8/8/2023 0 Comments Tighten proSetting 2 still was good, with a slightly worse performance at higher flows. In setting 1, I got really consistent results over a vast flow range until the extruder started skipping. Setting 1 is where the gears are the furthest apart from each other, recommended for PLA and all other non-flexible materials, Settings 2 to 5, where the gap constantly decreases for increasingly soft materials. The gears are disengaged for loading and unloading material in the first lever position. After each test, I cleaned the gears, adjusted the pretension from the lowest to the highest setting, and plotted the achieved flow rates. I did a ton of flow tests with each of the extruders, from slow extrusion speeds up to their limits to simulate increasing extrusion forces. Still, many say the hard and brittle nature with a low temperature-resistance makes PLA one of the more challenging materials to tune, and the overall results will be generally comparable. Of course, other materials behave slightly differently. I did my tests with regular DasFilament PLA. Then I tested the typical one-sided Ender-3 Extruder, E3Ds Hemera extruder, the OmniaDrop, and Bondtechs new LGX, which is special because instead of pretension, the LGX uses fixed distance gears which is something I’ve never worked with before. I tested Prusas MK3, which uses Bondtech gears, and that you also find in many of the BMG clones. So which pretension setting gives us consistent flows and the best hotend performance? I’ve done tests over the whole adjustment range of the most common extruders. It’s more acceptable for a user if you have some under-extrusion on a TPU part rather than a complete print that fails because the filament buckled. Due to the flexibility of TPU the teeth usually don’t really bite into the filament so grinding often means just that the gears are slipping but not really chewing away from the filament. So before the filament starts buckling, it grinds and under extrudes a little. See, with lower tension on the gears, you limit the maximum force you can apply onto the filament. Even though one would think that this is due to the flexibility of the material and not squishing it too much, another reason might be a fail-save feature. Printer manuals will often tell you to lower extruder tension when printing with these materials. Everyone who has already printed with flexibles will know that phenomenon, which usually happens when printing too fast. Here the column of filament buckles away under the load, and when the filament path is not perfectly constrained, it will find a way to get entangled in the extruder gears. If your extruder gears severely grind, it’s hard to recover because the more material they grind away, the less grip you will have – plus, the ground away material will clog your extruder gears, making it even harder to grip into filament.įinally, there is material buckling which usually happens with flexible materials. Why? Because when the extruder skips, you will get an inconsistent flow for a bit, but there is a chance that your print recovers. In most you want a motor that skips before it grinds on the filament. When only the filament jumps around, but the shaft turns, it usually means grinding. I usually paint a small line on the motor shaft to quickly see if the extruder is skipping because that’s when the shaft doesn’t turn continuously anymore. Skipping means that the stepper motor loses a step. If your extruder is not strong enough to push the material forward or to shear away the material, it will skip. Additionally, you’ll create more friction in the bearings and might even break your idler arm if the pretension is too high! Ideal pretension in most cases means that you have some indentation of the extruder gears on your filament so that enough torque can be transferred but not so much that you crush the material and waste energy at the extruder and make the deformed material harder to feed. Crushing, so permanent, plastic deformation takes a lot of the motor’s energy, and you, therefore, lose power to convey the material forward. This doesn’t only deform the material and makes it harder to feed. On the other hand, the filament literally gets crushed if you apply too much pressure. This causes grinding shows in grooves on the material. This way, only little force can be transmitted via positive engagement, and most of it will come from friction between the gear and the material. In this case, the teeth of the gears just barely dig into the filament.
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