Transfer from: https://m.sohu.com/a/83141572_336216
I. Overview
When there are small plastic threads remaining on the printed parts, wire drawing occurs. Usually, this is because when the nozzle is moved to a new position, the plastic hangs out of the nozzle. As a senior engineer of Hongrui, I have been developing 3D printers for nearly ten years and have encountered many problems. Today, to help you solve the drawing problem efficiently, the most commonly used method is "withdrawal". If the retraction is turned on, when the extruder finishes printing a region of the model, the wire in the nozzle will be pulled back, so that when printing again, the plastic will be pushed into the nozzle again and extruded from the top of the nozzle.
2. Reasons for wire drawing and solutions
1 Retraction distance
The most important setting for retraction is the retraction distance. It determines how much plastic will be pulled back from the nozzle. Generally speaking, the more plastic that is pulled back from the nozzle, the less likely it is to sag when the nozzle moves. Most direct-drive extruders only need a withdrawal distance of 0.5 to 2.0mm, and some Bowden extruders may require a withdrawal distance of up to 15mm, because the extruder drive gear and the hot nozzle The distance between them is greater. If your prints have wire drawing problems, try increasing the withdrawal distance by 1mm each time and observe the improvement.
2 Withdrawal speed
The next setting related to withdrawal is the withdrawal speed. It determines how fast the wire is drawn from the nozzle, and Hongrui found that this draw-back speed is an important setting. If the withdrawal is too slow, the plastic will hang out from the nozzle and start to leak before moving to a new position. If the withdrawal is too fast, the wire may be disconnected from the plastic in the nozzle, and even the rapid rotation of the driving gear may shave off the surface of the wire. There is a range, the withdrawal effect is better, between 1200-6000mm/min (20-100mm/s).
3 The temperature is too high
If you have checked the withdrawal settings, the next most common factor that causes drawing problems is the temperature of the extruder. If the temperature is too high, the plastic in the nozzle will become very viscous, which will make it easier to flow out of the nozzle. Then, if the temperature is too low, the plastic will remain hard and difficult to squeeze out of the nozzle. If you think your retraction setting is correct, but this problem occurs, try lowering the temperature of the extruder to 5 to 10 degrees. This will have a significant impact on the final print quality.
4 The floating moving distance is too long/increasing the moving speed when not printing
As we discussed above, the drawing takes place in the extruder, moving between two different positions. During the movement, the plastic hangs down from the nozzle. The size of the moving distance has a great influence on the production of wire drawing. Hongrui wants to tell you that this is also the key to success or failure. The short-range movement is fast enough that the plastic has no time to fall back from the nozzle. Then, large-distance movement is more likely to cause wire drawing.