Dual hob drive quick release high flow filament extruder

A filament drive for an extruder for an additive manufacturing system is provided. A drive gear is driven by a motor. A first driven gear is operably driven by the drive gear. A first hob has a toothed outer periphery connected to the first driven gear. A second driven gear is operably driven by the drive gear. A second hob has a toothed outer periphery connected to the second driven gear. The toothed outer peripheries of the first and second hobs define a filament receiving zone therebetween. A filament extruder including a heating element operated at greater than 48 volts may be provided.

FIELD OF THE INVENTION

This invention generally relates to filament extruders for additive manufacturing systems.

BACKGROUND OF THE INVENTION

One type of additive manufacturing system (e.g. 3D-printers) uses an extruder system to form layers of material to form 3D products. One extruder system uses a continuous filament fed through a heating barrel to melt the filament as it is being deposited to form the layers of the 3D product.

Filament extruders push plastic filament through the heating barrel by pinching the filament between two rollers. Usually, only one roller is toothed and is called a hob. The hob is rotated by a motor. The second roller is typically smooth and is free rolling. The second roller is simply used to apply a pinching force on the opposite side of the filament via spring load or screw tension.

Filament with a diameter larger than 3 mm requires a large force and is difficult to extrude with only single hob extruders. If one tries to extrude too fast, the hob wheel will slip on the filament. This often leads to a failed print.

Also, known extruders on the market rely on low voltage (<48V) circuitry to power the heating element that heats the heating barrel. Increasing the diameter of the filament means that more power (Watts) is required to melt the plastic at an acceptable rate. Keeping the same voltage requires a much higher amperage, which is problematic from a design and safety standpoint.

Embodiments of the present invention provide improvements over the current state of the art by allowing for improved additive manufacturing using larger diameter filaments.

BRIEF SUMMARY OF THE INVENTION

New and improved filament extruders, filament drives for filament extruders, and systems of multiple filament extruders are provided.

In one embodiment, a filament drive for an extruder for an additive manufacturing system is provided. The filament drive includes a motor, a driven gear, first and second driven gears and first and second hobs. The drive gear is driven by the motor. The first driven gear is operably driven by the drive gear. The first hob has a toothed outer periphery connected to the first driven gear such that rotation of the first driven gear rotates the first hob about a first hob axis of rotation. The second driven gear is operably driven by the drive gear. The second hob has a toothed outer periphery connected to the second driven gear such that rotation of the second driven gear rotates the second hob about a second hob axis of rotation. The toothed outer peripheries of the first and second hobs define a filament receiving zone therebetween.

In an embodiment, the system includes a first drive shaft between the first driven gear and the first hob. The first drive shaft is rotatably supported proximate the first driven gear and is rotatably supported proximate the first hob. The system includes a second drive shaft between the second driven gear and the second hob. The second drive shaft is rotatably supported proximate the second driven gear and is rotatably supported proximate the second hob.

In an embodiment, the second drive shaft is movably mounted relative to the first drive shaft such that the end of the second drive shaft proximate the second hob can be moved toward or away from the first hob to adjust a size of the filament receiving zone therebetween.

In an embodiment, the system includes a biasing system having an engaged state providing a first amount of biasing force biasing the second hob toward the first hob and a released state providing a second amount of biasing force biasing the second hob toward the first hob. The second amount of biasing force being less than the first amount.

In an embodiment, the biasing system includes a spring operably providing the first amount of biasing force.

In an embodiment, a release mechanism is provided that transitions the biasing system between the engaged state and the released state.

In an embodiment, the second drive shaft is mounted on a pair of self-aligning bearings.

In an embodiment, the first driven gear and second driven gear remain engaged with the drive gear when the second hob is moved relative to the first hob.

In an embodiment, the first driven gear and second driven gear remain engaged with the drive gear when at least one of the first or second hobs is moved to the disengaged state where it would not engage a filament being processed.

In an embodiment, the system includes a biasing system that provides a spring loaded biasing force biasing the second hob towards the first hob.

In an embodiment, the second hob is free floating under the spring loaded biasing force biasing the second hob towards the first hob.

In a further embodiment, a filament extruder including a filament drive according to one or more of the prior embodiments is provided. The filament extruder includes an extruder barrel defining a central cavity having an inlet end and an outlet end. The inlet end aligns with the filament receiving zone of the filament drive such that filament driven by the filament drive is driven into the inlet end of the extruder barrel. The filament extruder includes at least one heating element adjacent the extruder barrel to heat filament driven through the central cavity.

In a further embodiment, a filament extruder including a filament drive, an extruder barrel, at least one heating element and a power supply is provided. The extruder barrel defines a central cavity having an inlet end and an outlet end. The extruder barrel is aligned with the filament drive such that filament driven by the filament drive is driven into the inlet end of the extruder barrel. The at least one heating element is adjacent the extruder barrel to heat filament driven through the central cavity. The power supply provides power to the at least one heating element at a voltage greater than at least 48 volts.

In an embodiment, the power supply provides power at less than 20 amps, more preferably less than 10 amps and even more preferably less than 5 amps.

In a further embodiment, an additive manufacturing machine includes a control unit; a first filament extruder directly coupled to the control unit; a second filament extruder indirectly coupled to the control unit by being coupled to the first filament extruder. This configuration prevents the need for separate wiring harnesses to extend between the control unit and each of the filament extruders.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1illustrates a filament extruder100for performing additive manufacturing (e.g. 3D printing). The filament extruder100processes a continuous plastic filament102. The filament extruder100melts the plastic filament102and successive layers of material are extruded to form the end product.

Filament extruder100includes a heating arrangement104that includes, among other things, a heating barrel106, one or more heating elements108and a power supply110. The heating arrangement104, and particularly the heating barrel106, receives the plastic filament102in a solid state at an inlet end112and forces the plastic through the heating barrel106where it is melted. The melted plastic is then deposited out of an outlet end114that includes a nozzle116.FIG. 2illustrates the heating barrel106in cross-section and illustrates a central cavity118through which the material travels as it is melted.

The filament extruder100includes a filament drive120for driving the filament102through the heating arrangement104. With additional reference toFIG. 3, the filament drive120generally includes a motor122(FIG. 1), a drive gear123, first and second driven gears124,126, first and second drive shafts128,130and first and second hobs132,134.

The motor122drives drive gear123. Drive gear123is preferably in the form of a worm gear. The first and second driven gears124,126are located on opposite sides of an axis of rotation134of the drive gear123. The first and second hobs132,134are directly connected to the first and second driven gears124,126by corresponding first and second drive shafts128,130.

The first and second hobs132,134have toothed, concave outer peripheries configured to engage the plastic filament102. The first and second hobs132,134define a filament receiving zone136therebetween. The filament102is pinched between the first and second hobs132,134in operation. By including the pair of hobs132,134, the filament102is driven from both sides increasing the amount of force that may be applied to the filament102to drive it through the heating arrangement. As illustrated inFIG. 3, the filament receiving zone136is located aligned with and above the central cavity of the heating barrel106.

With reference toFIGS. 3 and 4, rotation of the drive gear123about axis of rotation138rotates the first and second driven gears124,126, first and second drive shafts128,130and first and second hobs132,134in opposite directions about their corresponding axes of rotation140,142.

The first drive shaft128is operably rotationally supported by a bearing143mounted to first support member144proximate first end146and rotationally supported by a bearing147mounted to a second support member148proximate an opposed second end150.

The second drive shaft130is operably rotationally supported by a bearing151mounted to first support member144proximate first end152and rotationally supported by a bearing153mounted to a third support member154proximate an opposed second end156.

Bearings151,153are preferably spherical self-aligning bearings that allow the orientation of second drive shaft130to be adjusted so as to allow for adjustment of the position of the second hob134relative to the first hob132, illustrated by arrow158without creating undo resistance against rotation of drive shaft130. These bearings151,153have an outer sleeve that supports an inner ring that is permitted to rotate within the outer sleeve to adjust the angle of the inner ring within the outer sleeve. Again, this allows the bearing to adjust to a change in orientation of the drive shaft130.

First, second and third support members144,148,154are operably mounted to a frame illustrated in the form of a pair of spaced apart plates160,162(see e.g.FIG. 1). While two plates are illustrated, in other embodiments, these two plates160,162could be unitarily formed such as being machined from a single piece of material. InFIGS. 3 and 4, only plate160is illustrated. First and second support members144,148are fixed relative to plates160,162. However, plates160,162include slots164,166(see e.g.FIG. 1) that allow third support member154slide laterally relative to the plates160,162as well as first and second support members144,148as illustrated by arrow168. It is noted that because bearing151is in a generally fixed location (albeit able to pivot), arrows158and168are not parallel to one another except when axes140and142are parallel to one another. This is because, as third support member154slides as illustrated by arrow168, the second drive shaft130pivot about a point defined bearing151which is, as noted above, a spherical self-aligning bearing. By allowing the second drive shaft130to adjust by pivoting about a point defined by bearing151, limited angular adjustment of the second drive shaft130can occur to adjust the spacing between the first and second hobs132,134while still keeping the second driven gear126engaged with drive gear123. Thus, the second hob134can be adjusted toward or away from the first hob132.

With reference toFIG. 5, a biasing system170is provided to bias the second hob134towards the first hob132, as illustrated by arrow172. The biasing system170includes a pair of pins174that carry springs176. The springs176operably press the third support member154toward the second support member148to bias the second hob134towards the first hob132.

The third support member154has a stepped region178through which the pins174extend and against which one end of the springs176presses. The stepped region178is allowed to slide along the pins176.

An abutment block180operably floats on pins174and is used to adjust the biasing force provided by the biasing system170and particularly springs176. The abutment block180can free float along pins174as illustrated by arrow182inFIG. 3. If abutment block180is moved away from stepped region178, increased biasing force is applied. If abutment block180is moved toward stepped region178, decreased biasing force is applied.

The biasing system170includes a cam arrangement that includes a cam member184that cooperates with a cam surface186provided by the abutment block180. The cam member184is carried on an end of first drive shaft128for rotation, but could be otherwise operably rotatably mounted to the frame such as to second support member148. The cam member has a varying radial dimension such that depending on its angular position about drive shaft128the abutment block180is spaced a different distance away from the first drive shaft128. Thus rotation of the cam member184such that different portions are in contact with the cam surface186will adjust the amount of compression in the springs176and the biasing force applied by the biasing system170.

While not illustrated inFIG. 5,FIGS. 1, 2 and 6illustrate that a handle member188may be attached to or otherwise provide the cam member184so as to provide for easier manipulation of the cam member184and adjust the biasing force provided by the biasing system170. Other biasing systems are contemplated such as simply tightening or loosening nuts on the end of the pins174. Further, the bores in abutment block180could be threaded to adjust the force applied by springs176. Further, even though the cam member184is provided to transition between a released state and an engaged state to provide different levels of engagement, where one level of engagement may be no engagement at all, fine adjustment of the amount of biasing force can be provided by tightening or loosening nuts on the ends of pins174in this embodiment. Alternatively, fine adjustment could be done where an embodiment threads the pins directly into the adjustment block by adjusting the amount of threading into the adjustment block.

In the illustrated embodiment, the cam member186has one segment that relates to a released state. It is portion that has the smallest radial dimension such that the abutment block180can be moved the closest to first drive shaft128. This released state allows the second hob134to be moved the furthest away from the first hob132such as when filament is not being driven by the hobs132,134, e.g. during initial setup or when the system is offline. Thus, the current biasing system is configured to easily transition between an engaged state and a released state by simply rotating handle member188and the cam member184. The handle member188and cam member184are in the released states inFIG. 1andFIG. 5. Thus, rotation of the cam member184and handle member188allows for easily switching between different amounts of biasing force. In the illustrated embodiment, a second amount of biasing force is 0 force because the second hob134is entirely disengaged from any filament. However, when engaged with a filament, a second higher level of force would be provided. As illustrated inFIG. 3, the second hob134is spaced laterally outward beyond central cavity118such that the second hob134would not be laterally biased against a side of the filament. The handle member188and cam member184may thus be considered a release mechanism that allows for easily transitioning between the released state and engaged state.

It is noted that in various figures, such asFIG. 1, the end of the second drive shaft130abuts with the handle member188. However, in implementation, the second drive shaft130would not be that long and would not contact or otherwise engage handle member188. The drawing simply has the drive shaft130drawn too long.

With reference toFIG. 4, the first and second drive shafts128,130are composite shafts that include outer sleeves190,192and inner shafts194,196. The outer sleeves190,192extend between and axially receive hub portions of the corresponding first and second driven gears124,126and first and second hobs132,134. The inner shafts194,196are received by and supported by bearings143,147,151,153. In other embodiments, the drive shafts could be formed from one or more components.

The power supply110preferably provides power at a voltage of greater than 48V to the heating elements108. In some embodiments, the voltage may be 60 V, 72V, 84V, 96V, 110V, 120 V, 220V, or other values above 48V. Further, the power supply110does not exceed an amperage of 20 amps. More preferably the power supply does not exceed an amperage of 10 amps. More preferably, the power supply does not exceed an amperage of 5 amps. Further, in some embodiments where multiple independent heating elements108are provided the various heating elements can be controlled at a same temperature (e.g. amount of power) or controlled independently to heat the extruder barrel differently (e.g. different heating elements can be provided different levels of power to heat the extruder barrel to different temperatures along the length thereof). While a single power supply is illustrated, multiple power supplies could be provided where each heating element has its own dedicated power supply. Further, a single power supply may be configured to independently regulate the heating output of each of the heating elements.

Further, while the system illustrates a single filament extruder100, multiple filament extruders may be daisy chained together.FIG. 7illustrates a schematic illustration of three filament extruders100A,100B,100C daisy chained together. A cable200(which may be a plurality of cables or wires) extends from a control unit210to a single one of the filament extruders, namely filament extruder100A. Filament extruder100A is connected to filament extruder100B by cable212. Filament extruder100B is connected to filament extruder100C by a cable214. As such, only a single cable200goes back to the control unit210rather than having each filament extruder100A,100B,100C directly connected back to the control unit210. Typically, each of cables212,214are routed separate from and remote from the routing of cable210between the control unit210and filament extruder100A.

Control unit210could be any device that is needed to be connected to operate the filament extruders100A,100B,100C. For example control unit210could be a controller that sends control signals to initiate or otherwise control the operation of the filament extruder, e.g. operation of motor122or other devices such as actuators for positioning the filament extruder. Further, the control unit210could be a power supply that powers the motor or provides power to the heating element.

By providing the daisy chained configuration, it is unnecessary to run cables for each filament extruder back to the control unit210which reduces weight as well reduces the issue of limited space for wiring and/or cable carriers.

Thus, in the embodiment ofFIG. 7, it can be seen that there is an additive manufacturing machine that has filament extruder100A directly connected to control unit210while filament extruders100B,100C are indirectly connected to the control unit through their direct (filament extruder100B) or indirect connection (filament extruder100C) to filament extruder100A.

While filament extruders100A,100B,100C are in a daisy chain configuration, each extruder100A,100B,100C, need not be identical. Further, the filament extruders100A,100B,100C need not all operate at the same time or be controlled in the same manner.