Patent Publication Number: US-2023141106-A1

Title: Surface Equalization Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of a provisional application No. 62/365,751 filed on Jun. 30, 2016. 
    
    
     TECHNICAL FIELD 
     The present disclosure pertains generally to an apparatus for surface finishing a part formed by 3D printing and enhancing mechanical properties of the part BACKGROUND 
     3D printing often results in a printed part having an uneven surface. For example, fused deposition modeling (FDM) is a 3D printing technology commonly used for modeling, prototyping, and production applications. FDM works on an “additive” principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part. This process may result in a “layered” surface, where individual steps associated with each layer progress in an overall direction. Such a surface may not be suitable for some application areas where a more sophisticated finish is desired. Additive manufacturing and 3D printing methods are not limited to those disclosed herein. 
     Due to the layered appearance and/or porosity of the body of a part produced by 3D printing, it may be desirable to equalize the surface of the part both internally and externally to give it a more finished appearance and improve function. Although the field is relatively new, methods of producing a finished appearance in a 3D printed part are known in the art. These include the use of adhesive film that is applied to the surface of the 3D printed part that bonds to the part and gives the appearance of an enhanced surface. Other methods include the use of solvents that erode the surface of the part to provide a smooth finish. 
     The drawbacks of the known systems are numerous, including limitations caused by incompatibility with a variety of materials and shapes. In existing systems, much experimentation may be required to discover the appropriate abrasive, adhesive, and/or solvent for each part. 
     Effective and efficient surface finishing for a wide variety of 3D printed materials and part shapes and sizes requires a system that is universally applicable. Therefore, a need exists for a surface equalization apparatus that can accommodate the wide and expanding variety of part types encountered in the fast-growing field of 3D printing and additive manufacturing. 
     SUMMARY 
     In the present disclosure, a solution to the problems of existing surface finishing methods and devices is provided through a surface equalization apparatus designed to be compatible with a wide variety of technologies, including EDM, PolyJet, DMLS, CBAM and the like, along with various composite materials and part geometries. The present disclosure describes a surface equalization apparatus that has a novel design and works together with software, abrasive and polishing materials and detergent for a synergistic effect on improving efficiency and effectiveness in surface finishing. 
     The surface equalization apparatus of the present disclosure includes an oblong input tank for holding media and a 3D printed part. The outer portion of the input tank is connected to a motor mount, which, in turn, is connected to an eccentric motor. When the motor is activated, the input tank begins to move in a vibrational manner, in a z direction. The input tank is attached to springs, generally adjacent the top, outer portion of the tank and the motion of the tank on the springs creates a rotational flow of media in the input tank. This rotational flow of media creates a consistent and calibrated low amplitude/high frequency movement of the part through the tank. 
     The rotational flow of the media works in conjunction with structures on the inside of the input tank, which include diverters and guide ribs. These structure help prevent the part from contacting the side of the tank and causing damage to the part. Media is replenished in the input tank through a set of spray nozzles positioned at intervals above the media in the input tank, and connected to a washer tank which supplies fresh media. Acoustic damping foam is positioned around the central components of the surface equalization apparatus. A cooling fan is integral with a side of a cabinet to allow air flow through the apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
         FIG.  1    shows a top perspective view of the surface equalization apparatus in accordance with the present disclosure. 
         FIG.  0 . 2    shows a top perspective view of the surface equalization apparatus in accordance with the present disclosure. 
         FIG.  3    shows a top perspective view of the surface equalization apparatus in accordance with the present disclosure. 
         FIG.  4    shows a cross-sectional side view of the surface equalization apparatus in accordance with the present disclosure. 
         FIG.  5    shows a cross-sectional side view of the surface equalization apparatus including a visualization of the direction of media in accordance with the present disclosure. 
         FIG.  6    shows a top view of the surface equalization apparatus in accordance with the present disclosure. 
         FIG.  7    shows a cross-sectional side view of the surface equalization apparatus in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, the various embodiments of the present invention will be described in detail. However, such details are included to facilitate understanding of the invention and to describe exemplary embodiments for implementing the invention. Such details should not be used to limit the invention to the particular embodiments described because other variations and embodiments are possible while staying within the scope of the invention. 
     Furthermore, although numerous details are set forth in order to provide a thorough understanding of the present invention, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present invention. In other instances details such as, well-known methods, types of data, protocols, procedures, components, networking equipment, processes, interfaces, electrical structures, circuits, etc are not described in detail, or are shown in block diagram form, in order not to obscure the present invention. 
     Referring now to  FIG.  1   , an embodiment of a surface equalization apparatus  100  in accordance with the present invention is shown. Surface equalization apparatus  100  may be used for finishing relatively large 3D parts. Lid  13  opens to allow placement of a 3D printed part in a media  44  (shown in  FIG.  5   ) held in input tank  16 . Input tank  16  may be preferably comprised of urethane. Control panel  10  allows a user to input initial pre-determined parameters such as time and motor speed. Eccentric motor  14  is shown below input tank  16 . Eccentric motor  14  is attached to input tank  16  such that when eccentric motor  14  is powered on, it causes input tank  16  to vibrate in a manner that results in surface equalization, or surface finishing. In some embodiments two eccentric motors  14  may be used side by side and/or on opposite sides on input tank  16 . 
     Referring now to  FIG.  2   , finisher chassis  19  surrounds input tank  16  and provides structural support for surface equalization apparatus  100 . Acoustic damping foam  18  is shown adjacent finisher chassis  19 . Electronics panel  28  (shown in  FIG.  3   ) controls operations for surface equalization apparatus  100 . 
     Referring now to  FIG.  3   , wastewater removal bucket  24  provides a means for separation of liquid from solid waste after wastewater leaves wastewater outlet  26 . Washer tank  12  contains media  44  for dispensing into input tank  16  through spray nozzles  22 , which are connected to washer tank  12  through spray nozzle piping  23 . 
     Spray nozzle  22  flow range is important for the present disclosure, such that in order to maximize the lubricity of the media these nozzles are evenly spaced to mist or spray into the chamber to create a homogeneous mixture. In a preferred embodiment, three spray nozzles  22  are spaced evenly at a top edge of input tank  16 . The position of the nozzles is fixed to point directly at the media  44  in input tank  16 . The flow rate of media  44  exiting spray nozzles  22  may be determined by onboard computer. Washer tank  12  is shown adjacent to input tank  16  to feed the spray valves. 
     Referring now to  FIGS.  4  and  5   , cross-sectional side views of the present disclosure shows eccentric motor  14  offset from a vertical axis running through the center of input tank  16 . As shown in  FIG.  5   , eccentric motor  14  rotates to cause vibrational motion of the U-shaped, oblong input tank  16 . Motor mount  30  allows the vibrational energy generated by eccentric motor  14  to be transferred to input tank  16  and media  44 . Eccentric motor  14  rotates in the opposite direction of the rotational flow of media  44 . Eccentric motor  14  has an applied angle to allow for the feed and discharge rate of the part in continuous motion. The angle of the eccentric motor  14  may be offset to 30° relative to a vertical axis in the preferred embodiment, although the angle may vary based on parameters of the part and surface equalization apparatus  100 . Media  44  is at an angle during operation of the apparatus (see Table 1 for relationships between media and other aspects of surface equalization machine  100 ). When a part reaches a complete cycle it goes through a slope phase, traveling from peak amplitude at a discharge, or exhaust, portion down to an intake portion. The machine is designed and calibrated to maintain the part below the surface of media  44  at all times. 
     As shown in  FIG.  4   , a key functional feature of the present disclosure is use of an eccentric motor  14  that causes springs  20  attached to the input tank  16  to move in a z-direction motion (or a bounce). Input tank  16  is suspended on springs  20 , which control a force applied by eccentric motor  14 , resulting in a z-direction, or vertical, motion on the order of 1-3 millimeters, in a preferred embodiment. 
     Eccentric motor  14  is positioned tangential to input tank  16  on motor mount  30 . Eccentric motor  14  spins, causing a frequency of motion that is harnessed to an up and down motion in the springs  20  attached to input tank  16 . The tension of the springs  20  generates a lifting motion. 
     Placing springs  20  at the top portion of input tank  16  creates a more stable system than having the springs  20  below input tank  16 , although it is possible that an effective system could be designed with the springs  20  below input tank  16 . Alignment of springs  20  to a metacentric height and the center of gravity, with respect to input tank  16 , is an important aspect of the present disclosure, and creates stable dynamic motion. A metacenter is defined as the point of intersection between a vertical line through the center of buoyancy of a floating body such as a ship and a vertical line through the new center of buoyancy when the body is tilted, which must be above the center of gravity to ensure stability. The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the center of gravity of a ship and its metacenter. A larger metacentric height implies greater initial stability against overturning. The motion center of the fluid mass abrading the surface the part in motion. 
     Eccentric motor  14  is calibrated to the combined mass of input tank  16 , eccentric motor  14 , and the media  44  contained in input tank  16 . The power ratio may be as follows: for every pound of mass (input tank  16 , media  44  contained in input tank  16 , and eccentric motor  14  combined), approximately 5.57 pounds of force is applied by eccentric motor  14 . For example, the range of force to weight may be approximately 4:1 to 7:1. The surface equalization apparatus  100 , in one embodiment used for larger 3D parts, may, for example, apply 1659 lbf to a weight of 298 lbs. 
     As shown in  FIG.  5   , media  44  flows rotationally, here illustrated in a counterclockwise direction, in response to activation of eccentric motor  14 , which rotates in the opposite direction of the rotational flow of media  44 ; here clockwise. While media  44  rotates, it carries a part to in a cycle through input tank  16 . Media  44  has a sloped, generally flat, surface during operation of surface equalization apparatus  100 . The effect on the part is delicate in nature with surface equalization apparatus  100  when compared to conventional surface finishing devices due to the low amplitude/high frequency ratio motion of the part. The part moves in a symmetrical, submerged, circuitous motion. The motion of the springs  20  causes the input tank  16  to move generally in a z-direction. This motion causes the part to be agitated within the media  44  containing abrasives and detergent, thereby generating heat energy and allowing complete immersion of the part such that all surfaces of the part receive consistent and simultaneous abrasion in a manner that effectively causes surface equalization. 
     Further, media  44  is formulated to avoid damage to delicate parts and keep the part below the surface of media  44  and away from solid portions of input tank  16 . The surface equalization apparatus  100 , in a preferred embodiment, may be effective for low density media/low density part surface equalization. Input tank  16  holds media  44  designed specifically for use in surface finishing. 
       FIGS.  4  and  5    show abrasive diverters, which include an exhaust diverter  36  and an intake diverter  37 , which modify the shape of the input tank  16 . Abrasive diverters are attached to the wall, or incorporated into the wall, of input tank  16  to modify the shape of the input tank  16  and may be preferably comprised of urethane. Abrasive diverters create directional energy transference, as exhaust diverter  36  and intake diverter  37  are energy dissipaters. In a preferred embodiment, exhaust diverter  36  and intake diverter  37  are positioned on opposing walls of input tank  16 , at the surface of media  44 . In some embodiments, only one abrasive diverter may be used. It is conceivable that no abrasive diverters would be necessary for certain applications. 
     As shown in  FIG.  5   , abrasive diverters are angled to properly direct the flow of media  44  in the input tank  16 . The abrasive diverters may be triangular in shape, and jut inward to direct media  44  flow so as to prevent the part from reaching the surface. The abrasive diverter is turning the part at the crest so that when the part is on the intake side there is fluid movement around the part. The abrasive diverter prevents the part from riding down the bed of media  44  on the surface, and maintains the part in a desirable position underneath the media  44  surface. 
     Optimal cubic foot of media  44  determines where the intake diverter  37  would be. The crest of each abrasive diverter may be, in a preferred embodiment, an inch above the slope of the surface of media  44 , or may also be approximately at the surface of media  44 . 
       FIG.  4    shows guide ribs  39 , which generally extend from one side of input tank  16  to the other. Guide ribs  39  may be semi cylindrical in shape and be spaced evenly longitudinally across input tank  16  and preferably be comprised of urethane. In a preferred embodiment there may be five guide ribs  39  in input tank  16 , and spaced evenly at a rate of seven guide ribs  39  per square cubic foot. Guide ribs  39  may preferably be ¼″ to 5″ in width and ¼″ to 3″ in depth. Guide ribs  39  create an inward force toward the center of input tank  16  on media  44  when eccentric motor  14  is powered on, thereby preventing the part from contacting the surface of input tank  16 , thereby preventing damage to the part. 
     The media  44  is selected to prevent contact with the wall of input tank  16 . Surface equalization apparatus  100  has a desired ratio of cubic foot of media  44  and open space to allow for the desired intake and discharge rates, while controlling the lubricity rates. 
     Media  44  may preferably have a density ranging from 20 lbs/ft 3  to 90 lbs/ft 3 , which is significantly lower than typical surface finishing media, thereby allowing a part to move inside the mass of media  44  as if the part were in a fluid, keeping media  44  between the part and the wall of input tank  16 . The media  44  may be described as a fluidized bed, such that conditions allow a solid to act like a fluid; those conditions creating the fluidized bed. 
     While surface equalization apparatus  100  is in operation, the breakdown, or attrition rate, of the media  44  is lower when compared to conventional surface finishing machines. The slowing of the attrition rate of media  44  in surface equalization apparatus  100  can, in part, be attributed to media  44  being applied over a period of time. 
     Addition of media  44  during operation has cleaning and cooling properties along with providing lubricity to media  44  in the input tank  16 . This addition of media  44  reduces unnecessary friction that would otherwise wear media  44  at an accelerated rate. Composite materials may be more susceptible to moisture absorption (parts are hygroscopic). The washer tank  12  may automatically add media  44  at a rate based on testing of the part. 
     The amplitude of the input tank  16 , or more specifically a ratio of lower amplitude and higher frequency, allows for reduced attrition of the media  44 . The shape of the input tank  16  is important for function. Further, the capability of tuning eccentric motor  14  from 900 to 4500 rpm allows for motion caused by eccentric motor  14  and the optimized frequency of the desired tunable ratio example of (k factor) for the requested amplitude (from 0.5 mm to 4 mm) from the springs  20  resulting in amplitude movement in input tank  16 . The z-direction motion of the media  44  mass is much lower in amplitude than it would be with lower operating frequency of the drive. Surface equalization machine  100  may operate based on DC or AC current, or equivalents thereof. 
     The U-shaped, curved, oblong walls of the input tank  16  are essential in generating the proper motion of the media  44  in order to create a conveyor belt type of rotational flow for surface equalization, as illustrated in  FIG.  5   . The center of mass under fluid motion is a key factor in determining the pattern of inlet and discharge rate. 
     An important feature of the present disclosure is an acoustic cabinet  11  (shown in  FIG.  2   ) surrounding input tank  16  that acoustically dampens at a spectrum of frequencies. Cabinet  11  is built in a way that allows room for the proper thickness of acoustic damping foam  18  (shown in  FIGS.  4  and  5   ). Acoustic damping foam  18  is necessary to optimize acoustic dampening of the noise caused by input tank  16  and media  44  motion. Acoustic damping foam  18  is placed throughout the eccentric motor  14 /input tank  16  cabinet. Input tank  16  is completely surrounded by acoustic damping foam  18  except for the top, open portion of the input tank  16 , which is covered only by lid  13 . 
     The ranges of frequencies of sound which are dampened are generally below 73 dBa. Input tank  16 , media  44  and eccentric motor  14  cause a frequency spectrum of sound, so during the development of the present invention, an engineering study was performed to find the proper way to dampen the appropriate frequencies. The intended amplitude, in a preferred embodiment, is from 1 mm to 3 mm and frequencies from 1200 rpm to 3600 rpm in order to have a desired feed and discharge rate from 4 to 180 seconds with regard to the density volume to noise ratio. 
     The sound generated by operation of the device creates dissipated energy at an absorption rate, so the surface equalization apparatus  100  also has a cooling fan  34  because eccentric motor  14  generates heat, and prior vibrational based finishing devices have been known to fail due to excessive heat caused by a motor. The present disclosure uses cooling fan  34  to solve this problem, along with acoustic dampening to create sufficient dissipation of heat in order to prevent the eccentric motor  14  from failing. 
       FIG.  0 . 6    shows a top view of surface equalization apparatus  100 , illustrating the spatial relationship of the spray nozzles  22  to input tank  16 . 
       FIG.  0 . 7    shows a power button  60  along with wastewater removal bucket  24  and drain well  40 . Further illustrated are caster wheels  70 , which may be coated in urethane for noise reduction. 
     In some embodiments of the present disclosure there may be two recovery tanks below input tank  16 . Recovery tanks collect drainage from input tank  16  and may use a weir system to separate solids from liquids. These recovery tanks have the ability to either recirculate or run on an open loop process. A hinge  35  having positive and negative resistance to hold the lid  13  in place is illustrated in  FIG.  0 . 4   . 
     In some embodiments of the present disclosure, a Beckhoff PLC/HMI provides the ability to run on an auto cycle. This system provides automatic run times, dosing, and flow control. Further, this system provides data monitoring of eccentric motor  14  frequencies, input tank  16  frequencies and amplitude, and enclosure temperature. 
     In some embodiments, separate spray valves allow two zones to be run with different settings at the same time, allowing for the use of different media  44  and different spray volumes and intervals. 
     Although the disclosure has been described with reference to certain preferred embodiments, it will be appreciated by those skilled in the art that modifications and variations may be made without departing from the spirit and scope of the disclosure. It should be understood that applicant does not intend to be limited to the particular details described above and illustrated in the accompanying drawings. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 Cycle 
                   
                   
                   
                   
                   
                   
               
               
                   
                 Motor 
                 Media 
                 Media 
                 Media 
                 Media 
                 Time- 
                 Front 
                 Back 
                   
                 Media 
                 3 ft 
                 6 ft 
               
               
                   
                 Force 
                 Volume 
                 Volume 
                 Mass 
                 Weight 
                 RPM 
                 Depth 
                 Depth 
                 Media 
                 Angle 
                 Sound 
                 Sound 
               
               
                 Media 
                 (lbs) 
                 (Gal) 
                 (ft{circumflex over ( )}3) 
                 (kg) 
                 (lbs) 
                 (sec) 
                 (in) 
                 (in) 
                 Slope 
                 (°) 
                 (dB) 
                 (dB) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 UPM 
                 1659 
                 1 
                 0.133681 
                 4.4 
                 9.68 
                 0 
                 0 
                 0 
                 0 
                 0 
                 87.1 
                 79.5 
               
               
                 UPM 
                 1659 
                 2 
                 0.267362 
                 8.8 
                 19.36 
                 5 
                 0 
                 0 
                 0 
                 0 
                 82.5 
                 78.5 
               
               
                 UPM 
                 1659 
                 3 
                 0.401043 
                 13.2 
                 29.04 
                 5 
                 10 
                 7 
                 0.3157894737 
                 17.52556837 
                 84.1 
                 78.1 
               
               
                 UPM 
                 1659 
                 4 
                 0.534724 
                 17.6 
                 38.72 
                 4.75 
                 10 
                 6 
                 0.4210526316 
                 22.83365418 
                 83.1 
                 76.7 
               
               
                 UPM 
                 1659 
                 5 
                 0.668405 
                 22 
                 48.4 
                 4 
                 8.5 
                 5 
                 0.3684210526 
                 20.22485943 
                 81.2 
                 76.5 
               
               
                 UPM 
                 1659 
                 6 
                 0.802086 
                 26.4 
                 58.08 
                 3.7 
                 6.75 
                 4 
                 0.2894736842 
                 16.14433878 
                 80.1 
                 75 
               
               
                 UPM 
                 1659 
                 7 
                 0.935767 
                 30.8 
                 67.76 
                 4 
                 5.5 
                 3.5 
                 0.2105263158 
                 11.88865804 
                 80 
                 75 
               
               
                 UPM 
                 1659 
                 8 
                 1.069448 
                 35.2 
                 77.44 
                 5 
                 4.25 
                 3 
                 0.1315789474 
                 7.49585764 
                 78.5 
                 75.5 
               
               
                 UAM 
                 1659 
                 1 
                 0.133681 
                 5.1 
                 11.22 
                 0 
                 0 
                 0 
                 0 
                 0 
                 89.9 
                 83.5 
               
               
                 UAM 
                 1659 
                 2 
                 0.267362 
                 10.2 
                 22.44 
                 4.75 
                 0 
                 0 
                 0 
                 0 
                 88.5 
                 81.2 
               
               
                 UAM 
                 1659 
                 3 
                 0.401043 
                 15.3 
                 33.66 
                 4 
                 10.5 
                 7 
                 0.3684210526 
                 20.22485943 
                 86.1 
                 79.3 
               
               
                 UAM 
                 1659 
                 4 
                 0.534724 
                 20.4 
                 44.88 
                 3.5 
                 10 
                 6 
                 0.4210526316 
                 22.83365418 
                 84.5 
                 78.6 
               
               
                 UAM 
                 1659 
                 5 
                 0.668405 
                 25.5 
                 56.1 
                 3.25 
                 9 
                 4.5 
                 0.4736842105 
                 25.34617594 
                 83.6 
                 77.3 
               
               
                 UAM 
                 1659 
                 6 
                 0.802086 
                 30.6 
                 67.32 
                 3.2 
                 7 
                 4 
                 0.3157894737 
                 17.52556837 
                 82.9 
                 76.5 
               
               
                 UAM 
                 1659 
                 7 
                 0.935767 
                 35.7 
                 78.54 
                 4 
                 6 
                 3.5 
                 0.2631578947 
                 14.74356284 
                 80 
                 75.5 
               
               
                 UAM 
                 1659 
                 8 
                 1.069448 
                 40.8 
                 89.76 
                 5 
                 4 
                 3 
                 0.1052631579 
                 6.009005957 
                 77 
                 74.9