged, I do a “cold pull.” Heat the nozzle up 20 – 25 degrees past what you use it at during printing. Then let it cool completely. The idea is that any debris will collect into the filament. Once it is cool, heat it up again but tug on it from the extruder end. It will break loose from the nozzle at a much lower temp than what you print at. Hopefully, any debris that was clogging the nozzle comes with it. Just cut the end of the filament off and feed it back in.

Your printer is supposed to be able to create a solid outline on the bed of your printer. Sometimes, though, your print will have little gaps in it and it will look like Morse Code. Most of the time that I see this, it is the result of a user having changed something regarding their extruder. Their gear may have worn out and they replaced it, they changed filament or nozzles and forgot to calibrate their e-steps, or their extruder is starting to fail.

For troubleshooting, first make sure that everything is mechanically sound. Take a look at your extruder gear and make sure it’s not missing any teeth.

Once you have determined that everything looks good, calibrate your e-steps.

Sometimes I print parts that have a top surface that look like a riverbed. There are valleys and branches going all across the surface of the part. This is usually a result of the nozzle being too close to the bed. Mechanically, there is too much filament coming out of the nozzle for the amount of space between the bed and the nozzle. When this happens the filament flows into other areas of the print and creates these valleys.

In short, your nozzle is too close to the bed if you have this. Adjust the height or redo your bed level.

These issues are easiest to identify on square parts. If you have mysterious blobbing on organic shapes, maybe try a cube test print to see if your printer has one of these issues on the corners. If you do end up with issues on your corners, and your printer has no other problems with printing, pressure advance (Klipper firmware) or linear advance (Marlin firmware) may solve your issue. Although they accomplish the task in different ways, both solutions solve the problem of issues with corners in 3d printing.

As a side note, when I am attempting to determine how accurate my machine is or to calibrate it, I first print a cube that I designed that has very large corner radii so that corner issues won’t bias my calibration.

If you spend any time reading through 3d printer help forums, it won’t be long before you see someone post about a problem that they are experiencing, to which someone else replies “you need to level your bed better.” But how good is good enough?

When it comes to 3d printer beds, I typically run into two variations:

  • 5 point bed level. This is a bed configuration that comes standard with many different firmware packages. It’s simple to set up and will give you pretty good results. The downside is that it doesn’t provide any flexibility in case your bed is warped in between the points. In doing some testing on this version, it seems like I started to have problems if my bed variance exceeded 0.05mm. Increasing my first layer height somewhat mitigated the problem, but didn’t solve it completely.
  • Mesh bed level. For this experiment, I used a 25 point (5×5 grid) mesh bed level. I allowed my bed variance to get close to twice my layer height, so for a 0.1mm layer height my bed variance was nearly 0.2mm. Then I set up my mesh bed level. I was able to see a slight difference in print quality near the base as the bed variance was increased, but it wasn’t significant. However, the differences that I observed were pretty minor and I believe that, in most cases, the resulting print would be considered “fit for use.”

Here is my recommendation. Get your bed as physically flat as you possibly can. See if you can get it to 0.05mm flatness. In most cases, this is possible as long as you have decent springs holding the bed up. Then run a mesh bed level to compensate for the variance that still exists. For most materials, I’m able to run prints without any hairspray, glue, tape, or anything else to hold the print onto the bed by following this methodology.

Some 3d printers end up with rough top layers. One thing that you can check if this happens to you is the rate of filament flow. Filament flow is affected by a couple of things, the most common issues are:

  • Flow rate setting in slicer. I normally set my flow rate to 105% – 110% for the first few layers, then turn it down to 100%. If this is set too high then your printer is adding more filament than you might need, resulting in a rough surface.
  • Extruder calibration. Run a simple extruder calibration to double check that you are extruding the amount that you think you are. If you are overextruding, you might be causing problems for yourself.

Although there are a couple of things that can cause parts to curl, I have found that it is usually related to the environment that the printer is in. If your parts initially print good layers, and then the print curls up away from the bed I would initially start to investigate whether the printer is in line with an HVAC vent or in a very drafty area. Ideally, put it in an enclosure.

I saw on a forum someone who was having problems with their mesh bed level. The advice that they were given was to disable the feature and use the screws tilt adjust features in the firmware. Here is what each of those features do.

Screws tilt adjust, in most firmware packages, allows you to set the distance between the bed and the nozzle. It does this in each of the four corners of the bed and in the center of the bed. The benefit of doing it this way is that it’s pretty simple to get started and the results are typically decent. No need to fix it if it ain’t broke. The downside of this method is that it assumes a pretty flat bed in between those points. If it isn’t, the firmware won’t be able to account for the variations simply because they haven’t been compensated. This was my situation. After replacing a warped bed a number of times I decided that it was time to do something different.

Mesh bed level. This method is more work to get set up, but it does account for a warped bed. To set up a mesh bed level, the firmware will allow the user to select a grid, usually 3×3 or 5×5. This grid is used to compensate for any warpage that may be present in the bed.

My typical approach is to mechanically make the bed as flat as possible. By adjusting the clamping pressure on each corner of the bed you can manipulate it to flex more. For now, don’t worry about the orientation, we’ll deal with that later. Once you get a bed that’s pretty flat, let’s go ahead and adjust the bed screws manually. Run the function to adjust the bed screws and make sure that your orientation is as good as you can make it. Next, adjust your mesh bed level. Some people do this before each print, I don’t. My environment is pretty stable so I just leave mine set up and run a mesh bed level from time to time.

A lot of times I’ll see someone asking for help online that goes something like this:

“I just changed the bed on my 3d printer to XYZ, bought a new extruder from LMNOP brand, updated my retraction, temperature, and speed settings, and now nothing works. How do I fix it?”

My advice to these folks is almost always to back it up a bit. What ends up happening is that they change so many things all at once that it’s impossible to tell which configuration change or setting change was the one that threw everything off.