Gantry Positioning Device Force Frame Torque Compensation
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Solution Overview
Problem
Gantry-type positioning devices face challenges in maintaining precise positioning accuracy under high process forces, as the leverage in these constructions can lead to deformation and displacement of the tool, especially in applications requiring forces over 500 N and sub-micrometer accuracy, such as thermocompression bonding.
Innovation Solution
The positioning device incorporates a force frame above the tool to transfer process forces to the carriages, using a pneumatic cylinder with an offset application to counteract torque and maintain stability, and includes flexible joints to accommodate slight carriage misalignments, with an adjustable angle for the pneumatic cylinder to optimize torque compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tool is placed offset from the cross bar to improve accessibility, then ease of operation is improved, but torque is generated that deforms the cross bar and reduces positioning accuracy
Solution Approach 1:
The positioning device is segmented into functionally independent modules: the cross bar for positioning, the toolholder for tool mounting, and the force frame for force bearing. This segmentation allows the tool to be offset for accessibility while the force frame independently handles the torque and forces, preventing cross-bar deformation and maintaining positioning accuracy.
Solution Approach 2:
The force frame acts as an intermediary structure between the tool and the cross bar. It receives and transfers process forces and torques directly to the linear guides, preventing these forces from acting on the cross bar and thus eliminating the harmful deformation while allowing the tool to remain offset for operational accessibility.
2Productivity
If high process forces are applied to the tool, then productivity is improved, but the cross bar deforms due to torque, reducing positioning precision
Solution Approach 1:
The force-bearing function is extracted from the cross bar and assigned to a dedicated force frame. This allows high process forces to be applied productively while the cross bar is relieved of these forces, maintaining its dimensional stability and positioning accuracy even under heavy loading conditions.
Solution Approach 2:
The force frame is positioned in a different spatial dimension (above the tool in the vertical direction) than the cross bar, creating a separate force transmission path. This dimensional separation allows high forces to be applied without affecting the horizontal positioning accuracy of the cross bar.
3Device complexity
If the toolholder is asymmetric to reduce complexity, then device complexity is reduced, but asymmetrical torque is generated that reduces positioning accuracy
Solution Approach 1:
The asymmetrical torque generated by the asymmetric toolholder is not eliminated but converted into a useful counteracting moment. A pneumatic cylinder applies an offset force that generates a torque specifically designed to counterbalance the asymmetrical torque from the toolholder, thereby maintaining positioning accuracy despite the asymmetric design.
Solution Approach 2:
The pneumatic cylinder's point of application is offset in the X-direction to change the force parameters, creating a counteracting torque that compensates for the asymmetrical torque from the toolholder. This parameter adjustment allows the asymmetric toolholder design to maintain positioning accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances positioning accuracy by minimizing torque-induced deformation and displacement, ensuring precise placement of components even under high forces, while maintaining flexibility and practicality.
Implementation Method 1
The process force is applied by a pneumatic cylinder which operates between the force frame and the toolholder, the point of application of the pneumatic cylinder on the toolholder being offset in the X-direction relative to the point of application of the process force on the tool
Data Source
AI summary
A positioning device in a gantry-type construction, include two parallel linear guides with integrated linear drives, each of which supports an X-carriage in a manner allowing movement in an X-direction, and having a cross bar which is joined to the two X-carriages and which, with the aid of an integrated linear drive, supports a carriage in a manner allowing movement in a Y-direction perpendicular to the X-direction. In addition, the positioning device has a toolholder which is guided on the Y-carriage in a Z-direction and bears a tool for processing a workpiece located in an X-Y plane, the tool being located next to the cross bar so as to be offset in the X-direction. A force frame, disposed above the tool in the Z-direction, transfers a process force acting on the tool, to the carriages, without deforming the cross bar by a torque.