CN111421809A

CN111421809A - High-density 3D printing method and printer applying same

Info

Publication number: CN111421809A
Application number: CN201910021218.8A
Authority: CN
Inventors: 严铜
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-01-09
Filing date: 2019-01-09
Publication date: 2020-07-17

Abstract

The invention discloses a high-density 3D printing method and a printer applying the same, and solves the defects of poor internal binding force and poor compactness of a printing model of the conventional FDM type 3D printer. The surface of the printing layer is preheated and maintained at the temperature in the process of forming the melting wire or heated after forming to be melted again, so that the printing wires which are contacted with each other can be fully fused, and the compactness and the mechanical property of the 3D printing material are improved.

Description

High-density 3D printing method and printer applying same

Technical Field

The invention belongs to the technical field of 3D printers, and particularly relates to a high-density 3D printing method and a printer applying the method.

Background

The 3D printing technology is a fast forming technology, which is a technology for forming an object by using forming materials such as metal, plastic, photosensitive resin and the like in a layer-by-layer printing mode on the basis of a digital three-dimensional model file, and belongs to additive manufacturing. At present, a 3D printer based on Fused Deposition Modeling (FDM) principle has become a 3D printer with the highest popularity due to the advantages of simple structure, rich types of applicable materials, low cost of equipment and consumables and the like.

The basic working principle of the FDM printer is to feed printing consumables into a melting cavity, melt the printing consumables and extrude the printing consumables from a nozzle, and the printer shapes the extruded fuse wire in the nozzle to a specified position by controlling the movement path of a spray head. These two features result in the extruded fuse wire not being able to achieve a good bond with the surrounding molded material due to the poor flowability of the plastic material and the rapid cooling of the fuse wire after extrusion.

The rapid cooling of the fuse wire results in failure to reflow the surrounding mold material because poor flow results in voids between the contact surfaces of the two fuses. In particular, the mechanical properties of the final printed model are greatly compromised because the contact surface of the peripheral model material is not sufficiently melted. Poor bonding force between two printing wires on the same layer can be compensated by optimizing a printing path, but the optimized printing path does not have the function of improving the bonding force between layers. Fig. 1 is a schematic cross-sectional view of a printing model of the current FDM type 3D printing technology, and a plurality of gaps 11 are formed because the molten filament 10 is cooled too fast after being extruded, so that the molten filament does not have enough time to fill the gaps at the contact surface position. Also, due to the too rapid cooling, the molten filaments cannot re-melt the formed material at the contact surface 12 after extrusion, thus resulting in an unsatisfactory bonding force between them.

The problem is particularly obvious when the printing is suspended for some reasons, if the printing is suspended in the printing process and the printing is continued on the basis of the previous printing after the temperature of the model is completely reduced, the model is most likely to be broken at the splicing part of the two times of printing, so that the current FDM printer can only finish the printing by one-time printing and forming when printing the model with higher requirements on mechanical performance, and needs to print again once the printing is suspended.

The above reasons not only cause the mechanical property of the model to be reduced, but also cause the transparency of the model to be poor when the transparent material is printed, so that even if the transparent material is used for printing, the model finally appears to be a semi-transparent or white opaque model according to the difference of the printing thickness. The light transmittance of the model is reduced because of a large amount of random refraction and reflection of light in the model due to a large amount of tiny gaps in the model and the fact that the contact surfaces are not completely plasticized and fused together.

Chinese utility model patent with application number CN201720861657.6 "a preheat the 3D printing device who prints the region through optic fibre laser" provides a device that adopts laser to preheat and improve cohesion between the printing model layer. The device can preheat the formed material in front of the melting wire before forming, thereby improving the interlayer bonding force of the printing model. The device has the defects that due to the high power density and the concentrated energy of the laser, the preheating area can be only a single small point, which is illustrated as a light spot not larger than 2mm in the embodiment, and due to the excessively small heating area, when the laser is removed and stops heating, the area can still be rapidly cooled, and the bonding performance between material layers can still be reduced.

The chinese patent application No. CN201810420252.8, a 3D printer head and a 3D printer, also provides a printer with a function of preheating a previous layer of printing layer material, which uses a heater with a heating plate, a high frequency heating or a laser heating to preheat a formed material. The method described in the patent specification is to print one layer by a print head, preheat the current layer by a heater, and print the next layer after the current layer is finished. The problem with this approach is that the preheating is separate from the printing, and the time during which the preheating process can be maintained is limited, so that when the printing model is large, the previous printed layer of the model will have cooled completely away before printing has ended.

Both of these patent applications propose preheating to solve the problem of poor interlayer bonding force of the printing model. The difference lies in that the former patent adopts a scheme of preheating and printing simultaneously, and the latter patent adopts a scheme of preheating firstly and then printing. However, the problem of poor interlayer structure cannot be well solved only by simply preheating the formed model, and the problems of printing compactness and non-transparency of the printed transparent material cannot be solved.

In summary, the current FDM printer has the defects of poor internal binding force and poor compactness of the printing model, so that the application range is limited to a certain extent.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a high-density 3D printing method and a printer using the method, and the method comprises the steps of preheating and maintaining the temperature of a printing material in a molding area in the molding process or heating the surface of the printing layer after molding to melt the printing layer for the second time, so that the extruded molten wire can be fully fused with the molded material part, and the molding compactness and interlayer mechanical property of a 3D printing model are improved.

Unless otherwise specified, the molten filament refers to a printing filament which is extruded from a spray head and not completely solidified, and the width of the printing filament refers to the width of the molten filament after deposition and formation.

In the case of a polymer material, the melting temperature is generally a range, and generally refers to a temperature range from melting to complete melting and plasticizing of the polymer material. Unless otherwise specified, a temperature lower than the melting temperature of a material herein means a minimum value in a range where the corresponding temperature is lower than the melting temperature of the material, a temperature equal to the melting temperature of the material means a temperature within a range where the corresponding temperature is within the melting temperature of the material, and a temperature higher than the melting temperature of the material means a maximum value in a range where the corresponding temperature is higher than the melting temperature of the material.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for high density 3D printing is proposed, comprising at least one of the following operations:

p1: preheating an area where a melting wire is to be deposited in the current layer printing process, and maintaining the temperature of the melting wire deposition area in the melting wire extrusion process;

p2: after the printing of the current layer is completed, the surface of the molded layer is heated again, and the surface of the printed layer is melted again.

The two operations are respectively used for heating the printing layer in the printing process and after printing. The P1 operation adopts the mode of preheating and maintaining temperature, so that the molten filament is fully fused with the contacted model material in the extrusion molding process; the P2 operation is to heat the entire layer completely after the pattern has been printed, and to melt the surface of the printed layer again, so that the materials between adjacent printed filaments and between adjacent printed layers of the same layer can be fully fused by the surface tension of the melted pattern material and the diffusion movement of the molecules inside. Therefore, the two operations of P1 and P2 can be independently carried out to achieve the purpose of improving the fusion effect between the adjacent printing wires, and can also complement each other to ensure that the fusion between the materials is more sufficient.

Preferably, the heating in the P1 operation is such that the model material temperature in the heated region is above the model build ambient temperature, and below or equal to the melting temperature of the model material; the heating in the P2 operation causes the surface temperature of the pattern material in the heated area to be no lower than the melting temperature of the material.

Preferably, non-contact heating, preferably hot air heating or infrared radiation heating, is used in the method.

Preferably, the heating region in the P1 operation is a circular region centered on the print head nozzle with a radius of 5 to 50 times the width of the print wire, preferably 10 to 20 times the width of the print wire. The heating zone is centered on the nozzle, which allows for both preheating of the area where the molten filament is to be deposited and maintaining the temperature of the area where the molten filament is deposited. If the heating area is too small, the temperature maintaining time is too short, and the forming effect is poor, whereas if the heating area is too large, a large area of area which is maintained at a temperature close to the melting temperature for a long time appears in the printing layer, and the model is easy to deform. When the radius of the heating area is 5 to 50 times of the width of the printing wire, preferably within the range of 10 to 20 times, the two aspects of prolonging the temperature maintaining time and reducing the deformation risk of the model can be well considered.

Preferably, the surface of the printing layer is heated again to melt the printing layer in the P2 operation to a depth of 1 to 5 times, preferably 1.5 to 2 times, the thickness of the printing layer. Too deep a melting depth easily causes the model to deform, so the melting depth needs to be controlled, the adjacent layers can be fully fused, and the risk of deformation of the model is reduced.

Preferably, the method further comprises the following steps: when the model is sliced, the printing path and the printing speed are optimized, so that the heating of each area of the model in the P1 operation is balanced, and overheating or insufficient heating is avoided.

The high-density 3D printer comprises a nozzle for extrusion molding of the molten filament and a heating mechanism, wherein the heating mechanism adopts a hot air heating or infrared radiation heating mode, and can heat the surface area of the printing layer.

Preferably, the heating mechanism comprises two heating devices: the first heating device is mounted on the print head and moves along with the print head. The heating zone of the heating device completely comprises a circular zone centered on the nozzle and having a radius of 5 times the width of the printing wire. The second heating device is arranged on one of the horizontal moving shaft sliding blocks, so that the heating component spans over the printing platform, and the whole printing area of the printing platform can be scanned and heated under the driving of the moving shaft.

Preferably, the heating region of the first heating device is a circular region with a radius of 10 to 20 times the width of the printing wire, centered on the nozzle.

Preferably, the first heating device is a hot air heater, and the second heating device is an infrared heating pipe.

Compared with the prior art, the high-density 3D printing method provided by the invention has the advantages that the printing layer surface is preheated and maintained at the temperature in the molten wire forming process or heated after forming to be melted again, so that the printing wires which are contacted with each other can be fully fused, the compactness and the mechanical property of the 3D printing model are improved, and the transparency of the transparent material model is also improved due to the improvement of the compactness.

Drawings

Fig. 1 is a schematic cross-sectional view of a prior art FDM type 3D printing technique printing model.

Fig. 2 is a schematic structural diagram of the high-density 3D printer of the present invention.

FIG. 3 is a schematic view of the working principle of the first heating device of the high-density 3D printer.

Fig. 4 is a schematic view of the working principle of the second heating device of the high-density 3D printer.

In the figure: 10. printing wires, 11 printing wire gaps, 12 printing wire contact surfaces, 21 spray heads, 22 first heating devices, 23 second heating devices, 24 heating areas of the first heating devices, 25 printing platforms, 341 current printing layers, 342 previous printing layers.

Detailed Description

The method for high-density 3D printing and the printer using the method according to the present invention will be further described in conjunction with the accompanying drawings and the detailed description, so as to more clearly understand the technical idea claimed in the present invention.

Example (b):

fig. 2 is a schematic structural diagram of the high-density 3D printer of the present invention. As shown in fig. 2, in this embodiment, the X-axis moving track is mounted on the frame, and the Y-axis moving track is mounted on the X-axis moving slider. The head 21 is mounted on the Y-axis moving slider, the first heating device 22 is fixedly mounted on the head 21, the first heating device 22 is a hot air heater, and the heating region 24 thereof is a circular region centered on the nozzle of the head 21. In this embodiment, the printing wire width is 1mm, and the radius of the circular area is 15 times the printing wire width, i.e. 15 mm. And a second heating device 23 is fixedly arranged on the X-axis moving slide block, the second heating device 23 spans above the printing platform 25, and the whole printing area of the printing platform 25 can be scanned and heated under the driving of the X-axis moving mechanism. The second heating device 23 is an infrared heating tube.

The implementation details of the high-density 3D printing method are explained in detail below based on an embodiment of the high-density 3D printer.

In a P1 operation, as shown in fig. 3, a molten filament is extruded from the nozzle 21 to form a current printed layer 341 over a previous printed layer 342. During the molding process, the first heating device 22 continuously heats the previous printing layer 342 and the current printing layer 341. The heating zone 24 of the first heating device 22 covers both the previous printed layer 342 in front of the print path and the current printed layer 341 behind the print path, while enabling preheating of the area where the molten filament is to be deposited and temperature maintenance of the molten filament deposition area.

The heating temperature of the first heating device 22 is controlled in a range higher than the model building environment temperature and lower than or equal to the model material melting temperature. The heating temperature refers to the temperature to which the hot air heater heats the surface of the lower die material, but not the temperature of the hot air itself. Because the printing head is in continuous movement, the heating temperature of the model material is lower than the temperature of the hot air, and the heating temperature has a direct relation with the movement speed of the printing head and the air volume of the hot air.

The heating temperature can be selected to be within the melting temperature range or a temperature value closer to the melting temperature according to different molding materials and the size of the heating area. The higher the temperature and the longer the duration, the better the fusion effect between the front and back layers, but the higher the temperature, the higher the risk of deformation of the model. In this embodiment, the molding material is polycarbonate, the melting temperature is 215-225 ℃, and the heating temperature of the first heating device in this embodiment is 205 ℃.

In the P2 operation, the second heating device 23 scans past from above the printing pattern under the drive of the X-axis movement mechanism, and realizes the overall heating of the current printing layer 341. And the heating power and the movement speed of the second heating device 23 are controlled, so that the surface layer material of the model can be melted, and the melting depth is about 1.5-2 times of the thickness of the printing layer. Increasing the depth of fusion allows better fusion between the upper and lower layers, but also increases the risk of deformation of the mould. The depth should therefore be controlled within 5 times the layer thickness, preferably 1.5 to 2 times the layer thickness. The heating temperature of the second heating device in this embodiment is 230 ℃, and the melting depth of the model surface layer material is controlled between 1.5 times and 2 times the layer thickness by selecting a suitable scanning speed.

In order to reduce the influence on the printing model, a non-contact heater is preferably used in the method, and in all non-contact heating methods, hot air heating and infrared heating are preferred. Therefore, in this embodiment, the first heating device is a hot air heater, and the second heating device is an infrared heating tube.

In order to further optimize the printing effect, the embodiment of the method further comprises optimizing the printing path and the printing speed when the model is sliced, so that the heating of each area of the model in the P1 operation is equalized, and overheating or insufficient heating is avoided. Because the heating region is for several times to tens of times print the silk width, consequently to the large tracts of land when filling, the condition of a large amount of repeated heating can appear, should reduce first heating device's heating power this moment to print with higher speed, to the printing region of similar narrow long strip, because its material concentration is low, print according to normal conditions, the condition that the heating is not enough easily appears, consequently need reduce the printing speed and improve first heating device's heating power when the section.

Various other changes and modifications to the above-described embodiments and concepts will become apparent to those skilled in the art from the above description, and all such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims

1. Method of high-density 3D printing, characterized in that the method comprises at least one of the following operations:

2. The method of highly densified 3D printing according to claim 1, wherein the heating in the P1 operation is such that the model material temperature in the heated region is above the model build environment temperature, and is less than or equal to the melting temperature of the model material;

the heating in the P2 operation causes the surface temperature of the pattern material in the heated area to be no lower than the melting temperature of the material.

3. Method of highly densified 3D printing according to claim 2, wherein non-contact heating, preferably hot air heating or infrared radiation heating, is used in the method.

4. The method of highly densified 3D printing according to claim 2, wherein the heating zone in the P1 operation is a circular zone centered on the print head nozzle with a radius of 5 to 50 times the width of the printing wire, preferably a radius of 10 to 20 times the width of the printing wire.

5. The method for highly densified 3D printing according to claim 2, wherein the surface of the printing layer is reheated and melted to a depth of 1 to 5 times, preferably 1.5 to 2 times, the thickness of the printing layer in the P2 operation.

6. The method of highly densified 3D printing according to claim 2, further comprising: when the model is sliced, the printing path and the printing speed are optimized, so that the heating of each area of the model in the P1 operation is balanced, and overheating or insufficient heating is avoided.

7. The high-density 3D printer can be used for printing by applying 1 or more high-density 3D printing methods in claims 1-6, comprises a nozzle for extrusion molding of a molten filament, and is characterized by further comprising a heating mechanism, wherein the heating mechanism adopts a hot air heating mode or an infrared radiation heating mode, and can heat the surface area of a printing layer.

8. The highly densified 3D printer of claim 7, wherein the heating mechanism includes two heating devices:

the first heating device is arranged on the printing head and moves along with the printing head; the heating area of the heating device completely comprises a circular area which takes a nozzle as the center and takes the width 5 times of the width of the printing wire as the radius;

the second heating device is arranged on one of the horizontal moving shaft sliding blocks, so that the heating component spans over the printing platform, and the whole printing area of the printing platform can be scanned and heated under the driving of the moving shaft.

9. The highly densified 3D printer of claim 8, wherein the heating zone of the first heating device is a circular zone centered on the nozzle with a radius of 10 to 20 times the print wire width.

10. The high density 3D printer of claim 8, wherein the first heating device is a hot air heater and the second heating device is an infrared heating tube.