Category: Stringing

3D printer stringing is a common problem that many beginners face when they start 3D printing. Stringing is when thin strands of filament are left behind on the print, creating a messy and unprofessional look. Stringing can ruin the appearance and functionality of your 3D printed objects, so it’s important to know how to prevent it and fix it.

There are several factors that can cause 3D printer stringing, but the main ones are:

  • Temperature: If the nozzle temperature is too high, the filament will melt too much and become more fluid. This makes it easier for the filament to ooze out of the nozzle when it’s not supposed to, creating strings. To avoid this, you should lower the nozzle temperature until you find the optimal setting for your filament type and brand. You can also use a cooling fan to cool down the filament as soon as it leaves the nozzle, reducing its viscosity and stringing tendency.
  • Retraction: Retraction is when the extruder pulls back the filament slightly before moving to a different part of the print. This prevents the filament from leaking out of the nozzle during travel moves, which can cause stringing. To enable retraction, you need to adjust the retraction distance and speed settings in your slicer software. The retraction distance is how much filament is pulled back, and the retraction speed is how fast it is pulled back. The optimal values depend on your printer model, extruder type, and filament material, but you can start with a retraction distance of 2-5 mm and a retraction speed of 40-60 mm/s and tweak them as needed.
  • Travel speed: Travel speed is how fast the nozzle moves from one point to another when it’s not printing. If the travel speed is too low, the filament will have more time to ooze out of the nozzle and create strings. To avoid this, you should increase the travel speed as much as possible without compromising the print quality. A good starting point is 150-200 mm/s, but you can experiment with different values until you find the best one for your printer and filament.
  • Z-hop: Z-hop is when the nozzle lifts up slightly before moving to a different part of the print. This creates a small gap between the nozzle and the print surface, which can prevent the nozzle from dragging across the print and leaving strings behind. To enable Z-hop, you need to adjust the Z-hop height setting in your slicer software. The Z-hop height is how much the nozzle lifts up, and it should be just enough to clear the print surface without causing too much vibration or noise. A typical value is 0.1-0.2 mm, but you can fine-tune it as needed.

If you are using silk PLA, you might have encountered a common problem: the extruder gear grinds a flat spot on your filament when you have retraction enabled. This can cause under-extrusion, clogging, and poor print quality. But if you disable retraction, you might get stringing and oozing. So how can you overcome this dilemma? Here are some tips that might help you.

  • Increase the extruder temperature. Silk PLA usually requires a higher temperature than regular PLA, around 210-230°C. This will reduce the resistance in the hot end and allow the filament to flow more easily.
  • I have also had success with reducing the extruder temperature to the very minimum temperature. When reducing the temperature the flow of PLA is slower, so a slower speed is also required to accommodate the lower temperature. This option allows me to disable retraction altogether.
  • Decrease the retraction distance and speed. Retraction pulls the filament back into the extruder to prevent oozing, but it also puts more stress on the filament. Try reducing the retraction distance to 2-3 mm and the speed to 20-30 mm/s. This will minimize the grinding and still prevent stringing.
  • Calibrate the extruder tension. The extruder tension is the force that the extruder gear applies on the filament to push it through the nozzle. If the tension is too high, it can cause grinding and flattening of the filament. If it is too low, it can cause slipping and under-extrusion. You can adjust the tension by turning a screw or a knob on your extruder. The ideal tension is when you can pull the filament out of the extruder with moderate force, but not too easily or too hard.
  • Use a high-quality filament. Silk PLA is a special type of PLA that has a shiny and smooth surface. However, not all silk PLA filaments are created equal. Some might have inconsistent diameter, impurities, or additives that can affect the print quality and performance. Make sure you buy from a reputable brand and store your filament in a dry and cool place.

Stringing is a common problem in 3D printing, especially with flexible materials like PETG. It occurs when thin strands of filament ooze from the nozzle as it moves between two points, creating unwanted hairs on your print. Stringing can ruin the appearance and quality of your print, so it’s important to know how to prevent it.

One of the main causes of stringing is wet filament. Filament can absorb moisture from the air over time, which can affect its printing properties. When wet filament is heated in the nozzle, it can create steam that pushes out excess filament, resulting in stringing. Wet filament can also cause popping noises, bubbles, and poor layer adhesion.

Another common cause of stringing is retraction settings. Retraction is a feature that pulls back the filament into the nozzle when it’s not extruding, to reduce the pressure and prevent oozing. Retraction settings include retraction distance, which is how much filament is retracted, and retraction speed, which is how fast the filament is retracted.

So how can you tell if your stringing is caused by wet filament or retraction settings? Here are some tips:

  • Check your filament spool for signs of moisture, such as condensation. If you see any, your filament is likely wet and needs to be dried before printing. You can use a filament dryer, an oven, or a dehumidifier to dry your filament.
  • Print a temperature tower test to find the optimal nozzle temperature for your filament. Too high or too low temperature can cause stringing, so you want to find the right balance between melting and flowing. A temperature tower test prints a series of blocks at different temperatures, and you can choose the one with the best quality.
  • Print a retraction test to find the optimal retraction settings for your printer and filament. Retraction settings can vary depending on your extruder type (direct-drive or Bowden), nozzle size, and filament type. A retraction test prints a series of pillars with gaps between them, and you can adjust the retraction distance and speed until you eliminate stringing.
  • Experiment with different travel speeds and minimum travel distances. Travel speed is how fast the nozzle moves between gaps when it’s not extruding, and minimum travel distance is how far the nozzle has to move before retraction is enabled. Increasing both of these settings can reduce stringing by minimizing oozing and enabling more retraction.

There are a lot of potential causes for stringing, or spider webs. Some of the most common are poor retraction settings, poor temperature settings, and an improperly calibrated extruder.

Also, keep in mind that ambient temperature can affect stringing if you don’t have an enclosure.

The first thing that I do if I find that my printer is stringing is print a retraction tower, a temperature tower, and recalibrate my extruder. This takes 30 minutes and saves tons of time.

If you do much 3d printing, you will eventually want to use a different spool of filament before your current one is finished. And, unless you live in a desert region, your filament will pick up moisture, leading to printing problems down the road. By the way, even if you do live in a desert, I would still argue that your filament will pick up moisture. 

I’ve seen some people dry out their filament and then store it in vacuum bags, then remove it when they are ready to continue printing. My preference is to just store it as-is, then dehydrate it when I plan to use it again. I use a modified food dehydrator to do this. I just cut out the middle part of the racks so that the dehydrator closes around the spool. Other people use purpose built dehydrators or other homemade versions. Airtight Tupperware seems to be popular for storage and dehydration.

I relearned something important over the Christmas break that I had forgotten. The word “At.” All of your settings only apply at specific temperature, retract settings, etc.

I increased my temperature, but didn’t change anything else. I know better, but I did it anyway. Oh well. Sometimes it takes a few times to learn a lesson. My print started stringing like crazy. The science of what was happening is simple in hindsight. I had all of my retraction set up for a particular printing speed, specific extrusion values, temperatures, retraction settings, etc. When I increased the temperature, it created a situation where my filament became more molten so it was oozing out of the nozzle and stringing everywhere.

I needed to tune my printer to the new settings. Live and (re)learn.

I was reminded recently that temperature and retraction are closely related. I had run a retraction tower and dialed in my settings. Then I ran an actual part in Cura and kept getting stringing. Turns out that I needed to run a temperature tower, then rerun my retraction tower. It’s an iterative process. Setting retraction, but then increasing the temperature (like I did) will cause the filament to ooze out of the nozzle and give you stringing, despite having the proper retraction settings.

 

A couple of days ago, I wrote about calibrating your extruder with Klipper. Today, I would like to talk about how to calibrate your extruder e-steps with Marlin firmware. Here is how I do it:

  • Move printhead to center of bed and about 150mm off the bed
  • Mark a spot (I use tape) on the filament about 125mm down from the bottom of the extruder
  • Use calipers to measure actual value of tape from extruder. We’ll call this “A” and say we have 126mm for this example
  • M503 – read current values and make a note of the current E value. We’ll call this value “B” and say we have a current E value of 400 for this example
  • M83 – enable relative mode on extruder
  • G1 E100 F100 – feed 100mm of filament at 100mm per minute
  • Let it finish the extrusion and measure the distance between the bottom of the extruder and the tape that we marked. We’ll call this value “C” and say that we have a current value of 24 for this example. If everything were already calibrated correctly it would be 126 – 100, or 26mm.
  • Calculate our new E-Steps value. 100 * B(A-C) is the formula. Substituting our values from this example we get 100 * 400/(126-24) = 392.16.
  • Update our esteps on our machine with M92 E392.16
  • Save our new value with M500

If frequency were the only indicator, you would guess that printing different versions of the Venom Symbiote was my favorite thing to print. I’ve printed green ones, black ones, and in this case, I printed a transparent one.

I had to completely rebuild my hotend after this one, over a very simple mistake.

I had purchased a new hotend (complete) to replace one that I was having problems with. I put it on my printer and started printing and you can see the results for yourself.

What I forgot to do is “hot tightening.” When assembling the hotend together (at room temperature) you screw in the nozzle and the heat break until they touch. My heat sink also has some setscrews that need to be tightened. At room temperature, everything is tight. However, when things heat up and expand, little gaps in between each of the components will occur. The solution to this is to heat up your hotend to around 20 degrees beyond what you intend to print at, and then finish tightening the components.

After trying to print a QR code over the weekend, I decided to tune in my retraction settings. Step 1, I printed a retraction tower. I printed a tower with different levels, with retraction distance set at 0mm, 2mm, 4mm, 6mm, 8mm, and 10mm.

2mm of retraction was a clear winner for my machine, so I decided to dial it in more. I printed another tower at 1mm, 1.5mm, 2mm, 2.5mm, 3mm, and 3.5mm. 2mm was again the clear winner for my machine, so next I decided to play with the retraction speed settings. Most source recommend a retraction speed of 35-40mm/s. I printed a retraction tower with speeds of 30mm/s, 35mm/s, 40mm/s, 45mm/s, 50mm/s, 55mm/s. 40 and 45 both looked pretty good so I printed another one that ranged from 39mm/s – 44mm/s.

Judging from the towers that I printed, my optimal settings are 2mm at 42mm/s.