Patent Application
20090198465
Not Applicable
Not Applicable
1. Technical Field
The present invention generally relates to quality control systems and methods in manufacturing operations. More particularly, the present invention relates to proximity sensing of work pieces from machine tools to maintain close manufacturing tolerances. Further, the present invention relates to proximity sensing systems that can communicate wirelessly or wired with remote data processing devices.
2. Related Art
Composites, which are materials comprised of two or more constituent materials having divergent properties, are frequently utilized in the manufacture of aircraft and other heavy machinery for its light weight, high strength, and extended fatigue life. However, composite materials are often difficult to properly machine because of expansion and movement associated with spring back—a reaction of the material to reduce the stress induced by shaping, and temperature and pressure changes. These dynamic characteristics adversely affect the manufacturability of the material, in that proper alignment to machine tools is difficult to maintain.
One conventional technique to ensure proper machining is the use of a trim fixture vacuum, which is used after positioning the material to stabilize and maintain its initial state relative to the precision tool surface. Positional integrity is maintained throughout the machining operations. In most instances, the machining is performed in an environmentally controlled room by a precision milling machine. Supplemental clamps are typically affixed around the periphery to maintain the vacuum. Trim fixture vacuums significantly improve out-of-tolerance movement during machining, drilling, and trimming operations. One difficulty with sole reliance upon the tool fixture vacuum, however, is that it is uncertain whether all areas of the composite part are properly distanced from the tool surface within the area inside the seal barrier prior to machining. Because this area is obscured and inaccessible, there is difficulty in determining proper contact of the part with respect to the machine tool.
It will be appreciated that validating the conformance of the distance between the composite part and the machine tool is critical, as the automated machines rely upon an initial offset to make all other machining decisions. If a part is not braced in such hidden areas, material may be removed excessively, resulting in a non-conformance. Without verifying the proximity of the material to the machine tool, there is a higher likelihood of it being machined outside the acceptable tolerance. This is particularly problematic in the manufacture of high-quality, tight tolerance parts such as those used in aircraft, where seemingly insignificant discrepancies are anything but. As a consequence, the supply chain is disrupted, production time is increased, and availability is reduced. Furthermore, manufacturing costs are increased because of the added labor and raw material costs. Generally, the quality of the final product is diminished when its constituent parts cannot be accurately and repeatedly produced.
One approach to the foregoing problems involves the use of feeler gauges being placed along the edges of the composite part to determine the amount of space between the tool and the part. Feeler gauges are wedge-like tools having graduated marks corresponding to sections of increasing thickness. This technique is limited, however, in that there is substantial variance from one machinist to the next due to the flexible verification procedures. Furthermore, feeler gauges are limited to those areas that can be accessed, and are also limited by the length constraints of the gauge. Due to the manual nature of this technique, it is difficult to maintain an efficient workflow during manufacturing operations, considering that prior to beginning each machining step, the spacing has to be verified. All of these factors combine to increase the probability that the composite part is out-of-tolerance in relation to the machine tool.
Accordingly, there is a need in the art for an improved manufacturing quality control system. More particularly, there is a need in the art for proximity sensing of work pieces from machine tools to maintain close manufacturing tolerances. Additionally, there is a need for proximity sensing systems that communicate with remote data processing devices over wireless data communication links.
According to one embodiment of the present invention, a manufacturing quality control system for monitoring the proximity of a workpiece to a machine tool is disclosed. The system may include a proximity sensor attached to the machine tool for deriving a first distance measurement based upon the distance between the workpiece and the machine tool. Additionally, the system may include a wireless transmitter that generates a radio frequency signal or maintain a wired connection to a data processing device. The radio frequency signal may include a first sequence of data representative of the first proximity distance measurement. The wireless transmitter may be provided with the first proximity distance measurement from the proximity sensor. Furthermore, the system may include a remote data processing device in communication with the wireless transmitter. The remote data processing device may include a sensor status module for generating proximity information. The value of the first distance measurement as represented by the first sequence of data derived from the received radio frequency signal may correspond to the proximity information.
In accordance with another embodiment of the present invention, there is disclosed a method for monitoring the proximity of a machine tool to a workpiece during manufacturing. The method begins with generating an analog value on a proximity sensor, in which the analog value corresponds to a first proximity distance measurement. Thereafter, the method continues with converting the analog value to a digital value storable in a data packet, and transmitting the data packet as a wireless signal. The method further includes the step of receiving the data packet, which contains the first distance measurement between the machine tool and the work piece. The first distance measurement is extracted from the data packet, and indicator data is displayed. The indicator data is based upon the first distance measurement.
Thus, the machinist can remotely monitor the positioning of the workpieces to the trim fixture vacuum, increasing manufacturing reliability and product throughput. Multiple proximity sensors may be monitored simultaneously to expand quality control coverage. The present invention will be best understood by reference to the following detailed description when read in conjunction with the accompanying drawings.
These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which:
Common reference numerals are used throughout the drawings and the detailed description to indicate the same elements.
The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the functions of the invention in connection with the illustrated embodiment. It is to be understood, however, that the same or equivalent functions and may be accomplished by different embodiments that are also intended to be encompassed within the scope of the invention. It is further understood that the use of relational terms such as first and second and the like are used solely to distinguish one from another entity without necessarily requiring or implying any actual such relationship or order between such entities.
With reference to
According to another embodiment, and as additionally shown in the flowchart of
It is contemplated that proximity sensor 24 is particularly configured for detecting composite materials. A variety of sensor types may be utilized, including, but not limited to: capacitance-type, reed-type, ultrasound-type, and radio frequency-type. Preferably, the proximity sensor 24 has a range of approximately 0 to 0.055 inches, an accuracy of approximately 0.001 inches, and a resolution of approximately 0.000039 inches. Although sensors of other ranges and tolerances may be substituted, in order to properly position the workpiece 12 for tight tolerance manufacturing operations, it is understood that there should not be a substantial deviation from the foregoing operational characteristics. Other preferred operational characteristics of the proximity sensor 24 include a refresh rate of 4 khz (or every 250 microseconds), and resistant to ambient noise having a frequency spectrum lower than 5 Ghz.
As shown in
The oscillation signal from the oscillator 28 is fed to a trigger circuit/frequency counter 30. With reference again to the flowchart of
With reference to
Referring to
Although the length of the first sequence of data as generated by the proximity sensor 24 is understood to be 10 bits, due to the data size limitations of the serial output port 32, only 8 bits may be transmitted at a time. In this regard, the first sequence of data may be delimited to two bytes of data. As long as the first sequence of data is no greater than 127, or 0111 1111 in binary, then the first byte of data correctly represents the specified number. The second byte of data is also sent, but with a mask represented by the most significant bit. Where the most significant bit is zero, then all data in the second byte is removed as being irrelevant. On the other hand, where the most significant bit is one, and bits 0, 1, and 2 are removed, and bits 7, 8, 9 are transferred to the first byte.
According to one embodiment of the present invention, the wireless transmitter 50 is Bluetooth-compliant. As is well known in the art, Bluetooth is ideal for short-range, low-power data transfer applications where the communicating devices are in relatively close proximity to each other. The range of the wireless transmitter 50 may be approximately 30 feet. Alternative network modalities such as wireless USB, WiFi, and the like are also contemplated.
According to one embodiment of the present invention, power is supplied to the wireless transmitter 50 and the proximity sensor 24 from an on-board battery 53. The on-board battery 53 preferably supplies 18VDC to the proximity sensor 24, while the wireless transmitter 50 is supplied with 5VDC. Alternatively, self-sufficient power modalities are also contemplated for supplying the wireless transmitter 50 and the proximity sensor 24. By way of example only and not of limitation, there may be mechanical actuators linked to the operation of the machine tool 14, which power a miniature generator 55.
As shown in
According to one embodiment, the remote data processing device 52 is a handheld computer running the Windows Mobile operating system. The above-mentioned modules may be implemented as software code that is downloadable and executable on the Windows Mobile platform. Such software may be programmed in C#, Visual Basic, or any one of numerous programming languages/environments available for the platform. It will be recognized that any other computing platform may be utilized, whether mobility-oriented or not, including Windows XP, Windows XP for TabletPC, PalmOS, and so forth.
As indicated above, the wireless receiver 62 accepts the radio frequency signal 48 as broadcast by the wireless transmitter 50. The radio frequency signal 48 is representative of the serial data packet containing the first sequence of data. According to step 208, the method of monitoring the proximity of the machine tool 14 to the workpiece 12 continues with extracting the first proximity distance measurement 22 from the serial data packet. With further particularity, the decoder module 56 extracts the relevant bytes of data from the serial data packet, as it contains other data useful for error-free communications and troubleshooting, but is otherwise unused in processing the first proximity distance measurement 22. Additionally, the decoder module 56 performs a concatenation of the first transmitted byte and the second transmitted byte, the reverse of the delimiting step described above. Thus, the decoder module 56 produces a 10-bit wide numerical value that is representative of the first distance measurement 22.
Unless there is intimate familiarity with the operation of the proximity sensor 24, the numerical value thus produced by the decoder module 56 has no apparent significance. The decoder module 56 sends the numerical value to the sensor status module 58, where, according to step 210, proximity information is displayed on the display device 64. Generally, it is understood that the proximity information is based upon the first proximity distance measurement 22 and that it holds operational significance to the machinist, as will be further described below. It is expressly contemplated that the proximity information is updated in real time as the radio frequency signal 48 is received by wireless receiver 62.
With reference to
As further illustrated by
Each of the foregoing examples have referred to a single proximity sensor 24 taking measurements and transmitting the same to the remote data processing device 52. It is expressly contemplated, however, that the manufacturing quality control system 10 may include more than one proximity sensor 24, with measurements being simultaneously taken and reported to the remote data processing device 52. As illustrated in
Another visualization technique is contemplated, which is understood to be particularly useful for tracking multiple proximity sensors 24 employed for a single workpiece 12. It will also be appreciated that single proximity sensors 24 employed for a one of a plurality of machining operations may be similarly tracked. As shown in
The appearance of the sensor indicators 86 is based upon a relationship between the first distance measurement 22 acquired by the corresponding one of the proximity sensors 24, and a predetermined threshold. If the first distance measurement 22 exceeds the threshold, an alert is displayed as the proximity information. In the particular embodiment shown in
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
