Wobble attenuator

Abstract

An wobble attenuation apparatus for a 3D printer comprises an elongated, stiff, vertically oriented rail that is rigidly affixed to a frame member of the 3D printer; a first horizontal rigid plate that is rigidly affixed against or to the rail; and a second rigid plate having a distal end that is rigidly affixed to the rail, wherein a body of the second rigid plate is rigidly affixed to a shaft of the 3D printer that comprises a ball shaft. Embodiments effectively attenuate wobble of the printer's ball shaft in the X-Y directions with minimal to no effect on vertical (Z-axis) movement.

Description

ATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 1 of 9WOBBLE ATTENUATORCross-Reference To Related Application

[0001] This application claims the benefit of provisional application 63 / 769448, filed March 10, 2025. the entire contents of which are hereby incorporated by reference for all purposes as if fully set forth herein.Technical Field

[0002] One technical field of the present disclosure is 3D printers. Another technical field is mechanical structures for attenuating wobble in the ball shaft of a 3D printer.Background

[0003] The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.

[0004] 3D printers commonly use a motorized, movable platform to move a printed workpiece vertically as a melted filament or resin is deposited from the printing head onto the workpiece. A rotatable ball screw, coupled to a motor at one end and with a lifting nut affixed to the platform, is commonly used as a vertical transporter or actuator. The ball screw can be fully exposed within the printer or covered using a tubular shaft to protect screw threads from exposure to resin or filament.

[0005] In such an arrangement, the ball screw and / or shaft may wobble during the operation of the printer. “Wobble” refers to an irregular lateral or longitudinal movement and can cause imperfections in the printed part. Ball screw wobble, commonly on the order of >50 microns, results in noticeable imprecision, most notably visible as "wavy lines” defects along the sides of 3D-printed parts. Wobble occurs due to the almost inevitable imperfection in the straightness of the ball screw or shaft. A very7slightly bent ball screw or shaft will tend to push the entire system not only in the desired up / down direction but also in the undesired sideways direction as it rotates.

[0006] Several mechanical arrangements have been attempted in the past to eliminate, dampen, or attenuate wobble, but they are typically complicated to install and maintain.

[0007] Based on the foregoing, the referenced technical fields have developed an acute need for better ways to attenuate wobble in the ball screw and / or shaft of a 3D printer.ATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 2 of 9Summary

[0008] The appended claims may serve as a summary of the invention.Brief Description of the Drawings

[0009] In the drawings:

[0010] FIG. 1 illustrates an apparatus for attenuating ball screw wobble.

[0011] FIG. 2 models, as an electrical filter circuit equivalent to the mechanical system of FIG.1, the forces managed through plate configuration and orientation.

[0012] FIG. 3 is a front perspective view of a portion of the apparatus of FIG. 1.Detailed Description

[0013] 1. GENERAL PRINCIPLES OF DISCLOSURE

[0014] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

[0015] This disclosure may describe one or more different inventions, with alternative embodiments to illustrate examples. Other embodiments may be utilized, and structural, logical, software, electrical, and other changes may be made without departing from the scope of the particular inventions. Various modifications and alterations are possible and expected. Some features of one or more of the inventions may be described with reference to one or more particular embodiments or drawing figures, but such features are not limited to usage in the one or more particular embodiments or figures with reference to which they are described. Thus, the present disclosure is neither a literal description of all embodiments of one or more inventions nor a listing of features of one or more inventions that must be present in all embodiments.

[0016] Headings of sections and the title are provided for convenience but are not intended to limit the disclosure in any way or as a basis for interpreting the claims. Devices described as in communication with each other need not be in continuous communication with each other unless expressly specified otherwise. In addition, devices that communicate with each other may communicate directly or indirectly through one or more intermediaries, logical or physical.ATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 3 of 9

[0017] A description of an embodiment with several components in communication with one another does not imply that all such components are required. Optional components may be described to illustrate a variety of possible embodiments and to illustrate one or more aspects of the inventions fully. Similarly, although process steps, method steps, algorithms, or the like may be described in sequential order, such processes, methods, and algorithms may generally be configured to work in different orders unless specifically stated to the contrary. Any sequence or order of steps described in this disclosure is not a required sequence or order. The steps of the described processes may be performed in any order practical. Further, some steps may be performed simultaneously. The illustration of a process in a drawing does not exclude variations and modifications, does not imply that the process or any of its steps are necessary to one or more of the invention(s), and does not imply that the illustrated process is preferred. The steps may be described once per embodiment but need not occur only once. Some steps may be omitted in some embodiments or occurrences, or some steps may be executed more than once in a given embodiment or occurrence. When a single device or article is described, more than one device or article may be used in place of a single device or article. Where more than one device or article is described, a single device or article may be used instead of more than one device or article.

[0018] The functionality or features of a device may be alternatively embodied by one or more other devices that are not explicitly described as having such functionality or features. Thus, other embodiments of one or more inventions need not include the device itself. Techniques and mechanisms described or referenced herein will sometimes be described in singular form for clarity. However, it should be noted that particular embodiments include multiple iterations of a technique or manifestations of a mechanism unless noted otherwise. Process descriptions or blocks in figures should be understood as representing modules, segments, or portions of code, including one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of embodiments of the present invention in which, for example, functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved.

[0019] 2. EXAMPLE EMBODIMENTS

[0020] FIG. 1 illustrates an apparatus for attenuating ball screw wobble. Ball screw wobble, represented in FIG. 1 by the arrows 1, commonly exceeding 50 pm, if not addressed, results inATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 4 of 9noticeable imprecision manifested in a finished part as visible, wavy line defects along the side of printed parts. Wobble derives from imperfection in the straightness of the ball screw 10 and / or shaft assembly. Due to the wobble, the system consisting of the aforementioned parts moves in the undesired X-Y (sideways) direction as well as the intended Z (up / down) direction.

[0021] A second source of undesirable motion is deforming brackets, since metal plates bend readily perpendicular to their surface planes in the direction noted with reference numeral (2). Comparatively, the plates do not deform parallel to their surface planes. Plate alignment restricts undesirable movement in the direction of force arrows (4).

[0022] In an embodiment, as part of a 3D printer, an elongated ball screw 10 extends vertically through a first horizontal rigid plate 12 and a shaft collar 13 that terminates a shaft 21. A second, vertically mounted lateral plate 14 comprises a body 22 that is affixed at a right angle to the first horizontal plate and to the shaft collar 13 or shaft 21. A third vertically oriented plate 16 is rigidly affixed to a distal end 15 of the plate 14 via fasteners extending through both plates and affixed to a rail coupler 18.

[0023] The third vertically oriented plate 16 comprises an inwardly extending arm 17 that is rigidly affixed to a frame member 20 of a frame of the printer. The rail coupler 18 is rigidly affixed to a rigid vertical rail 3. The first horizontal plate 12 has a forward face 24 that is rigidly affixed against or to the rigid vertical rail 3.

[0024] All elements shown in FIG. 1 are typically formed from rigid cast, machined, or extruded metal, such as steel, aluminum, or ferrous alloys. The plates are typically steel to promote rigidity7, whereas frame member 20 may be an elongated aluminum extrusion to reduce weight and improve the printer's portability. Fasteners may be machine screws, other screws, or bolts in compatible threaded holes that are formed with a high degree of precision to form a rigid, stiff frame for the printer.

[0025] The ball screw 10 has a distal end 40 that is rotatably driven by a motor (not shown): rotation of the ball screw- drives vertical movement of the first horizontal plate 12, w hich can affix to a w orking floor of the printer and thus carry the floor and a part during printing in the Z (vertical) direction as needed to facilitate printing the part.

[0026] In an embodiment, the ball screw 10 is extremely rigidly coupled in the Z direction due to the orientation of the metal plate 14 between the ball screw7and the linear bearing 13. In an embodiment, the rail (3), bolted to the stiff frame members, absorbs any remaining wobble force, reducing displacement. Practical implementations can limit mechanical imprecision byATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 5 of 9at least 2x in either direction and, in fact, 5x in the y direction and as much as lOx as the ball screw 10 nears the end of its travel range.

[0027] With embodiments, wobble attenuation of at least 2x (less than 25 gm) allows 3D printers to produce matte-finish tolerance articles. Further progress, such as less than 10 pm, is possible through supplementary techniques such as interferometry. For example, fabrication at a 5 pm tolerance, which is needed to manufacture new ball screws 10, becomes feasible.

[0028] An added benefit of the stiff rail (3) derives from the possibility of on-site reinforcement. Large metal plates weighing a few hundred kilograms can be bolted to the frame's comer. These plates, configured as a box along all planes of force, directly displace pressures through solid metal. Several tons of force would be needed before any inelastic deformation occurs. Thus, the printer remains calibrated to 0.5 pm tolerances, which are enabled by visible light microscopes. A lightweight machine, moveable by tw o humans, fits through standard commercial doorways. This compact arrangement is unusually mechanically favorable.

[0029] The arrangement optimizes the ball screw 10, motor, and shaft to be as close as possible to the rail (3). The minimal torque required to rotate this ball-bearing-based lead screws technology will directly twist only the stiff rail with its thick reinforcing column underneath. This contrasts with depending on a lengthy mechanical link between the motor and the rail that must then constrain the entire mechanism from rotating.

[0030] This smaller area (5) and the thick reinforcing column underneath the rail (3) reduce mechanical imprecision when traveling first in one direction (e.g., down), then in the opposite direction (e.g., up), known as 'backlash' due to unavoidable elasticity. We expect this backlash to be less than 5 pm in practical arrangements.

[0031] Leveling the surface of the working area, known as tramming, is achieved by driving each of the usually three or four ball screws at the comers independently, using leverage to tilt the surface. Placing the ball screws as close to the comers of the machine as possible maximizes this leverage (6), which also minimizes the amount of tilt per the amount of travel, maximizing the range and precision of this auto-leveling capability. Better than 1 pm repeatability (accuracy) is observed in practical implementations when a tool is brought into contact with the work surface.

[0032] An additional design feature accommodates thermal expansion by leveraging the flexibility of a plate's plane. 3D printers generate heat when printing a part and the interior ofATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 6 of 9the printer can become quite warm. FIG. 3 is a front perspective view of a portion of the apparatus of FIG. 1. FIG. 3, arrow (7) demonstrates the direction of flexibility when the long extruded frame member 20 inside the heated enclosure heats and cools, causing expansion in the direction of arrow (8). Additionally, the long extruded frame member 20 benefits from being slightly shorter than the gap it spans, thereby reducing linear bearing load at high temperatures and providing preload at low temperatures.

[0033] To assist understanding, FIG. 2 models the mechanical system as an electrical filter circuit, equivalent to the mechanical system, showing the forces managed through the plate configuration and orientation. In FIG. 2, an AC source (4) represents the shaft wobble diagrammed previously (Fig. 1, 1). The shaft flex (1), plate flex (2), and rail flex (3) each pose resistance to movement described earlier. Large masses in the machine, which are virtually immovable, are represented by electrical grounds (3), also seen in Fig. 1, element 1.

[0034] 3. BENEFITS, SCOPE. AND EXTENSIONS

[0035] The overall described approach delivers substantial improvement over current designs. Typically, 3D printers attach 3D-printed plastic brackets between the ball screw nut or other drive mechanism and the machine's work surface. Plastic 3D-printed brackets also couple the machine work surface to an unsupported, small-diameter, smooth rod. These methods (a) directly couple the wobble forces into displacements of the work surface, (b) allow the work surface to move along those wobble forces within the flexibility of the 3D printed plastic bracket to the linear bearing, (c) allow the work surface to move along those wobble forces within the flexibility7of the long unsupported smooth rod, and (d) allow large displacements from the weakness, thermal expansion, hygroscopic expansion, of plastic brackets, especially because plastic is a weak, unstable material.

[0036] In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary' from implementation to implementation. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicants to be the scope of the invention, is the literal and equivalent scope of the set of claims issued from this application in the specific form in which such claims issue, including any subsequent correction.

Claims

ATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 7 of 9CLAIMSWhat is claimed is:

1. An apparatus comprising:an elongated, stiff, vertically oriented rail that is rigidly affixed to a frame member of a 3D printer;a first horizontal rigid plate that is rigidly affixed against or to the rail; and a second rigid plate having a distal end that is rigidly affixed to the rail, wherein a body of the second rigid plate is rigidly affixed to a shaft of the 3D printer that comprises a ball shaft.

2. The apparatus of claim 1 , further comprising a rail coupler that is rigidly affixed to the rail and to a third vertically oriented rigid plate that is rigidly affixed to the frame member.

3. The apparatus of claim 1, further comprising:a rail coupler that is rigidly affixed to the rail and to the second rigid plate; and a third vertically oriented rigid plate that is rigidly affixed to the frame member.

4. The apparatus of claim 1, further comprising one or more metal plates affixed to comers of a frame of the 3D printer and configured as a box along all planes of force to displace pressures through solid metal.

5. The apparatus of claim 2, wherein the first plate, the second plate, and the third plate are formed of rigid steel.

6. A 3D printer comprising:a frame comprising a plurality of elongated frame members;an elongated, stiff, vertically oriented rail that is rigidly affixed to a first frame member; a first horizontal rigid plate that is rigidly affixed against or to the rail; andATTORNEY DOCKET NO. PATENT APPLICATION 092142.0104Page 8 of 9a second rigid plate having a distal end that is rigidly affixed to the rail, wherein a body of the second rigid plate is rigidly affixed to a shaft of the 3D printer that comprises a ball shaft.

7. The 3D printer of claim 5, further comprising a rail coupler that is rigidly affixed to the rail and to a third vertically oriented rigid plate that is rigidly affixed to the frame member.

8. The 3D printer of claim 5, further comprising:a rail coupler that is rigidly affixed to the rail and to the second rigid plate; and a third vertically oriented rigid plate that is rigidly affixed to the frame member.

9. The 3D printer of claim 5, further comprising one or more metal plates affixed to comers of the frame of the 3D printer and configured as a box along all planes of force to displace pressures through solid metal.

10. The 3D printer of claim 5, wherein the first plate, the second plate, and the third plate are formed of rigid steel.

Images