EXTRUDER FOR FUSED FILAMENT FABRICATION 3D PRINTER

Abstract

Disclosed is an improved extruder head for a fused filament fabrication 3D printer. It would be beneficial with a thinner nozzle diameter and higher extrusion speed without slippage in the feeding mechanism. The proposed improved extruder head enables extrusion of thinner extruded material at a higher extrusion speed without any slippage in filament feeding mechanism, thereby allowing higher overall building speed of the 3D printer with high quality build. Higher feed-rate of the filament material is achieved by increased usable friction between pinch wheel and filament by increasing the grippable area of the filament. This is done by feeding the filament into the feeding mechanism at an angle different to the outlet angle and routing it around the pinch wheel, back supported by a plurality of support rollers, so that the filament is in frictional contact with the pinch wheel along a greater part of its circumference, thereby increasing the surface contact area between the pinch wheel and the filament. Owing to non-slippage of the filament feeder, nominal volume of extruded material is exactly the same as desired volume with high filament feeding rate. Due to compact feeding mechanism, total mass of extruder kept small enough to enable higher acceleration of the printing nozzle resulting higher printing speed. Owing to horizontal loading of the filament material, feed roll can be mounted just above the extruder for smooth filament supply and compact size of 3D printer.

Claims

1. An extruder head for a 3D printer of the fused filament fabrication type, having a filament feeder comprising of a filament inlet, a driven pinch wheel, and a plurality of support rollers arranged outside the pinch wheel to form an arc-shaped filament conduit between pinch wheel and support rollers, the support rollers being spaced from the pinch wheel to receive and guide a filament along the filament conduit in frictional contact with the pinch wheel, the center points of the two outermost support rollers and the pinch wheel defining a filament contact angle to increase the usable friction area between pinch wheel and filament material.

2. A feeder unit according to claim 1, where the filament contact angle is between 30 and 180 degrees.

3. The feeder unit according to claim 1, where the pinch wheel is knurled, hobbed or toothed to have friction in order to give traction of the filament

4. The feeder unit according to claim 1, where at least one of the support rollers is spring loaded towards the pinch wheel.

5. The feeder unit according to claim 1, where the distance between at least one support roller and the pinch wheel is adjustable.

6. The feeder unit according to claim 1, where guide means are provided along the arc-shaped filament conduit to guide the filament to initially find the correct path through the filament conduit.

7. An extruder head for a 3D printer of the fused filament fabrication type, having a filament feeder comprising of a filament inlet, a driven pinch wheel, and support means arranged outside the pinch wheel to form an arc-shaped filament conduit between pinch wheel and support means, the support means being spaced from the pinch wheel to receive and guide a filament along the filament conduit in frictional contact with the pinch wheel, the arc-length of the support means defining a filament contact angle to increase the usable friction area between pinch wheel and filament material.

8. A feeder unit according to claim 7, where the filament contact angle between 30 and 180 degrees.

9. The feeder unit according to claim 7, where the pinch wheel is knurled, hobbed or toothed to have friction in order to give traction of the filament.

10. The feeder unit according to claim 7, where the support means is spring loaded towards the pinch wheel.

11. The feeder unit according to claim 7, where the distance between the support means and the pinch wheel is adjustable.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0006] FIG. 1 shows a schematic layout of a 3D printer indicating the extruder head in relation to other key components.

[0007] FIG. 2 shows a 3D view of the extruder

[0008] FIG. 3 shows an exploded view of the extruder

[0009] FIG. 4 shows an exploded view of the extruder cold end

[0010] FIG. 5 shows a cross-sectional drawing of the extruder

[0011] FIG. 6 shows a detail of the extruder hot end.

[0012] FIG. 7 shows an embodiment with 180 degree filament contact angle

DESCRIPTION OF EMBODIMENTS

[0013]

TABLE-US-00001 Table of Components 1 Stepping motor 2 Motor mount 3 Extruder head 4 Worm gear 5 Extruder bracket 6 Cooling fan 7 Cold end heat sink 8 8a Cover A, 8b Cover B 9 9a-9f Support rollers 10 Pinch wheel 11 Pinch wheel shaft 12 Worm wheel 13 Worm wheel bearing 14 Filament inlet 15 Pinch wheel bearing 16 Hot end pipe 17 Thermal insulator 18 Hot end heat sink 19 Heater block 20 Temperature sensor 21 Heater 22 Nozzle 23 Filament 24 Filament outlet direction 25 Cold end 26 Hot end 27 3D printer 28 Filament roll 29 Building surface 30 Filament contact angle v 31 Support roller center distance d 32 Horizontal beam 33 Vertical beam 34 Filament roll support beam 35 Building surface linear guide 36 Partly molten polymer 37 Molten polymer 38 Extruded string of molten polymer 39 Filament guide groove 40 Filament guide tube 41 Filament inlet direction

[0014] Referring to FIG. 1, according to the preferred embodiment, there is provided a 3D printer 27 having a horizontal build surface 29 movable in the horizontal Y direction guided by linear guide 35, and an extruder head 3 arranged on a horizontal beam 32 to be movable in the horizontal x and vertical z directions, and a filament roll 28 arranged on filament support beam 34 above the maximum movement of extruder head 3 on a rotation axle in order to freely dispense of filament indicated at 23 on demand into the extruder head 3 via filament inlet 14.

[0015] Moving to FIG. 2 and FIG. 3, the extruder head 3 generally comprises a cold end 25 and a hot end 26. The cold end comprises an extruder head 3 which houses a filament feed unit for pulling filament 23 off from filament roll 28 and pushing it into the hot end 26 via hot end pipe 16 into heater block 19 where it is liquefied by heat created by heater 21. Temperature is monitored by a temperature sensor 20 and fed back into a computer control unit which is not shown. Connected to the cold end 25 is a stepping motor 1, mounted on a motor mount 2 which is connected to the extruder head 3. Attached to motor mount 2 is a cool end heat sink 7 and cooling fan 6.

[0016] Now referring to FIGS. 4 and 5 for details of the extruder head 3 and the feeder unit. Inside the extruder head 3 is arranged a worm gear 4 driven by stepping motor 1. The worm gear 4 drives worm wheel 12 which is connected to pinch wheel 10 via pinch wheel shaft 11. The pinch wheel 10 is equipped with gripping means, preferably teeth, to maximize the pulling or pushing force on the filament 23. Arranged outside pinch wheel 10 on machined shafts are preferably three support rollers generally indicated at 9. The support rollers 9a, 9b and 9c in the preferred embodiment are preferably ball bearings of the same size and preferably distributed equally along an arc shape at equal support roller center distances d 31 from pinch wheel 10 and spaced from the pinch wheel 10 so that the gap between them forms a conduit suitable to receive and guide a filament 23 tight enough to give the pinch wheel 10 appropriate driving friction against filament 23. There may be an additional filament guide groove 39 to help the filament finding its way through the filament conduit. The center points of the support rollers 9a and 9c and the center point of pinch wheel 10 define a filament contact angle v 30. The filament contact angle v 30 is what defines the total grippable area by pinch wheel 10 on the filament 23. The force between pinch wheel 10 and filament 23 is defined by the gap between support rollers 9a, 9b, 9c and pinch wheel 10. The gap is smaller than the size of the filament 23, which forces the pinch wheel 10 to dig into the filament against the support force of support wheels 9a-9c. Therefore what defines the total available pulling or pushing force of pinch wheel 10 on filament 23 is defined by the filament contact angle v and the gap between pinch wheel 10 and support rollers 9a, 9b and 9c.

[0017] Now referring to FIG. 5 for details of the hot end 26. Filament 23 is pushed out from the feeding unit along a filament outlet direction indicated at 24, into the hot end pipe 16. Hot end pipe 16 leads the filament 23 from the cold end 25, where it is in a solid state, into the hot end 26 where it is liquefied by heat generated by heater 21 inside heater block 19 and finally extruded in liquid form through nozzle 22. To isolate the cold end 25 from the higher temperatures in the hot end 26, there is a hot end heat sink 18 to remove heat from hot end pipe 16, and a thermal insulator 17 to insulate the extruder head 3 from remaining heat in hot end pipe 16 and hot end heat sink 18.

[0018] In another embodiment of the extruder head 3, it should be obvious for anybody skilled in the art that the number of support rollers generally indicated at 9 may vary depending on the size of them or the filament contact angle 30 desired. Therefore the distance between support rollers 9 may be shorter or longer depending on need. For example, instead of using three support rollers 9a, 9b and 9c, it is imaginable that four or five support rollers could be used to fill the desired filament contact angle v 30, if the individual rollers size was smaller and adequate to fill the space available under filament contact angle v 30. Equally, it is imaginable that only two support rollers may be used as long as the filament contact angle v 30 is longer than if using only one support roller. In case a greater filament contact angle 30 is required, for example 180 degrees, as many as six support rollers 9 may be needed, as indicated in FIG. 7. Support roller 9e may in this case, having six support rollers 9 giving a filament contact angle v 30 of 180 degrees, have to be larger to allow a sufficiently large bending radius of filament 23.

[0019] In yet another embodiment of the extruder head 3, it is imaginable that the support rollers generally indicated at 9 may be substituted by a general support means of low friction. For example, an arc-shaped guide designed to support the filament 23 over a filament contact angle v 30 but relying in low friction against the filament 23 whilst still providing sufficient pressure against pinch wheel 10. Such low friction could for example be achieved by a PTFE coat or highly polished surface on a steel guide.

[0020] In still another embodiment of the extruder head 3, it should be well known by someone skilled in the art that friction between pinch wheel 10 and filament 23 could be maximized in a number of ways, for example the surface of the pinch wheel 10 could be knurled, toothed, hobbed or otherwise surface treated to increase friction.

[0021] In a final embodiment of the extruder head 3, the support rollers 9 or support means may be spring loaded to provide a controlled pressure against pinch wheel 10.