CN111805890A

CN111805890A - Printing end of high-viscosity ink-jet printing head and high-viscosity ink-jet printing head

Info

Publication number: CN111805890A
Application number: CN202010671103.6A
Authority: CN
Inventors: 冯佳华; 王莉; 卢秉恒; 傅浩杰; 王嘉健; 冯学明; 韦诗嘉; 巴佳豪
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2020-07-13
Filing date: 2020-07-13
Publication date: 2020-10-23

Abstract

The invention belongs to the technical field of 3D printers, and discloses a printing end of a high-viscosity ink-jet printing head, which comprises a shell, a PVDF (polyvinylidene fluoride) tube, a piezoelectric ceramic tube and a printing nozzle, wherein the PVDF tube and the piezoelectric ceramic tube are positioned in the shell; the outer side of the printing nozzle is sleeved with a spring heating ring. PVDF heat-shrinkable tubes are used as pressure cavities, so that energy lost during extrusion of the piezoelectric ceramic tubes is greatly reduced, and high-viscosity liquid drops are easier to spray; a spring heating ring is additionally arranged outside the printing nozzle. The invention also discloses a high-viscosity ink-jet printing head with the printing end, which further comprises an ink supply end, wherein a heating element is additionally arranged at the ink supply end, the smoothness of ink supply can be effectively ensured by heating the ink supply end first and compensating and heating the printing head, the viscosity of ink drops is reduced by heating the ink supply end, the smoothness of ink supply is ensured, the compensation and heating of the printing head ensures the liquid viscosity of the part of the printing head, and the ejection of liquid drops is ensured.

Description

Printing end of high-viscosity ink-jet printing head and high-viscosity ink-jet printing head

Technical Field

The invention belongs to the technical field of 3D printers, and particularly relates to a printing end of a high-viscosity ink-jet printing head and the high-viscosity ink-jet printing head.

Background

The droplet jet printing technology is a printing technology which generates a pressure difference between an ink chamber and the outside in a certain extrusion mode, so that the internal pressure of a nozzle is larger than the outside pressure, and ink is pushed out of the nozzle to generate tiny ink droplets. Inkjet print heads are generally classified into piezoelectric type inkjet print heads and thermal bubble type inkjet print heads according to the manner of generating ink droplets. The piezoelectric ink jet print head uses the deformation of piezoelectric material to generate force to jet ink drops; a thermal bubble type inkjet printhead ejects ink droplets by expansion of bubbles generated in ink by heating.

Generally, piezoelectric print heads can be classified into four types, i.e., squeeze print heads, bending print heads, shear print heads, and push print heads, according to the driving principle. However, the general extrusion type printing head uses glass or other relatively hard materials as a pressure cavity, the pressure cavity is extruded by the piezoelectric ceramic tube, ink drop ejection is realized, the hard materials can greatly offset the extrusion force, the extrusion energy is consumed, and the viscosity range of ejected ink drops is greatly limited. Meanwhile, the piezoelectric ink-jet printing head commonly used in the market at present can only jet a material with low viscosity (0-30 ℃ P), and is easy to block a material with high viscosity.

Disclosure of Invention

The invention aims to provide a printing end of a high-viscosity ink-jet printing head and the high-viscosity ink-jet printing head, which solve the problem that materials with high viscosity cannot be sprayed at present.

The invention is realized by the following technical scheme:

the printing end of the high-viscosity ink-jet printing head comprises a shell, a PVDF (polyvinylidene fluoride) tube, a piezoelectric ceramic tube and a printing nozzle, wherein the PVDF tube and the piezoelectric ceramic tube are positioned in the shell; and a spring heating ring is sleeved outside the printing nozzle.

Further, the outer side of the printing nozzle is also sleeved with a heat insulation gasket, and the heat insulation gasket is arranged above the spring heating ring.

Furthermore, a conductive adhesive is arranged between the piezoelectric ceramic tube and the PVDF tube, and the lead is adhered to the positive electrode and the negative electrode of the piezoelectric ceramic tube through the conductive adhesive.

Further, the joint of the PVDF pipe and the printing nozzle is filled through a sealant; the lower pipe is bonded with the upper end of the PVDF pipe through a sealant.

Furthermore, an end cover is connected to the bottom of the shell, and the spring heating ring is sealed in the shell through the end cover.

Furthermore, a clapboard is arranged at the lower part of the shell, and a mounting hole for mounting the printing nozzle is arranged on the clapboard.

Further, a flow restrictor was connected to the upper end of the PVDF tube.

Furthermore, the current limiter comprises an upper pipe and a lower pipe, a first hole and a second hole which are communicated with each other are formed in the upper pipe along the axial lead, a plurality of current limiting holes are formed in the lower pipe along the axial direction, and the first hole and the central lines of the current limiting holes are arranged in a staggered mode; the lower pipe is positioned in the second hole and connected with the upper end of the PVDF pipe.

The invention also discloses a high-viscosity ink-jet printing head with the printing end, and the high-viscosity ink-jet printing head also comprises an ink supply end, wherein the ink supply end comprises a shell, an ink bottle, ink and an ink supply pipe, the ink bottle is positioned in the shell, the ink supply pipe extends into the top of the ink bottle, a heating element is arranged in the ink bottle, and a heat insulation sleeve is arranged between the ink bottle and the shell.

Further, the heating element and the spring heating coil are connected with a temperature controller.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention discloses a printing end of a high-viscosity ink-jet printing head, which comprises a shell, a PVDF (polyvinylidene fluoride) pipe, a piezoelectric ceramic pipe and a printing nozzle, wherein the PVDF heat-shrinkable pipe is used for replacing a glass pipe as a pressure cavity, so that the energy lost during the extrusion of the piezoelectric ceramic pipe is greatly reduced, and high-viscosity liquid drops are easier to jet; the printing nozzle is externally provided with a spring heating ring, the viscosity of the sprayed liquid drops is reduced by utilizing the principle of temperature rise and viscosity reduction, and the viscosity of the high-viscosity liquid drops can be reduced to the spraying range of the printing head by heating, so that the spraying of the high-viscosity liquid drops is realized.

Further, still the cover is equipped with heat insulating gasket in the outside of printing the nozzle, and heat insulating gasket avoids heating spring heating ring direct and the partial contact of the shell that is close to piezoceramics pipe on the one hand, and the heat that transmits for piezoceramics pipe is reduced to the greatest extent, prevents that piezoceramics from leading to "depolarizing" because the high temperature, and on the other hand heat insulating gasket and end cover can play the fixed action, prevent the removal of heating spring heating ring.

Furthermore, as the flow rate of the liquid at the axle center in the printing head is higher than that at two sides, the upper end of the PVDF pipe is connected with the current limiter to limit the axle center of the printing head, and ink is supplied at two ends of the current limiter, the backflow of the liquid can be effectively reduced, the pressure wave can be ensured to be transmitted to the nozzle as much as possible, and the liquid drop injection is ensured.

Furthermore, the structure of the current limiter is specifically designed, the current limiter is designed into two parts, the open holes of the upper part and the lower part do not correspond to each other, and the liquid close to the axis is limited, so that the ink flowing out of the upper pipe flows into the limiting holes on the periphery of the lower pipe, and the backflow of the ink can be effectively reduced.

The invention also discloses a high-viscosity ink-jet printing head with the printing end, which further comprises an ink supply end, wherein a heating element is additionally arranged at the ink supply end to heat ink, the smoothness of ink supply can be effectively ensured by heating the ink supply end first and compensating and heating the printing head, the viscosity of ink drops is reduced by heating the ink supply end, the smoothness of ink supply is ensured, the compensation and heating of the printing head ensures the liquid viscosity of the printing head part, the ejection of liquid drops is ensured, and meanwhile, the stability of the ink temperature can be ensured by double heating.

Drawings

FIG. 1 is a schematic view of the external structure of the printing end of a high viscosity ink jet print head according to the present invention;

FIG. 2 is a schematic view of the internal structure of FIG. 1;

FIG. 3 is a schematic view of another configuration of a flow restrictor;

FIG. 4 is a cross-sectional view A-A of FIG. 2;

fig. 5 is a schematic diagram of the ink supply end structure of the high viscosity ink jet print head of the present invention.

The printing device comprises a shell 1, a current limiter 2, a printing nozzle 3, an end cover 4, a PVDF pipe 5, a conductive adhesive 6, a piezoelectric ceramic pipe 7, a spring heating ring 8, a heat insulation gasket 9 and a partition plate 10, wherein the shell is arranged at the 1 part;

21 is an upper tube, 211 is a first hole, and 212 is a second hole; a lower pipe 22 and a flow limiting hole 221;

the heating element 11, the ink box end cover 12, the shell 13, the heat insulation sleeve 14, the ink bottle 15, the ink 16 and the ink supply pipe 17.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The invention discloses a printing end of a high-viscosity ink-jet printing head, which comprises a shell 1, a PVDF (polyvinylidene fluoride) tube 5, a piezoelectric ceramic tube 7 and a printing nozzle 3, wherein the PVDF tube 5 and the piezoelectric ceramic tube 7 are positioned in the shell 1, the piezoelectric ceramic tube 7 is sleeved on the outer side of the PVDF tube 5, and the printing nozzle 3 is arranged at the bottom of the PVDF tube 5 and connected with the PVDF tube 5, as shown in figures 1-2.

The PVDF tube 5 is used for replacing a glass tube to serve as a pressure cavity of a printing head, the piezoelectric ceramic tube 7 is sleeved on the PVDF tube 5, the positive electrode of the piezoelectric ceramic tube 7 is led out by the conductive adhesive 6, a lead is adhered or welded on the positive electrode and the negative electrode of the piezoelectric ceramic tube 7 by the conductive adhesive 6, a driving voltage is applied to the lead, and due to the inverse piezoelectric effect, the piezoelectric ceramic can deform and extrude the PVDF tube 5. Since the PVDF material is much less hard than glass, the piezoelectric ceramic tube 7 will deform the PVDF tube 5 more and lose less energy, thereby facilitating the ejection of droplets. The printing nozzle 3 is provided with a jet hole with the aperture of 40-240 microns, and liquid drops are jetted from the jet hole.

The driving voltage is generally generated by a function generator, then is input into a voltage amplifier, is amplified to the required voltage, and then is connected to the positive electrode and the negative electrode of the piezoelectric ceramic tube 7.

Compared with the PET heat shrinkable tube, the minimum shrinkage temperature of the PET heat shrinkable tube is about 80 ℃, the heating temperature can not exceed 70 ℃ theoretically in order to prevent the pressure chamber from deforming caused by overlarge temperature, the minimum shrinkage temperature of the PVDF heat shrinkable tube is about 175 ℃, and the heating temperature can be increased to about 90 ℃ in consideration of the limitation of Curie temperature of the piezoelectric ceramic tube 7. Since the PTFE material is non-tacky as compared with the PTFE heat shrinkable tube, the PTFE heat shrinkable tube needs to be surface-treated, and the related process is troublesome, and the PVDF tube 5 does not have such a limitation.

The space between the PVDF tube 5 and the print nozzle 3 is filled with a sealant. The sealant is generally epoxy resin adhesive.

The shell 1 is made of a nylon shell 1, and nylon has poor thermal conductivity and can play a certain role in heat preservation on the ink 16; the nylon has poor conductivity, the highest voltage can reach 100-200V due to the fact that the printing head needs to conduct electricity during working, and the nylon shell 1 can effectively prevent the danger of electric leakage; the nylon material is more convenient to process.

Because the liquid in the pipe close to the axle center has the fastest flow rate, the flow restrictor 2 is designed to limit the flow of the liquid at the axle center position, prevent the liquid from flowing back upwards during the injection, and simultaneously, the liquid can flow into the printing head from the ink supply cavity at two sides. The flow restrictor 2 is composed of an upper part and a lower part which are hermetically bonded through epoxy resin glue and are bonded with the PVDF pipe 5.

Specifically, the upper end of the PVDF tube 5 is connected with a flow restrictor 2, as shown in fig. 2 and 3, the flow restrictor 2 includes an upper tube 21 and a lower tube 22, a first hole 211 and a second hole 212 which are communicated with each other are formed in the upper tube 21 along the axial line, as shown in fig. 2 to 4, a plurality of flow restricting holes 221 are formed in the lower tube 22 along the axial direction, and the central lines of the first hole 211 and the flow restricting holes 221 are arranged in a staggered manner; the lower pipe 22 is fitted into the second hole 212, and the lower pipe 22 is connected to the upper end of the PVDF tube 5.

The joint of the upper handle and the lower pipe 22 is sealed by a sealant which is epoxy resin glue.

As shown in FIG. 2, the second bore 212 is a cylindrical bore, with the solid central portion of the lower tube 22 being cylindrical; as shown in fig. 3, the second hole 212 is formed by a cylindrical hole and a tapered hole, and the upper side of the central solid portion of the lower tube 22 is reversely tapered. Both configurations are such that the solid central portion of the lower tube 22 is opposite the first aperture 211 of the upper tube 21, which acts as a flow restriction.

The configuration of the flow restrictor 2 is not limited to that shown in fig. 2 and 3, but only two configurations of the flow restrictor 2 are shown in fig. 2 and 3.

More preferably, a heating module is added in the ink jet system, and the viscosity of the jetting material is reduced by heating by utilizing the principle of temperature rise and viscosity reduction.

The heating portion of the printhead comprises a housing 1, a spring heating coil 8 and an end cap 4. We fit the spring heating ring 8 on the print nozzle 3 to heat the print nozzle 3, and the heating temperature is limited below 90 ℃ due to the curie temperature of the piezo-ceramic tube 7. The nylon casing 1 prevents heat from being dissipated on the one hand and protects the main body of the print head on the other hand.

Preferably, a heat insulating gasket 9 is further sleeved outside the printing nozzle 3, and the heat insulating gasket 9 is arranged above the spring heating ring 8. The heat insulating gasket 9 avoids the spring heating ring 8 to directly contact with the part of the nylon shell 1 close to the piezoelectric ceramic tube 7, reduces the heat transferred to the piezoelectric ceramic tube 7 as much as possible, prevents the piezoelectric ceramic from causing depolarization due to over-high temperature, and the heat insulating gasket 9 and the end cover 4 can play a role in fixing and prevent the movement of the spring heating ring 8.

As shown in fig. 5, the high viscosity inkjet printhead of the present invention further includes an ink supply end, a heating part is disposed at the ink supply end, the ink supply end includes a housing 13, an ink bottle 15, ink 16 and an ink supply tube 17, the ink bottle 15 is disposed in the housing 13, the ink supply tube 17 extends into the top of the ink bottle 15, a heating element 11 is disposed in the ink bottle 15, a heat insulation sleeve 14 is disposed between the ink bottle 15 and the housing 13, and the ink 16 in the ink bottle 15 flows into the PVDF tube 5 after flowing into the restrictor 2 through the ink supply tube 17. The heating element 11 is generally a heating rod.

Preferably, the heating element 11 and the spring heating coil 8 are connected to a temperature controller, the model of which is PLK3000A, which is provided with two temperature-sensitive wires, one connected to the spring heating coil 8 and the other connected to the heating element 11. The heating temperature of the heating element 11 and the spring heating coil 8 is controlled by a temperature controller to be within a proper range.

When the liquid drops are ejected, the ink bottle 15 is heated by a heating rod to heat the ink 16 in the ink bottle 15 to a required temperature, so that the problem that the ink 16 is insufficiently heated in the heating part of the printing head to cause a choke plug is avoided. Meanwhile, the shell 13, the ink box end cover 12 and the heat insulation sleeve 14 are used for preserving heat of the ink bottle 15, so that heat loss is prevented. The ink 16 can be heated to a relatively stable temperature by heating the ink supply end first and compensating heating of the print head portion, facilitating ejection of high viscosity droplets.

Claims

1. The printing end of the high-viscosity ink-jet printing head is characterized by comprising a shell (1), a PVDF (polyvinylidene fluoride) tube (5), a piezoelectric ceramic tube (7) and a printing nozzle (3), wherein the PVDF tube (5) and the piezoelectric ceramic tube (7) are positioned inside the shell (1), the piezoelectric ceramic tube (7) is sleeved on the outer side of the PVDF tube (5), and the printing nozzle (3) is arranged at the bottom of the PVDF tube (5) and is connected with the PVDF tube (5); the outer side of the printing nozzle (3) is sleeved with a spring heating ring (8).

2. A high viscosity ink jet print head according to claim 1, wherein a thermal insulating washer (9) is also sleeved on the outside of the print nozzle (3), the thermal insulating washer (9) being arranged above the spring heating ring (8).

3. The high viscosity ink jet print head according to claim 1, wherein a conductive adhesive (6) is provided between the piezoelectric ceramic tube (7) and the PVDF tube (5), and the lead wires are bonded to the positive and negative electrodes of the piezoelectric ceramic tube (7) through the conductive adhesive (6).

4. The high viscosity ink jet print head according to claim 1, wherein the junction of the PVDF tube (5) and the print nozzle (3) is filled with a sealant; the lower pipe (22) is bonded with the upper end of the PVDF pipe (5) through a sealant.

5. A high viscosity ink jet print head according to claim 1, wherein an end cap (4) is attached to the bottom of the housing (1), and the spring heating coil (8) is enclosed in the housing (1) by the end cap (4).

6. A high viscosity ink jet print head according to claim 1, wherein a partition plate (10) is provided in a lower portion of the housing (1), and mounting holes for mounting the printing nozzles (3) are opened in the partition plate (10).

7. The high viscosity inkjet printhead according to claim 1, characterized in that a flow restrictor (2) is connected to the upper end of the PVDF tube (5).

8. The high viscosity ink jet print head according to claim 7, wherein the restrictor (2) comprises an upper tube (21) and a lower tube (22), a first hole (211) and a second hole (212) communicating with each other are formed in the upper tube (21) along the axial center line, a plurality of restrictor holes (221) are formed in the lower tube (22) along the axial center line, and the first hole (211) is arranged to be offset from the center line of the restrictor holes (221); the lower pipe (22) is positioned in the second hole (212), and the lower pipe (22) is connected with the upper end of the PVDF pipe (5).

9. A high viscosity ink jet print head having a printing end according to any of claims 1 to 8, further comprising an ink supply end comprising a housing (13), an ink bottle (15), ink (16) and an ink supply tube (17), the ink bottle (15) being located within the housing (13), the ink supply tube (17) extending into the top of the ink bottle (15), a heating element (11) being located within the ink bottle (15), and a thermal insulating sleeve (14) being located between the ink bottle (15) and the housing (13).

10. A high viscosity inkjet printhead according to claim 9, wherein the heating element (11) and the spring heating coil (8) are connected to a temperature controller.