Patent Application
20240109158
The present disclosure relates to a work piece processing device with a servo-elastic actuator system having simultaneous precision force and position control, a weight compensating elastic member and a locking mechanism for locking out the elastic member during tool movement.
This section provides background information related to the present disclosure which is not necessarily prior art.
Work piece processing devices as used herein are devices that apply force to a work piece (or work pieces) during processing of the work piece. In some devices, the force is part of and contributes to the performance of the work on a work piece (or work pieces), such as in welding, and in other cases, the force is not part of the performance of the work on the work piece but rather is applied to clamp the work piece in place as the work is performed on the work piece. Such work processing devices have actuators that apply the force to the work pieces such as by moving a tool against the work piece or applying a clamp to the work piece to hold it in place during processing. Such work piece processing devices can include devices for ultrasonic, vibration, laser, thermal, spin or infrared processing of plastics or metal where force is applied to the work piece, such as welding, staking, swaging, and cutting. Work piece processing devices that apply force to the work piece during processing need actuators that can control both force and position.
Pneumatic actuators are good at providing a constant force regardless of the actuator's position when in contact with a relatively stiff surface, but are not very precise at controlling position. Servo-actuators on the other hand are precise at controlling position but not that good at controlling force when in contact with a relatively non-compliant or stiff surface. A servo-actuator is a mechanism that provides position controlled motion in a mechanical system in response to an electrical input signal using feedback of an output of the servo actuator for position control.
Use of servo-actuators for ultrasonic welding, vibration welding, laser welding, thermal welding, spin welding, infrared welding and ultrasonic cutting could control position very accurately, about a thousandth of an inch, but could not control force to under plus or minus 40 pounds. The problem arises from the relative non-compliance of the material of the work piece being pressed against during welding. Even though the servo-actuators can resolve the position to within a thousandth of an inch, this small relative motion, given the stiffness of the material being pressed against, results in a large change in force— of about 40 pounds for a typical piece of plastic, and even higher for a piece of metal. This problem of force to position sensitivity is inherent with servo-actuators when pushing against a relatively non-compliant surface, regardless of how good the control system is for the servo-actuator.
Servo actuators often have a torque control mode that gives a degree of control of the force, such as that described in U.S. Pat. No. 8,720,516 for “Ultrasonic Press Using Servo Motor with Delayed Motion.” But again, because of the noncompliance of the surface being pushed against, the force varies by a high percentage of the total load.
One well understood method in the prior art to control force precisely with a servo-actuator is to have the servo-actuator press against a long travel spring. This gives very good force control, but does not have any position control. U.S. Pat. No. 4,817,848 for “Compliant Motion Servo” discloses the use of a long travel spring with a servo-actuator to control force, but switches over to a closed loop position control at the end of motion, and therefore loses control of force at the end of the process.
JP2013-063521 for an “Ultrasonic Welding Device, Ultrasonic Welding Method, Wiring Device” discloses an ultrasonic welder which performs ultrasonic welding by pressing a tool horn attached to an ultrasonic sliding unit slidable relative to a body frame against a work piece that includes a first linear scale for measuring a moving amount of the tool horn, a compression spring pressing the ultrasonic sliding unit, a driving means compressing the compression spring, a second linear scale measuring a compressed amount of the compression spring, and a load cell measuring a pressing force by the compression spring. When compressing the compression spring by driving the driving means, the pressing force by the compression spring measured by the load cell, the moving amount of the tool horn measured by the first linear scale, and the compressed amount of the compression spring measured by the second linear scale are fed back to the driving means and controlled to perform ultrasonic welding while imparting an optional pressing force to the work piece. However, when the compression spring can only be in compression, the weight of the tool horn and carriage bottom out and the system is not able to distinguish forces exerted on the work pieces being welded at forces below the weight load of the tool horn and carriage.
Commonly assigned U.S. Pat. No. 10,864,608 discloses a work piece processing device with a servo-elastic actuator system that provides improved force control of a servo-actuated work piece processing device.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
In a compliant assembly in series with an actuator, for example U.S. Pat. No. 10,864,608 the changes in velocity can cause a reaction in the springs. This reaction causes harmonic ‘ringing’ movement at the transitions that lasts for a time dependent on mass and change in velocity. This limits the possible set values when there is a desired impact or force build up on the work piece. The present disclosure provides a mechanism to restrict the movement of the compliant assembly when desired and allow the compliant assembly to move freely when desired. The mechanism will have an adjustable range to allow the compliant assembly to adjust to any changes in mass of the overall system. The mechanism may be able to control the length of the assembly to return to a desired length for a given mass. The mechanism may have an adjustable stop to prevent the compliant assembly from further extending but allowing compression. The mechanism may engage a damper to restrict movement and disengage to allow for free movement.
Locking the spring assembly during the transitions eliminates the harmonic response, then unlocking at a set constant velocity or set acceleration allows for utilizing the spring system as desired with more control over the impact and force build up. This allows for faster velocities, heavier horns, or a combination thereof, while remaining in control and having wider ranges possible for impact and force build up. This also allows for lower force profiles for smaller, delicate parts and more repeatable force profiles at low forces, for example.
A work piece processing tool includes a tool device and a work piece holder. A servo-elastic actuator system includes a servo actuator and a compliance elastic member that connects the tool device to the servo actuator. The servo-elastic actuator system moves the tool device toward the work piece holder. A locking mechanism engages the tool device to the servo actuator to limit movement of the tool device relative to the servo actuator.
A method of operating a work piece processing tool having a tool device for processing a work piece on a work piece holder and including a servo-elastic actuator system including a servo actuator and a compliance elastic member, wherein the servo-elastic actuator system moves the tool device toward the work piece holder includes engaging a locking mechanism between the tool device and the servo actuator; actuating the servo actuator to lower the tool device to the work piece; disengaging the locking mechanism; and actuating the tool device and the servo-actuator to perform a desired processing of the work piece.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
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One or more of the elements disclosed above including controller 22 may include or be implemented in one or more processing circuitries such as hardware including logic circuits; a hardware/software combination such as a processor executing software; or a combination thereof. For example, the processing circuitries more specifically may include, but is not limited to, a central processing unit (CPU), an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, application-specific integrated circuit (ASIC), etc.
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In operation, the work piece 34 is placed on the work piece holder 32 and the locking mechanism 40, 140, 240, 340, 440, 540 is engaged in order to prevent or inhibit the relative movement of the tool device 30 or work piece holder 34 relative to the actuator member 20 as one of the tool device 30 and work piece holder is moved toward the other of the tool device 30 and the work piece holder 32 by the actuator member 20. Accordingly, the locking mechanism 40, 140, 240, 340, 440, 540 prevents the harmonic movement of the tool device 30 or the work piece holder 32 as the tool device 30 or work piece holder 32 is moved toward the other of the tool device 30 or work piece holder 32. Accordingly, the tool device 30 or work piece holder 32 can be moved at higher velocities and/or heavier tool devices can be used while maintaining control of the movement thereof. The locking mechanism 40, 140, 240, 340, 440, 540 can then be disengaged and the tool device 30 can then be activated by the controller 22 to perform the desired processing to the work piece 34. The spring 16 provides compliance that allows for lower force profiles and more repeatable force profiles.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer, or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
