RU2714332C2 - First layer printing control method on 3d printer - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: invention relates to synthesis technologies, i.e. manufacture of three-dimensional physical objects by additional deposition (layering) using, in particular, polymer materials, and more specifically to techniques of jet 3D printing, auxiliary operations of said technologies and equipment for performing auxiliary operations, specifically to a method for controlling printing of a first layer on 3D printer. Method of controlling printing of a first layer on 3D printer includes feeding plastic material through a thread control unit, which by means of an encoder measures parameters of a thread passing through it and transmits them to 3D printer control module, where the measured parameters are compared to the nominal value of the parameter calculated for the same period of time, in which the given parameter was measured, and depending on the ratio of the measured and nominal values of the parameter, the distance between desktop of 3D printer and its nozzle is changed, wherein control module compares ratio of ratio with three of its settings: free supply setting, setting difficult delivery and setting partial supply interruption, and makes a decision accordingly on increase, reduction or preservation of previous value of gap between nozzle and desktop of 3D printer.

EFFECT: higher flexibility of settings, possibility of controlling the process and achieving maximum adhesion of the first printing layer.

6 cl, 5 dwg

Description

The invention relates to the field of synthesis technologies, i.e. manufacturing of three-dimensional physical objects by additional deposition (layering) using, in particular, polymeric materials, and more specifically to 3D inkjet printing technologies, auxiliary operations of these technologies and equipment for auxiliary operations, namely, to a method for controlling the printing of the first layer on a 3D printer.

The prior art device for detecting material shortages and blocking material for a 3D printer based on FDM print control, the method of operation of which can be selected as the closest analogue of the claimed method (see CN 106079449 A, 11/09/2016). The material shortage detection and material blocking circuit includes a material shortage detection device and a material blocking device, wherein the material shortage detection device and the material blocking device include a stepper motor, a photoelectric sensor, a tube, wire material and a nozzle, and further comprises an anomaly detection circuit and a single-chip microcomputer.

The disadvantage of this system is that it has a rigid, non-flexible operation logic, since there are only two values at the system output: logical zero (when an error occurs, the printer stops working and goes into operator standby mode) and logical unit (the printer works in normal mode). The system described in the closest analogue does not provide the possibility of separating errors, but only fixes them, and the system is not intended for independent stabilization of work. And most importantly, the system indicated as the closest analogue is not designed to control the first printing layer, which ensures its maximum adhesion not only by eliminating the deficit of the thread, but also by eliminating the situation when the thread will be fed in excessive quantities.

The technical result of the claimed method is to increase the flexibility of settings, providing the ability to control the process and achieving maximum adhesion of the first print layer.

The claimed technical result is achieved by creating a method for printing the first layer on a 3D printer that includes feeding plastic material through the filament control unit, which measures the parameters of the filament passing through it with an encoder and encoder sensor and transfers them to the 3D printer control module, where the measured parameters are compared with the nominal the value of the parameter calculated for the same period of time in which the given parameter was measured and, depending on the ratio of the measured and nominal values The values of the parameter change the distance between the desktop of the 3D printer and its nozzle, the thread feeding mechanism feeds the thread into the heat insulator, the thread is heated in the heating block and the thread is forced through the nozzle to the desktop, where the circuit is printed, which is placed around the intended contour of the printed part, in the process of printing which aligns the desktop using the height control system of the first layer to obtain information about the height of the nozzle above the working platform along the entire perimeter, thus determining ahozhdeniya all extreme points of the working platform in the required admission if all end points are in tolerance, the system notifies the operation is successful, if some points are determined out of tolerance, the system alerts the user that is necessary to align the work platform relative to the plane of movement of the print head.

In a particular embodiment of the method, the encoder disk creates maximum friction with plastic thread, while the number of threads is counted by a photosensor, which is used as a sensor for counting the number of threads.

In a particular embodiment of the method, the encoder unit reads the information with a magnetic sensor from the magnetic disk of the encoder, and the magnetic sensor is used as a sensor for counting the number of threads.

In a particular embodiment of the method, the number of pulses of the extruded plastic or the length of the plastic passed through can be selected as a parameter measured by the thread control unit.

The claimed invention is illustrated by the following figures:

FIG. 1 is a general diagram of the elements of a 3D printer;

FIG. 2 is a diagram of the elements of the print head;

FIG. 3 is a process simulation diagram in which a plastic thread is fed at the correct height to provide the necessary adhesion of the material;

FIG. 4 is a process simulation diagram in which a plastic thread is fed at too low a height;

FIG. 5 is a process simulation diagram in which the nozzle is too high above the working platform.

In FIG. 1-5:

1 - Encoder Block

2 - Material feeding mechanism (feed gears or rollers)

3 - Thermal insulator (thermal barrier)

4 - Heating block

5 - Material feed nozzle

6 - Plastic thread (print media)

7 - Photosensor

8 - Encoder disk with a contact wheel.

9 - The print head.

10 - Rail guide along which the print head moves.

11 - Desktop.

12 - Coil of working material.

The claimed method of controlling the printing of the first layer on a 3D printer allows us to solve the technical problem by using two methods simultaneously: control the print height of the first layer (control the pressure of the first layer) and control the uniformity of calibration of the desktop.

The control of the print height of the first layer ensures the most accurate adhesion (pressure or adhesion) of the first layer of the part to the table. This function ensures the stability of obtaining a positive result as a result of printing. If the first layer has insufficient adhesion or is too high, either during the printing process the part may peel off from the desktop and the printing process will be damaged or the print head may become clogged, as a result of which the media will stop and the printing process will also be damaged.

Monitoring the uniformity of the calibration of the desktop allows the user to fully automatically test the calibration of the uniformity of the table in order to achieve maximum adhesion over the entire surface of the table. As a result of this check, if successful, you can start printing, or give recommendations to the user that it is necessary to align the desktop relative to the plane of movement of the print head.

In the process of printing a 3D printer of the first layer, several possible events are possible:

The plastic thread is fed at the correct height to ensure the necessary adhesion of the material (Fig. 3).

The plastic thread is fed at too low a height (Fig. 4), as a result of which the nozzle is too close to the working platform and the plastic thread from the nozzle cannot be fed or is fed in too small a quantity. As a result, blocking (clogging) of the print head may occur.

The nozzle is too high above the working platform (Fig. 5), as a result of which the plastic thread does not touch the working platform and does not have the necessary adhesion to it. As a result, the printed model cannot form the required geometry.

The control of the print height of the first layer is implemented by means of a device containing a control unit for the yarn-encoder unit 1, which consists of an encoder disk with a contact wheel 8 to create maximum friction with plastic thread. The encoder unit can also be built on a magnetic disk and a special sensor for determining the position of this magnetic disk (also with a contact wheel).

Material feeding mechanism 2 feeds plastic during printing. The plastic thread 6 passes through the channel through the heat insulator 3, is heated in the heating block 4 and is pressed through the material feed nozzle 5 to form a thin thread at the outlet of the nozzle, and as a result, a printed model is built.

During printing, the plastic thread 6 passes through the encoder unit 1 and, in it, is in contact with the encoder disk 8. As a result of tight contact and maximum friction with the contact wheel, the translational movement of the plastic thread is converted into rotational movement of the encoder disk 8. The photosensor 7 monitors the rotation disk 8, as a result of which the system counts how many plastic threads passed through it.

The control unit can count the number of pulses per N mm (a custom value that determines the sensitivity of the system) of the extruded plastic or by calculating the length of the plastic passed (quantity, volume, etc., or their derivatives). Next, the number of pulses is divided by the nominal value for the same period of time, while receiving the value of the ratio of the measured and nominal values, which is transmitted to the control module.

An example is a system where the control module has 3 settings:

1. Free feed setting.

2. The setting of the difficult feed.

3. Setpoint for partial feed lock.

Comparing the correlation coefficient with the settings, the module decides to increase, decrease or maintain the previous value of the gap between the nozzle and the desktop of the 3D printer.

The 3D printer control module may have a full feed lock setting, which is used when there is no plastic feed.

The above example algorithm may vary from system to system.

In each printhead, the encoder block is calibrated and based on the data obtained, it is possible to determine all three situations and respond to them by adjusting the height of the first layer.

Monitoring the uniformity of the calibration of the desktop is as follows.

For printing on the entire plane of the work platform, it must be uniformly calibrated around the entire perimeter. The tolerance of uniformity should be within the thickness of the print layer, if this condition is not met, for example, one side will be higher than the tolerance and the other lower, then on the one hand the print head will feed material over the work platform, as a result of which adhesion will not be necessary, on the other hand, the height between the nozzle and the working platform will be so low that the material cannot be fed from the nozzle at all.

To solve this problem, it is proposed to start printing the part and align during the printing of the part itself. Alignment, in the particular case of the method, is performed by forming a special frame, which is printed in priority over the part. While the printer is printing this skirt, the height of the first layer will be leveled. Alignment is also possible in the printing process of the first layer.

To do this, use the height control system of the first layer to obtain information about the height of the nozzle above the working platform around the entire perimeter, thus determining the location of all extreme points of the working platform in the required tolerance.

If all the extreme points are within the tolerance, the system notifies you of the successful operation. If some points are determined outside the tolerance, the system notifies the user that it is necessary to align the working platform relative to the plane of movement of the print head (calibration of the working platform).

Given the foregoing, we can conclude that the claimed method will allow using simple technical means to solve the problem of controlling the first print layer on the quality of execution of which depends on the quality of execution of all other layers.

Claims (6)

1. A method of controlling the printing of the first layer on a 3D printer, including feeding plastic material through a filament control unit, which measures the parameters of the filament passing through it and passes them to the 3D printer control module, where the measured parameters are compared with the nominal value of the parameter calculated for this the same time interval in which this parameter was measured, and depending on the ratio of the measured and nominal values of the parameter, the distance between the desktop of the 3D printer and its nozzle is changed, at m, the control unit compares the correlation coefficient with its three settings: setting free feed setpoint and setpoint difficult feed partial suspension flow and decides accordingly on increase, decrease or retain the previous value of the gap between the nozzle and the 3D desktop printer. 2. The control method according to p. 1, characterized in that in the absence of plastic supply, the control module applies the setting for completely blocking the feed. 3. The control method according to p. 1, characterized in that the plastic material is fed to the desktop, where the circuit is printed, which is placed around the alleged contour of the printed part, during the printing of which the desktop is aligned using the height control system of the first layer to obtain information about the height of the nozzle above the working platform along the entire perimeter, thus determining the location of all extreme points of the working platform in the required tolerance. 4. The control method according to claim 1, characterized in that the encoder disk creates maximum friction with plastic thread, while the number of threads is counted by a photosensor, which is used as a sensor for counting the number of threads. 5. The control method according to claim 1, characterized in that the encoder unit reads the information with a magnetic sensor from the magnetic disk of the encoder, while the magnetic sensor is used as a sensor for counting the number of threads. 6. The control method according to claim 1, characterized in that, as a parameter measured by the thread control unit, the number of pulses of extruded plastic or the length of the plastic passed through can be selected.

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