Abstract:
A system and methods for precision marking are disclosed. A spring-loaded mechanical marking tool comprising an optical retro-reflector is operable to interface with a metrology system to expedite determination of a desired feature location. The tool simplifies user operation of metrology targeting devices, and reduces or eliminates process non-conformance, potential surface damage and miss-location.

Description:
FIELD 
     Embodiments of the present disclosure relate generally to manufacturing assembly, and more particularly relate to manufacturing assembly metrology. 
     BACKGROUND 
     In manufacturing assembly, contours and locations of components, tooling, and machining should be accurately measured and positioned to match assembly specifications. Laser trackers are a particularly accurate method of measuring a position, and are often used in portable measurement systems. 
     A laser tracker generally operates by measuring a time for a laser beam to make a round trip from a reflector device. The reflector device is generally a retro-reflector, which is a device that reflects a light ray back in a direction of a source of the light ray. In other words, the light ray is reflected back along a vector that is parallel to but opposite in direction from the source of the light ray. A laser tracker can measure a distance and a direction to the retro-reflector. In this manner, the laser tracker can measure a location of the retro-reflector relative to the laser tracker. 
     For manufacturing assembly, a retro-reflector is positioned on an assembly component and a measured position/location is adjusted to match assembly specifications. When the measured position matches the assembly specifications to a sufficient accuracy, a mark such as a small dent is used to mark the location. The location can then be used in assembly by drilling, machining, fastening to another part, and the like. 
     Retro-reflectors are generally mounted in a spherical housing often referred to as a spherically mounted retro-reflector (SMR). The SMR may be mounted on a stable holder often referred to as an SMR nest. Existing processes for precision positioning of an existing SMR nest often require multiple technicians to perform the process. While one technician holds the existing SMR nest in a desired location, another technician inserts a duplicating punch into the existing SMR nest, and strikes the duplicating punch with a hammer marking the location with a small indentation. In addition to potentially damaging or leaving a permanent mark on the surface being worked, the existing process can also result in miss-located holes or parts. The existing process may also be very inefficient because of a need for additional labor and the associated labor cost. 
     Thus, there is a need for an SMR nest that can be efficiently used by a single operator, and does not cause damage or leave a permanent mark on the surface being worked. 
     SUMMARY 
     A system and methods for precision marking are disclosed. A spring-loaded mechanical marking tool (Center Marking Nest) comprising an optical retro-reflector is operable to interface with a metrology system to expedite determination of a desired feature location. The spring-loaded mechanical marking tool simplifies user operation of metrology targeting devices, and reduces or eliminates process non-conformance, potential surface damage and miss-location. 
     A first embodiment comprises a metrology system. The metrology system comprises a base member operable to slide over a surface, and a plunger coupled to the base member and operable to move in relation to the base member. The metrology system also comprises a location marking device coupled to the plunger. The metrology system further comprises a magnetic ring operable to hold a retro-reflector, and a magnetic ring retainer operable to couple the magnetic ring to the plunger. The metrology system also comprises a spring coupled to the plunger and operable to elevate the location marking device away from the surface. 
     A second embodiment comprises a method for using a metrology system. The method comprises measuring a distance from a tracker device to a retro-reflector based on a reflection of a light beam. The method also comprises determining a position of a spring-loaded mechanical marking tool based on the distance and a direction of the retro-reflector, and recognizing the position is substantially a desired mark location. The method further comprises depressing a plunger of the spring-loaded mechanical marking tool comprising a location marking device. The method also comprises marking the desired mark location using the location marking device in response to depressing the plunger. 
     A third embodiment comprises a method of fabricating a spring-loaded mechanical marking tool. The method comprises providing a base member operable to slide over a surface. The method further comprises providing a plunger operable to couple to the base member and a location marking device. The plunger is also operable to move in relation to the base member. The method further comprises providing a magnetic ring operable to hold a retro-reflector, and providing a magnetic ring retainer operable to couple the magnetic ring to the plunger. The method also comprises providing a spring coupled to the plunger and operable to elevate the location marking device away from the surface. The method also comprises assembling the base member, the plunger, the magnetic ring, the magnetic ring retainer, and the spring, and accurately aligning the base member, the plunger, the magnetic ring, the magnetic ring retainer, and the spring. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure are hereinafter described in conjunction with the following figures, wherein like numerals denote like elements. The figures are provided for illustration and depict exemplary embodiments of the disclosure. The figures are provided to facilitate understanding of the disclosure without limiting the breadth, scope, scale, or applicability of the disclosure. The drawings are not necessarily made to scale. 
         FIG. 1  is an illustration of a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure. 
         FIG. 2  is an illustration of a portion of the spring-loaded mechanical marking tool of  FIG. 1  showing a location marking device according to an embodiment of the disclosure. 
         FIG. 3  is an illustration of an exemplary operation environment of a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure. 
         FIG. 4  is an illustration of a system comprising a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure. 
         FIG. 5  is an illustration of a calibration method of a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure. 
         FIG. 6  is an illustration of a display readout of a control system for a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure showing the mechanical marking tool in an out-of-position state. 
         FIG. 7  is an illustration of a display readout of a control system for a spring-loaded mechanical marking tool comprising an optical retro-reflector according to an embodiment of the disclosure showing the mechanical marking tool in an in-position state. 
         FIG. 8  is an illustration of a flow diagram showing an exemplary process for using a spring-loaded mechanical marking tool in a metrology system according to an embodiment of the disclosure. 
         FIG. 9  is an illustration of a component breakdown of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
         FIG. 10  is an illustration of a plunger assembly of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
         FIG. 11  is an illustration of a base member of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
         FIG. 12  is an illustration of a magnetic ring retainer of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
         FIG. 13  is an illustration of a magnetic ring of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
         FIGS. 14-15  is an illustration a flow diagram showing an exemplary process for fabricating a spring-loaded mechanical marking tool according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following detailed description is exemplary in nature and is not intended to limit the disclosure or the application and uses of the embodiments of the disclosure. Descriptions of specific devices, techniques, and applications are provided only as examples. Modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the disclosure. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding field, background, summary or the following detailed description. The present disclosure should be accorded scope consistent with the claims, and not limited to the examples described and shown herein. 
     Embodiments of the disclosure may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For the sake of brevity, conventional techniques and components related to laser technology, metrology, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail herein. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with manufacturing and assembly of a variety of different aircraft structures, ship structures, automotive structures, electrical systems, buildings, and the like. Those skilled in the art will also appreciate that the system described herein is merely one example embodiment of the disclosure. 
     Embodiments of the disclosure are described herein in the context of a practical non-limiting application, namely, a manufacturing assembly. Embodiments of the disclosure, however, are not limited to such assembly applications, and the techniques described herein may also be utilized in other applications. For example, embodiments may be applicable to home building, construction, welding, automotive manufacturing, ship building, and the like. 
     As would be apparent to one of ordinary skill in the art after reading this description, the following are examples and embodiments of the disclosure are not limited to operating in accordance with these examples. Other embodiments may be utilized and structural changes may be made without departing from the scope of the exemplary embodiments of the present disclosure. 
     A spherically mounted retro-reflector (SMR) is often mounted on a stable holder often referred to as a nest. Embodiments of the disclosure comprise a spring-loaded mechanical marking tool operable to mark a center point (center mark) on a surface. The spring-loaded mechanical marking tool (center marking nest) is operable for precision location of the center mark on the surface. 
       FIG. 1  is an illustration of a spring-loaded mechanical marking tool  100  comprising an optical retro-reflector according to an embodiment of the disclosure. The spring-loaded mechanical marking tool  100  comprises an SMR  102 , a magnetic ring  104 , a plunger  106 , a spring  108 , a base member  110 , and a location marking device  202  ( FIG. 2 ). 
     The SMR  102  (optical retro-reflector  102 ) comprises at least one optical retro-reflector housed in a spherical hollow ball  114  comprising an optical opening  116  in the spherical hollow ball  114 . A laser light from a source can enter the spherical hollow ball  114  through the optical opening  116  such that the optical retro-reflector  102  can be reflected back along an incident angle to the source. The spherical hollow ball  114  may comprise, for example but without limitation, steel or another magnetic material. The optical opening  116  may be surrounded by a cover (not shown) configured to reduce or eliminate glare and protect the optical retro-reflector  102 . 
     The magnetic ring  104  is operable to hold the optical retro-reflector  102 . The magnetic ring  104  comprises a magnetic material, for example but without limitation, samarium-cobalt magnets, neodymium-iron-boron magnets, and the like. 
     The plunger  106  is coupled to the magnetic ring  104  by a magnetic ring retainer (not shown in  FIG. 1 , see  FIG. 9 ) and coupled to the base member  110 . The plunger  106  is operable to move in relation to the base member  110  by, for example but without limitation, sliding in a lubricated sleeve (e.g., the outer component  918  in  FIG. 9 ). The plunger  106  is also operable for coupling to a location marking device such as the location marking device  202  ( FIG. 2 ). 
     The spring  108  is coupled to the plunger  106  and the base member  110 , and is operable to elevate the location marking device  202  ( FIG. 2 ) away from an assembly object surface  112 . 
     The base member  110  is coupled to the plunger  106  and shaped to hold the plunger  106  substantially perpendicular to the assembly object surface  112 . The base member  110  is also operable to slide over the assembly object surface  112 , and to provide a solid structural support for the plunger  106  to press the location marking device  202  ( FIG. 2 ) on to the assembly object surface  112 . 
     The assembly object surface  112  may comprise, for example but without limitation, metal, composite, ceramic, ceramic metal composite, plastic, glass, wood, rock, fabric, paper, and the like. 
       FIG. 2  is an illustration of a portion of the spring-loaded mechanical marking tool of  FIG. 1  showing the location marking device  202  according to an embodiment of the disclosure. The location marking device  202  is coupled to the plunger  106  and operable to be pressed on to the assembly object surface  112  to mark a location. According to various embodiments of the disclosure, the location marking device  202  may comprise any type of marking device operable to mark a location on the assembly object surface  112 . For example but without limitation, the location marking device  202  may comprise a stamp, a heated imprinting or branding device, a thermal printing device, an ink-jet, a laser scribing device, a paint gun, a chalk stick, an ink pen, and the like. 
     The stamp may comprise, for example but without limitation, rubber, metal, plastic, wood, and the like. The stamp may be mounted on a ridged material, such as but without limitation, steel, plastic, acrylic, and the like. An image or pattern (e.g., colored, gray scale, etc.) may be formed on the stamp by, for example but without limitation, carving, molding, laser engraving, vulcanization onto rubber, and the like. A type of ink may be applied to the image or pattern formed on the stamp to create a mark on the assembly object surface  112 . The ink may be made of, for example but without limitation, dye, pigment, or the like. Alternatively, a liquid wax or paint may be used instead of ink. The stamp can be pressed by the plunger  106  onto the assembly object surface  112  such that the mark is transferred to the assembly object surface  112 . 
     Alternatively, the mark may be provided by the assembly object surface  112 . For example but without limitation, the assembly object surface  112  may be operable to change color in response to an applied pressure from the stamp to mark the assembly object surface  112 . For example but without limitation, the assembly object surface  112  may be coated with a pressure reactive paint, and the like. 
     Alternatively, the mark may be provided by an intermediate material (not shown) located between the location marking device  202  and the assembly object surface  112 . Applied pressure from the stamp to the assembly object surface  112  can transfer the mark from the intermediate material to the assembly object surface  112 . The intermediate material may comprise, for example but without limitation, carbon paper, and the like. 
     In the embodiments where the location marking device  202  comprises the heated imprinting (branding) device or the thermal printing device, the assembly object surface  112  may be operable to change color in response to receiving thermal heat. In this manner, the assembly object surface  112  may be operable to change color to create a mark on the assembly object surface  112  in response to applied heat from the location marking device  202 . For example but without limitation, the assembly object surface  112  may be coated with a thermally reactive paint, and the like. Alternatively, the mark may be provided by an intermediate material (not shown) located between the location marking device  202  and the assembly object surface  112 . In this manner, the applied heat from the location marking device  202  to the assembly object surface  112  can create a mark on the assembly object surface  112  by transferring the mark from the intermediate material. The intermediate material may comprise, for example but without limitation, thermal printing paper, and the like. 
       FIG. 3  is an illustration of an exemplary operation environment  300  of a spring-loaded mechanical marking tool  302  comprising an optical retro-reflector  314  according to an embodiment of the disclosure. The spring-loaded mechanical marking tool  302  is positioned on a test object  304  comprising a contoured surface  306 . The spring-loaded mechanical marking tool  302  may be manually slid over the test object  304  to mark locations for assembly activities, such as but without limitation, hole drilling, welding, machining, and the like. The test object  304  is located on a test bench  308 , and a laser tracker  310  directs a laser beam  312  to the optical retro-reflector  314  of the spring-loaded mechanical marking tool  302 . 
       FIG. 4  is an illustration of a system  400  comprising a spring-loaded mechanical marking tool  402  comprising an optical retro-reflector ( 102  in  FIG. 1 ) according to an embodiment of the disclosure. The system  400  may also comprise a laser tracker  404 , a laser tracker controller  406 , a computer  408 , and a display  410 . 
     The system  400  may comprise any number of communication modules, any number of network communication modules, any number of processor modules, and any number of memory modules. The illustrated system  400  depicts a simple embodiment for ease of description. Those skilled in the art will understand that the various illustrative blocks, modules, circuits, and processing logic described in connection with the embodiments disclosed herein may be implemented in hardware, computer-readable software, firmware, or any practical combination thereof. To clearly illustrate this interchangeability and compatibility of hardware, firmware, and software, various illustrative components, blocks, modules, circuits, and steps are described generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software depends upon the particular application and design constraints imposed on the overall system. Those familiar with the concepts described herein may implement such functionality in a suitable manner for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. 
     The laser tracker  404  is controlled by the laser tracker controller  406 , and is operable to determine a position location of the spring-loaded mechanical marking tool  402 . The laser tracker  404  operates by measuring a time for a round trip from the optical retro-reflector  102 . The optical retro-reflector  102  reflects a laser ray back in a direction of the laser tracker  404 , which is a source of the laser ray. Thus, the laser ray is reflected back along a vector that is parallel to but opposite in direction from the laser tracker  404 . The laser tracker  404  measures a distance and a direction to the optical retro-reflector  102 . In this manner, the laser tracker  404  can measure a location of the optical retro-reflector  102  relative to the laser tracker  404 . 
     The computer  408  is operable to display the position location of the spring-loaded mechanical marking tool  402  on the display  410 . The computer  408  may comprise a processor module  412 , and a memory module  414 . 
     The processor module  412  may be implemented, or realized, with a general purpose processor, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof, designed to perform the functions described herein. In this manner, a processor may be realized as a microprocessor, a controller, a microcontroller, a state machine, or the like. A processor may also be implemented as a combination of computing devices, e.g., a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other such configuration. The processor module  412  comprises processing logic that is configured to carry out the functions, techniques, and processing tasks associated with the operation of the laser tracker  404 . In particular, the processing logic is configured to create a mathematical model (model) of a contoured surface to be marked by the spring-loaded mechanical marking tool  402  and determine a location of mark position relative to a position of the optical retro-reflector  102 . The processor module  412  may also be suitably configured to calibrate the model to measured points on the contoured surface  304 . In practical embodiments the processing logic may be resident, for example but without limitation, in the laser tracker  404 , the laser tracker controller  406 , the computer  408 , and the like, and/or may be part of a network architecture that communicates with, for example but without limitation, the laser tracker  404 , laser tracker controller  406 , or the computer  408 , or be a standalone portable device. 
     Furthermore, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in firmware, in a software module executed by the processor module  412 , or in any practical combination thereof. A software module may reside in the memory module  414 , which may be realized as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In this regard, the memory module  414  may be coupled to the processor module  412  such that the processor module  412  can read information from, and write information to, memory module  414 . As an example, processor module  412 , and the memory module  414 , in their respective ASICs. The memory module  414  may also be integrated into the processor module  412 . In an embodiment, the memory module  412  may include a cache memory for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor module  412 . The memory module  414  may also include non-volatile memory for storing instructions to be executed by the processor module  412 . 
     The memory module  414  may comprise a mark location database (not shown) in accordance with an exemplary embodiment of the invention. The mark location database may be configured to store, maintain, and provide data as needed to support the functionality of system  400  in the manner described below. Moreover, mark location database may be a local database coupled to the processor  412 , or may be a remote database, for example, a central network database, and the like. The mark location database may be configured to maintain, for example but without limitation, mark locations, locations to be marked, track error, and the like. 
       FIG. 5  is an illustration of a calibration environment  500  of a spring-loaded mechanical marking tool  502  comprising an optical retro-reflector ( 314   FIG. 3 ) according to an embodiment of the disclosure. The calibration may be achieved by placing the spring-loaded mechanical marking tool  502  at each of three location points  506 / 508 / 510  on a contoured surface  504  and measuring a position of the retro-reflector  314  of the spring-loaded mechanical marking tool  502  at each of the three location points  506 / 508 / 510 . From a position at each of the three locations  506 / 508 / 510  a positioning of the contoured surface  504  may be estimated by the computer  408 . The computer  408  matches the three location points  506 / 508 / 510  to three model location points in the model in the computer  408  taking into account the distance from the optical retro-reflector  314  to the contoured surface  504 . The optical retro-reflector  314  is mounted on the spring-loaded mechanical marking tool  502  at a substantially perpendicular predetermined distance from the contoured surface  504 . 
       FIG. 6  is an illustration of a display readout  600  of a control system for a virtual spring-loaded mechanical marking tool  610  comprising an optical retro-reflector  606  according to an embodiment of the disclosure showing the virtual spring-loaded mechanical marking tool  610  in an out-of-position state. The display readout  600  may be displayed on a display screen such as the display  410 . The display readout  600  shows a list  602  of location coordinates X, Y, Z, and distance d of the spring-loaded mechanical marking tool  100  on the assembly object surface  112  relative to a desired mark location  612 . The distance d may be calculated by any of a variety of distance metrics such as a Euclidian distance, a p-norm, a maximum distance, and the like. The display readout  600  also shows visual distance indicators  604  on a visual representation  608  of the assembly object surface  112 . The visual distance indicators  604  represent distance from the desired mark location  612 . In response to an operator moving the spring-loaded mechanical marking tool  100  on the assembly object surface  112 , the virtual spring-loaded mechanical marking tool  610  moves on the display readout  600  to represent the movements, along with corresponding changes to the location coordinates X, Y, Z, and distance d listed in the list  602 . In this manner, the operator can position the spring-loaded mechanical marking tool  100  at the desired mark location  612  on the assembly object surface  112  with a high degree of accuracy. 
       FIG. 7  is an illustration of a display readout  700  of a control system for a virtual spring-loaded mechanical marking tool  710  comprising an optical retro-reflector  706  according to an embodiment of the disclosure showing the spring-loaded mechanical marking tool  710  in an in-position state. The display readout  700  may be displayed on a display screen such as the display  410  in response to an operator moving the spring-loaded mechanical marking tool  100  into the desired mark location  712  ( 612  in  FIG. 6 ) on a visual representation of a contoured surface  708 . The virtual spring-loaded mechanical marking tool  710  shows accuracy of the desired mark location  712  on the list  702 . The operator may then stamp the spring-loaded mechanical marking tool  100  to mark the desired mark location  712 . The desired mark location may be permanently left on the assembly object surface  112 . 
       FIG. 8  is an illustration a flow diagram showing an exemplary process  800  for using a spring-loaded mechanical marking tool in a metrology system according to an embodiment of the disclosure. The various tasks performed in connection with the process  800  may be performed by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of the process  800  may refer to elements mentioned above in connection with  FIGS. 1-7 . In practical embodiments, portions of the process  800  may be performed by different elements of the spring-loaded mechanical marking tool  100  such as the SMR  102 , the plunger  106 , the location marking device  202 , and the laser tracker  404 . Process  800  may have functions, material, and structures that are similar to the embodiments shown in  FIGS. 1-7 . Therefore common features, functions, and elements may not be redundantly described here. 
     Process  800  may begin by generating a light beam operable for measuring a distance from the laser tracker  404  (task  802 ). Process  800  may continue by directing the light beam in a direction to the SMR  102  coupled to the spring-loaded mechanical marking tool  100  (task  804 ). Process  800  may continue by automatically aligning a mirror in the laser tracker  404  to ensure an emitted light pathway for the light beam and a reflected beam pathway are the same path (task  806 ). Process  800  may continue by receiving a reflection of the light beam at the laser tracker  404  (task  808 ). Process  800  may continue by measuring the distance from the laser tracker  404  to the SMR  102  based on the reflection of the light beam (task  810 ). Process  800  may continue by determining a position of the spring-loaded mechanical marking tool  100  based on the distance and the direction (task  812 ). Process  800  may continue by recognizing the position is substantially a desired mark location (task  814 ). Process  800  may continue by depressing the plunger  106  of the mechanical marking tool  100  to mark the desired mark location (task  816 ) with the location marking device  202 . Process  800  may continue by elevating the location marking device  202  via the spring  106  coupled to the plunger  106  (task  818 ). 
       FIG. 9  is an illustration of a component breakdown of a spring-loaded mechanical marking tool  900  operable for mounting an optical retro-reflector according to an embodiment of the disclosure. The mechanical marking tool  900  comprises a magnetic ring  902 , a magnetic ring retainer  904 , a spring  906 , a plunger assembly  908 , a base member  910 , a location marking device  912 , and a plurality of surface sliders  914 . 
     The magnetic ring  902  is operable to hold the optical retro-reflector  102  ( FIG. 1 ). The magnetic ring  902  comprises a magnetic material, for example but without limitation, samarium-cobalt magnets, neodymium-iron-boron magnets, and the like. The magnet ring retainer  904  couples the magnetic ring  902  to the plunger assembly  908 . The magnetic ring  902  and the magnet ring retainer  904  comprise a mount for the location marking device  912 . The mount may be, for example but without limitation, cylindrical, disc, or the like shaped to form a recessed conical nest, which holds the optical retro-reflector  102 . Alternatively, a three-point conical nest known as a kinematic mount may be used. 
     The plunger assembly  908  comprises an inner component  916 , an outer component  918 , and the spring  906  for causing relative movement between the inner component  916  and the outer component  918 . The inner component  916  is coupled to the outer component  918 , and operable to move (e.g., slide) relative to the outer component  918 . The inner component  916  is coupled to the location marking device  912 . The spring  906  is operable to elevate the location marking device  912  away from the assembly object surface  112  ( FIG. 1 ). The inner component  916 , the outer component  918 , and the spring  906  of the plunger assembly  908  may comprise, for example but without limitation, metal, plastic, composites, and the like. The plunger assembly  908  is coupled to the magnetic ring  902  and the magnetic ring retainer  904 . 
     The base member  910  may be secured to the plunger  908  by, for example but without limitation, a suitable adhesive, welded, press fit, and the like. The base member  910  is shaped to hold the plunger  908  perpendicular to the assembly object surface  112  ( FIG. 1 ). The base member  110  is also operable to slide over the assembly object surface  112  via the surface sliders  914 , while providing a solid structural support for the plunger  106 , when used to press the location marking device  912  on to the assembly object surface  112 . The surface sliders  914  may comprise any number of sliders, such as but without limitation, three sliders, and the like. 
       FIG. 10  is an illustration of a plunger assembly  1000  of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. The plunger assembly  1000  corresponds to the plunger assembly  908 . In the embodiment shown in  FIG. 10 , the plunger assembly  1000  comprises a cylindrical shape. Alternatively, the plunger assembly  1000  may comprise, for example but without limitation, an ellipsoidal shape, a multisided shape, a square shape, a rectangular shape, and the like. The plunger assembly  1000  may be, for example but without limitation, about 8 cm in height  1016 , and about 1.1 kg in weight. The plunger assembly may be made of, for example but without limitation, metal, plastic, composites, and the like. The inner component  1002  may be, for example but without limitation, about 5 cm in height  1006 , about 3 cm in inner diameter  1008 , about 4 cm in outer diameter  1010 , and about 0.5 kg in weight. The outer component  1004  may be, for example but without limitation, about 5 cm in height  1012 , about 4 cm in inner diameter  1014 , about 5 cm in outer diameter  1016 , and about 0.5 kg in weight. As mentioned above the plunger  1000  comprises a spring  906  ( FIG. 9 ) to elevate the location marking device  912  away from the assembly object surface  112  ( FIG. 1 ). The spring  906  may be, for example but without limitation, about 1 m in length, about 3 mm in diameter, and about 0.1 kg in weight. 
       FIG. 11  is an illustration of a base member  1100  of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. The base member  1100  corresponds to the base member  910 . In the embodiment shown in  FIG. 11 , the base member  1100  has a cylindrical shape with a narrow upper body  1102  and an enlarged bottom pedestal  1104 . Alternatively, the base member  1100  may have, for example but without limitation, an ellipsoidal shape, a multisided shape, a square shape, a rectangular shape, and the like. The narrow upper body  1102  may be, for example but without limitation, about 3 cm in height  1106 , about 5 cm in inner diameter  1108 , and about 6 cm in outer diameter  1110 . The enlarged bottom pedestal  1104  may be, for example but without limitation, about 1 cm in height  1112 , about 6 cm in inner diameter  1114 , and about 7 cm in outer diameter  1116 . The base member  1100  may be, for example but without limitation, about 1.0 kg in weight, and may be made of, for example but without limitation, metal, plastic, composites, and the like. 
       FIG. 12  is an illustration of a magnetic ring retainer  1200  of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. The magnetic ring retainer  1200  corresponds to the magnetic ring retainer  904 . In the embodiment shown in  FIG. 12 , the magnetic ring retainer  1200  comprises a dual annulus shape with an inner annulus  1202  and an outer annulus  1204 . Alternatively, the magnetic ring retainer  1200  may have, for example but without limitation, an ellipsoidal shape, a multisided shape, a square shape, a rectangular shape, and the like. The inner annulus  1202  may be, for example but without limitation, about 0.2 cm in height, about 3 cm in inner diameter, and about 4 cm in outer diameter. The outer annulus  1204  may be, for example but without limitation, about 0.1 cm in height, about 4 cm in inner diameter, and about 5 cm in outer diameter. The magnetic ring retainer  1200  may be, for example but without limitation, about 0.2 kg in weight, and comprise metal, plastic, composites, and the like. 
       FIG. 13  is an illustration of a magnetic ring  1300  of a spring-loaded mechanical marking tool according to an embodiment of the disclosure. The magnetic ring  1300  corresponds to the magnetic ring  902 . The magnetic ring  1300  comprises an annulus shape. Alternately, the magnetic ring  1300  may have, for example but without limitation, an ellipsoidal shape, a multisided shape, a square shape, a rectangular shape, and the like. The magnetic ring  1300  may be for example but without limitation, about 0.2 cm in height, about 3 cm in inner diameter, about 4 cm in outer diameter, about 0.1 kg in weight, and comprise metal, plastic, composites, and the like. 
       FIGS. 14-15  is an illustration a flow diagram showing an exemplary process  1400  for fabricating a metrology system comprising a spring-loaded mechanical marking tool according to an embodiment of the disclosure. The various tasks performed in connection with the process  1400  may be performed by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of the process  1400  may refer to elements mentioned above in connection with  FIGS. 1-13 . In practical embodiments, portions of the process  1400  may be performed by different elements of the mechanical marking tool  900  such as the magnetic ring  902 , the plunger assembly  908 , and the base member  910 . The process  1400  may have functions, material, and structures that are similar to the embodiments shown in  FIGS. 1-13 . Therefore common features, functions, and elements may not be redundantly described here. 
     Process  1400  may begin by providing a location marking device operable to indicate (e.g., mark) a location (task  1402 ). Process  1400  may continue by providing a base member operable to slide over a surface (task  1404 ). Process  1400  may continue by providing a plunger. The plunger couples to the base member and a location marking device, and can move in relation to the base member (task  1406 ). Process  1400  may continue by providing a magnetic ring operable to hold a spherically mounted retro-reflector (task  1408 ). Process  1400  may continue by providing a magnetic ring retainer operable to couple the magnetic ring to the plunger (task  1410 ). Process  1400  may continue by providing a spring coupled to the plunger and operable to elevate the location marking device away from the surface (task  1412 ). Process  1400  may continue by assembling the base member, the plunger, the magnetic ring, the magnetic ring retainer, and the spring (task  1414 ). Process  1400  may continue by accurately aligning the base member, the plunger, the magnetic ring, the magnetic ring retainer, and the spring (task  1416 ). 
     Additionally, process  1400  may further continue by providing the spherically mounted retro-reflector (task  1418 ) to reflect a light beam, and mounting the spherically mounted retro-reflector on the magnetic ring (task  1420 ). Process  1400  may also accurately align the spherically mounted retro-reflector (task  1422 ), for example, with the location marking device, the base member, the plunger, the magnetic ring, the magnetic ring retainer, and/or the spring. Process  1400  may also accurately align the location marking device (task  1424 ), for example, with the base member, the plunger, the magnetic ring, the magnetic ring retainer, and/or the spring. The process  1400  may also comprise verifying performance of the spring-loaded mechanical marking tool (task  1426 ), and verifying a quality of the spring-loaded mechanical marking tool (task  1428 ). The quality of the spring-loaded mechanical marking tool may be verified by, for example but without limitation, comparison to an ideal spring-loaded mechanical marking tool, via statistical quality metrics, and the like. 
     While at least one example embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the example embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application. 
     The above description refers to elements or nodes or features being “connected” or “coupled” together. As used herein, unless expressly stated otherwise, “connected” means that one element/node/feature is directly joined to (or directly communicates with) another element/node/feature, and not necessarily mechanically. Likewise, unless expressly stated otherwise, “coupled” means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically. Thus, although  FIGS. 1-14  depict example arrangements of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the disclosure. 
     Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as mean “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, a group of items linked with the conjunction “and” should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as “and/or” unless expressly stated otherwise. Similarly, a group of items linked with the conjunction “or” should not be read as requiring mutual exclusivity among that group, but rather should also be read as “and/or” unless expressly stated otherwise. Furthermore, although items, elements or components of the disclosure may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent.