Bourdon Spring Autofrettage and Laser Welding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for producing Bourdon springs face issues such as crevice corrosion, dimensional inaccuracies, and high rejection rates due to TIG welding, leading to hysteresis and kinematic problems, and do not ensure even heating of the spring and process carrier, resulting in suboptimal measurement performance.
Innovation Solution
The method involves using a straight profile tube with a rectangular cross-section, welding one end and clamping the other to a tool holder, bending it over a mandrel, and applying pressure 10 to 100 times the nominal pressure to achieve autofrettage, which compresses the material and smooths the surface, followed by laser welding to connect it to a process carrier, ensuring precise and reproducible production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If TIG welding is used to connect the Bourdon spring to the process carrier, then the spring can be joined to the carrier, but crevice corrosion occurs inside the spring and severe heating occurs on the outside, leading to hysteresis and measurement deterioration
Solution Approach 1:
The patent replaces TIG welding with laser welding technology. Laser welding provides precise, localized heating that minimizes heat-affected zone and avoids the severe external heating and crevice corrosion problems associated with TIG welding. The laser beam delivers energy concentrated at the weld point, preventing the glow-out effect that deteriorates measurement results while still achieving strong joint connection.
Solution Approach 2:
The patent changes the welding parameters by using laser welding instead of TIG welding. This involves changing the heat source characteristics (focused laser beam vs. distributed arc), heating rate, and temperature distribution. The laser welding process parameters enable precise control of thermal input, avoiding the excessive heating that causes hysteresis while maintaining joint strength.
2Strength
If TIG welding is used by hand, then the spring can be joined to the carrier, but the dimensional accuracy after welding is outside the tolerance of + - 0.1 mm, meaning kinematics for subsequent adjustment are not guaranteed
Solution Approach 1:
The patent replaces manual TIG welding with automated laser welding. This substitution eliminates the variability inherent in manual operation and provides consistent, repeatable welding results. The automated laser welding system maintains precise control over weld parameters, ensuring dimensional accuracy within the required + - 0.1 mm tolerance and guaranteeing proper kinematics for subsequent adjustment.
Solution Approach 2:
The patent changes from manual to automated welding control, transforming the welding process from a variable manual operation to a precisely controlled automated process. This parameter change ensures consistent heat input, weld bead geometry, and joint strength, all while maintaining dimensional accuracy within specification limits.
3Duration of action of stationary object
If only the spring is heated during temperature treatment and not the entire system, then the spring can be treated, but a high level of testing is necessary with regard to tightness because up to 30% rejects occur in the case of springs with a wall thickness of 0.07 mm
Solution Approach 1:
The patent merges the heating process to include both the spring and the process carrier simultaneously, rather than heating only the spring. This combined heating approach ensures uniform temperature distribution across the entire assembly, preventing thermal stress concentrations at the weld interface that could compromise tightness. The unified thermal treatment reduces rejects by ensuring the entire system reaches the required temperature for proper material properties.
4Measurement precision
If the Bourdon tube wall thickness is reduced to 0.07 mm for precise measurement, then measurement precision is improved, but up to 30% rejects occur during tightness testing
Solution Approach 1:
The patent replaces TIG welding with laser welding, which provides more precise and controlled heating for thin-walled tubes. Laser welding's focused energy delivery minimizes heat-affected zone and reduces the risk of weld defects in 0.07 mm wall thickness material. This substitution dramatically reduces tightness testing rejects while maintaining the thin wall thickness needed for precise measurement.
Solution Approach 2:
The patent changes the welding process parameters by using laser welding with controlled heat input specifically suited for thin-walled materials. This parameter change enables reliable welding of 0.07 mm wall thickness tubes without the excessive heating and defect formation that occurs with TIG welding, thereby reducing rejects while maintaining measurement precision.
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 process enhances the service life and tightness of the Bourdon spring, reduces hysteresis and linearity deviations, and allows for precise installation without further adjustments, improving the overall performance and reliability of the pressure measuring device.
Implementation Method 1
applying pressure to the Bourdon spring (1) with 10 to 100 times the pressure above the nominal pressure of the Bourdon spring (1)
Implementation Method 2
applying pressure to the Bourdon spring (1) with 10 to 100 times the pressure above the nominal pressure of the Bourdon spring (1)
Implementation Method 3
laser welding to connect it to a process carrier
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a method for manufacturing a Bourdon spring 1 with or without a process carrier 2.To simplify the production of the Bourdon springs 1 and reduce potential rejects of manufactured Bourdon springs 1, as well as to obtain significantly improved hysteresis, the invention provides that a Bourdon spring 1 is produced in the following steps: - using a straight profile tube 10 with an approximately rectangular cross-section, - closing one end of the profile tube 10 with a welded end piece, - welding the second end of the profile tube 10 to a process carrier 1 or receiving the second end of the profile tube 10 in a tool holder 12, - bending the profile tube 10 over a mandrel 18 to form a Bourdon spring 1, - applying two shaped pieces 20, 21 to the contour of the pre-bent Bourdon spring 1, and - pressurizing the Bourdon spring 1 with a pressure 10 to 100 times above the nominal pressure of the Bourdon spring 1.