░▒▓█ Summary █▓▒░

The external cleaning of the nozzle of the FDM printer often receives little attention because this point is difficult to achieve, as well as requiring additional tools that are conventional in construction are not available. However, it is necessary to pay attention to this because a variety of problems can be prevented. So for example it is beneficial within a Printing process to carry out a cleaning without disturbing the existing printing process, as well as a having to lose the print. As visualized in Fig (A) to (C) and - using Marlin - started with the G-Code G12, the printing process is being paused and the nozzle is being moved to the brush holder along the x axis. The nozzle is being brushed within the rotating brushes to clean it. The nozzle will return and continue to print afterwards.

░▒▓█ Mechanical design █▓▒░

The mechanical design is composed of rotating brushes that, due to their vertical orientation, have direct contact with the nozzle and not with the surrounding surfaces. The brushes are driven by a 5.9 V servomotor (Fig.: (B, 1)), which is driven by a V-belt (Fig.: (C, 6)) drives three guide wheels (Fig.: (C, 5)) which are mounted on individual ball bearings (Fig.: (B, 2)) transmit the power to two brush holders (Fig.: (B, 3)). In order to counter direct the rotation of the brush heads, three ball bearings were chosen, as well as one meandering guidance of the V-belt (Fig.: (C)). The components were all in one case pressed in (Fig.: (B, 4)). 

░▒▓█ Electric Design █▓▒░

The BigTreeTech-SKR-V1.3 mainboard used has only a few freely available I/O pins. of On the other hand, these inputs are provided with a pull-up resistor (e.g. endstops Y-1.26, thermistor TH1 0.25 ) and a permanently applied high level (3,3 V ). To supply an additional component, an additional electrical circuit can be added. The designed as follows.; the digital input to the I/O pins is controlled by an inverter circuit tion (Fig.: (A, 2)) brought to a low level. The NPN small-signal transistor (BC337-40) was used, which was connected to the base of the pin P1.26 of the motherboard, as well as a 220 Ω series resistor. 5V is sourced from the mainboard, with the collector of the BC337- 40 connected and a 1 kΩ series resistor installed. In order to implement an energy supply for the motor, the main circuit board is available supplied +24 V input voltage. For controlling a high-side transistor switch is used for the power supply. Here, for the small a BC327-40 PNP transistor is used for the signal side and a BD239C NPN transistor is used for the voltage supply. Transistor (Fig.: (A, 3)). The transformation of the +24 V input voltage to +5.9 V is carried out using a ready-made LM2596 DC-DC step-down converter (Fig.: (A, 4)). A high-torque cylinder mini motor was used as the drive (Fig.: (A, 5)), which obtained from a CD-ROM drive.