METHODS AND APPARATUS FOR PROCESSING AND DISPENSING MATERIAL DURING ADDITIVE MANUFACTURING
1. A system for additive manufacturing, comprising:
- a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes, wherein the nozzle is operably coupled to;
an extruder having an outlet and including a screw disposed within a barrel; and
a pump having an inlet and an outlet, the inlet being coupled to the extruder, and the outlet being in fluid communication with the nozzle; and
a controller configured to adjust a speed of the pump with respect to a speed of the screw to apply a target pressure at the outlet of the extruder.
A system for additive manufacturing includes a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes, wherein the nozzle is operably coupled to: an extruder having an outlet and including a screw disposed within a barrel, and a pump having an inlet and an outlet. The inlet is coupled to the extruder, and the outlet is in fluid communication with the nozzle. The system also includes a controller configured to adjust a speed of the pump with respect to a speed of the screw to apply a target pressure at the outlet of the extruder.
- 1. A system for additive manufacturing, comprising:
a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes, wherein the nozzle is operably coupled to; an extruder having an outlet and including a screw disposed within a barrel; and a pump having an inlet and an outlet, the inlet being coupled to the extruder, and the outlet being in fluid communication with the nozzle; and a controller configured to adjust a speed of the pump with respect to a speed of the screw to apply a target pressure at the outlet of the extruder.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- 9. A system for additive manufacturing, comprising:
a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes, wherein the nozzle is operably coupled to; an extruder including a screw disposed within a barrel; and a pump having an inlet and an outlet, wherein the inlet is coupled to the extruder, and the outlet is in fluid communication with the nozzle; and a controller configured to modify a size of a bead extruded by the nozzle to maintain an approximately constant sized overlap between a plurality of adjacent beads.
- View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
- 17. An additive manufacturing method for delivering a flowable material from a nozzle of a programmable computer numeric control machine (CNC), the method comprising:
actuating an extruder to form a flowable material; delivering the flowable material to a pump; operating the pump at a speed; and adjusting at least one of the speed of the pump or a rate of translation of the nozzle based on a size of a boundary area formed by at least one adjacent bead of flowable material.
- View Dependent Claims (18, 19, 20)
This application is a continuation-in-part of pending U.S. patent application Ser. No. 15/253,290, filed Aug. 31, 2016, the entirety of which is incorporated by reference herein.
Aspects of the present disclosure relate to apparatus and methods for fabricating components. In some instances, aspects of the present disclosure relate to apparatus and methods for fabricating components (such as, e.g., automobile parts, medical devices, machine components, consumer products, etc.) via additive manufacturing techniques or processes, such as, e.g., 3D printing manufacturing techniques or processes.
Additive manufacturing techniques and processes generally involve the buildup of one or more materials to make a net or near net shape (NNS) object, in contrast to subtractive manufacturing methods. Though “additive manufacturing” is an industry standard term (ASTM F2792), additive manufacturing encompasses various manufacturing and prototyping techniques known under a variety of names, including freeform fabrication, 3D printing, rapid prototyping/tooling, etc. Additive manufacturing techniques are capable of fabricating complex components from a wide variety of materials. Generally, a freestanding object can be fabricated from a computer-aided design (CAD) model.
A particular type of additive manufacturing is more commonly known as 3D printing. One such process commonly referred to as Fused Deposition Modeling (FDM) comprises a process of melting a very thin layer of a flowable material (e.g., a thermoplastic material), and applying this material in layers to produce a final part. This is commonly accomplished by passing a continuous thin filament of thermoplastic material through a heated nozzle, which melts the thermoplastic material and applies it to the structure being printed. The heated material is applied to the existing structure in thin layers, melting and fusing with the existing material to produce a solid finished product.
The filament used in the aforementioned process is generally produced using an extruder. In some instances, the extruder may include a specially designed screw rotating inside of a barrel. The barrel may be heated. Thermoplastic material in the form of small pellets is introduced into one end of the rotating screw. Friction from the rotating screw, combined with heat from the barrel softens the plastic, which then is forced under pressure through a small opening in a die attached to the front of the extruder barrel. This extrudes a string of material which is cooled and coiled up for use in the 3D printer as the aforementioned filament of thermoplastic material.
Melting a thin filament of material in order to 3D print an item is a slow process, which is generally only suitable for producing relatively small items or limited number of items. As a result, the melted filament approach to 3D printing is too slow for the manufacture of large items or larger number of items. However, 3D printing using molten thermoplastic materials offers many benefits for the manufacture of large items or large numbers of items.
A common method of additive manufacturing, or 3D printing, generally includes forming and extruding a bead of flowable material (e.g., molten thermoplastic), applying the bead of material in a strata of layers to form a facsimile of an article, and machining such facsimile to produce an end product. Such a process is generally achieved by means of an extruder mounted on a computer numeric controlled (CNC) machine with controlled motion along at least the X, Y, and Z-axes. In some cases, the flowable material, such as, e.g., molten thermoplastic material, may be infused with a reinforcing material (e.g., strands of fiber) to enhance the material'"'"'s strength. The flowable material, while generally hot and pliable, may be deposited upon a substrate (e.g., a mold), pressed down or otherwise flattened to some extent, and leveled to a consistent thickness, preferably by means of a tangentially compensated roller mechanism. The flattening process may aid in fusing a new layer of the flowable material to the previously deposited layer of the flowable material. In some instances, an oscillating plate may be used to flatten the bead of flowable material to a desired thickness, thus effecting fusion to the previously deposited layer of flowable material. The deposition process may be repeated so that each successive layer of flowable material is deposited upon an existing layer to build up and manufacture a desired component structure. When executed properly, the new layer of flowable material may be deposited at a temperature sufficient enough to allow a new layer of such material to melt and fuse with a previously deposited layer, thus producing a solid part.
In the practice of the aforementioned process, a major disadvantage has been encountered. Material extruders, of the type used in near net shape 3D printing, are designed to operate at a constant steady rate in order to produce a steady, consistent homogeneously melted plastic bead. In most cases, however, the majority of heat energy required to melt the plastic is generated by friction from a screw turning inside a barrel. This steady extrusion rate, however, creates difficulties when 3D printing. Specifically, the computer numeric controlled (CNC) machine used to move the extruder-based print head cannot start and stop instantaneously, and must, by necessity, vary in speed as it traces the path required to print the part.
This combination of a machine moving at variable speeds and an extrusion head outputting material at a constant rate results in a print bead that could vary in size. That is, the bead is thicker when the machine head is moving slowly, and thinner when the machine operates at a relatively higher speed.
A common approach employed in addressing the aforementioned problem is to servo-control the extrusion screw, speeding it up when the machine is moving faster and slowing it down as the machine motion slows. Since much of the energy used to melt the plastic is generated by rotation of the screw in the barrel of the extruder, varying the speed not only varies the rate by which material is pumped through the extruder but it also varies the amount of heat energy generated for melting the flowable material, such as, e.g., thermoplastic. The consequential increased temperature results in the thermoplastic material being less viscous; and, therefore, flowing faster than when it is cooler and thereby more viscous. The effect is that the flow rate from the extruder at any point in time is determined not only by the rotational speed of the extrusion screw, but also by the recent history of rotation, which determines how hot and thus how viscous the melted material is. This means that in a system where the rotation speed of an extruder varies randomly with time, the amount of material flowing from an extruder at a specific rotation speed will not be at a constant rate. Therefore, if the extruder screw is servo-controlled to operate at a specific rotational speed for a specific velocity of the print head, the resulting printed bead will not be consistent. Thus, method and apparatus are needed to produce a consistent print bead size when 3D printing.
Furthermore, the extruder may function to take polymer material in pellet form, heat, soften, and mix the material into a homogenized melt, and then pump the melt under pressure into a die to form the material into a useful extruded shape. This may be accomplished by providing an auger-type screw rotating inside a heated barrel, for example. The geometry, clearances, composition, and functionality of the screw and a barrel of the extruder may be determined as necessary to provide an extruder that operates as desired.
The extruder may be provided with the goal of completely mixing the melted material (e.g., polymer material) into a smooth, consistent form with no unmelted pellet portions or temperature variations in the melted material. One method of achieving this objective includes installing a breaker plate at the exit end of the extruder. A breaker plate may be, for example, a disk or plate that has a series of holes that provide resistance to the flow of the polymer melt. The holes in the breaker plate may be uniform holes approximately 0.125″ inches in diameter, and may be machined through the entire thickness of the breaker plate so as to be aligned with the flow direction of the polymer melt. This breaker plate may restrict the flow of material, increasing pressure inside the extruder barrel which assists in the melting and mixing process. One or more mesh screens or filters may be installed before the breaker plate to further restrict flow and increase pressure to aid mixing.
There may an optimal pressure range within which a particular extruder operates most effectively. Generally, a breaker plate and one or more mesh screens are installed in an effort to generate and maintain this desired pressure during operation of the extruder. While the inclusion of a breaker plate and/or screen may improve some mixing characteristics, they may also introduce drawbacks. For example, the additional restriction to flow may reduce throughput. Additionally, different polymers may require different breaker plate and/or screen configurations to achieve a desired pressure. Thus, the breaker plate and/or screen may need to changed each time the polymer being extruded changes in order to achieve a desired pressure that corresponds to the extruded polymer.
Another approach to achieve enhanced mixing may be to include knobs or other shapes on the extrusion screw, creating a “mixing section” which agitates the melt. This approach may also reduce flow of the melt and, in some cases, the friction caused by the mechanical mixing action can create unwanted heat in the mixing section.
Another purpose of the screen and/or breaker plate may be to create a generally fixed amount of resistance to the material flow in the extruder. This may facilitate generating and maintaining a steady state melt process within the extruder. If the breaker plate and/or screen were not in place in a typical extruder configuration, the amount of resistance to melt flow, and thus the operating pressure inside the extruder may depend solely or nearly primarily on the amount of resistance created by the shape of the forming die through which the melt flows after exiting the extruder. It may then become difficult to achieve consistent operation since the extruder may process material through a variety of different die shapes, each with a different resistance to flow. Some dies may generate insufficient resistance to flow to achieve optimal operating pressure while others may generate significantly higher pressure than is desired.
Aspects of the present disclosure relate to, among other things, methods and apparatus for fabricating components via additive manufacturing, such as, e.g., 3D printing techniques. Each of the aspects disclosed herein may include one or more of the features described in connection with any of the other disclosed aspects.
In one aspect, a system for additive manufacturing may include a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes, wherein the nozzle may be operably coupled to: an extruder having an outlet and including a screw disposed within a barrel, and a pump having an inlet and an outlet. The inlet may be coupled to the extruder, and the outlet may be in fluid communication with the nozzle. The system may also include a controller configured to adjust a speed of the pump with respect to a speed of the screw to apply a target pressure at the outlet of the extruder.
In another aspect, a system for additive manufacturing may include a nozzle configured to translate along a first axis, a second axis perpendicular to the first axis, and a third axis orthogonal to the first and second axes. The nozzle may be operably coupled to: an extruder including a screw disposed within a barrel, and a pump having an inlet and an outlet wherein the inlet may be coupled to the extruder, and the outlet may be in fluid communication with the nozzle. The system may include a controller configured to modify a size of a bead extruded by the nozzle to maintain an approximately constant sized overlap between a plurality of adjacent beads.
In another aspect, an additive manufacturing method for delivering a flowable material from a nozzle of a programmable computer numeric control machine (CNC) may include actuating an extruder to form a flowable material, delivering the flowable material to a pump, and operating the pump at a speed. The method may also include adjusting at least one of the speed of the pump or a rate of translation of the nozzle based on a size of a boundary area formed by at least one adjacent bead of flowable material.
As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus. The term “exemplary” is used in the sense of “example,” rather than “ideal.”
It may be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary aspects of the present disclosure and together with the description, serve to explain the principles of the disclosure.
The present disclosure is drawn to, among other things, methods and apparatus for fabricating multiple components via additive manufacturing techniques, such as, e.g., 3D printing. More particularly, the methods and apparatus described herein comprise a method for eliminating, or otherwise substantially minimizing variations in the flow-rate of a molten flowable material (e.g., a thermoplastic material) in an additive manufacturing process, by, e.g., providing a servo-controlled fixed-displacement pump (e.g., polymer pump) between the output of an extruder and an application nozzle of a CNC additive manufacturing machine. For purposes of brevity, the methods and apparatus described herein will be discussed in connection with fabricating parts from thermoplastic materials. However, those of ordinary skill in the art will readily recognize that the disclosed apparatus and methods may be used with any flowable material suitable for additive manufacturing, such as, e.g., 3D printing.
In one aspect, the present disclosure is directed to an extruder-based 3D printing head that can deposit melted material (e.g., thermoplastic material) when the print head is traveling at a high rate of speed. In another aspect, the present disclosure is directed to depositing material at a consistent controlled rate at any time regardless of melt temperature variations caused by the history of changes in rotational speed of a screw of the extruder.
In certain sectors of the plastics industry, there are applications in which polymer pumps (also referred to herein as a gear pump) are sometimes utilized, in conjunction with plastic extruders. A polymer pump is a fixed displacement gear pump, which meters a fixed amount of material with each rotation of the pump. Polymer pumps are typically used in operations such as the co-extrusion of two or more materials, where synchronization of the flow rates is critical.
In order for a polymer pump to function properly, the plastic extruder must supply melted material to the input of the polymer pump at a relatively fixed input pressure. The aforementioned method of controlling the rotation of the extruder screw by means of a servo loop (e.g., speeding up the rotation when the pressure drops, or is too low, and slowing down the rotation when the pressure is high) works well in a basic extrusion application because input pressure variations in such a situation are generally slight. As a result, only minor changes to the rotational speed of the extruder screw are necessary to ensure the polymer pump receives melted material at a relatively constant input pressure.
In 3D printing, however, the addition a polymer pump alone to regulate flow-rate does not work satisfactorily. The 3D printing process by nature requires frequent variations in the speed of the print head due to a number of factors. For example, one factor may include speed changes, which are required when applying material in tight arcs or through corners. Speed changes may be necessary when a change in direction of travel for the print head is required. Even with the addition of a polymer pump, variations in the flow rate of such a pump can be dramatic, resulting in servo demands for rapid and substantial changes in extruder rotation speed. A rapid change in extruder screw rotation speed does not immediately translate into a rapid change in flow rate of the melted flowable material. There is a substantial delay between a change in extruder screw speed and a resulting change in flow rate of the melted material. This delay makes the traditional steady state servo approach unworkable when operating with a polymer pump that varies in output rate. For example, if the extruder accelerates quickly, as material is advanced within, the input pressure to the polymer pump will drop, resulting in the servo system quickly increasing the speed of the extruder screw. A delay in the drop in input pressure until after material is moving in the polymer pump, combined with a delay in increased flow rate from the extruder, may allow the input pressure to drop low enough to interrupt a proper flow of material, which results in a deposited bead of inconsistent size and shape.
To address the aforementioned problem, the present disclosure utilizes a modified servo signal approach. Using special algorithms, the control system coordinates the extruder speed with the speed of the polymer pump (gear pump) so that speed increases and/or decreases in both units at the same time. In addition to being simultaneous, the speed changes may be proportional.
With reference now to
Machine 1 includes a bed 20 provided with a pair of transversely spaced side walls 21 and 22, a gantry 23 supported on side walls 21 and 22, carriage 24 mounted on gantry 23, a carrier 25 mounted on carriage 24, an extruder 60, and an applicator assembly 26 mounted on carrier 25. Supported on bed 20 between side walls 21 and 22 is a worktable 27 provided with a support surface disposed in an x-y plane, which may be fixed or displaceable along an x-axis. In the displaceable version, the worktable 27 may be displaceable along a set of rails mounted on the bed 20 by means of servomotors and rails 28 and 29 mounted on the bed 20 and operatively connected to the worktable 27. Gantry 23 is disposed along a y-axis, supported at the ends thereof on end walls 21 and 22, either fixedly or displaceably along an x-axis on a set of guide rails 28 and 29 provided on the upper ends of side walls 21 and 22. In the displaceable version, the gantry 23 may be displaceable by a set of servomotors mounted on the gantry 23 and operatively connected to tracks provided on the side walls 21 and 22 of the bed 20. Carriage 24 is supported on gantry 23 and is provided with a support member 30 mounted on and displaceable along one or more guide rails 31, 32 and 33 provided on the gantry 23. Carriage 24 may be displaceable along a y-axis on one or more guide rails 31, 32 and 33 by a servomotor mounted on the gantry 23 and operatively connected to support member 30. Carrier 25 is mounted on a set of spaced, vertically disposed guide rails 34 and 35 supported on the carriage 24 for displacement of the carrier 25 relative to carriage 24 along a z-axis. Carrier 25 may be displaceable along the z-axis by a servomotor mounted on carriage 24 and operatively connected to carrier 25.
As best shown in
As shown in
With reference to
With reference to
In some embodiments, machines 1 and 1A may include a velocimetry assembly (or multiple velocimetry assemblies) configured to determine flow rates (e.g., velocities and/or volumetric flow rates) of material 53 being delivered from applicator heads 43 and 43A. The velocimetry assembly preferably transmits signals relating to the determined flow rates to the aforementioned controller coupled to machine 1, which may then utilize the received information to compensate for variations in the material flow rates.
In the course of fabricating a component, pursuant to the methods described herein, the control system of the machine 1, in executing the inputted program, may control the several servomotors described above to displace the gantry 23 along the x-axis, displace the carriage 24 along the y-axis, displace the carrier 25 along a z-axis, pivot lower applicator segment 42 about an axis disposed in an x-y plane and rotate bracket 47 about a z-axis thereof, in accordance with the inputted program, to appropriately deliver material 53 and provide the desired end product or a near duplicate thereof. The control system of machine 1A may control the several servomotors to display gantry 23, carriage 24, and carrier 25A in a similar manner to appropriate deliver material 53.
With reference now to
A stable flow rate into conduit 52 and through application nozzle 51 may be regulated by providing servo control of the speed of gear pump 66, through an exemplary controller formed by the machine'"'"'s control computer 81 and servo control system, based on the speed of the CNC machine'"'"'s moving axes. The speed of extruder screw 63 likewise may be regulated in proportion with the speed of gear pump 66 by a servo control loop. A signal from the gear pump servo loop is processed to control the output of the extruder servo drive in proportion with that of gear pump 66, thus synchronizing the speed of the extruder with that of the gear pump by a predetermined proportion. In other words, the operation speed of gear pump 66 and extruder screw 63 may be dependent on one another. That is, the speed of extruder screw 63 may be determined as a function of the speed of gear pump 66, and vice versa. The speed of extruder screw 63 also may be modified by inputs from one or more sensors 72 (e.g., a pressure sensor or a flow sensor) operably coupled to the extruder.
As the feed rate of the CNC machine changes, representative servo feedback signals from the moving axes are processed in the machine control computer 81 to control the speed of output pump 66, and correspondingly, the speed of extruder screw 63. Stated differently, machine control computer 81 serves to increase and/or decrease the speeds of extruder screw 63 and gear pump 66 based on increases/decreases in movement of CNC machine 1 during a 3D printing manufacturing process. In embodiments where sensor 72 is a pressure sensor, sensor 72 may monitor the pressure at the inlet of gear pump 66, outputting an analog signal into servo controller 79 and/or machine control computer 81, which in turn, influences the servo loop controlling the extruder screw 63 to bias, adjust, or otherwise fine tune the synchronized speed between extruder screw 63 and gear pump 66, in order to compensate for pressure changes at the inlet of gear pump 66. That is, changes in pressure at the inlet of gear pump 66 may further be used to modify the speeds of extruder screw 63 and/or gear pump 66 and the relative speeds thereof. By coordinating the speed of the gear pump 66 with the speed of the extruder screw 63, while compensating for pressure variations, a constant output proportional to the feed rate of the CNC machine may be achieved at the output of gear pump 66, and through application nozzle 51. With this approach, input pressure is relatively constant because the extruder screw 63 and gear pump 66 change speeds at the same time, with minor adjustments being made to compensate for variables resulting from melt-temperature and pressure variations. Thus, the dimensions of a deposited bead of material remains relatively consistent and dimensionally stable throughout the application process.
In addition to providing a consistent and dimensionally stable bead of material, CNC machines 1, 1A may also include a gear pump control switch 80 that provides a user the ability to modify a size of the deposited bead of material. Control switch 80 may be a hardware switch connected to machine control computer 81 and may control a speed (e.g., revolutions per minute) of gear pump 66, for example. By manipulating (e.g., rotating) control switch 80, an operator may cause machine control computer 81 to increase or decrease the size of the deposited bead, as described below. After this manipulation, the modified size may be deposited in a consistent and dimensionally stable manner. Control switch 80 may be a knob, button(s), lever, or other physical switch. When physical, control switch 80 may be provided on a cabinet of machine control computer 81, or may be provided at a location separate from machine control computer 81. Control switch 80 may also be implemented as a “soft” switch (e.g., a switch, button, lever, or other feature) displayed on a touch-screen that may be operated by a user.
The ability to achieve a target pressure at an input of the melt pump by controlling the relative speeds of the extruder and gears of gear pump 66 may also create the ability to further refine a CNC machine such as CNC machine 1A, improving throughput while generating a properly mixed and thermally homogenized melt. For example, in an exemplary configuration shown in
CNC machines 1, 1A may be configured to generate and maintain a controlled target pressure at the input end of the gear pump 66. As the input end of the gear pump 66 may also be an exit end of the extruder 60, it may not be necessary to install a breaker plate or screen at the exit of the extruder to generate the pressure required for proper mixing in the extruder. The pressure at the inlet end of gear pump 66 may be determined or measured by one or more sensors 72, which may include a pressure sensor as described above. As shown in
In an exemplary embodiment, the CNC machines 1, 1A may generate the required pressure by controlling gear pump 66 via machine control computer 81. Machine control computer 81 may be configured (e.g., programmed with software) to allow a target pressure to be adjusted. Thus, extruder 60 and gear pump 66 may be able to accommodate different requirements that may be necessary for different materials (e.g., different polymers). In one aspect, machine control computer 81 may control extruder 60 and gear pump 66 to generate required pressure and/or adjust the pressure for a plurality of different polymers or flowable materials. For example, target pressures for a corresponding plurality of thermoplastic materials may be stored in a memory of machine control computer 81. Thus, when a first material having a first target pressure is extruded, machine control computer 81 may control the relative speeds of extruder 60 (e.g., screw 63) and gear pump 66 to reach and maintain this target pressure. When the extruded material changes to a second material, machine control computer 81 may change these relative speeds to reach and maintain a second target pressure, allowing the CNC machines 1, 1A to extrude multiple materials at different respective pressures. In one example, changing the relative speeds of the gear pump 66 and the extruder 60 may be performed by maintaining the speed of the extruder 60 constant while changing the speed of gear pump 66, or instead by maintaining the speed of gear pump 66 constant while changing the speed of extruder 60. The relative speeds may also be changed by modifying both of these speeds by differing amounts.
The ability to generate the required pressure may be accomplished with a lower-cost system that reduces mechanical complexity without the need for a breaker plate or a screen (such as a filter) between an end of the screw 63 and gear pump 66, as shown in
In an exemplary configuration, nozzle 51 may have an open round shape (
Melt pumps may be used in steady state plastic extrusion processing for two exemplary purposes. First, melt pumps may provide a way of assuring a steady flow of material which overcomes the tendency of extruders to vary the flow rate or “surge” over time. Second, melt pumps may increase the pressure from the extruder to help force material through extrusion dies, which may have significant resistance to flow. Extruders may have a particular pressure range within which they operate optimally. If a die is provided and the pressure required to flow material through the die is higher than the optimal range, a melt pump may be used generate this higher pressure. However, by controlling flow with a gear pump (e.g., by restricting flow when necessary), the need for a breaker plate or a die may be eliminated. An optimal pressure within extruder 60 may be maintained, while pressure may be varied in a controllable manner. Thus, a predetermined pressure which is based on the requirements of the particular polymer material being extruded may be provided without changing parts. The configuration may also generate a consistent, controllable flow rate to the print nozzle, resulting in a quality print process.
Controlling flow with a gear pump may also eliminate the need for a mixing section, such as knobs, protrusions, or other shapes on the threading of an extruder screw. Thus, each of the threads of an extruder screw may present a uniform, even thread surface.
When additive manufacturing is performed to form a three-dimensional object, an example of which is shown in
With reference to
One potential process to counteract the formation of squeeze-out material 102 may employ a program that causes the nozzle 51 to move over the distance including the desired overlap, plus an estimated amount of squeeze-out material 102, which may continue increasing. The nozzle 51 would have to move over different distances when printing subsequent rows, which may make programming difficult.
In order to keep the amount (e.g., percentage) of overlap 101 constant for each adjacent bead and keep the nozzle 51 moving over the same consistent amount for each row formed by a bead 53, the size (e.g., width) of the third and any subsequent bead 53 may be reduced by a particular (e.g., the same) amount to prevent squeeze-out material 102 from building up. This reduction may be equal to a calculated amount of squeeze-out material 102 that would form if a size of the third bead is not reduced. This reduction may be the same for the third bead 53 and for each subsequent bead 53 adjacent to the third bead 53 in a direction perpendicular to a deposition direction.
In order to print the third bead 53 (and a subsequent bead 53) with a reduced size, the print head may provide the ability to both: produce a consistent-sized bead 53 at different machine speeds, and change the bead 53 to a smaller or larger sized bead as desired, while still producing the bead 53 with a consistent (changed) size. This may be performed altering the relationship between the machine speed (e.g., a translation speed of nozzle 51) and the melt pump speed. For example, a ratio of the machine speed to the gear pump 66 speed may be altered. Such an alteration of the machine or nozzle translation speed to the melt pump speed may be performed by at least one of a CNC “G” code program, or manually, by operating melt pump control switch 80. In one aspect, the ratio of machine speed to nozzle translation speed may be changed to a first value based on a program stored by machine control computer 81, thereby adjusting the size of the bead 53 by a first amount. The ratio of machine speed to nozzle translation speed may be changed to a second value based on the operation of control switch 80, thereby adjusting the size of the bead 53 by a second amount. In one aspect, machine control computer 81 may increase or decrease the size of the bead 53 by a first amount. Manipulation of melt pump control switch 80 may increase or decrease the size of the bead 53 by a second amount. Thus, melt pump control switch 80 may be used to increase or decrease the first amount.
The machine speed to melt pump speed relationship may be altered in the CNC program to cause an increase or decrease in bead 53 size by a particular percentage. The bead 53 size can be increased or decreased by a lesser amount than the amount specified in the CNC program by operating control switch 80. Thus, the control switch 80 may operate separately from the adjustment in the program, allowing manual adjustment of the size of the bead 53.
For example, when first starting to print a three dimensional object, the bead 53 may differ by small amount than what was originally specified by the printing program. In one aspect, a slight operation of the control switch 80 may bring the bead 53 to the exact size that was used to program the production of the three dimensional object.
In one aspect, by providing a program and/or control switch for changing bead size during printing, the formation of holes, which may be present if the bead is smaller than what was specified in the printing program, may be avoided. Additionally, excessive squeeze-out, which may be present if every bead were produced larger than a size was specified in the printing program, may also be avoided. Thus, a part may be printed in a precise manner.
As shown in
In one aspect, machine control computer 81 may be programmed to evaluate the boundary or fill area 104 and apply a standard size (e.g., width) for bead 53. A standard width may be specified by slicing software. Machine control computer 81 may determine when the area 104 can be filled without a void by using the standard width, and deposit beads 53 accordingly.
In one aspect, control computer 81 may determine when void 103 would be formed if bead width 53 is provided with the standard width (e.g., a value initially specified in a slicing software program). Machine control computer 81 may be configured to determine when, by varying a width of a plurality of beads 53 by a particular (e.g., the same) amount, a void 103 may be filled. This may include modifying a size of a plurality, or all, of the beads 53 within boundary or fill area 104. When control computer 81 (or a separate controller) determines that a void 103 will be formed in area 104, as shown in
In one aspect, the slicing software programmed in control computer 81 may control the servo controller 79 to increase or decrease the machine speed (e.g., translation speed of nozzle 51) to gear pump 66 speed relationship by the amount (e.g., percentage) required to change the bead width to completely fill the boundary or fill area 104 as shown in
While principles of the present disclosure are described herein with reference to illustrative embodiments for particular applications, it should be understood that the disclosure is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, embodiments, and substitution of equivalents all fall within the scope of the embodiments described herein. Accordingly, the inventions described herein are not to be considered as limited by the foregoing description.