3D Printing Basics 9 – Common Issues and Solutions

3D Printing Basics: When things go wrong! (Ep9)

3D printing doesn’t always work perfectly. I hate to say it, but, you know, when even commodity inkjet printers still need a bit of help every now and then, I think 3D printers are actually pretty good on that front today. But, still, there are things that can go wrong due to user error, the manufacturer not doing their homework, or because of bad materials. We’re going to look at some of the most common hiccups you can run into and where to start when fixing them.

I gotta tell you, it’s one thing when you’re trying to get a printer to work better, but trying to get it to produce sub-par prints with just the right issues so that I can show you what they look like… well, that’s one that only some people will enjoy doing. I’m sorry Mini that I had to do this to you.

What does a good print look like?

But before we start going through what bad prints look like, I think we should start with what an actual good print looks like, because I pretty often see people asking about how they can fix things they think are wrong with their setup, but are actually just inherent properties of the filament printing process. And by the way, you can actually hide or emphasize these just by changing the lighting and the angle you photograph your parts from.

One of the things you might see that are actually normal is a bit of texture on the layers, again if photographed from the right angle, small details aren’t always going to print well, especially when a part ends up in a pointy spot where the nozzle doesn’t have a chance to move away and give that area a chance to cool, the underside of parts might have a few loose loops where the geometry just wasn’t all that great and you will always see the layer start point, you can hide them on the model, but there will always be at least a little dot visible.

There might also be a bit of ringing visible on edges and some gaps in top layers, but you know, with the current tech we have, some things are just not worth optimizing away because you’re going to have to make some big compromises to get rid of that one artifact that you may end up introducing other issues in the process.

And the fact that these prints aren’t perfect is one of the reasons why for example glittery filament has become so popular. It distracts your eye.

Since we’re usually printing at layer heights of 150µ or so, the layers themselves often visually disappear, that’s why prints done with big nozzles and at large layer heights, like with the Volcano, tend to look more appealing or more consistent than ones where you try to get everything perfect, but you can never quite make it and anything that is still wrong then sticks out like a sore thumb. Anyway, that’s just to say, 3D prints, especially with filament printers, are never perfect, it’s often just an art of hiding the flaws that are still there well enough so that you stop noticing them.

But there are still a few “real” issues that can be fixed and need addressing. I’ll go over what they look like and where to start looking for fixes for them, and I’ll have guides linked in the description below to where you can find more details, but obviously I can’t go through all the possible fixes and permutations of them in this video.

Extrusion Problems

Let’s start with extrusion problems. Obviously, those are going to be the most common ones since the rest of the printer, mechanically, isn’t much more than a light motion system and those aren’t that complex of a beast to tame. But we’ll get to that in a second.

Too little – Too much Filament

First, what I’d group into “too little” or “too much filament”. If your filament toolhead is consistently extruding but is laying down the wrong amount of material, you are going to get what’s known as underextrusion or overextrusion.

Underextrusion manifests as poor performance on overhangs, on top solid layers with gaps in there, or on sloping top surfaces where, again, you might start seeing gaps. Parts will also be much weaker than necessary. Now, most printers are actually set up to underextrude by about 5% out of the box – that makes for prettier prints than overextruding by 5%, and most people are not going to notice prints that don’t look perfect much more than they’ll notice parts that break a bit more easily, so they just veer on the safe side. But when there is too much underextrusion, it starts becoming a real issue. You can experiment directly on your printer’s LCD and then, the easiest way to make that permanent is to save it in your slicer.

Overextrusion is a lot more easily noticeable – worst case, prints end up with blobs and literally overflowing walls, but it’s actually most noticeable on top surfaces where the material can’t escape out to the side, but end up piling up on top so that the nozzle ends up dragging through the material. Same idea as with underextrusion, you can live play around with the multiplier directly on the printer and then save it in the slicer.

So over- and underextrusion are both things that are continuous, so they’re present from the very first layer all the way to the last.

Clogging

There are a bunch of hiccups that can happen at any time during a layer. So what’s actually somewhat common is that your print will start out fine, but at some point you’ll notice that you’re not getting enough filament anymore.

That can be a whole bunch of things. 1) Some particle clogging your hotend. 2) The PTFE liner in your hotend kinking. For both of those, see episode 4 of this series on how to do a cold pull and how to repair the PTFE. 3) The hotend overheats. That’s down to either a poorly assembled hotend, issues with the cooling fan or just using a poorly-made all-metal hotend. 4) Overheating in the extruder due to motor heat. Add cooling or reduce the stepper current for that motor. 5) Bad filament with, for example an inconsistent diameter that gets stuck or even just simply rubs somewhere along the extrusion path.

Blobs and Stringing

Next, what if you get blobs on your prints? For that, we should distinguish between tiny blobs that you get from moisture pops and bigger blobs you get where the printer starts and stops a line. So, for that first one, use dryer filament, or dry the filament you have. For the second one, your retract settings are not quite perfect. Now, there is not one perfect set of settings here, yet, but generally, if your retract settings are too aggressive, you’ll end up with blobs, if they are not aggressive enough, you’ll get stringing on your prints.

And some hotends just aren’t great for filament flow control, so in those cases where you can’t seem to find a good compromise for retract settings, I’d personally rather have a bit of stringing, since that’s easy to either tear off or quickly melt off with a hot air gun.

Temperature Problems

Other extrusion issues can stem from temperature problems – either printing at usually too low of a temperature, remember, hotends even in the same model of printer can vary by quite a lot in whether they report a temperature that is too high or too low, or from an inconsistent temperature in the hotend itself. A good way to track how stable the temperatures are is to use the graph in Octoprint or even just the one in Pronterface.

Just connect your printer via USB and you can keep track of what’s happening during a print. If the temperature is wandering around, it’s time to check if everything on the hotend is correctly assembled and if it is, but temperature is still inconsistent, a PID tune might be in order. Again, I’ve linked those more advanced tutorials below.

Again, covering every fix in full detail would have made this a two-hour-long unwatchable mess, so I’m trying to keep it relatively short here.

Bed Adhesion and Warping

Alright, let’s move on to bed adhesion and warping. Five things to check if your parts come loose during printing or you’re seeing the corners start to lift up:

1) Compatibility between the filament you’re using and the bed surface on your printer, for example the textured PEI sheets are best for prints with large contact areas or for typically high-adhesion PETG filament, while smooth PEI gives you maximum adhesion even with small PLA prints 2) Sufficient ambient temperature, 3) Correct bed and nozzle temperature for your filament 4) Correct nozzle distance for the first layer and 5) a level, square, trammed bed, however you want to call it.

Let’s go over bed leveling real quick: The goal is to get an even, well-enough squeezed-down first layer. If you look at it, it should be smooshed down enough to eliminate gaps, but no so much that the nozzle is digging through material.

And of course, it needs to be even throughout the entire area you’re printing on. If you’ve got a printer with sensor-based auto-leveling, you just need to set the nozzle distance, on the Prusas, there’s a specific test print feature for that, but on other printers you can just watch the first layer and make adjustments as you go. For leveling, the most common way to get it done is to use a piece of paper, preheating your printer, and, with the nozzle at the “zero” height, checking above each leveling spot and adjusting until the nozzle just barely brushes against the paper.

That should give you a good starting point for absolute height as well. And as a tip so you don’t have to get it absolutely perfect, you can also increase the first layer height and extrusion width to make that make that layer more robust against small imperfections in the leveling. 

More Temperature Issues: Curling, molten down Details, Gaps

Staying with temperature-related issues, if you’re seeing curling, molten down fine details and gaps in your top solid layers, chances are you are printing too hot, too fast or with not enough cooling. All settings you can adjust in the “Filament” tab in your slicer – try one at a time and see which one helps the most.

If you’re printing too cold or with too much cooling for your filament, you’ll get brittle and dull-looking parts instead. If adjusting temperatures doesn’t help with top layers, you might simply need to increase the amount of top solid layers and the infill percentage.

Mechanical Issues

Now, lastly, mechanical issues. There’s three distinct ones that I want to go over. The first one is kind of hard to spot if you’re not exactly sure what to look for. If bearings, motors or other functional parts are loose or worn down, you might end up seeing inconsistent vertical surfaces. If you grab your printer’s moving axes, it’s ok if you can slightly flex them, but if there is actual play in them, you should probably investigate further into you printer’s bearing and structural setup.

If you’re seeing ripples on sharp corners, that’s commonly known as ghosting or ringing and it’s a result of excessive flex along the X or Y axes of a machine. A common suggestion would be “tighten the belts”, but that can only get you so far if the setup is just built with too much flex. For example cheap belts will often be way more springy than quality ones or if the forces from acceleration and deceleration of the toolhead and bed have to be transferred through flimsy bits of material.

You can work around that by reducing the “Jerk” and “Acceleration” settings on your printer, but don’t just slam those as low as you can because you’ll be introducing other issues on your prints with that and they will take significantly longer to complete.

If you’re seeing a small gap on the top solid infill of your parts where it looks like there’s something wrong with only every second gap, somewhere on the machine you have backlash from either a loose pulley on a motor or for example excessive friction on one of the linear axes.

So as always, you want to have things tight, but not too tight. If in doubt, I would go with “less tight than you might think”.

And lastly, the dreaded shifts.

These can be a bit unpredictable as to when and where they happen, but the base cause is always the same: The stepper motor on that axis is asked to produce more torque than it can deliver. That can be down to, again, a sticky axis, dirt on your linear guide surface that a wheel or bearing gets caught on, or even resonances where the printer is doing many small, repeated moves that just hit one of the resonant frequencies that excites the combination of for example bed, belt and motor combination. A simple, but inelegant solution would be to just increase the current going to the stepper motor, but drivers have a limit to how much current they can provide and if they overheat, might in turn also cause skipped steps when they shut themselves down for safety. If you can touch the driver chips without getting burnt, they usually still have some headroom left. How exactly to adjust them depends on your exact printer model, but again, adjusting stepper driver currents is usually not something that needs to be done by you, the user. At least if you have a decent printer to start with. You can also, again, decrease acceleration and jerk here, which helps a lot with issues from resonances. 

Overtuning

So of course, this is not a full list of every single thing that can go wrong, but it also doesn’t mean that everything that I just listed will go wrong. And as with any of the tweaks that I’ve shared on my videos, if you overdo them, chances are you’re still going to fix your original issue, but end up making other things worse that you’re only going to notice down the road. So if you’ve made a bunch of changes to your print settings etc, maybe try going back to stock and using what you’ve learned along the way to go for a less intrusive fix next time.

And of course, if you’re having problems with a specific printer, it’s always advisable to get in touch with the manufacturer first since they are the ones who should know their machines the best. 

I hope this video helped you at the very least to start looking in the right direction for fixes – if it did, get subscribed – but again, not every machine is the same and the exact procedures might be different on different machines. 

So that’s it for this one, in the next and last video of this series, we’ll look at where you can go from here, now that you have a working, reliable printer. Until then, thank you for watching, keep on making, and I’ll see you later.


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3D Printing Basics – Episodes

  1. What is a 3D printer?
  2. Choosing a machine
  3. Resin printers
  4. Filament printer parts and maintenance
  5. Acquiring print files
  6. Basic slicer settings
  7. Whole 3D printing process
  8. Requirements for 3D printing
  9. Common issues
  10. Where to go from here

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