Sakata PLA Stringing Issues on Ender 3v2

Hey all,

So I’m trying to print with this baby blue Sakata PLA, (200/50 nozzle/plate) and it lays down the draft guard fine, then maybe one or two small outlines before it starts stringing/nesting at the nozzle. Like all of a sudden the filament decides to not stick to the build plate and instead to the nozzle. I’ve cleaned my plates, I’ve had no issues like this with my other filaments… I’m really puzzled. There’s nothing that should be blocking the nozzle and the filament moves smoothly in the bowden tube and the extruder mechanism was recently upgraded and confirmed working.

What else should I be checking for?

Proceedurally, you’re doing everything right. The mistake is in believing the label.

First of all, it’s tempting to believe that the manufacturer couldn’t be wrong, but it is my experience, and that of many other’s I’ve read about, that the values posted on the reel are only a guide.

I had one roll, that I posted about here, where I used the manufacturer’s settings and ended up with the stringiest prints I’ve ever had. It turns out it prints just fine 20C below the recommended settings.

Other people have reported different settings being needed for the same brand of filament by the same manufacturer, just different colours. Maybe the dye added to the filament changes it’s melting point, or maybe it’s just poor quality control from one batch to the next. Who knows? Just expect it.

The second problem, which I’m experiencing myself, is that the bed temperature is measured by a thermistor attached to the bottom of the bed, but is not necessarily the temperature experienced by the filament on top of the bed. In my case, I removed the magnetic build surface provided by creality and replaced it with a piece of glass. It made a huge improvement in the consistency and quality of my first layer, and it eliminated the bulge in the build surface. The “penalty” is that I find that I have to increase my bed temperature by 10-15C. Literally, as I’m writing this, the reason why is finally dawning on me. I had originally thought it was because glass is an insulator, which no doubt contributes to it, but I’ve just realised that, because the build plate from Creality isn’t perfectly flat, but the glass is, there must therefor be gaps between the glass and the heated plate. Gaps, of course, means poor heat flow. No wonder I’ve been having problems. But this isn’t about diagnosing my problem it’s about fixing yours…

So, here’s what I suggest:

  1. Increase the nozzle temperature by 10C.

  2. Raise the bed temperature by 10C.

If 1) and 2) aren’t sufficient, try:

  1. I’m assuming your bed is already level. That being the case, turn the knobs under the bed clockwise when viewed from above to raise the bed slightly. Turn each of them by exactly the same amount to maintain the levelness of the bed. The knobs have notches for your fingers. Turn them one notch then try a print. Basically, you’re trying to “squish” the first layer into the base plate. If you squish too much, you’ll hear the extruder start to click as it begins to slip. If the clicking starts, turn each of the knobs counterclockwise one notch until the clicking stops. That should get you to the point where your first layer is being pushed into the build surface so as to make maximum contact.

You were getting stringing and previously extruded filament sticking to the nozzle because the filament isn’t coming out hot enough or close enough, or both, to bond to the build surface. It therefor hangs around loose until it comes in contact with the nozzle at which point it sticks better to the nozzle and starts getting dragged around by it.

Ideally, filament should come out hot enough that it remains a liquid when it contacts the surface below it (whether build plate or previous filament layers). Stringing occurs when the filament has a chance to solidify before it can bond with the object below.

There are five possible starting positions:

  1. Nozzle way too close to the bed: This is the second worst of the evils and must be avoided. . This lays down little to no filament on the bed and will eventually cause the exturder to start clicking as it can’t push the filament out. It will also cause filament to heat up inside the hot end with no outlet (called heat creep) which can completely jam the hot end and put a stop to all printing. If you hear clicking or your first layer is missing or thin to the point of transparency, rotate each of the four bed knobs counterclockwise, one notch at a time until it stops.

  2. Nozzle too close but extruder not clicking: This is the lesser of the two remaining evils and is a good intermediate target on your way to perfection. Extruded filament comes out OK and is squished tighly into the bed but has enough flow to prevent the exturder from clicking which means you wont get heat-creep, which means your hot end won’t jam up. The layer gets laid down thick enough to be opaque but will often have a rough feel to it because the layer is being squished out the sides and forms a ridge. It’s not perfect, but you can live with it. Layers placed on top of this layer will eventually cover up the roughness, so for most models you won’t notice much difference. It does make a difference on models where the first layer has detail in it (writing for example), but in most cases, as I say, you can live with it and, as I also say, it’s a good target to reach on the way to perfection.

  3. Nozzle is at the perfect height: This is nirvana. If you can achieve it consistently, pat yourself on the back. The first layer has no air gaps and bonds perfectly with the work surface but has a smooth finish on top. Details on the first layer are preserved.

  4. Nozzle is slightly too high: This is the second-best evil. Your first layer sticks somewhat weakly to the build plate because there are gaps. Filament, of course, is extruded as a long cylinder. Imagine two cylinders lying side-by-side. There’s an air-gap between them at the bottom. At the perfect height (3) the filament gets squished into the gap, forcing the air out and maximising contact with the build plate. When you’re slightly too high, you aren’t filling in the gap. It may look OK on the top where the edges of the cylinders are touching, but underneath, it’s not fully contacting the build plate. If it’s not too severe, you can work with this.

  5. Nozzle is way too high. This is the absolute worst of the evils and it’s what you’re likely experiencing. Extruded filament doesn’t make enough contact with the build plate to stick properly, if at all. Even if you can successfully get the first layer to stick, such that you can build on it, the model will be easily knocked off as the build continues. Any contact with the nozzle will cause the filament to let go of the build plate and start sticking to the nozzle. Unattended this ends up in a giant blob that ultimately blocks the nozzle from the outside (see my unattended creation below) and is worse than (1) because, not only will it lead to a jam inside the hot end but it can also completely encase the hot end externally too and lead to damage to the hot end thermistor and heater cables. It’s the number 1 reason you should never leave a new print unattended for the first couple of layers.

I knew you’d pull through @LEGOManiac ! I haven’t the energy right now to test every theory you’ve posted, but I am suspecting that it has to do with the heat of bed/nozzle.

I’ll have to fix my fan/hot end cover first though (see my other post, scratch that, I see you’ve already replied there!)

But thank you so much for all your advice, you are an absolute wealth of knowledge!