Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1999-11-01
2002-10-15
Noland, Thomas P. (Department: 2856)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C073S011010, C073S579000, C073S593000, C100S099000, C702S056000
Reexamination Certificate
active
06466840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to press vibration monitoring, and, more particular, to a method of reducing dynamic factors during press operation, thereby lowering production press vibration severity levels.
2. Description of the Related Art
It has been found through experimentation that as press speed increases there are many additional die loads that occur that are not present at slower press speeds. There are actually several additional sources of significant die loads that, in general, many press owners, manufacturers, and operators do not know exist. At higher speeds, even though not exceeding the capacity of the press, the press requires more force to make the output part, and must also contend with several additional forces, which in turn creates a different set of more severe vibration conditions.
Vibration stress magnifications, created by the multiple dynamic load increases, can cause many problems with press structures. At certain definable vibration severity levels, as described in U.S. Pat. No. 5,094,107, stress magnification levels will be present, thus creating increased maintenance problems for the press and tooling. Vibration monitoring systems of the prior art shut down the press at an individual predetermined level, which when reached would begin to cause long term reliability damage to the press.
U.S. Pat. No. 5,094,107 measures this vibration severity while in actual production, and allows the press operator and production manager to know the long term liability effects of running the press at any combination of sensed speed and load. By monitoring the actual vibration severity level of the die application, and comparing the corresponding operation vibration severity level to a previously produced vibration severity zone chart, either manually or electronically the long term press operation may be graded.
What is needed in the art is a methodology for detecting and detailing the particular die process functions that create production press vibration severity levels and tipping moment conditions during increased speed operation. By reducing such production press vibration severity levels, increased productivity, reliability and optimization of existing metal forming dies may result.
SUMMARY OF THE INVENTION
According to the present invention, the press for use with an existing metal die is used to identify the rate of escalation of vibration severity and/or tipping moment as production speed is increased. The system utilizes and creates a data set regarding a trend path of the press and tool by monitoring press speed versus vibration severity and other parameters.
The present invention, in one form thereof, identifies the details of vibration acceleration levels at different press operating speeds, thereby identifying attributing factors that add or multiply, to create an overall vibration severity level. After such data is acquired, concentration and optimization on major contributing parameters is utilized to reduce portions of the vibration severity curve.
The invention, in another form thereof, includes a method for determining die tipping conditions with a vibration severity monitoring apparatus. Conditions regarding the slide stripper plate, or bed tipping and die station activity may all be monitored, recorded, and analyzed with the present invention.
The invention, in one form thereof, is directed to a method of monitoring the operation of a press machine which is run through a plurality of press running cycles. According to the method, there is first defined a plurality of press operating events associated with the operation of the press machine. Each of these press operating events has an associated modifiable control function. For each one of the press operating events, there is provided a measure of the vibrational activity associated therewith that is present in the press machine during each one of the press running cycles. A vibration measurement signal is generated which is representative of the vibrational activity measurement. The vibration measurement signals associated with each press operating event are then processed to identify the presence of a vibration trend therein that meets a defined trending criteria. The respective control function of each press operating event that is associated with the identification of the vibration trend is then modified.
The press operating events include, but are not limited to, stripper plate impact on the downstroke of the press machine slide, punch impact on a workpiece, snap-through activity, and stripper plate impact on the upstroke of the press machine slide.
The vibrational activity measurements are preferably generated by an arrangement of accelerometers coupled to the press machine.
The predefined trending criteria, in one form thereof, involves a rate of change in the vibration measurement signals that exceeds a predetermined threshold level.
The monitoring method is preferably applied to a press machine that is run through press running cycles characterized by a variable press running speed. Alternately, the press running cycles may be characterized by a variable load developed within the press machine.
The invention, in another form thereof, is directed to a method of monitoring the operation of a press machine which is run through a plurality of press running cycles. According to the method, there is first provided a respective measure of the vibrational activity that is present in the press machine during each one of the press running cycles. There is generated a respective vibration measurement signal which is representative of the vibrational activity measurement. Next, there is defined a plurality of press operating events which are associated with the operation of the press machine, wherein each press operating event has an associated modifiable control function. The respective vibration measurement signal associated with each one of the press running cycles is then resolved into a corresponding set of component vibration signals each associated with a respective one of the press operating events. The respective set of component vibration signals associated with each one of the press running cycles is processed to identify the presence of a vibration trend therein that meets a defined trending criteria. This identification of the vibration trend is made in relation to component vibration signals that are associated with the same press operating event. The respective control function of each press operating event which corresponds to the component vibration signals associated with identification of the vibration trend is then suitably modified.
The monitoring method, in another form thereof, further involves correlating the respective vibration measurement signal associated with each one of the press running cycles to a preselected press operating parameter; and correlating the occurrence of each one of the press operating events to the preselected press operating parameter. These correlation operations facilitate the correlation of the respectively corresponding set of component vibration signals of each respective vibration measurement signal to respective ones of the plurality of press operating events. The preselected press operating parameter preferably includes a measure of the press machine slide displacement relative to bottom dead center.
The invention, in another form thereof, is directed to a system for monitoring the operation of a press machine over a plurality of press running cycles. The system includes a means for defining a plurality of press operating events associated with the operation of the press machine, wherein each respective one of the press operating events has a modifiable control function associated therewith. The system further includes a measurement means for providing, with respect to each one of the press operating events, a respective measure of the vibrational activity associated therewith that is present in the press machine during each one of the press running cycles, and for generating
Knuth Randall J.
Noland Thomas P.
The Minster Machine Company
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