Patent Publication Number: US-2023135083-A1

Title: Milling machines, systems, and related methods

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a road construction machines, and more particularly, to milling machines, systems, and related methods. 
     BACKGROUND 
     The present invention relates to milling machines that are used in road surface repairs. Milling machines are typically utilized to mill and, optionally, remove a layer or layers of old or defective road surface in preparation for resurfacing or other road treatment. Machines, such as cold planers, rotary mixers, and other milling machines, are used for scarifying, removing, mixing, or reclaiming material from ground surfaces, such as, grounds, roadbeds, and the like. Such machines include a rotor enclosed within a rotor chamber. Some machines, including cold planers, include a conveyor assembly, which conveys fragments from the rotor chamber away from the road surface, for example, to a truck. The rotor includes a cylindrical drum or shell member and a number of cutting assemblies mounted on the shell member. When the machine is performing a cutting operation, cutting bits of the cutting assemblies impact the surface and break it apart. Thus, the cutting assemblies are arranged to cut the surface and to leave a milled surface that meets a known texture or surface finish requirement. Another function of the cutting assemblies is to form an auger that moves material within the rotor chamber, for example, to a central area of the rotor chamber from where it can be moved by the conveyor assembly to the truck. In these aspects, the arrangement and/or pitch of the cutting assemblies may affect the cutting operation, including, for example, the resulting texture, surface finish, and/or roughness of the resulting milled surface. 
     French Patent No. 2789415, issued to Medinger on August 11, 200 (“the &#39;415 patent”), describes a milling machine with two rotors. The rotors are positioned between four wheels under a frame of the machine, and the two rotors are transversely spaced apart. The rotors scour and crush the soil traversed by the machine. The two rotors may increase the traction of the machine. Additionally, the second rotor is positioned lower than the first rotor, so that the first rotor may work a first portion of the ground surface, and the second rotor may work a second portion of the ground surface. However, the rotors of the &#39;415 patent may not provide sufficient adjustment and/or control of the characteristics of the resulting surface finish formed by the milling machine. The machines, systems, and related methods of the present disclosure may solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem. 
     SUMMARY 
     In one aspect, a milling machine may include a frame, a plurality of wheels or track members coupled to the frame, a moldboard movably coupled to the frame, a first rotor, and a second rotor. The first rotor may be rotatably coupled to the frame. The second rotor may be positioned to the rear of the first rotor and rotatably coupled to the moldboard. 
     In another aspect, a milling system may include a first rotor and a second rotor. The first rotor may include a plurality of cutting assemblies spaced apart by a first pitch. The second rotor may be positioned to the rear of the first rotor. The second rotor may include a plurality of cutting assemblies. The plurality of cutting assemblies positioned on the second rotor may be spaced apart by a second pitch that is smaller than the first pitch. 
     In yet another aspect, a milling machine may include a frame, a plurality of wheels or track members, one or more side doors forming a milling chamber, a first rotor positioned within the milling chamber, and a second rotor positioned to the rear of the first rotor. The first rotor may be rotatably coupled to the frame. The second rotor may be rotatably positioned within the milling chamber. The second rotor may be laterally movable within the milling chamber via a supporting hydraulic cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side schematic view of an exemplary machine. 
         FIG.  2    is an enlarged view of a rotor chamber of the machine of  FIG.  1   , including first and second rotors. 
         FIG.  3    is a bottom view of the rotor chamber of the machine of  FIG.  1   , including the first and second rotors. 
     
    
    
     DETAILED DESCRIPTION 
     Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. 
     For the purpose of this disclosure, the term “ground surface” is broadly used to refer to all types of surfaces that form typical roadways (e.g., asphalt, cement, clay, sand, dirt, etc.) or can be milled in the removal or formation of roadways. In this disclosure, relative terms, such as, for example, “about,” “substantially,” and “approximately” are used to indicate a possible variation of ±10% in a stated value. Although the current disclosure is described with reference to a milling machine, this is only exemplary. In general, the current disclosure can be applied as to any machine, such as, for example, a cold planer, reclaimer, or another milling-type machine. 
       FIG.  1    illustrates a perspective view of an exemplary milling machine  10 , according to the present disclosure. Machine  10  includes a frame  12  and a milling system or a milling assembly  14  positioned on the underside of frame  12 . Milling assembly  14  may be integrally formed with frame  12  or may be otherwise coupled to machine  10 . Machine  10  also may include a conveyor assembly  16  configured to advance the milled material from milling assembly  14  away from the ground surface, for example, to be deposited into a bed of a truck. Machine  10  includes a plurality of wheels or track members  18 , which may be coupled to frame  12  via a plurality of adjustable supports, for example, hydraulic cylinders  20 . The movement and/or position of hydraulic cylinders  20  may control the height of frame  12  and milling assembly  14  from the ground surface. The movement and/or position of hydraulic cylinders  20  may depend on the movement and pressure of hydraulic fluid, within hydraulic cylinders  20 , as is known to one having skill in the art. In some aspects, machine  10  also includes a moldboard  22  positioned to the rear of milling assembly  14  via a moldboard support structure  24 . As discussed in detail below, milling assembly  14  includes a forward or first rotor  26  and a rear or second rotor  28 . First rotor  26  may be rotatably coupled to frame  12 , for example, via one or more support arms or mounting structures (not shown). Second rotor  28  may be rotatably coupled to moldboard  22  via one or more coupling elements  40  ( FIG.  2   ), or otherwise coupled to frame  12 . For example, second rotor  28  may be slidable relative to moldboard  22 , for example, to slide in and/or out of the milling chamber. Alternatively or additionally, second rotor  28  may be coupled to frame  12  via a hook-on and/or quick mount coupling. 
     First rotor  26  and second rotor  28  may rotate in the same direction, for example, counter-clockwise in  FIGS.  1  and  2   , to mill the ground surface. Alternatively, first rotor  26  may rotate in a first direction, for example, counter-clockwise in  FIGS.  1  and  2   , to mill the ground surface, and second rotor  28  may rotate in a second, different direction, for example, clockwise in  FIGS.  1  and  2   , to mill the ground surface. Second rotor  28  may be smaller than first rotor  26 , for example, in diameter. In this aspect, second rotor  28  may be lighter and/or more easily carried or otherwise manipulated than first rotor  26 . In another aspect, second rotor  28  may be substantially the same size (e.g., in diameter) as first rotor  26 . In either of these aspects, first rotor  26  and second rotor  28  may each be positioned substantially horizontal (i.e., parallel to a lateral axis of frame  12  of machine  10 ), and may thus be positioned parallel to each other. In some aspects, second rotor  28  may be positioned at or below a milling depth of first rotor  26 , for example, to cut at a lower plane than first rotor  26  (e.g., by a height H, as shown in  FIG.  2   ). Furthermore, second rotor  28  may be shorter (e.g., in a lateral width) than first rotor  26 . Alternatively or additionally, second rotor  28  may be formed by two or more rotor sections, for example, with one or more support elements connecting and/or supporting the rotor sections. In one or more aspects, second rotor  28  may have a different cutting bit spacing, or pitch, than first rotor  26 . In one or aspects, a scraper blade (not shown) may be positioned between first rotor  26  and second rotor  28 , for example, to help direct milled material toward conveyor assembly  16  and/or to help prevent milled material from impacting and/or impairing the milling of second rotor  28 . With a scraper blade positioned between first rotor  26  and second rotor  28 , second rotor  28  may rotate in an opposite direction as first rotor  26 . Furthermore, machine  10  may include a controller  102  and one or more user interfaces  104 , for example, positioned at one or more operation stations on machine  10  and/or remote from machine  10 . Controller  102  and/or user interface  104  may help control various aspects of machine  10 , including milling assembly  14 . 
     It is noted that milling assembly  14  may include side doors  30  on each side portion of milling assembly  14 . However,  FIGS.  1 - 3    only illustrate one side door  30  in order to illustrate features of milling assembly  14 . Moldboard  22 , side doors  30 , and a front door  31  ( FIG.  2   ) form a milling chamber and enclose milling assembly  14 , including first rotor  26  and second rotor  28 , such that milling assembly  14  may engage and mill the ground surface. Each side door  30  may be movably coupled to frame  12  via at least one side hydraulic cylinder  32 , for example, in order to raise side door  30  to inspect or repair milling assembly  14  and/or the internal drum assembly. Front door  31  may extend parallel to a rotational axis of first rotor  26 , and a position of front door  31  may also be adjustably controlled via a hydraulic cylinder. The front door may float on the ground surface ahead of milling assembly  14 . The front door may also be movable, for example, to access first rotor  26  for repair, replacement, inspection, etc. 
     In some aspects, moldboard  22  may help milling assembly  14  to remove the ground surface by removing any loose aggregate or debris that has not been captured by the milling drum assembly. Moldboard  22  may help to push the loose aggregate back toward the milling drum assembly, which may then urge the aggregate to conveyor assembly  16 . Removing the loose aggregate may help yield a clean and smooth milled surface behind machine  10 , which may then be more easily resurfaced. In order to help urge any loose aggregate toward the milling drum assembly, although not shown, moldboard  22  may also include an angled interior surface and/or nozzles to dispense fluid. As discussed in greater detail below, moldboard support structure  24  connecting moldboard  22  to machine  10  may help increase the range and/or degree of freedom of motion of moldboard  22  to accurately traverse the ground surface. 
     Moldboard  22  may be mounted to a rear portion of machine  10  via moldboard support structure  24 . As shown in  FIG.  2   , moldboard support structure  24  includes a rear hydraulic cylinder  34 . Rear hydraulic cylinder  34  may include a piston rod  36  movable within and extending from a piston barrel  38 . The movement and position of piston rod  36  relative to piston barrel  38  may depend on the movement and pressure of hydraulic fluid, as is known to one having skill in the art. Although not shown, moldboard support structure  24  may include a trunnion mount, which may be coupled to piston barrel  38  in order to couple rear hydraulic cylinder  34  to milling assembly  14  or to frame  12 . The trunnion mount may allow rear hydraulic cylinder  34  to pivot in one or more directions. Additionally, moldboard  22  may include a scraper blade  22 A, for example, to engage with the milled ground surface. Scraper blade  22 A may help to smooth the ground surface and/or to direct milled material toward conveyor assembly  16 . 
     In one or more aspects, second rotor  28  may be mounted to moldboard  22 , for example, to a bottom portion  22 B of moldboard  22 . As shown in  FIG.  2   , second rotor  28  may be mounted to moldboard  22  via one or more coupling elements  40 . Coupling element(s)  40  may fixedly couple second rotor  28  to moldboard  22 , with moldboard  22  being vertically movable. Alternatively, coupling element(s)  40  may be movable (e.g., pivotable swing arms), to allow for adjustment of the vertical position of second rotor  28  relative to moldboard  22 . In these aspects, movement (e.g., vertical movement) of moldboard  22  relative to frame  12  may adjust a position of second rotor  28 , for example, relative to frame  12  and first rotor  26 . As discussed below and as shown in  FIG.  3   , second rotor  28  may be movable (e.g., laterally movable) relative to moldboard  22  and/or to frame  12  via movement of a supporting hydraulic cylinder  42 . For example, supporting hydraulic cylinder  42  may include a rod that is movable relative to a barrel, such that movement of the rod relative to the barrel may control a lateral position of second rotor  28  relative to frame  12  and/or first rotor  26 . For example, second rotor  28  may be movable via hydraulic cylinder  42 , and hydraulic cylinder  42  may be attached to a linkage arm set (not shown). Hydraulic cylinder  42  may be positioned within the milling chamber. In another aspect, at least a portion of hydraulic cylinder  42  may extend partially outside of the milling chamber with one or more rods and/or linkages that extend into the milling chamber and attach to one or more portions of second rotor  28 . Although not shown, second rotor  28  may alternatively be rotatably coupled to one or more other components of the milling chamber and/or frame  12 . In this aspect, second rotor  28  may be rotatably coupled to a separate adjustable support structure positioned within the milling chamber and/or otherwise coupled to the milling chamber and/or the frame. The movement of moldboard  22  and/or second rotor  28  may be controlled by controller  102  and/or user interface(s)  104 . In one or more aspects, second rotor  28  may be rotatable via a hydraulic motor that is coupled to (e.g., directly coupled to) a drive axis of second rotor  28 . In another aspect, second rotor  28  may be rotatable via a hydraulic motor positioned in a gear box and/or chaincase external to the milling chamber. Furthermore, in another aspect, second rotor  28  may be driven by a coupling to first rotor  26 , for example, via a chaincase, gearbox, clutch mechanism, etc., such that second rotor  28  is driven by the same power source (e.g., engine and/or drive mechanism) that drives first rotor  26 . In this aspect, second rotor  28  may be driven as a different rotational speed, power, torque, etc. than first rotor  26 , for example, via a gearbox and/or clutch set. 
     In these aspects, second rotor  28  may include a second rotor pitch, for example, formed by cutting assemblies  28 A mounted on a second rotor drum  28 B. The second rotor pitch may be the same as or similar to a first rotor pitch, for example, formed by cutting assemblies  26 A on a first rotor drum  26 B. The pitch of second rotor  28  may be the same as the pitch of first rotor  26 , such that first rotor  26  and second rotor  28  have the same spacings of respective cutting assemblies. However, lateral movement of second rotor  28 , for example, via supporting hydraulic cylinder  42 , may adjust the position of the cutting elements on second rotor  28  relative to the cutting elements on first rotor  26 , for example, to a shifted position shown as second rotor  28 ′ in  FIG.  3   . In these aspects, positioning second rotor  28  in alignment with first rotor  26  may form a first surface finish on the ground surface, and positioning second rotor  28  out of alignment with first rotor  26  (e.g., off-center) may form a second surface finish on the ground surface, for example, smoother than the first surface finish. Alternatively or additionally, second rotor  28  may include a smaller or finer pitch, such that second cutting assemblies  28 A may be positioned closer together than the spacing of first cutting assemblies  26 A on first rotor  26 . In these aspects, second rotor  28  may form a smoother surface finish on the ground surface than first rotor  26 . 
     In one or more aspects, controller  102  and/or user interface(s)  104  may help to control a position of second rotor  28 , for example, relative to frame  12  and/or first rotor  26 . Controller  102  and/or user interface(s)  104  may also help to control a position of first rotor  26 , for example, by controlling one or more of hydraulic cylinders  20  that couple frame  12  to track members  18 . Additionally, controller  102  and user interface  104  may help to control one or more additional aspects of machine  10 , for example, a speed of conveyor assembly  16 , a speed of machine  10  (e.g., via speed(s) of track members  18 ), a height of frame  12  and/or milling assembly  14  (e.g., via hydraulic cylinders  20 ), etc. In these aspects, controller  102  and user interface  104  may be coupled (e.g., wired or wirelessly). Additionally, although not shown, controller  102  may be coupled to (e.g., through a wired or wireless connection) one or more sensors, one or more controllers, and/or one or more actuators on machine  10 . For example, controller  102  may be coupled to one or more sensors, one or more controllers, and/or one or more actuators for track members  18 , hydraulic cylinders  20 , first rotor  26 , second rotor  28 , side hydraulic cylinder  32 , rear hydraulic cylinder  34 , supporting hydraulic cylinder  42 , etc. 
       FIGS.  2  and  3    illustrate milling assembly  14 , including first rotor  26  and second rotor  28 . As shown, first rotor  26  includes a plurality of first cutting assemblies  26 A mounted on a first rotor drum  26 B. As shown in  FIG.  3   , first cutting assemblies  26 A may be arranged in a spiral pattern on first rotor drum  26 B. Similarly, second rotor  28  includes a plurality of second cutting assemblies  28 A mounted on second rotor drum  28 B, and second cutting assemblies  28 A may be arranged in a spiral pattern on second rotor drum  28 B. In one or more aspects, and as shown in  FIGS.  2  and  3   , second cutting assemblies  28 A may be smaller than first cutting assemblies  26 A. In another aspect, second cutting assemblies  28 A may be closer together (i.e., have a smaller pitch) than first cutting assemblies  26 A. First cutting assemblies  26 A and second cutting assemblies  28 A may include different materials or other characteristics. As shown in  FIG.  3   , first rotor  26  may include one or more first material deflectors  26 C, and second rotor  28  may include one or more second material deflectors  28 C. First material deflector(s)  26 C and second material deflector(s)  28 C may be positioned in laterally central positions of first rotor  26  and second rotor  28 , respectively, and may help to directed milled material, for example, toward conveyor assembly  16 . Furthermore, in one or more aspects, each of first cutting assemblies  26 A and second cutting assemblies  28 A may each include one or more of a rotor standoff, a drum block, a tool block or a base block, a tool holder, and a cutting tool. The cutting tools may be replaceable, for example, as the cutting bits may wear down during milling procedures. Additionally, one or more other components of first cutting assemblies  26 A and second cutting assemblies  28 A may also be replaceable. In one or more aspects, second cutting assemblies  28 A may have different material properties than first cutting assemblies  26 A. For example, second cutting assemblies  28 A may be harder than first cutting assemblies  26 A. In this aspect, second cutting assemblies  28 A may be formed of a diamond-like material, and first cutting assemblies  26 A may be formed of a steel or other appropriate metallic material. 
     As mentioned above, second rotor  28  may be separately controllable from first rotor  26 . For example, first rotor  26  may be coupled to a first rotor drive (not shown) in order to drive the rotation of first rotor drum  26 B, and second rotor  28  may be coupled to a second rotor drive (not shown) in order to drive the rotation of second rotor drum  28 B. In these aspects, first rotor  26  and second rotor  28  may rotate at different rates. Additionally, one or more of first rotor  26  or second rotor  28  may rotate to mill the ground surface, while the other of first rotor  26  or second rotor  28  may be stationary. Alternatively or additionally, first rotor  26  and second rotor  28  may rotate at different rotational speeds, with different powers or torques, other otherwise with different characteristics. For example, second rotor  28  may rotate at a greater speed than first rotor  26 , but with less power or torque. 
     As mentioned above, second rotor  28  may be mounted to or otherwise coupled to moldboard  22 . For example, as shown in  FIG.  2   , coupling element(s)  40  may couple second rotor  28  to moldboard  22 . In one or more aspect, although not shown, milling assembly  14  may include left and right coupling elements to rotatably couple second rotor  28  to moldboard  22 . In these aspects, adjusting a height of moldboard  22  may adjust the vertical position of second rotor  28 . For example, moldboard  22  may be lowered via rear hydraulic cylinder  34  (e.g., extending piston rod  36  relative to piston barrel  38 ). In this aspect, lowering moldboard  22  also lowers second rotor  28 . For example, first rotor  26  may be fixedly coupled to frame  12 , and hydraulic cylinders  20  may control the position of frame  12 , and thus the position of first rotor  26 . Then, rear hydraulic cylinder  34  may control the position of moldboard  22 , and thus second rotor  28 , relative to frame  12 . In these aspects, moldboard  22  may be positioned such that second rotor  28  is positioned at the same height as first rotor  26 , as shown in  FIG.  2   . Moreover, moldboard  22  may be lowered such that second rotor  28  is positioned at a height lower than first rotor  26 , for example, by a height H below a cutting plane formed by first rotor  26 . Alternatively, although not shown, second rotor  28  may be mounted to or otherwise coupled to one or more elements of frame  12  or milling assembly  14 , for example, via an adjustable support structure, such that the vertical position of second rotor  28  may be adjustable. 
     In these aspects, first rotor  26  may cut the ground surface to a first depth, and then second rotor  28  may follow behind first rotor  26  and cut the ground surface to a second depth, for example, with the second depth being deeper than the first depth by height H. Furthermore, the cut in the ground surface formed by first rotor  26  may be greater than height H, such that first rotor  26  cuts a greater depth or amount of ground surface material than second rotor  28 . In these aspects, second rotor  28  may be a finishing rotor, for example, forming a smoother surface finish than first rotor  26 . Additionally, the position of first rotor  26  (i.e., via frame  12  and hydraulic cylinders  20 ) and/or the position of second rotor  28  (i.e., via moldboard  22  and rear hydraulic cylinder  34 ) may be controlled by one or more of controller  102  and/or user interface  104 . Alternatively, in one aspect, second rotor  28  may be positioned at a fixed position relative to first rotor  26 , for example, at height H below the cutting plane formed by first rotor  26 . 
     As shown in  FIG.  3   , second rotor  28  may be mounted on supporting hydraulic cylinder  42 . Supporting hydraulic cylinder  42  may control a lateral position of second rotor  28  relative to frame  12  and/or first rotor  26 . In these aspects, the lateral position of second rotor  28  may affect the surface finish on the ground surface formed by machine  10  and milling assembly  14 . As discussed above, in some aspects, second cutting assemblies  28 A of second rotor  28  may be substantially aligned with first cutting assemblies  26 A of first rotor  26 . In this configuration, milling assembly  14  may form a first surface finish on the ground surface. Furthermore, supporting hydraulic cylinder  42  may adjust (i.e., laterally sideshift left or right in direction A) second rotor  28  such that second cutting assemblies  28 A are no longer aligned with first cutting assemblies  26 A. In this configuration, milling assembly  14  may form a second surface finish on the ground surface. In some aspects, the second surface finish may be smoother than the first surface finish. In one or more aspects, the configuration of supporting hydraulic cylinder  42 , and thus second rotor  28 , may be continuously activated, moved, driven, or otherwise adjusted (e.g., side-shifting or oscillating left and right). In this aspect, supporting hydraulic cylinder  42 , and thus second rotor  28 , may be continuously adjusted between a left-most position and a right-most position (e.g., relative to frame  12  of machine  10 ). Continuously oscillating or side-shifting supporting hydraulic cylinder  42  and thus second rotor  28  may form another surface finished on the ground surface, for example, smoother than the first surface finish and/or the second surface finish. Moreover, in some aspects, the lateral position of second rotor  28  (i.e., via supporting hydraulic cylinder  42 ) may be controlled by one or more of controller  102  and/or user interface  104 . 
     As mentioned, moldboard  22  is coupled to frame  12  via moldboard support structure  24 . In these aspects, moldboard  22  may be lifted, for example, away from the ground surface, by retracting piston rod  36  relative to piston barrel  38 . Lifting moldboard  22  may provide for access to second rotor  28 , for example, to repair, replace, or otherwise inspect various portions of second rotor  28 . For example, an operator may clean second rotor  28 , repair one or more cutting assemblies  28 A, replace one or more cutting assemblies  28 A, replaced second rotor  28  (e.g., by uncoupling second rotor  28  from coupling element  40  and/or supporting hydraulic cylinder  42 ), or otherwise access second rotor  28 . In one aspect, the operator may adjust the configuration of one or more cutting assemblies  28 A, for example, by adjusting an orientation of one or more cutting bits, to modify the pitch of second rotor  28 , which may modify the surface finish on the ground surface milled by machine  10 . In another aspect, the operator may replace second rotor  28  with another second rotor. The another second rotor may be the same as second rotor  28 , for example, if second rotor  28  was in need of significant repairs, cleaning, and/or replacement. Alternatively, the another second rotor may have a different size (i.e., a larger drum), a different pitch of cutting assemblies, a different size of cutting assemblies, or one or other different characteristics. In these aspects, machine  10  and milling assembly  14  may form a different surface finish on the ground surface with the another second rotor. 
     INDUSTRIAL APPLICABILITY 
     The disclosed aspects of machine  10  may be used in any milling machine to assist in removal of the milled material, while allowing for variations in milling depth, variations in the surface finish produced by machine, access to the milling chamber, etc. As mentioned above, second rotor  28  may be positioned to the rear of first rotor  26 , so that first rotor  26  may perform a bulk of the milling procedure performed by milling assembly  14 . Second rotor  28  may be smaller, have a different pitch of cutting assemblies  28 A, move laterally within the milling chamber, rotate faster, or otherwise operate to perform secondary milling and to form a smoother surface finish than first rotor  26 . Additionally or alternatively, second rotor  28  may be selectively activated. In this aspect, second rotor  28  may be selectively driven to rotate such that second rotor  28  engages and mills the ground surface, for example, to leave a surface finish that is smoother than the surface finish formed by first rotor  26 , to mill the ground surface to a greater depth than first rotor  26  (e.g., by height H), etc. Moreover, second rotor  28  may be selectively activated, moved, driven, or otherwise adjusted between a left-most position and a right-most position (e.g., side-shifted or oscillated). Furthermore, some milling procedures may not require a smoother surface finish. In such instances, second rotor  28  may be positioned above the cutting plane of first rotor  26 , such that second rotor  28  is not actively engaged in milling the ground surface, preserving and/or extending the working life of second rotor  28  and its cutting assemblies  28 A for other milling procedures. As mentioned, the position(s) of second rotor  28  (and thus the resulting surface finish on the ground surface) may be controlled by controller  102  and/or one or more user interfaces  104 . In these aspects, second rotor  28  may allow an operator to adjust a surface finish produced by machine  10  without adjusting first rotor  26 , improving the efficiency, efficacy, and/or production of milling assembly  14  and machine  10 . 
     Second cutting assemblies  28 A may be formed of a harder material (i.e., a cutting bit) than first cutting assemblies  26 A. As second rotor  28  is milling an already milled surface and/or a smaller depth of material, second cutting assemblies  28 A may wear at a lower rate than first cutting assemblies  26 A. Additionally, second rotor  28  may be coupled to moldboard  22 , for example, via coupling element  40 , or otherwise positioned adjacent to or near moldboard  22  ( FIGS.  1 - 3   ). As such, raising moldboard  22  may provide access to second rotor  28 , for example, to repair, replace, or otherwise inspect various portions of second rotor  28 . As mentioned, an operator may clean second rotor  28 , repair one or more of second cutting assemblies  28 A, replace one or more of second cutting assemblies  28 A, replace second rotor  28  (e.g., by uncoupling second rotor  28  from coupling element  40  and/or supporting hydraulic cylinder  42 ), or otherwise access second rotor  28 . 
     Additionally, second rotor  28  may be smaller and/or lighter than first rotor  26 , for example, allowing for second rotor  28  to be more easily manipulated and/or replaced than first rotor  26 . In this aspect second rotor  28  may be replaced when damaged. Alternatively or additionally, second rotor  28  may be exchanged for a different second rotor  28 , for example, with a different pitch, hardness, or one or more other characteristics of second cutting assemblies  28 A, which may provide a different surface finish on the ground surface. In another aspect, the operator may access second rotor  28  to adjust one or more characteristics of second rotor  28 , for example, adjusting an arrangement of cutting bits on cutting assemblies  28 A, replacing the cutting bits with different (i.e., harder, wider, etc.) cutting bits, etc. For example, a method may include performing a first milling procedure with a first second rotor  28  to form a first surface finish on the milled ground surface. The method may then include accessing the milling chamber and removing the first second rotor  28 . The method may then include coupling another second rotor  28  to milling assembly  14  (e.g., to moldboard  22 ), with the another second rotor  28  having one or more different milling properties than the first second rotor  28 . Alternatively, the method may include modifying one or more characteristics of the first second rotor  28  to change the milling properties. Then, the method may include performing another milling procedure, with the changed milling properties forming a second surface finish on the milled ground surface. Furthermore, in some aspects, second rotor  28  may help to protect moldboard  22 , for example, from larger pieces of milled material impacting or otherwise damaging moldboard  22 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed machine without departing from the scope of the disclosure. Other embodiments of the machine will be apparent to those skilled in the art from consideration of the specification and practice of the milling devices, systems, and methods disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.