Patent Publication Number: US-2017361406-A1

Title: Orbital Friction Surfacing of Remanufactured Cast-Iron Components

Description:
TECHNICAL FIELD 
     The present disclosure relates to remanufacturing or refurbishing of cast-iron components. More specifically, the present disclosure relates to such methods for remanufacturing cast-iron components that use orbital friction to lay down new material that may be used to repair the components. 
     BACKGROUND 
     Cast-iron components are used in many industries but have been particularly useful in machinery used in construction, earth-moving and the like as well as engine components. As can be imagined, wear or damage may occur to these cast-iron components over time that may cause them to become unusable due being out of tolerance or excessively damaged. These components may be expensive to manufacture from raw materials and/or it may be useful to fix such components in the field if there is a scarcity of replacement components. In either case, it is desirable to be able to remanufacture or refurbish the component to save time or money. 
     Previous methods used for remanufacturing such components include conventional metallurgical bond methods and welding. However, these methods may require a high preheat temperature that can leave an undesirable high hardness heat affected zone. Therefore, these methods often create some sort of compromised metallurgical structure that may lead to cracking of the base material. As a result, the cast-iron component may need rework sooner than is desired. 
     SUMMARY OF THE DISCLOSURE 
     A machine for orbital friction surfacing of components that defines a Cartesian coordinate system including X, Y and Z axes is provided. The machine comprises at least one component that is movable along the X and Y axes and at least another component that is movable along the Z axis, a rotating spindle, a motor that powers the spindle, a tool attachment mechanism that is operatively associated with the rotating spindle, a position sensor and force transducer that are in communication or operative association with the spindle, and a controller that is configured to sense the position of the spindle via the position sensor and the force exerted on the spindle via the force transducer and to move at least one component that is movable along any of the X, Y and Z axes in order to maintain a desirable force exerted on the spindle. 
     The method of orbital friction surfacing of components using a consumable featureless solid tool comprises rotating the consumable featureless solid tool, plunging the tool toward a component until a desired spindle force is attained, and moving the component relative to the tool to lay down a deposition of material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a CNC milling machine that is capable of at least three axis linear movement and rotation of a tool for performing machining operations on a workpiece. 
         FIG. 2  is a perspective view of a consumable rod according to an embodiment of the present disclosure that may be attached to the spindle of the milling machine of  FIG. 1  using a tool adapter and collet tool retaining mechanism. 
         FIG. 3  is partial front cross-sectional view of a tool adapter with a set screw tool retaining mechanism holding a consumable rod that may be attached to the spindle of the milling machine of  FIG. 1 . 
         FIG. 4  is a simplified perspective view showing the use of a solid consumable rod that is used in a method of orbital friction surfacing of remanufactured cast-iron components. 
         FIG. 5  is a flowchart depicting various steps of a method or process in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In some cases, a reference number will be indicated in this specification and the drawings will show the reference number followed by a letter for example,  100   a ,  100   b  or a prime indicator such as  100 ′,  100 ″ etc. It is to be understood that the use of letters or primes immediately after a reference number indicates that these features are similarly shaped and have similar function as is often the case when geometry is mirrored about a plane of symmetry. For ease of explanation in this specification, letters or primes will often not be included herein but may be shown in the drawings to indicate duplications of features discussed within this written specification. 
     Orbital friction surfacing may be achieved by the rotation motion of one consumable solid tool as it traverses across the surface of a workpiece that is intended to be remanufactured or refurbished. The surface of the workpiece may be perpendicular to the axis of rotation of the consumable solid tool. During the process, the material may be deposited in a solid state mode, thereby drastically reducing the heat input, which has the effect of mitigating distortion, reducing or eliminating cracking, reducing or eliminating the requirement for preheat of the workpiece component, and reducing or eliminating dilution between the substrate and the consumable tool. This may enable the salvage of cast iron engine components currently deemed “unsalvageable” due to the aforementioned effects of conventional welding processes. These components may be, but are not limited to: engine heads, blocks, turbochargers, exhaust components, etc. This may also be used on work tools such as buckets, tips, and the like, etc. It is contemplated that the machine and method described herein may be adapted for use with other materials as well. 
     Looking at  FIG. 1 , it depicts a machine that may be used for orbital friction surfacing of components. The machine  100  defines a Cartesian coordinate system including X, Y and Z axes and happens to be a CNC programmable machine. The machine  100  comprises at least one component  102  that is movable along the X and Y axes and at least another component  104  that is movable along the Z axis, a rotating spindle  106 , a motor  108  that powers the spindle  106 , a tool attachment mechanism  110  that is operatively associated with the rotating spindle  106  for powering the rotation of the spindle  106 , a position sensor  112  and force transducer  114  that are in communication or operative association with the spindle  106 , and a controller  116 . The controller  116  is configured to sense the position of the spindle via the position sensor  112  and the force exerted on or by the spindle  106  via the force transducer  114  and to move at least one component  102 ,  104  that is movable along any of the X, Y and Z axes in order to maintain a desirable force exerted on or by the spindle  106 . A consumable solid tool  200  is attached to the tool attachment mechanism  110  that will be described in further detail later herein. 
     Still referring to  FIG. 1 , the machine comprises a table or bed  102  that is configured to translate along the X and Y axes. A series of collapsible and expandable plates  118  are located on each side of the bed  102  along the X axis that protect mechanisms used to move the bed  102 . The plates  118  on the right side of the bed  102  in  FIG. 1  will collapse when the bed  102  moves in the positive X direction and will expand when the bed moves in the negative X direction. Contrarily, the plates  118 ′ on the left side of the bed in  FIG. 1  will expand when the bed  102  moves in the positive X direction and contract when the bed  102  moves in the negative X direction. Another series of plates  118 ″ are positioned forward of the bed  102  along the negative Y axis that expand when the bed  102  moves in the positive Y direction and contract when the bed  102  moves in the negative Y direction. 
     Typically, a workpiece attachment mechanism  120  is attached to the bed  102  such as a vise or the like using the dovetail shaped grooves  122  that separate the rails  124  of the bed  102 . Alternatively, a workpiece may be clamped down on the bed to hold it in place using clamps that have fingers that press on top of the workpiece using a fastener that connect the fingers to holding members that are retained in the dovetail shaped grooves. When a ferrous workpiece is used such as steel, cast-iron, etc., a magnetic chuck  126  may be employed that uses electromagnets that are embedded in the rails  124  of the bed  102  and hold the workpiece  128  in place once activated. For the embodiment shown in  FIG. 1 , such a magnetic chuck  126  is being shown used to hold a cast-iron workpiece  128  in place. In such a case, the grooves  122  may be omitted, allowing the bed  102  to have a continuous flat surface. 
     As shown in  FIG. 1 , the spindle  106  is configured to translate along the Z axis and to rotate about a Z′ axis, which is parallel with the Z axis. The spindle  106  is attached to head  104  that is movably attached to a vertical guide rail  130  that defines dovetail shaped grooves  132  between the support column  134  of the machine and the vertical guide rail  130 . A rack and pinion mechanism or another similar mechanism (not shown) may allow the head  104  and spindle  106  to translate up and down along the vertical guide rail  130  in a direction parallel to the Z axis. As mentioned previously, the bed  102  is able to move in the X and Y directions. It is contemplated that these roles of the head and bed may be reversed in other embodiments and other movable components and other more complex movements may be provided in yet further embodiments. 
     A tool attachment mechanism  110  is shown at the bottom of the spindle  106  and is fixed to the spindle  106  such that any rotation of the spindle  106  is imparted to the tool attachment mechanism  110  and a tool  200  that is attached to that mechanism. The tool attachment mechanism  110  may take any form known or that will be devised in the art including a chuck or a tool adapter  134  that is configured to hold the tool  200  and be readily attached and detached from the machine  100  in a manner that will be described in more detail later. For the embodiment shown in  FIG. 1 , a tool adapter  134  is used and the machine  100  further comprises a tool adapter indexer  136  that allows tool adapters and tools  200  to be changed when worn or when a different tool is desired to be used to perform work on the workpiece  128 . 
     The controller  116  in  FIG. 1  may be of any type known or that will be devised in the art and may use any type of processing device, digital logic, etc. to control the various movements and functions of the machine  100 . For this embodiment, the controller may be an Allen Bradley or similar type controller that is configured to monitor the wear of the consumable solid tool  200  until the wear reaches a threshold. At which time, the tool adapter indexer  136  may be activated to move and change out the worn tool  200 , replacing that tool with a fresh tool. Alternatively, a signal may be given alerting an operator to change the tool out. 
     During set up, an operator may install the workpiece  128  such that it is held by the workpiece attachment mechanism and may make certain dimensional measurements that will be discussed in more detail momentarily. Then, the operator may enter these measurements or variables into the controller  116 , which is configured to receive input of the variables and calculate the appropriate operating parameters of the machining process to be performed on that workpiece. Alternatively, the measurements and data input may be performed by another technician remotely from the machine such as during tool setup and the data input and calculations may be downloaded to the machine. Examples of input data include, but are not limited to, the diameter of the tool, the material of the tool, the length of extension of the tool from the tool attachment mechanism, etc. Examples of calculated machine parameters include, but are not limited to, linear feed rate of the workpiece, force exerted by the spindle, rotational speed of the spindle, etc. 
     Turning now to  FIGS. 2 and 3 , details of the consumable solid tool  200 , methods of attachment to a tool adapter  134 , and pertinent dimensions are shown in more detail and will be discussed.  FIG. 2  is a perspective fragmentary view of a consumable solid tool  200  that extends upwardly from the extension portion  138  of a tool adapter  134 . As shown, the tool  200  points upward instead of downward but the orientation of the tool  200  may be varied as needed or desired depending on a particular application such as the configuration of the machine  100  being used. As can be seen, the tool  200  has a cylindrical configuration but this may be varied as needed or desired. A collar/collet retention mechanism is shown holding the tool  200  in place such that the tool  200  is retained by the tool adapter, fixing the Z position of the tool  200  relative to the tool adapter  134  (see  FIG. 1 ). The collet  202  is only partially shown but is to be understood to be made of a unitary piece made from a spring steel type of material with a cam surface and slits. The collar  204  is threadedly attached to the extension  138  of the tool adapter  134 . As the collar  204  is tightened, its cam surface (not shown) contacts the cam surface of the collet, causing the collet to collapse as the slits are contracted, until the inner diameter of the collet  202  clamps onto the outer diameter D of the tool  200 , fixing its position rotationally and translatably. The pertinent dimensions that may affect the process are shown in  FIG. 2  to include the diameter D of the tool  200 , the length L of extension of the tool  200 , and the material from which the tool is made (not shown). 
     As illustrated by  FIG. 2 , the term “consumable solid tool” means herein that the tool is meant to add material to a workpiece rather than remove it as is the case with conventional tools such as end mills and drills. Hence, the tool is a sacrificial item instead of the workpiece. Furthermore, the tool is in a solid state, that is to say, it is not molten anywhere between the workpiece and the tool adapter except for the small layer being deposited on the workpiece as will be described in more detail later herein. Also, the solid tool may be characterized as lacking features typically associated with cutting tools such as flutes, cutting edges, cutting points, apertures, angled features for facilitating the creation and removal of chips, etc. Hence, the consumable solid tool may be considered featureless. The type of material used to make the tool may vary as needed or desired but it is contemplated that tool may be made from a Nickel-Iron alloy when the workpiece is made from cast-iron. 
       FIG. 3  shows another tool adapter  134  that uses a set screw  206  that interfaces with a notch  208  on the side of the tool  200  to hold the tool  200  in position.  FIG. 3  also shows some distances between various parts of the tool  200  or tool adapter  134  and the workpiece  128  that are useful for setting up the machine  100  and process. The tool adapter  134  includes a tapering shank  210  that is configured to match with a tapering recess (not shown) in the spindle  106  and a flattened tang  212  that cooperates with a complimentary shaped recess (not shown) in the spindle  106  for communicating torque to the tool adapter  134 . It also includes a thru-slot  214  that may be used to accept a wedge (not shown) of the spindle  106  that holds the tool adapter  134  in the spindle  106 . The extension portion  138  of the tool adapter  134  extends into a pocket  218  and is held in the main body  216  of the tool adapter  134  using a retaining mechanism  220  that is known in the art. Accordingly, a detailed description of the retaining mechanism is not warranted. Alternatively, the extension portion  138  may be formed integral with the main body  216  of the tool adapter  134 . Other configurations of the tool adapter are possible. 
     During setup, the operator may use a gauge block to measure the distance D 200  from the tip of the tool to the workpiece, and enter a corresponding offset into the controller  116 . This dimension D 200  would correspond to the movement in the Z direction that would constitute a “soft crash” if the head  104  and spindle  106  were to move more than this distance. The controller  116  may be configured to calculate the distance D 134  from the workpiece  128  to the tool adapter  134  by adding the “soft crash” dimension D 200  to the length of extension L (shown in  FIG. 2 ). This distance may be referred to as the “hard crash” dimension. Of course, it is desirable to approach the soft crash dimension slowly to avoid damage to the tool and even more desirable to avoid approaching the hard crash dimension for fear of damaging the tool adapter, spindle, head, and possibly other parts of the machine. In practice, the controller  116  may be configured to monitor the actual position P of the tip of the tool  200  in order to calculate the amount of wear W the tool  200  has experienced. As the wear occurs, the amount of force exerted by the spindle as well as other variables may be adjusted in order to achieve the desirable adhesion of added material. 
     As mentioned earlier, if enough wear has occurred, then the tool  200  may be changed out for a fresh tool. The amount of acceptable wear W may be expressed as a percentage of the length of extension L or as a percentage of the actual distance P of the tip of the tool  200  from the workpiece  128  versus the hard crash depth D 134 . For example, either of these methods may be expressed in terms of 70-90% of the length of extension L or the hard crash dimension D 134  depending on the application. Other values and methods are possible. 
     The length of extension L may be proportional to the diameter D of the tool  200  (see  FIG. 2 ) in order to prevent buckling of the tool that could cause the process to be halted. The rate of linear movement of the workpiece may be altered depending on the force exerted on the spindle, rate of rotation of the spindle, etc. It is further contemplated that the linear movement may occur in the X, Y and/or Z direction depending on the profile of the workpiece. 
     INDUSTRIAL APPLICABILITY 
     In practice, a machine  100  may be sold or retrofitted with the capabilities to implement any method or process discussed herein. Similarly, a method or process as discussed herein may be used to add material to a workpiece or other component for the purpose of remanufacturing or refurbishing that component. 
       FIG. 4  illustrates the mechanics of the process from a purely conceptual viewpoint. The consumable solid tool  200  is rotated and pressed down on a component  128  while that component  128  is moved in any of the X, Y, and Z directions or combinations thereof. The combination of the force exerted F on the component  128  as well as the force −F exerted on the consumable solid tool  200 , movement  220  of the component  128 , and rotation R of the tool  200  deposits a thin viscous layer  222  of molten material on the component  128  at lower temperatures compared to other prior techniques, lowering the heat affected zone between the substrate  128  and deposited material  222 , providing a more robust bonding of the newly deposited material  222  to the substrate  128 . 
     It should be noted that the forces and movements of the tool and the component/workpiece may be expressed purely relative to each other. For example, the downward force exerted onto the tool may be equally and oppositely balanced by a force provided by a rigid and incompressible platform on which the bed of the machine rests, which in turn, rests on a rigid and incompressible surface such as that provided by concrete and the like. Similarly, the rotation may be imparted to the component or workpiece while the linear movement may be imparted to the tool, etc. Therefore, all language contained herein should include relative equivalents. 
       FIG. 5  contains a flowchart depicting various steps of a method for adding material to a component using orbital friction surfacing. The method  300  may comprise the steps of rotating the consumable featureless solid tool (see step  302 ), plunging the tool toward a component until a desired spindle force is attained (see step  304 ), and moving the component relative to the tool to lay down a deposition of material (see step  306 ). 
     The method  300  may further comprise monitoring the wear of the tool (see step  308 ) and attaching the tool to a tool attachment mechanism, fixing the position of the tool relative to the tool attachment mechanism (see step  310 ). 
     The method  300  may further comprise monitoring the spindle force (see step  312 ) and moving the spindle or workpiece or altering some other process variable to maintain a desirable spindle force (see step  314 ). 
     The method may further comprise changing out the tool once a threshold of wear is measured (see step  316 ). 
     In other embodiments, the method may further comprise using at least one of the tool diameter, length of extension of the tool from the tool attachment mechanism, and the material of the tool to calculate at least one of the appropriate linear feed rate of the component, appropriate force exerted on the spindle and the appropriate rotational speed of the spindle (see step  318 ). 
     The method may further comprise using the material of the component to calculate at least one of the appropriate linear feed rate of the component, force exerted on the spindle and rotational speed of the spindle (see step  320 ). 
     In yet further embodiments, the method may further comprise changing at least one of the linear feed rate of the component, force exerted on the spindle and rotational speed of the spindle if any of these variables falls outside of desirable parameters (step  322 ). 
     In some cases the desired material deposition time or machine limitations are known limits. Then, the method may comprise using at least one of the desired linear feed rate, force exerted on the spindle, and rotational speed of the spindle to calculate at least one of the appropriate tool diameter, length of extension of the tool from the tool attachment mechanism, and material of the tool or component (step  324 ). 
     It is contemplated that this method may be accomplished through experimentation using examples of tools and components made from a particular material. Specifically, the tool may be made from a nickel-iron alloy while the component may be made from cast-iron. Various variables may be tested and tables or curves fitted to the experimental data may be used by a controller to implement a process that will provide suitable results. 
     Exemplary values for various process values and dimensions of the tool will now be given. It is contemplated that rotational speed of the spindle may range from 150 to 2000 RPM, that the diameter of the tool may range from 0-25 mm or more, that the linear feed rate may range from 1-5 mm/s or more, that the depth of deposited material added per pass of the tool may range from 0-0.2 mm, and that the force exerted on the tool may range from 0.66-3.3 KN (150-750 lbs) or more when the substrate comprises cast-iron and the tool comprises a nickel-iron alloy. The length of extension of the tool may be calculated by avoiding the buckling load for the tool using the following equation: 
         L =( F /(π 2   EI )) 1/2  where
 
     F=Z force on the tool, E is the modulus of elasticity of the material of the tool, I is the moment of inertia of the tool which for a circular cross-section is I=π/4(D/2) 4 . Similar calculations may be made for axial compressive stress and bending stress using equations well-known in the art. Accordingly, the verbatim recitation of these equations herein is not deemed warranted. The process may be altered as needed to avoid exceeding the compressive or bending stress as well. 
     These process variables and dimensions may be varied depending on the application and the materials of the substrate and the tool. As mentioned previously, experimental data may be developed to create tables or curve fits that will facilitate the optimization of the process via the controller of the machine for various applications. 
     It will be appreciated that the foregoing description provides examples of the disclosed assembly and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
     Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the apparatus and methods of assembly as discussed herein without departing from the scope or spirit of the invention(s). Other embodiments of this disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, some of the equipment may be constructed and function differently than what has been described herein and certain steps of any method may be omitted, performed in an order that is different than what has been specifically mentioned or in some cases performed simultaneously or in sub-steps. Furthermore, variations or modifications to certain aspects or features of various embodiments may be made to create further embodiments and features and aspects of various embodiments may be added to or substituted for other features or aspects of other embodiments in order to provide still further embodiments. 
     Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.