This disclosure relates generally to a method and system for inspecting components and more particularly to a method and system for optically inspecting the internal physical characteristics of internally threaded components, such as nuts and other internally threaded components having varied configurations.
As society becomes increasingly reliant upon technology, mechanical and electromechanical systems, such as aircraft, automobiles, weapons systems and power systems, are called upon to perform an ever increasing number of functions. One downside to this is that, in some situations, a failure of a single threaded component in the system may cause a catastrophic failure of the entire system possibly resulting in the loss of millions of dollars and hundreds of lives. In an attempt to reduce the probability of a catastrophic systems failure, critical and some non-critical systems are required to satisfy predetermine operating tolerances before they may be used. As such, key threaded components within these systems, i.e. threaded components whose failure may cause a catastrophic system failure such as internally threaded rings, nuts and/or plain and threaded ring gages, must also satisfy operating tolerances. If a threaded component fails to satisfy these required design tolerances and/or performance specifications, a degradation of system performance and/or a total system failure may occur resulting in damage to the system and/or injury/loss of life to an operator and/or bystander.
Current systems used for inspecting physical characteristics of an internally threaded component employ an attribute inspection approach that measures the characteristics of the threaded component via a contact measurement technique. This technique typically uses GO and/or NO GO threaded work plugs that are calibrated to specifications. The internal thread size measurement are conducted via GO and/or NO GO working plugs and gages. Unfortunately, this technique only measures the functional size and does not protect and ensure the dimensional integrity of product design limits and because this approach is attribute gagging and is dependent upon human interaction, this technique has the disadvantage of being time consuming, subjectively inaccurate and unreliably repeatable for tight operating tolerances over multiple measurements. Accordingly, threaded components having dimensionally non-conforming characteristics are allowed to pass inspections. Moreover, because these systems use contact measuring techniques, there is a considerable wear factor on the measuring instruments, requiring the GO, NO GO, threaded working plugs and variable internal gauging elements to be inspected and replaced often.
An inspection system for measuring the threaded surface of an internally threaded component is provided and includes at least one measuring probe, wherein the at least one measuring probe includes an emitter and a receiver and is sized and shaped to be positionable adjacent at least a portion of the threaded surface at an offset distance, wherein the emitter is configured to emit electromagnetic energy that is incident upon the threaded surface to generate reflected electromagnetic energy responsive to the threaded surface and wherein the receiver is configured to receive at least a portion of the reflected electromagnetic energy and generate threaded surface data. A processing device is also provided and is in signal communication with the measuring probe to receive the threaded surface data and process the threaded surface data to determine physical characteristics of the threaded surface.
A method for measuring the threaded surface of an internally threaded component using an inspection system is provided, wherein the inspection system includes a measuring probe having an emitter and a receiver and is sized and shaped to be positionably adjacent at least a portion of the threaded surface at an offset distance. The emitter is configured to emit electromagnetic energy incident upon the threaded surface to generate reflected electromagnetic energy responsive to the threaded surface and wherein the receiver is configured to receive at least a portion of the reflected electromagnetic energy and generate threaded surface data. The method includes associating the internally threaded component with the inspection system via an electromagnetic and positioning the measuring probe inside a cavity of the internally threaded component. The method further includes deactivating the electromagnet to cause the internally threaded component to be positioned relative to measuring probe such that an offset distance exists between the measuring probe and the threaded surface. The method also includes activating the electromagnet to securely re-associate the internally threaded component with the inspection system and operating the inspection system to cause the measuring probe to measure at least a portion of the threaded surface and to generate initial threaded surface data. Furthermore, the method includes processing the threaded surface data to generate physical characteristics of the at least a portion of the threaded surface.
A computer-readable storage medium encoded with machine-readable computer program code is provided, where the program code includes instructions for causing a controller to implement a method for measuring the threaded surface of an internally threaded component using an inspection system, wherein the inspection system includes a measuring probe having an emitter and a receiver and is sized and shaped to be positionably adjacent at least a portion of the threaded surface at an offset distance, wherein the emitter is configured to emit electromagnetic energy incident upon the threaded surface to generate reflected electromagnetic energy responsive to the threaded surface and wherein the receiver is configured to receive at least a portion of the reflected electromagnetic energy and generate threaded surface data. The method includes associating the internally threaded component with the inspection system via an electromagnetic and positioning the measuring probe inside a cavity of the internally threaded component. Furthermore, the method includes deactivating the electromagnet to cause the internally threaded component to be positioned relative to measuring probe such that an offset distance exists between the measuring probe and the threaded surface. The method further includes activating the electromagnet to securely re-associate the internally threaded component with the inspection system and operating the inspection system to cause the measuring probe to measure at least a portion of the threaded surface and to generate initial threaded surface data. Moreover, the method includes processing the threaded surface data to generate physical characteristics of the at least a portion of the threaded surface.
The foregoing and other features and advantages of the present invention will be more fully understood from the following detailed description of illustrative embodiments, taken in conjunction with the accompanying drawings in which like elements are numbered alike in the several Figures:
a shows a side view of an internal inspection system of
b shows a side view of an alternative embodiment of an internal inspection system having multiple measuring probes;
a shows a side view of an internal inspection system of
b shows a front view of a component associated with the internal inspection system of
An exemplary embodiment is described herein by way of illustration as may be applied to the measurement and inspection of internally threaded gages, products and components, such as nuts and other internally threaded components. However, while an exemplary embodiment is shown and described hereinbelow, it should be appreciated by those skilled in the art that the invention is not limited to the embodiment(s) and application(s) as described herein, but also to any component and/or measurement where accuracy in tolerance measurement is critical, such as gears, internal bores, integral plain cylindrical bores, internal threads, internal diameters and/or material composition and/or strength. Moreover, those skilled in the art will appreciate that a variety of potential implementations and configurations are possible within the scope of the disclosed embodiments.
In accordance with the invention, an inspection system is provided and may be used to inspect and measure internal characteristics of an internally threaded product (and/or gage, plain and/or threaded ring gage) using a measuring device, such as an optical triangulation probe which uses a Laser to map the surface being measured. In fact, the internal inspection may be used to inspect and measure the physical characteristics of most apparatus or structures having an internal surface and/or enclosure and is not limited to threaded/non-threaded products, working GO & NO GO ring gages and/or master threaded rings. In accordance with the present invention, the desired internal characteristics may include, but are not limited to, the Lead, Flank Angle (Included), Flank Angle (Leading), Flank Angle (Trailing), Pitch Diameter, Taper, Minor Diameter, Major Diameter, Major Diameter Clearance, Out-of-Round and/or Functional Size.
Referring to
In accordance with the invention, the measuring probe 2002 is shown as being an optical triangulation type probe having a Laser emitter/receiver portion 2014 that is capable of emitting and receiving a Laser beam with a measurement resolution of about 20 millionths of an inch and which is configured to emit a Laser beam having a spot size ranging from about one ten thousandths of an inch to about five ten thousandths of an inch. It should be appreciated that the resolution may be based, at least in part, upon the mirror configuration within the optical triangulation probe. The measuring probe 2002 may be communicated with the processing device 2010 via a fiber optic cable 2016 to communicate data (such as a surface map data and/or image data (shadow or picture)) between the measuring probe 2002 and the processing device 2010. It is contemplated that a signal (data) conditioning circuit may be associated (internally or externally) with the processing device 2010 to condition the signal before and/or after receipt of the data by the processing device 2010. Additionally, it is contemplated that the data may be transmitted to the processing device 2010 via a wireless method/device or via a hard-wired connection where the data is converted into electrical signals prior to being transmitted to the processing device 2010. Furthermore, the measuring probe collar 2004 may be provided to cover the measuring probe 2002 to ensure that there is a sufficient standoff distance between the measuring probe 2002 and the surface of the product being measured. It should be appreciated that although the measuring probe 2002 is shown and described herein as being an optical triangulation type probe that uses a Laser source, any type of measuring device which emits electromagnetic energy (all along the electromagnetic spectrum) and which is suitable to the desired end purpose may be used, such as non-Laser collimated light, optical, borescope, MASER, electron beam, etc.
The measuring probe locating device 2006 is supported by the measuring probe support device 2008 such that the measuring probe locating device 2006 can move the measuring probe 2002 into and out of the internal space of the product being measured. This measuring probe locating device 2006, which is disclosed herein as a ball slide unit, but which may be any locating device suitable to the desired end purpose (such as, for example, an electric or pneumatic positionable device), allows the measuring probe 2002 to be precisely located within the product and adjacent the surface being measured where the measuring probe locating device 2006 may be precisely controlled via the processing device 2010 or some other (external or internal) device. The product retention device 2012 is provided to securely hold and position the product being measured.
In accordance with one embodiment of the present invention, the internal inspection system 2000 operates as follows. Referring again to
The product retention device 2012 is then reactivated to cause the electromagnet to magnetize causing the product 2018 to be securely held in place against the electromagnet of the product retention device 2012 as shown in
It is contemplated that (as described above) the measuring probe 2002 may be removed from the cavity (at least in part) prior to removing the measuring probe collar 2004. Or the measuring probe collar 2004 may be removed (at least in part) while the measuring probe 2002 is still positioned within the cavity. Or the measuring probe 2002 may not include a measuring probe collar 2004, but rather that the standoff distance be determined and implemented by determining the location of the probe relative to the surface being measured and adjusting the standoff distance by moving either the probe 2002, the component 2018 or both of the probe 2002 and the component 2018. In accordance with one embodiment of the invention, this allows the proper positioning of the product 2018 relative to the measuring probe 2002. It is contemplated that the positioning of the measuring probe 2002 and/or measuring probe collar 2004 may be accomplished (at least in part) using the measuring probe locating device 2006 or a separate positioning device controlled in whole or in part via the processing device 2010 or via any other device/method suitable to the desired end purpose. It is also contemplated that multiple measuring probes 2002 (or one measuring probe 2002 having multiple emitter/receiver portions 2014) may be implemented and may be used to measure both the 0° position and the 180° position, as shown in
Referring to
It should be appreciated that in one embodiment, the optical triangulation probe that is being used as the measuring probe 2002 may operate by emitting a Laser beam which is incident upon the surface being measured. The reflection (or a portion of the reflection) of the Laser beam from the surface is received by the measuring probe 2002 thus allowing for the generation of a surface profile image (such as a shadow image). It is also contemplated that other frequencies of the electromagnetic spectrum (such as Radar, Masers, etc) may be used and/or that other measuring devices may be used, such as a camera which may be used in place of an optical triangulation probe to generate an image of the surface. It should be appreciated that all measurements and characteristics may then be generated using the same (or similar) methods and/or algorithms as discussed herein. For the internal measurements, the major diameter may be measured to assure clearance of maximum material conditions of the major diameter of external threads. It is further contemplated that the product may be associated with the product retention device 2012 using any method/device suitable to the desired end purpose, such as by hand or by a device configured to perform such a task. It is also contemplated that the components herein may be configured differently to obtain the desired end result. For example, although the measuring probe 2002 is illustrated as being movable and the product 2018 is illustrated as being stationary, it is contemplated that the measuring probe may 2002 be stationary and the product 2018 (or product retention device 2012) may be movable.
Referring to
In accordance with an exemplary embodiment, it is contemplated that multiple measurements may be made at each of the measurement locations in a manner responsive to component thread specifications or other factors. Moreover, the data may be processed to comprise a plurality of discrete pixel elements. The processing device 2010 may examine each pixel (or selected pixels) of the plurality of discrete pixel elements to determine the physical characteristics of the surface as discussed hereinabove. It is further contemplated that the data may be displayed (as an image or other output) via any display device suitable to the desired end purpose, such as a paper printout, a computer screen, a television, a plasma display and/or a Liquid Crystal Display (LCD). Although the component physical characteristics are determined by processing the data as discussed hereinabove, the component physical characteristics may be determined by processing the data using any device and/or method suitable to the desired end purpose. Inspection system 2000 may also be operated and/or monitored via a network connection, such as a wireless network (cellular, pager, RF), Local Area Network, Wide Area Network, Ethernet and/or Modem.
It is further contemplated that processing device 2010 may cause the data and/or measurement results to be stored in a data storage device and/or a volatile memory of the processing device 2010 (e.g. RAM). It should also be noted that the data may be stored in a volatile and/or a non-volatile memory location which may be disposed in any location suitable to the desired end purpose, such as a remote server. In addition, the data storage device may be used to store individual component data and/or group component data which may be specific to a desired purpose, such as data for a specific user, component part and/or a specific end user device, wherein the component data may include a large range of information, such as user specific data and/or component part history data.
It is further contemplated that the system 2000 may include a display device, such as a flat panel display device, for displaying obtained or resultant data (such as an image). Although the display device is described herein above as being a flat panel display, the display device may be any display device suitable to the desired end purpose. Additionally, although the processing device 2010 may be a computer system operating an MS Windows operating system (or higher version), the processing device 2010 may be any processing device suitable to the desired end purpose. Although measuring probe locating device 2006 may include a stage with a glass slide and a linear motor having crossed rollers with anti-creep technology, any measuring probe locating device 2006 suitable to the desired end purpose may be used. The linear motor may allow for sufficient travel in any direction to accomplish the desired measurement (for example, plus and minus five (5) inches of travel in any desired direction). Measuring probe locating device 2006 may also be configured to operate via a hardwired and/or a wireless controller and may be capable of supporting movement in the X, Y and/or Z axis, as shown in
As is known, a component thread is a combination of a thread ridge and thread groove, typically of uniform section, that is produced by forming a groove with a helix on an external or internal surface of a cylinder or cone. Because the component thread is designed to operate in association with an opposing component thread, it is essential that certain key physical characteristics relating to thread size and thread form be tightly controlled. Deviation from acceptable tolerances of these key characteristics can result in catastrophic failure of the system and/or loss of life. As such, it is desirable to measure these thread size characteristics and thread form characteristics as accurately as possible. The thread size characteristics include the major diameter, the minor diameter, the functional diameter and the pitch diameter and the thread form characteristics include the pitch, the lead, the uniformity of helix angle, the flank angle and the included angle, each one of which is discussed in more detail herein.
Referring to
The pitch of an internal thread having uniform spacing may be defined as the distance, measured parallel to the axis, between corresponding points on adjacent thread forms in the same axial plane and on the side of the axis. Thus, the pitch may be defined as the number of threads per inch (TPI) and the pitch distance may be defined as 1/TPI, wherein TPI is measured parallel to the thread axis, from a point on one flank to the corresponding point on the next available flank. The pitch diameter of the component is the diameter or width of an imaginary cylinder, called the pitch cylinder, whose surface would be parallel to the axis of the thread or component and whose surface would intersect the profile of a straight thread such that the width of the thread ridge and the thread groove are equal.
The lead may be defined as the axial distance moved by the component in relation to the amount of angular rotation, when a threaded component is rotated about its axis with respect to a fixed mating thread. Thus, the lead is the amount of axial travel when the threaded component is turned one full turn or 360° and pitch is the distance measured parallel to the axis from a point on one flank to the corresponding point on the adjacent flank. Any deviation in lead tends to decrease the functional diameter of the internal thread and rapidly consumes the allowed operating pitch diameter tolerance of a threaded component. A deviation in lead may result in non-engagement of a thread with its mating part at all but a few points. Thus, when the threaded parts are assembled, and torque is applied, the result is pressure being applied to only a few, and possibly only one pressure flank. As such, any deviation in lead may produce a non-engagement condition for some threads and cause a failure in engaging threads at the point of pressure flank engagement due to non-engagement.
The helical path deviation of a thread is a wavy deviation from a true helical advancement or a non-uniformity of helix angle. In a similar manner as the lead, a deviation in the helical path causes a decrease in the functional size of the internally threaded component in proportion to the amount of waviness. Thus, all of the statements that were made concerning a deviation in lead also apply to a deviation in helical path and similarly, a deviation of helical path may result in partial engagement of the thread flanks with the result that torque pressures may not be evenly distributed and may result in pre-load relaxation.
The included angle of a thread is the angle between the flanks of the thread measured in an axial plane. The flank angles are the angles between the individual flanks and the perpendicular to the axis of the thread measured in an axial plane. A flank angle of a symmetrical thread is commonly referred to as the half included angle or the half angle of a thread. A deviation in the flank angle may result in a failure of the thread when the product is exposed to line loads, when torque is applied or when vibration occurs. This is because an improper flank engagement may create an unevenly distributed pressure load along the flank rather than the pressure load being distributed evenly along the flank.
Other important physical characteristics of the component include the functional size diameter, the taper characteristic of the pitch cylinder and the out-of-roundness, all of which can generate a non-engagement condition. In fact, distortion or deviation from specifications of any of the physical characteristics discussed herein may cause varying degrees of non-engagement.
The functional, or virtual, diameter of an internal thread may be defined as the resultant size of the product thread taking into account the effect of lead, helical path deviation, flank angle deviation, taper and out-of-roundness. As such, it may be seen that the functional diameter is the pitch diameter of the enveloping thread of perfect pitch, lead and flank angles, having full depth of engagement, but that are clear at crests and roots, of specified lengths of engagement. For an internal thread, the functional diameter may be derived by subtracting the cumulative effects of deviations to the pitch diameter, including variations in lead and flank angles over a specified length of engagement. Thus, it should be clear that the effects of taper, out-of-roundness and surface defects may be positive or negative on the functional size of the internal threads.
The taper characteristic of the pitch cylinder is simply a tapering of the pitch cylinder of the thread. Thus, a tapered thread fails to give a complete thread engagement, which may lead to a product failure caused by uneven torque pressure conditions on pressure flanks and pre-load relaxation.
The out-of-roundness of the pitch cylinder, which is any deviation of the pitch cylinder from round, limits the thread engagement and allows for only line contact with the mating thread and typically includes two types of out-of-roundness: Multi-lobe or Oval.
With the desired physical characteristics of a threaded component to be measured explained hereinabove, an overall method for measuring these characteristics is provided and described hereinbelow. Furthermore, it is contemplated that each of the methods, calculations and algorithms described herein, may be performed via a system operator and/or via an automated system.
Once data for the surfaces being measured (i.e. the 0° and 180° sides of the threads) is obtained, the Flank angle may be determined. Using the data, the minor radius, the major radius, the pitch radius, the lead pitch, the leading/trailing flank angles and/or the included angles can be determined. The major radius may be determined via the major diameter, which is a composite measurement based on the major radius of the 0° and corresponding 180° side of the threads. Thus, the major radius can be determined by summing the individual measurements and dividing by the number of measurements collected. The number of measurement locations may be determined by taking 70% of the thread width, as given by thread tables, and centering them on the center of the thread. This major radius average may then be combined from both the 0° and the 180° sides to get the major diameter. The pitch diameter calculation, which is based on the leading and trailing angles, major diameter, pitch lead and crest width at the location in question, may be determined by the equation:
PD=MD−(Cot(PL/2)-CW),
where, PD is pitch diameter, MD is major diameter, PL is pitch lead and CW is crest width. The lead front measurement, which is responsive to the difference between the groove distance and the ridge distance along the leading/trailing/leading flanks may be determined by various known methods.
In an additional embodiment, the determination of the Pitch Diameter (PD) may include a Correction Factor (CF) to adjust for any aberrations that may be present in the data. Referring to
To compensate for any aberrations of the shadow image 4008 within the image data, a Correction Factor (CF) may be generated and applied to the process for determining the Pitch Diameter (PD). As such, the Pitch Diameter (PD) may be represented by the equation:
PD
Final
=PD
Observed
−CF,
wherein PDFinal is the Pitch Diameter (PD) adjusted for any aberrations, PDobserved is the Pitch Diameter (PD) as measured and containing any aberrations and CF is the Correction Factor (CF) representing any aberrations.
For example, as illustrated for internal threads, one embodiment for compensating for any aberrations includes generating a Correction Factor (CF) responsive to unwanted reflections or ‘splash’ and ‘subtracting’ the Correction Factor (CF) from the data generated by the sensing device, wherein the Correction Factor (CF) may be determined by parametrically representing one flank of a thread (i.e. the rear side of a thread ridge) in 3-D space having an x-axis, a y-axis and a z-axis as an embedding of a strip into a 2-D space having only the x-axis and the z-axis. Referring to
x=r cos(t),
y=r sin(t), and
z=mr+Lt/2n.
This embedding can then be projected onto the x-z plane by using the equations:
x=r cos(t), and
z=mr+Lt/2n,
to obtain the determinant of the Jacobian matrix, wherein the Jacobian matrix is defined by:
As is well known, the Jacobian matrix is the matrix of all first-order partial derivatives of a vector-valued function and may be representative of the ‘best’ linear approximation to a differential function near a given point.
Thus, using the equations as derived hereinabove,
x=r cos(t), and
z=mr+Lt/2n,
the Jacobian matrix J(x1 . . . xn) may be represented as:
Solving the Jacobian matrix J(x1 . . . xn) to find the set of points of the shadow image (i.e. ribbon) on the x-z plane gives the following:
J=((L/2π)cos(t)+mr sin(t))=0
where,
r=−(L/(2πm tan(t))).
Referring to
and combining equation (1) with equation (2) gives the following:
which must be solved for each given value of L, m and R. Having the flank angle, t, these equations may be solved to obtain r, wherein half of the displacement of the Pitch Diameter (PD) is the x-coordinate of the point on the ribbon minus the x-coordinate of the Pitch Diameter (PD) point (x,y,z)=(R,0,mR) or simply, r cos(t)−R. Thus, it should be appreciated that the Correction Factor (CF) may be assumed to be twice this amount and may be given by the equation:
CF=2(r cos(t)−R).
Thus, the Pitch Diameter for a symmetrically internally threaded object adjusted for any aberrations, PDFinal, may be determined by applying the Correction Factor (CF) above into equation (1) to give the following equation:
PD
Final
=PD
Observed−2(r cos(t)−R),
In a similar fashion, for objects or components having asymmetrical threads, such as buttress threads, the methodology applied hereinabove may be used for both flanks (due to the asymmetry the calculations should be conducted for each flank). As such, a simple geometric argument using the above approach for both flanks may combine the two results in a kind of weighted average to give:
wherein d1 and d2 are the shadow corrections for the two flank angles treated separately as symmetrical internal threads and a1 and a2 are the respective flank angles. Given the above, the Pitch Diameter for an asymmetrically internally threaded object adjusted for any aberrations, PDFinal, may be determined by applying the Correction Factor (CF) above into equation (1) to give the following equation:
Referring to
CF=2(r cos(t)−R),
However, if the object is an internally threaded object having asymmetrical threads, then the predetermined algorithm may be at least partially responsive to the equation:
Referring to
At this point, the 2nd thread 0° side measurements, the 1st full thread 180° side measurements may be conducted on the first full thread on the 180° side and the minor radius, the major radius, the pitch radius and the lead pitch may be determined. The 2nd thread 180° side measurements may be made on the second full thread on the 180° side and the major radius, pitch radius and lead pitch may be determined. The component values and limits may be updated and the results may be stored, displayed to a system operator and/or printed out.
To account for anomalies in the measurements as described herein, the following novel and unique algorithms can be applied to the invention as disclosed herein and in U.S. application Ser. Nos. 11/391,521 and 11/502,678 and U.S. Pat. No. 7,227,163, the contents and disclosures of which are incorporated herein by reference in their entireties.
For ‘smoothing’ various parameters of the internally threaded component measurements (as desired), the following regression analysis approach may be used to obtain final smoothing data and includes:
1) Conduct a standard least square linear regression analysis;
2) Conduct a q-trimmed linear regression analysis; and
3) Conduct a resistant regression procedure.
This approach may be conducted in whole or in part and in any order desired and suitable to the desired end result. The terminal residuals outside of ±2 sigma standards may be generated and the refits may be generated. Accordingly, excessive deviations from the “true line” can be removed using at least one of two approaches as follows:
1) The first approach includes fitting a least squares line, which consists of minimizing,
where, a is the intercept of b, b is the determined/theoretical slope (can be estimated), k is the number of values generated, xk and yk are the residuals for each coordinate pair, wk is included/excluded least square lines fit, where the values of wk will be either zero (excluded) or one (included). Then determine the theoretical estimates for the slope b and the intercept a as follows,
where
r
k
=y
k−(â+{circumflex over (b)}xk).
This is the amount by which the data points differ from the corresponding points predicted to lie on the line and r(k) is the residual for each coordinate pair xk, yk. Sort the residuals from lowest to highest (or highest to lowest if desired) as given by,
r
(1)
≦r
(2)
≦ . . . ≦r
(n).
These values may be trimmed by identifying those points whose residuals have the highest absolute values and either remove them or weight them using a weight variable w. One way to generate the weight variable w is by setting wk=0 for the points to be trimmed. Once this is done, the least squares line may be refit and used to determine the required parameters for the internally threaded component. Although as many as about 30% of the points may be trimmed, typically only about 5%-10% of the points are trimmed prior to the refit of the least squares line.
The second approach may include:
2) fitting the least squares line and calculating the residuals. However, this approach involves trimming those residuals outside of about 2 or 2.5 standard deviations given by, where n is the number of residuals,
By using a two (2) standard deviation criterion, approximately about 5% of the data will be trimmed and the line can be refit by using the least squares estimates on the reduced data set. In both of the above approaches, the algorithm can be simply stated as,
1) Fit line to original data generated in accordance with the thread profile;
2) Compute screw thread geometric parameters using re-trimmed data set.
To account for anomalies in the measurements as described herein, the following novel and unique algorithms can be applied to the invention as disclosed herein and in U.S. application Ser. Nos. 11/391,521 and 11/502,678 and U.S. Pat. No. 7,227,163, the contents and disclosures of which are incorporated herein by reference in their entireties. It should be appreciated that the above approaches can be applied to all measurements including the major diameter, the pitch diameter, lead, angles, minor diameter, and helix variation. It is contemplated that, rather than using a least squares fit, another approach may use a minimum absolute deviation fit, where it is minimized by,
It is also contemplated that an orthogonal least squares approach could also be used, i.e. measure the deviations perpendicular to the screw thread flank. However, the calculations for this approach are more complex. It should be further appreciated that the full data set should be retained and each point referenced by whether it is retained or trimmed. In particular, the higher the standard deviation of the residuals, the lower quality the screw thread.
To account for deviations in the functional size of the internally threaded component 2018, the following algorithm may be used:
fs=pd+L+A.
Accordingly, it should be appreciated that if there is no error (i.e. dp=0), then fs=pd. However, if error is present (i.e. dp=±) then fs=pd+L+A, where pd=pitch diameter of the thread profile, L=lead error of the thread profile and A=angle error of the thread profile.
In accordance with an exemplary embodiment, inspection system 2000 may be a self-calibrating and automated system for inspection of multiple components in a single fashion or an assembly line fashion. Moreover, inspection system 2000 allows for non-contact measurements which reduce and/or eliminate high inspection costs, operator feel, fatigue, uncertainties and/or error. Inspection system 2000 allows for the generation of automatic certificates and information output files. Moreover, inspection system 2000 may include built-in repeatability and reliability (R&R) qualification and testing programs and allow for an extremely fast measurement cycle.
A machine-readable computer program code and/or a medium encoded with a machine-readable computer program code for causing a controller to implement the methods disclosed herein (in whole or in part) via the inspection system 2000 is also provided, where the processing of the methods may be implemented via a controller that is disposed internal to, external to or internally and externally to the inspection system 2000. Thus, the controller may operate in response to a computer program where in order to perform the prescribed functions and desired processing, as well as the computations therefore (e.g. execution control algorithm(s), the control processes prescribed herein, and the like), the controller may includes, but not be limited to, a processor(s), computer(s), memory, storage, register(s), timing, interrupt(s), communication interface(s), and input/output signal interface(s), as well as combination comprising at least one of the foregoing.
The invention may be embodied in the form of a computer or controller implemented processes. The invention may also be embodied in the form of computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, and/or any other computer-readable medium, wherein when the computer program code is loaded into and executed by a computer or controller, the computer or controller becomes an apparatus for practicing the invention. The invention can also be embodied in the form of computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer or controller, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein when the computer program code is loaded into and executed by a computer or a controller, the computer or controller becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor the computer program code segments may configure the microprocessor to create specific logic circuits.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. For example, although the internal inspection system is discussed herein in reference to a Laser frequency source, other measuring sources/devices (optical or non-optical) or combination of sources/devices suitable to the desired end purpose may be used, such as but not limited to collimated light, x-rays, cameras, borescope, MASER, electron-microscopes, etc . . . . In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed herein as the best mode contemplated for carrying out this invention.
This application is related to and claims priority from U.S. Provisional Patent Application Ser. No. 61/134,497 filed Jul. 10, 2008 entitled “Internal Inspection System and Method for implementing same”, the contents and disclosure of which is incorporated herein by reference in its entirety. Additionally, the invention disclosed herein is related to U.S. application Ser. No. 12/383,141 filed Mar. 20, 2009 entitled “Inspection System and Method for implementing same,” the contents and disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
---|---|---|---|
61134497 | Jul 2008 | US |