Mechanical arm type food 3D printing ink supplementing device

Abstract

The invention discloses a mechanical arm type printing ink supplementing device for food 3D printing, and relates to the technical field of food additive manufacturing. The system comprises a linear peristaltic pump, a silica gel hose, a stepping motor driver, a 24V direct-current power supply, a PP hose adapter, a liquid level sensor, an STM32 control panel, an upper computer, a plastic rolling belt, a plurality of Dupont lines and a UART communication line. The control of the material supplementing device, such as the starting, pause, acceleration and deceleration functions of the linear peristaltic pump, is directly regulated and controlled by the user software of the upper computer; the corresponding running speed is determined according to the viscosity information of the food ink, or the running speed of the device is manually regulated and controlled. The device is safe, environmentally friendly, easy to build, simple in principle and easy and convenient to control, feeding and supplementing work of food ink within a certain viscosity range can be completed, the labor cost and errors existing in manual charging can be reduced, and the breakthrough of continuous printing of a mechanical arm type food additive manufacturing technology can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of food additive manufacturing, and in particular to a device for ink replenishment based on mechanical arm type food 3D printing. Background Art

[0002] 3D printing technology, also known as additive manufacturing, is a technology that builds three-dimensional solid objects by stacking materials layer by layer. In contrast to traditional removal manufacturing techniques (such as milling, cutting, etc.), 3D printing makes the production of complex structures simpler and more efficient by directly converting digital design files into physical objects. Therefore, 3D printing technology is widely used in multiple industries, such as medical, manufacturing, aerospace, construction, food, etc.

[0003] In the field of food biological 3D printing, extrusion-based 3D printing is the most widely studied method in 3D food printing due to its high technical maturity and wide range of applicable food materials. However, most traditional food 3D printers are box-type printers that only allow the nozzle to move on a plane and the printing space is relatively small.

[0004] Therefore, in recent years, researchers have paid more and more attention to multi-degree-of-freedom robotic arm food 3D printing equipment, which has the advantages of higher degrees of freedom, flexible operation, stable operation and strong adaptability, making the robot competent for various production tasks. Although the existing technology has a certain foundation, the loading process based on robotic arm extrusion food 3D printing is still manually dependent, which is prone to introduce artificial defects such as bubbles, resulting in unpredictable interruptions in the printed lines, which increases labor costs and reduces printing accuracy. In addition, the printing barrel needs to be fixed at the reset point before printing, making it impossible to replenish materials immediately during the printing process. Once the ink is exhausted, the printing is interrupted, and continuous operation cannot be achieved, which limits the size and large-scale production of the product.

[0005] In addition, given the increasing popularity of automation technology, many existing research on feeding systems is aimed at box-type food 3D printers, and the operation of the device still requires manual operation, and there is very little research on feeding and refilling of robotic arm food 3D printing. Therefore, integrating automation technology into robotic arm food 3D printing can give full play to the personalized customization advantages of robotic arm food additive manufacturing. Summary of the invention

[0006] The purpose of the present invention is to provide a mechanical arm type food 3D printing ink replenishing device, the control of the device is directly regulated by the host computer user software; the device is safe and environmentally friendly, easy to build, simple in principle, simple and convenient to control, and can complete the feeding and replenishing of food ink within a certain viscosity range, reducing labor costs and errors caused by manual loading.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] A device for replenishing ink for mechanical arm type food 3D printing comprises: a linear peristaltic pump, a silicone hose, a stepper motor driver, a 24V DC power supply, a PP hose adapter (polypropylene hose adapter), a liquid level sensor, an STM32 (STMicroelectronics 32-bit series microcontroller chip) control board, a host computer, a plastic rolling strip, a plurality of DuPont cables and a UART communication line (universal asynchronous receiver / transmitter), wherein the 24V DC power supply is connected to and supplies power to the stepper motor driver; the stepper motor driver adopts a common anode connection method; a silicone hose is installed in a pump head of the linear peristaltic pump, and a body is connected to an output end of the stepper motor driver; an input end of the stepper motor driver and the liquid level sensor are both connected to the STM32 control board; and the STM32 control board is connected to the host computer via the UART communication line.

[0009] Furthermore, the body of the linear peristaltic pump is a stepper motor, which is connected to the pump head of the linear peristaltic pump through a coupling to drive the rotor to rotate. It is driven by a stepper motor driver and controlled by a pulse signal sent by an STM32 control board. Its rotation speed is proportional to the frequency of the pulse signal.

[0010] Furthermore, the silicone hose is divided into three sections. The first section is installed in the pump head of the linear peristaltic pump as an extrusion hose. The rotation of the rotor can alternately squeeze and release it, so that a pressure difference is formed in the extrusion hose to pump food ink; the second section is installed on the left side of the pump head of the linear peristaltic pump as a suction hose; the third section is installed on the right side of the pump head of the linear peristaltic pump, which is used as a lift hose. A PP hose adapter is installed at the end of the hose for connection with the printing barrel. The card slot on the PP hose adapter can be stably fixed to prevent it from being squeezed out due to the effect of air pressure during 3D printing; every two sections of the hose are connected with a PP hose adapter. In order to further ensure the tightness of the connection between the hoses, a plastic rolling belt is used to fix the connection between the hoses.

[0011] Furthermore, the type of liquid level sensor is a capacitive sensor. Its detection principle is based on the conductivity of ink, with a response time of 500ms. It can penetrate non-metallic containers and does not come into direct contact with ink, ensuring the concept of safety and environmental protection during the transportation of food ink. It is fixed to the outside of the printing barrel with a plastic rolling belt; when ink is detected, the indicator light turns on and sends a high-level signal to the STM32 control board, changing the level of the pin connected to the ENA-port (motor enable negative terminal) of the stepper motor driver, and suspending the feeding behavior of the linear peristaltic pump.

[0012] Furthermore, the host computer has a user software designed in the present invention, the design of the software is based on the Matlab app designer (application designer) tool, and the user interface mainly includes a serial port configuration module and a feed speed adjustment module;

[0013] Furthermore, the specific method of designing the serial port configuration module is:

[0014] Create a blank app designer project. In the view interface, drag and drop buttons, indicator lights, text boxes, drop-down lists and other components to build a GUI (graphical user interface). Set serial port parameters in the GUI, including port number, baud rate, data bits, stop bits, check bits, etc. These parameters need to match the parameters of the serial port device. Create a callback for the drop-down box and call the serialport function to create a serial port object. Use the configureCallback function to set the callback function and use the Try catch structure to set the error service. If the connection fails, use the msgbox function to display "Serial port connection failed".

[0015] Furthermore, the specific method for designing the feed speed adjustment module is as follows:

[0016] Drag and drop buttons, indicator lights, value boxes and other components in the GUI; the buttons include: start, stop, accelerate, decelerate, calculate, and send. Add callbacks for each button. The "calculate" button is responsible for converting the viscosity information entered by the user into speed information based on the fitted mathematical model of viscosity and speed. In the callbacks of the remaining buttons, use the writeline function to send the value string in the value box to the serial port, and set the terminator of the string to "CR / LF" (carriage return / line feed). The STM32 control board converts the received data into decimal form for judgment and completes the speed control function of the linear peristaltic pump.

[0017] Furthermore, the specific method by which the STM32 control board converts the received data into decimal form is:

[0018] Get the length of the received string, get the ASCII code (American Standard Code for Information Interchange) of each character and subtract 48 respectively, so that the character '1' can be converted into the number 1. Multiply each digit by its corresponding bit weight and then sum them up, so that the string '123' can be converted into the number 123 for subsequent calculations and judgments;

[0019] Furthermore, the specific method of creating a mathematical model of viscosity and rotation speed is:

[0020] The viscosity range of food ink was established, several kinds of food inks with different viscosities were prepared within this range, and the mass flow rate of each food ink at different pumping speeds was measured. Finally, the mathematical model of ink viscosity and speed was obtained by using the polynomial curve fitting method.

[0021] Furthermore, the viscosity range of food ink is established based on the printability of the material and the upper limit of the linear peristaltic pump itself; the printability standard is set as whether the layers of the printed product are clear after five layers are stacked, and the critical point between clear and unclear is used as the lower limit of the viscosity range; the outlet pressure of the linear peristaltic pump is ≤0.2MPa, and its speed will gradually decay when transporting viscous materials, and the viscosity value corresponding to the decay to zero speed is used as the upper limit of the viscosity range of food ink;

[0022] Further, the specific method of mass flow measurement is as follows:

[0023] The STM32 control board sends a pulse signal to make the linear peristaltic pump run until its hose is filled with food ink. Set an external interrupt program and trigger it through the buttons of the STM32 control board to control the linear peristaltic pump to run at different speeds for the same time. Use an analytical balance to weigh the mass of the pumped food ink. Repeat the steps and take the average of the weighed mass to ensure the repeatability and accuracy of the experiment. Finally, the mass flow rate of food inks with different viscosities at different pumping speeds is obtained.

[0024] Furthermore, a polynomial curve is fitted between the mass flow rate and the corresponding rotational speed, and the peak value of the curve is taken as the optimal pumping speed of the food ink with this viscosity. The optimal pumping speeds of other food inks with different viscosities are found in the same way, and polynomial curve fitting is performed to finally obtain a polynomial mathematical model of the viscosity and pumping speed of the food ink. The number of points collected is required to be less than the maximum number of polynomial fittings. The more points collected, the more accurate the fitting, and the closer the square of R is to 1, the better the fitting effect.

[0025] Furthermore, the control of the feeding device, such as the start, pause, acceleration and deceleration of the linear peristaltic pump, is directly controlled by the host computer user software.

[0026] The present invention has the following beneficial effects:

[0027] The present invention provides an ink refilling device for robotic arm type food 3D printing, which can replace the traditional manual feeding method, can reduce labor costs and reduce errors caused by human operation, and can realize refilling during the food 3D printing process, realize continuous printing of robotic arm type food additive manufacturing, break through the limitations of traditional robotic arm type food 3D printing on the quantity and size of printed products, and expand the printing form of food 3D printed products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The functional structure diagram of the ink replenishing device for the robotic arm type food 3D printing of the present invention: wherein 1 is a suction hose; reference numerals 2, 6, and 8 are all PP hose adapters; 3 is an extrusion hose; 4 is a rotor; 5 is a linear peristaltic pump head; 7 is a lift hose; 9 is a capacitive liquid level sensor; 10 is a printing barrel; and 11 is a scale line.

[0029] Figure 2 Schematic diagram of the host computer user software interface functions.

[0030] Figure 3 A schematic diagram of the overall process of printing and refilling of an ink refilling device for robotic arm-type food 3D printing based on the present invention. DETAILED DESCRIPTION

[0031] The following describes the principles and features of the present invention in conjunction with the accompanying drawings to illustrate the specific implementation methods of the present invention. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. It should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "pin" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; there is no clear definition of a specific "pin", as long as the pin can achieve the corresponding function, it can be used. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood through specific circumstances. The components, materials, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0032] Example

[0033] Reference Figure 1The functional structure diagram of the device is a mechanical arm type food 3D printing ink refilling device, including: a linear peristaltic pump, a silicone hose, a stepper motor driver, a 24V DC power supply, a PP hose adapter, a liquid level sensor, an STM32 control board, a host computer, a plastic rolling strip, a number of DuPont wires and a UART communication line. The connection relationship between the components is: the 24V DC power supply is connected to the stepper motor driver to power it; the stepper motor driver adopts a common anode connection method; a silicone hose is installed in the pump head of the linear peristaltic pump, and the body is connected to the output end of the stepper motor driver; the input end of the stepper motor driver and the liquid level sensor are both connected to the pin of the STM32 control board; the STM32 control board is connected to the host computer through the UART communication line. The 24V DC power supply and the STM32 control board share the same ground. The silicone hose includes: a suction hose 1, an extrusion hose 3, and a lift hose 7; the linear peristaltic pump includes: a linear peristaltic pump head 5, a rotor 4, and a body. PP hose adapters 2 and 6 are used to connect two sections of silicone hoses, and PP hose adapter 8 is used to connect the lift hose to the printing barrel; the capacitive liquid level sensor 9 is fixed to the outside of the printing barrel 10 by a plastic rolling belt. The scale line 11 is used as a reference line for the near exhaustion of food ink. The rotor can transport the food ink in the storage box to the printing barrel by rotating clockwise.

[0034] The following figure introduces the control method of the device:

[0035] Reference Figure 2 When using this device, functions such as starting, pausing, accelerating and decelerating of the linear peristaltic pump are directly controlled by the host computer software. First, search and connect the UART serial port number of the STM32 control board connected to the host computer, click the switch button, and the indicator light next to it changes from red to green, indicating that the connection is successful; if the viscosity of the food ink being transported is known, you can enter the viscosity value in the viscosity box, click the calculation button, and the speed value will be converted according to the polynomial mathematical model of viscosity and speed and displayed in the "Speed" box. Click Send to pass the target speed to the STM32 control board to control the pumping speed of the linear peristaltic pump; if the viscosity of the food ink being transported is unknown, you can manually enter the speed value in the speed box and click Send to control the linear peristaltic pump to run at this speed. Click the start button, if the indicator light next to it changes from red to green, it means that the start is successful and the feeding device starts to run. Set the input range of the speed box. If the input value exceeds this range, the linear peristaltic pump stops running, and the interface prompts "The input speed range is incorrect, please re-enter". The deceleration or acceleration button controls the linear peristaltic pump to decelerate or accelerate at the current speed. The values ​​in the pre-scaling coefficient and reload coefficient boxes are internal preset parameters and cannot be edited by the user.

[0036] The following is a description of the overall process of printing and refilling of an ink refilling device for food 3D printing based on a robotic arm according to the present invention, in conjunction with the figure:

[0037] Reference Figure 3 , install the empty printing barrel on the fixture of the robotic arm; connect the lift hose of the feeding device to the printing barrel; open the host computer software, complete the serial port connection with the STM32 control board, set the viscosity value or speed value of the food ink, and click Start to start the feeding device to feed; wait until the sensor on the outside of the printing barrel detects the ink, and the feeding stops automatically; start the robotic arm printing program and start printing. When the ink in the printing barrel is reduced to the bottom scale line, pause the printing program and prepare for feeding; repeat the steps to complete a new round of feeding. If the ink in the printing barrel remains sufficient, you can wait for printing until the printing program is completely completed.

[0038] The above description is only a preferred example of the present invention and is not intended to limit the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A mechanical arm type food 3D printing ink refilling device, characterized in that include: Linear peristaltic pump, silicone hose, stepper motor driver, 24V DC power supply, PP hose adapter, liquid level sensor, STM32 control board, host computer, plastic rolling strip, several DuPont cables and UART communication cables; 24V DC power supply is connected to the stepper motor driver to power it; The stepper motor driver adopts the common anode connection method; a silicone hose is installed in the pump head of the linear peristaltic pump, and the body is connected to the output end of the stepper motor driver; the input end of the stepper motor driver and the liquid level sensor are both connected to the STM32 control board; the STM32 control board is connected to the host computer through the UART communication line; the DuPont line is used for circuit connection between various hardware parts.

2. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The body of the linear peristaltic pump is a stepper motor, which is connected to the pump head of the linear peristaltic pump through a coupling to drive the rotor to rotate. It is driven by a stepper motor driver and controlled by a pulse signal from the STM32 control board. Its speed is proportional to the frequency of the pulse signal. The silicone hose is divided into three sections. The first section is installed in the pump head of the linear peristaltic pump as an extrusion hose. The rotation of the rotor can squeeze and release it alternately, so that a pressure difference is formed in the extrusion hose to pump food ink; the second section is installed on the left side of the pump head of the linear peristaltic pump as a suction hose; the third section is installed on the right side of the pump head of the linear peristaltic pump as a lift hose, and a PP hose adapter is installed at the end for connection with the printing barrel. The card slot on the PP hose adapter can be stably fixed to prevent it from being squeezed out due to the effect of air pressure during 3D printing; and every two sections of the hose are connected with a PP hose adapter. In order to further ensure the tightness of the connection between the hoses, plastic rolling belts are used to fix the hoses at the connection.

3. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The liquid level sensor is a capacitive sensor. Its detection principle is based on the conductivity of ink. The response time is 500ms. It can penetrate non-metallic containers and has no direct contact with ink, ensuring the concept of safety and environmental protection during the transportation of food ink. It is fixed to the outside of the printing barrel with a plastic rolling belt. When ink is detected, the indicator light lights up and sends a signal to the STM32 control board to suspend the feeding behavior of the linear peristaltic pump.

4. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The host computer has a user software designed in the present invention, the design of the software is based on the Matlab app designer tool, and the user interface mainly includes a serial port configuration module and a feed speed adjustment module; The specific method of serial port configuration module design is: Create a blank app designer project. In the view interface, drag and drop components such as buttons, indicator lights, text boxes, and drop-down lists to build a GUI (graphical user interface); set serial port parameters in the GUI, including port number, baud rate, data bits, stop bits, check bits, etc. These parameters need to match the parameters of the serial port device; create a callback for the drop-down box and call the serialport function to create a serial port object; use the configureCallback function to set the callback function, and use the Try catch structure to set the error reporting service; The specific method of designing the feed speed adjustment module is: Drag and drop components such as buttons, indicator lights, value boxes, etc. in the GUI; The buttons include: start, stop, accelerate, decelerate, calculate, and send. A callback is added for each button. The "calculate" button is responsible for converting the viscosity information entered by the user into speed information based on the fitted mathematical model of viscosity and speed. In the callbacks of the remaining buttons, the writeline function is used to send the numerical string in the value box to the serial port. The STM32 control board converts the received data into decimal form for judgment and completes the speed control function of the feeding device.

5. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The specific method for creating a mathematical model of viscosity and rotation speed is as follows: establish the viscosity range of food ink, prepare several food inks with different viscosities within this range, measure the mass flow rate of each food ink at different pumping speeds, and finally use the polynomial curve fitting method to obtain the mathematical model of ink viscosity and rotation speed.

6. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The establishment of the viscosity range of food ink is based on the printability of the material and the upper limit of the linear peristaltic pump itself; the printability standard is set as whether the layers of the printed product are clear after five layers are stacked, and the critical point between clarity and unclearness is used as the lower limit of the viscosity range; the outlet pressure of the linear peristaltic pump is ≤0.2MPa, and its speed will gradually decay when transporting viscous materials. The viscosity value corresponding to the decay to zero speed is used as the upper limit of the viscosity range of food ink.

7. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The specific method of mass flow measurement is as follows: The STM32 control board sends a pulse signal to make the linear peristaltic pump run until its hose is filled with food ink; set an external interrupt program and trigger it through the buttons on the STM32 control board to control the linear peristaltic pump to run at different speeds for the same time; use an analytical balance to weigh the mass of the pumped food ink, repeat the steps and take the average of the weighed mass to ensure the repeatability and accuracy of the experiment; finally, obtain the mass flow rate of food inks with different viscosities at different pumping speeds.

8. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The mass flow rate and the corresponding rotation speed are fitted with a polynomial curve, and the peak value of the curve is taken as the optimal pumping speed of the food ink with this viscosity. The optimal pumping speed of other food inks with different viscosities is found in the same way, and polynomial curve fitting is performed to finally obtain a polynomial mathematical model of food ink viscosity and pumping speed. The number of points collected is required to be less than the maximum order of polynomial fitting. The more points collected, the more accurate the fitting, and the closer the square of R is to 1, the better the fitting effect.

9. The device for replenishing ink for 3D printing of food by a robotic arm according to claim 1, characterized in that: The design of the feeding device has been perfected in terms of its construction and functions. The control of the feeding device, such as the start, pause, acceleration and deceleration of the linear peristaltic pump, is directly controlled by the host computer user software.

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