Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2002-07-09
2003-12-30
Gandhi, Jayprakash N. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S117000, C700S180000, C029S03300H, C345S215000
Reexamination Certificate
active
06671572
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and computer programs for automated design and manufacture of custom workholding fixtures or other similar objects requiring machining of substantially unique mounting geometries. More particularly, the present invention concerns a method and computer program providing for substantially automated CAD/CAM design and manufacture of custom workholding fixtures used to locate and secure workpieces or other items on which work, such as, for example, machining, welding, or assembly, is to be performed, wherein computer models of support structures and locating and clamping devices, including dimensions and mounting geometries associated therewith, facilitate development and testing of a workholding concept, production of fixture drawings, and generation and formatting of a corresponding control program for controlling a machine for manufacturing the fixture.
2. Description of the Prior Art
It is often desirable to create a custom workholding fixture to locate and clamp, hold, or otherwise secure parts, workpieces, or other items on which it is desired to perform manufacturing operations such as, for example, machining, welding, or assembly. Unfortunately, developing such a workholding fixture, from design to actual manufacture, can be a slow, expensive, and generally inefficient process.
Presently, fixture creation begins with development of a “workholding concept” or strategy for holding the workpiece during the manufacturing operations. A common method starts with a support or base structure, typically including, for example, a horizontal mounting plate, a tower structure, an angle plate, a window structure, and other support structures. A designer selects and arranges one or more locating and clamping devices in a manner sufficient to adequately and safely locate and secure the workpiece on the support structure. Such selection and arrangement is made with hard-won experience and is based on such considerations as, for example, the specifications and characteristics of the workpiece, the devices, and the support structure; the particular application and operations to be performed on the workpiece; and the particular circumstances surrounding those operations.
As will be appreciated by those with skill in the art, development of the workholding concept is a custom process for each different workpiece. There are no set standards, meaning every person engaged in this type of work may do things differently. Thus, with little or no standardization, the process can require considerable knowledge and experience in designing and in developing workholding concepts, and can include substantial risks of costly and time-consuming human errors.
Once the workholding concept is complete, it must be implemented to produce the actual workholding fixture. First, detailed design drawings must be produced by a fixture drawing draftsperson, wherein is shown and identified each locating and clamping device in its proper position on the support structure. The drawings must also show and dimension each device's mounting geometry, including, for example, fastening features or hole patterns, with which the device will be secured to the support structure. Furthermore, all of the mounting geometries usually are dimensioned referenced to a common locating axis on the support structure for manufacturability purposes. If, during production of the drawings, insufficient clearances between devices, the support structure, and the workpiece are discovered, the workholding concept must be re-designed so as to avoid the interference or other problem.
Next, a computer numerical control (CNC) program must be developed by a CNC programmer. The CNC program is based upon the workholding concept and upon the workholding fixture drawings and is therefore similarly unique to each fixture. The CNC program provides the machine code needed to direct a CNC machine to manufacture the support structure, including milling, drilling and tapping or otherwise implementing the mounting geometries for the devices. Additionally, the CNC programmer will develop a tooling list which identifies all tools needed and will group similar steps or steps involving similar tools so as to streamline preparation work by reducing or eliminating redundant or otherwise inefficient or wasteful actions.
Next, a machine operator, using the fixture drawing and the CNC program, prepares the machining operation for making the support structure. This includes verifying the CNC program by loading any required tooling and carefully stepping through the machining of each workpieces' mounting geometry to ensure that each will be properly made in accordance with the fixture drawing. Typically, there will be only one unique support structure made for each type of workpiece to be held, regardless of the total number of workpieces, necessitating that every step from development of the workholding concept, production of the fixture drawing, programming of the CNC program, and machining of the support structure be absolutely correct or else every instance of the workpiece will be improperly manufactured.
Once the support structure is completed, the various locating and clamping devices can be mounted, after which the support structure is ready to hold the workpiece for the machining, welding, or assembly process.
It will be appreciated that this process is slow, inefficient, and fraught with potential for error. Typically, four skilled people are involved, including the workholding concept designer, the fixture drawing draftsman, the CNC program programmer, and the machine operator. Lead time from start to finish can easily reach or exceed four weeks. Errors committed at any point in the process can be carried through and possibly magnified, and may not be discovered until the support structure is assembled and the workholding devices cannot be properly mounted because of incorrect hole patterns, or, in some cases, the hole patterns may be correct but the workholding device placement may be wrong. Where errors are found, it may be possible to fill incorrect holes and redrill the support structure rather than start anew, though, in either case, time and money is lost.
Due to the above-identified and other problems and disadvantages in the art, a need exists for an improved process for designing and manufacturing custom workholding fixtures.
SUMMARY OF THE INVENTION
The present invention provides a distinct advance in the art of methods and computer programs for automated design and manufacture of custom workholding fixtures or other similar objects requiring machining, fabricating, or assembling of substantially unique mounting geometries. More particularly, the present invention provides a method and computer program for substantially automated CAD/CAM design and manufacture of custom workholding fixtures used to locate and secure workpieces on which work, such as, for example, machining, welding, or assembly, is to be performed, wherein computer models of support structures and locating and clamping devices, including dimensions and mounting geometries associated therewith, facilitate development and testing of a workholding concept, production of fixture drawings, and generation and formatting of a corresponding control program for controlling a CNC machine for manufacturing the workholding fixture.
In a preferred embodiment, the present invention is embodied in a computer program stored on and executed by a system comprising a substantially conventional computing device coupled with and operable to direct and control the substantially conventional CNC machine to machine the workholding fixture. The workholding fixture comprises the support structure and one or more of the workholding devices, which may be, for example, swing clamps, work supports, special use clamps, edge clamps, or collet vises, of an electric, hydraulic, or manual nature.
In a preferred embodiment, the computer program supplements existing CAD software, and broadly comprises code segments rel
Craft Roger L.
Kroeker Stan
Nye Frank Michael
Agile Technology Partners, LLC
Gandhi Jayprakash N.
Hovey & Williams, LLP
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