The invention relates to a method for feeding filament base material to ensure the supply of operational base material for 3D printers. In the method a filament feeding unit is used, having a stand and a shaft mechanically integrated with it, the shaft accommodates, holds and enables the rotation of a filament storage drum, the shaft is provided with a drum support element. The weight of the drum together with the filament stored on it, is continuously measured with a mass measuring cell arranged in measurement connection with the shaft or the drum support element, the rotation of the drum is continuously measured with a rotation detector arranged in measurement connection with the shaft and the drum on the drum support element.

The invention further relates to a filament feeding unit for ensuring the supply of operational base material for 3D printers, the filament feeding unit has a stand and a shaft mechanically integrated with it, the shaft accommodates, holds and enables the rotation of a filament storage drum, the shaft is provided with a drum support element. The weight of the drum together with the filament stored on it, is continuously measured with a mass measuring cell arranged in measurement connection with the shaft or the drum support element, the rotation of the drum is continuously measured with a rotation detector arranged in measurement connection with the shaft and the drum on the drum support element.

Today, 3D printers are common tools that can be used to solve many tasks. In the case of these devices, the so-called filament, the base material of printing is fed to the printer from a feeding drum. These drums are usually standardized according to their size, weight and the base material, i.e., the thickness of the filament. The present solution does not affect the material of the filament, which is known in the art. According to the present invention the filament is stored in the form of a wire of a given thickness on a drum, from which the 3D printer itself pulls in the necessary raw material from the feeding unit.

Patent application No. US2017151715 (A1 ) proposes a solution that increases the efficiency of the printing process by using an anti-scanning additive. However, this does not allow the recognition of typical printing errors and the corresponding intervention.

In many cases, problems arise when the filament breaks or when the activation head of the 3D printer - where the molten material is emitted - becomes clogged. In these cases, the printing is interrupted and the product becomes scrap. According to the current state of the art, no measures have been taken to prevent this.

The aim of the present invention is to have an effect on the operation of the 3D printer in the event of a breakage and/or blockage, and to provide the operator with relevant information.

In its most general embodiment, the invention is a method according to the introductory paragraph where the output signals of the mass measuring cell and the rotation detector are fed into an evaluation circuit, whose intervening output and warning output are activated during operation of the 3D printer as follows: a) if the output signal of the mass measuring cell is constant and greater than a first given value, where the first given value is greater than the empty weight of the filament storage drum and the output signal of the rotation detector is zero, then the operation of the related 3D printer is stopped by activating the intervening output, and a "breakage" message is sent to the warning output; b) if the output signal of the mass measuring cell and the output signal of the rotation detector jump alternately between two values, then by activating the intervening output, the operation of the 3D printer is stopped and a "blockage" message is sent to the warning output; c) if the output signal of the mass measuring cell is constant at or below the first given value and the output signal of the rotation detector is zero, then the operation of the 3D printer is stopped by activating the intervening output and a "filament out" message is sent to the warning output. Furthermore, the shaft is formed tilted at an angle between 5 and 40 degrees relative to the vertical.

In its most general embodiment of the filament feeding unit according to the second paragraph of the preamble, the output signals of the mass measuring cell and the rotation detector are fed into an evaluation circuit, the evaluation circuit has an intervening output that interrupts the operation of a 3D printer, and a warning output connected to a display panel. Furthermore, the shaft is tilted at an angle between 5 and 40 degrees relative to the vertical.

In the following, the invention will be described with reference to the accompanying drawings in which:

Figure 1 is a perspective view of the filament feeding unit according to the invention, and Figure 2 shows a possible design of a filament runout sensor according to the invention.

Figure 1 shows the filament feeding unit 1 according to the invention. Its base is formed by a stand 2, on which the unit serving the filament storage drum 3 is arranged. In it, the mass measuring cell 6 that continuously measures the weight of the filament storage drum 3 together with the filament stored on it is arranged in measuring connection with a shaft 4 or a drum support element 5, and a rotation detector 7 that continuously measures the rotation of the filament storage drum 3 is located on the shaft 4 and arranged in measuring connection with the filament storage drum 3 on the drum support element 5. Preferably, the drum support element 5 is mounted on bearings and designed in such a way that the standard filament drum can be fixedly placed on it in terms of rotation. This arrangement makes it possible to monitor the current state of the filament, thus making it possible to ensure economic operation through intervention.

In an advantageous embodiment the shaft 4 can be slightly inclined compared to the vertical which enables optimal unwinding of the filament. This inclination is preferably between 5- 40 degrees, advantageously between 10-20 degrees, compared to the vertical. Tilting of the shaft 4 is important for two reasons. Firstly, because of the minimal pre-tension of the filament. Secondly, if the product were to be used horizontally, there would be a risk of its falling off the holder during rotation.

In a further embodiment, a so-called a filament runout sensor is installed. This is a switch that can monitor filament breakage, in such a way that the switch is in an electrically open state when the filament passes through a closed tube, and the contact of the limit switch touches it until the filament - with a diameter of 1.75 mm, made of insulating material - passes through it. If the filament is broken or run out, the switch is electrically closed through its spring contact. In this way, we provide one more option to indicate breakage and runout and/or to interrupt the operation of the 3D printer.

The operating procedure of the filament feeding unit 1 according to the invention is explained in the following description.

The output signals of the mass measuring cell 6 and the rotation detector 7 are led to an evaluation circuit, the evaluation circuit has an intervening output that interrupts the operation of the 3D printer, and a warning output connected to a display panel. The weight of the filament storage drum 3, together with the filament stored on it, is continuously measured by a mass measuring cell 6 arranged in measurement connection with the shaft 4 or the drum support element 5, the rotation of the filament storage drum 3 is continuously measured with a rotation detector 7 arranged in measurement connection with the shaft 4 and the filament storage drum 3 on the drum support element 5. Preferably, the rotation detector 7 is an inductive rotation detector 7. The output signals of the mass measuring cell 6 and the rotation detector 7 are fed into an evaluation circuit, whose intervening output and warning output are activated during operation of the 3D printer as follows: a) if the output signal of the mass measuring cell 6 is constant and greater than a first given value E1 , where the first given value E1 is greater than the empty weight of the filament storage drum 3 and the output signal of the rotation detector 7 is zero, then the operation of the related 3D printer is stopped by activating the intervening output, and a "breakage" message is sent to the warning output; b) if the output signal of the mass measuring cell 6 and the output signal of the rotation detector 7 jump alternately between two values, then by activating the intervening output, the operation of the 3D printer is stopped and a "blockage" message is sent to the warning output; c) if the output signal of the mass measuring cell 6 is constant at or below the first given value E1 and the output signal of the rotation detector 7 is zero, then the operation of the 3D printer is stopped by activating the intervening output and a "filament out" message is sent to the warning output.

In another possible case: d) if the output signal of the mass measuring cell 6 is continuously decreasing below a second given value E2, where the second given value E2 is greater than the first given value E1 , and the output signal of the rotation detector 7 is not zero, then "filament will run out" message is sent to the warning output.

The first given value E1 and the second given value E2 can be easily determined from experience.

Preferably, the display panel is an LED panel that shows the possible error cases. They can be displayed by LEDs according to the messages. They can be placed on itself the filament feeding unit 1 , on the 3D printer, or somewhere else in its vicinity.

In the case of a further embodiment, the breakage or running out of the filament can be detected with an additional security-enhancing device. This is shown in Figure 2 through an example. Here, in the filament feeding unit 1 , there is a filament run-out sensor 8, which is arranged in a housing 10 having a closed tube section in which the filament 13 passes through and is provided with a switch 9. The switch 9 has a spring-loaded pre-stressed arm 12 protruding from it. During operation its end opposite to the switch 9 leans on the continuous filament 13 in an open part of the tube section - preferably provided around the middle portion of the tube section - and the switch 9 is in a first state, which can be either open or closed. In the absence of the filament 13, the switch 9 is in a second state opposite to the first state. Then the closed and open states are exchanged. Both cases can be used. The point is that it should also be connected to the intervening output that interrupts the operation of the 3D printer, so that without the presence of the filament 13, the operation of the 3D printer is stopped. Thus, stopping the printer and/or controlling the warning output is doubly assured.

In the case of the latter version, the switch 9 can be a known limit switch equipped with a roller 1 1 arranged at the opposite end of the spring-loaded pre-stressed arm 12 of the switch 9.

The advantage of the solution according to the present invention is that it makes the operation of a 3D printer more reliable and economical.