TECHNICAL FIELD

The invention relates to the field of 3D printers, and particularly to a print head for a thermoplastic material fused deposition type 3D printer.

BACKGROUND

At present, heads of integrated constant diameter nozzles are the most common in a fused material layer deposition technology. No matter how the sizes of models vary, all the models are printed according to the same transverse plane resolution, and the resolution of a vertical plane can only be changed through the thickness of the layer. In order to ensure that the transverse plane resolution is relatively high, nozzles having different diameters can be used, but the nozzles can be changed only when in halt. Several nozzles are adopted when one-time printing is performed, because the nozzles need to be changed even a thousand times in this process, and therefore this method is unfeasible.

Some extruders of 3D printers adopt print heads having different diameters. These nozzles are mounted one after the other. In this way, the sizes of the extruders are significantly enlarged, and multiple kinds of nozzles can influence use sense.

A print head of an extruder of a Robox printer is provided with two nozzles: one has a large diameter, and the other has a small diameter. A printing mechanism feeds a material for one of them. In general, the nozzle having a small diameter is used to generate a shape of an outer model, and the nozzle having a large diameter is used to generate filling of the model and uppermost and downmost layers.

A US patent application US20150093465 discloses use of 3 print nozzles having different diameters, accordingly, one, which has an optimal path generated by each of the 3 print nozzles, in 3 nozzles, can be selected in a control firmware of a printer to be used. SUMMARY

There is a need to provide an adjusting structure capable of varying the print resolution at any time and flexibly adjusting a print head.

There is disclosed a print head adjusting structure for a 3D printer, comprising an extruder, a heating block, a nozzle body, a feeding assembly and a material guiding tube, wherein the print head adjusting structure is characterized by further comprising a plurality of pieces of adjusting vanes, an adjusting swivel and fixing pins, wherein the various adjusting vanes are respectively mounted at the bottom of the nozzle body via the fixing pins, and are in rotatory arrangement to be at an inclined angle with respect to one another, wherein the adjusting swivel drives the angle arrangement change of the adjusting vanes through the fixing pins.

Preferably, the extruder is fixed outside the upper part of the feeding assembly, the nozzle body is arranged outside the lower part of the feeding assembly, and the material guiding tube penetrates through the feeding assembly and the center of the nozzle body, and wherein the adjusting swivel is arranged outside the nozzle body and wherein the center of the bottom of the nozzle body is provided with a nozzle, the center of which is connected with the material guiding tube and the outside, and wherein the inner sides of the adjusting vanes are inserted into the center of the nozzle.

Preferably, the adjusting vanes revolve around the fixing pins.

Preferably, the inner side wall of the adjusting swivel is provided with a plurality of internally protruded push assemblies, wherein one push assembly is respectively arranged beside the tail end of each adjusting vane.

Preferably, distances between the push assemblies and the adjusting vanes are the same.

Preferably, the heating block is internally provided with a temperature sensing tube for feeding back a heating temperature and a heating tube for generating heat.

Preferably, the printing head adjusting structure further comprises transmission teeth, a servo motor, a driving gear and a transmission crank, wherein the transmission crank and the servo motor are connected to be jointly rotatable, the driving gear and the transmission crank are fixed, and wherein the transmission teeth are meshed with the driving gear and driven to rotate by the driving gear, and wherein the transmission teeth are located on the lateral surface of the adjusting swivel.

Preferably, the printing head adjusting structure further comprises an adjusting wrench, a nozzle hole size scale and a nozzle hole size displayer, wherein the adjusting wrench, the nozzle hole size scale and the nozzle hole size displayer are all located outside the adjusting swivel.

Preferably, the printing head adjusting structure further comprises a movable bar coupled with the adjusting swivel. Preferably, the movable bar is adjustable by a fixed bar along the path of movement of the print head.

Preferably, the printing head adjusting structure further comprises a lever fixed to the adjusting swivel.

Preferably, the lever is adjustable by a fixed bar along the path of movement of the print head.

Preferably, the rate of extrusion of printing consumables by the extruder is controlled as a function of the size of the nozzle outlet hole set by the adjusting swivel.

Preferably, the printing head adjusting structure comprises a controlling module with an extruder controller that is driven by a signal from a servo encoder coupled with a servo motor.

The advantage achieved by the invention is that a nozzle having a variable outlet hole size is used, so that a model having a high resolution can be smoothly generated, and meanwhile, it is not needed to prolong print time. A narrow path width can be used when the shape of the outside of the model is printed - therefore a transverse surface resolution is high, which is beneficial to quality and detail formation. Meanwhile, a wide path can be used for supporting and inner filling of the model, and the transverse surface resolution is relatively low, therefore shorter print time can be ensured, and the detail of the model is more firm. As the path width variation is consecutive rather than discrete, the transverse surface resolution can be adjusted according to a vertical surface resolution, namely the layer thickness. A print material is extruded by only using one tube, so smooth feeding can be ensured, and higher strength and detail quality can also be ensured. Furthermore, a print nozzle can be completely sealed, and thus a material can be prevented from being unexpectedly overflowed, which has great effect on printing of a granulated material, in particular an elastic polymer or a polymer similar to rubber. Moreover, the nozzle can be opened to clean sundries in a print head tube, which contributes to a situation of accident material blocking.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is shown by means of example embodiment(s) on a drawing, wherein:

Fig. 1 shows a sectional diagram of a print head adjusting structure; Fig. 2 shows a top view of the adjusting structure with a servo motor;

Figs. 3 and 4 show a top view and a front view of the adjusting structure which is manually adjustable by means of a wrench;

Fig. 5 shows the adjusting structure which is adjustable by means of a movable bar; Fig. 6 shows the adjusting structure which is adjustable by means of a lever;

Figs. 7A-7C show the adjusting structure dependent on the direction and/or distance of displacement of the printing head;

Fig. 8 shows a functional schematic of a 3D printer; DETAILED DESCRIPTION

Directional terms, such as "upper, lower, left, right", which are referred in the following examples, indicate only directions of accompanying drawings, and therefore, the used directional terms are intended to only illustrate, but not to limit the invention.

A print head adjusting structure of a 3D printer comprises an extruder 7, a heating block 4, a nozzle body 8, a feeding assembly 1 and a material guiding tube 2. The extruder 7 may be fixed outside the upper part of the feeding assembly 1 , the nozzle body 8 may be arranged outside the lower part of the feeding assembly 1 , and the material guiding tube 2 may penetrate through the feeding assembly 1 and the center of the nozzle body 8. The print head adjusting structure further comprises a plurality of pieces of adjusting vanes 12, an adjusting swivel 9 and fixing pins 1 1 . Various adjusting vanes 12 may be respectively mounted at the bottom of the nozzle body 8 via the fixing pins 1 1 and may be in rotatory arrangement to be at an included angle with respect to one another. The adjusting swivel 9 may be arranged outside the nozzle body 8 and may drive the angle arrangement change of the adjusting vanes 12 through the fixing pins 1 1 . The center of the bottom of the nozzle body 8 is provided with a nozzle 3, the center of which is connected with the material guiding tube 2 and the outside. The inner sides of the adjusting vanes 12 may be inserted into the center of the nozzle 3.

The adjusting vanes 12 may revolve around the fixing pins 1 1 . The inner side wall of the adjusting swivel 9 may be provided with a plurality of internally protruded push assemblies 10, wherein one push assembly 10 is respectively arranged next to the tail end of each adjusting vane 12. Distances between the push assemblies and the adjusting vanes 12 may be the same. The heating block 4 may be internally provided with a temperature sensing tube 6 for feeding back a heating temperature and a heating tube 5 for generating heat.

The adjusting vanes 12 have a cross-section that narrows towards the center of the nozzle. In the cross-section, the adjusting vanes 12 have three sides: two sides of the vanes are straight and arranged slidably along the sides of the neighbor vanes, while the third side can be circular. The size of the printhead outlet decreases equally through the feeding hole, along the length of the vanes, thereby the material is continuously shaped along the feeding hole. Another advantage is that the height of the nozzle is constant for different hole sizes (therefore the head position does not have to be compensated in the Z axis). The arrangements of the vanes for various nozzle outlet hole sizes can be seen on Figs. 5 and 6.

In one embodiment, as shown in Fig. 2, the adjusting structure may further comprise transmission teeth 13, a servo motor 16, a driving gear 14 and a transmission crank 15. The transmission crank 15 and the servo motor 16 may be connected such as to be jointly rotatable. The driving gear 14 and the transmission crank 15 may be fixed. The transmission teeth may be meshed with the driving gear and driven to rotate by the driving gear. The transmission teeth may be located on the lateral surface of the adjusting swivel 9.

In another embodiment, as shown in Fig. 3 and 4, the adjusting structure may further comprise an adjusting wrench 19, a nozzle hole size scale 18 and a nozzle hole size displayer 17. The adjusting wrench, the nozzle hole size scale and the nozzle hole size displayer may be all located outside the adjusting swivel 9. The wrench 19 is mainly used to adjust the hole size. This wrench may be mounted over the adjusting swivel 9. The operation of the wrench can make the adjusting swivel 9 operate at the same angle, and the hole size of the outlet of the nozzle can be read using a gauge and a scale.

In another embodiment, as shown in Fig. 5, the adjusting structure may comprise a movable beam 21 coupled with the adjusting swivel 9. For example, the coupling may be provided by coupling teeth provided on the movable beam 21 and the adjusting swivel 9, respectively. The movable bar 31 may be movable manually or by a servo motor.

In another embodiment, as shown in Fig. 6, the adjusting structure may comprise a lever 22 fixed to the adjusting swivel 9 for moving the adjusting swivel 9. In another embodiment, as shown in Figs. 7A-7C, the adjusting structure may comprise fixed bars 20 positioned at the ends of a parallel axis. The bars 20 may cooperate with the beam 21 (as shown in Fig. 7A and 7C) or the lever 22 (as shown in Fig. 7B) to rotate the adjusting swivel 9 depending on the direction and/or distance of displacement of the printing head. For example, when the head hits the bar 20 on one side (as shown in Fig. 7A), the beam 21 or the lever 22 may be shifted such as to increase the hole size of the nozzle outlet, and when the head hits the bar 20 on the opposite side, the beam 21 or the lever 22 may be shifted such as to decrease the hole size of the nozzle outlet.

The adjusting structure may operate as follows. Print consumables are put in the extruder 7 and enter into the inside of the material guiding tube 2 of the feeding assembly 1 of the print head. The heating block 4 is heated using the heating tube to a temperature convenient for fusing the print material, and a temperature inside the print head is controlled using the temperature sensing tube.

Next, adjusting swivel 9 is driven to rotate. It can be set manually or automatically, according to an angle set in a program. For example, in the embodiment of Fig. 2, the servo motor 16 may drive the gear 14 by connecting the crank according to an angle set in a program. The gear synchronously operates with the transmission teeth on the adjusting swivel 9 on the nozzle body 3, in such a way, the adjusting swivel 9 is driven to rotate.

Rotation of the adjusting swivel 9 results in movement of the push assemblies 10. The angle displacement of the adjusting vanes 12 are driven due to arrangement of the push assemblies, and meanwhile, rotation of the adjusting vanes 12 can realize that the outlet hole of the nozzle becomes smaller or larger. The shape of the outlet hole can be a regular polygon of which the edge shape is limited by the quantity of the vanes of the nozzle. The more the vanes 12 are, the more the edges of the polygon are, and the closer the shape of the outlet hole is to a round shape. Fig. 8 shows a functional schematic of a 3D printer in which the print head adjusting structure can be used. A firmware module 1 10 with a firmware block 1 1 1 controls the operation of a controlling module 120.

In the controlling module 120, an extruder motor controller 121 for controlling an extruder motor 122 for feeding the print consumables. A servo controller 123 for controlling a servo motor 124 with a servo encoder 125 for adjusting the hole size of the nozzle outlet. An X/Y/Z axis controller 126 controls an X/Y/Z axis motor 127 with an encoder 128.

An extrusion rate control module 130 comprises an extrusion rate controller 133 that controls the speed of extrusion of the print consumables depending on the feeding rate provided by a feeding rate block 131 and the nozzle outlet hole size provided by a nozzle hole size block 132.

As a result, a 3D object 141 is printed in the printing module 140.

Typically, the firmware operates according to a G-code that comprises information related to the shape and parameters of the object to be printed, including the speed of displacement along the X/Y/Z axes and the rate of feeding the material. However, the G-code typically does not include information about the change of nozzle hole size along the process.

The servo encoder 125 may be configured to feedback information related to the position of the servo motor, and in addition to feedback information to the extruder motor controller, so that the rate of extrusion may be dependent on the nozzle hole size. In other words, the controlling module contains a feedback loop for controlling the rate of extrusion depending on the nozzle hole size. For example, the larger the hole size, the higher extrusion rate. The dependency may be linear or non-linear and may be selected depending on various parameters, such as the type of the print consumables used, the ambient temperature, the desired level of accuracy etc. It is particularly advantageous that this feedback is realized in the controlling module 120, without the need to adapt the firmware or the G-code. This improves the efficiency of operation of the extruder.

While the invention presented herein has been depicted, described, and has been defined with reference to particular preferred embodiments, such references and examples of implementation in the foregoing specification do not imply any limitation on the invention. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader scope of the technical concept. The presented preferred embodiments are exemplary only, and are not exhaustive of the scope of the technical concept presented herein.

Accordingly, the scope of protection is not limited to the preferred embodiments described in the specification, but is only limited by the claims that follow.