Stepped Forming Mandrel for Uniform Hollow Body Cavity Profiles
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Solution Overview
Problem
Existing methods for forming hollow bodies result in cross-sectional narrowing of the cavity due to material-related elastic recovery or additional component attachment, making it difficult to insert a counterpart into the formed hollow body.
Innovation Solution
A stepped forming mandrel with expanded and reduced cross-sections is used, along with a forming die, to create a wall profile on the hollow body, compensating for elastic recovery and allowing for uniform cavity cross-section adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a forming mandrel with uniform cross-section is used for forming the hollow body wall, then the forming process is simple and efficient, but the cavity cross-section narrows after forming due to elastic recovery, making it difficult to insert a counterpart
Solution Approach 1:
The forming mandrel is segmented into different cross-sectional sections along its length. Specifically, the mandrel has a first section with a larger cross-section and a second section with a smaller cross-section, allowing different regions of the hollow body to be formed with different dimensional characteristics to compensate for elastic recovery variations.
Solution Approach 2:
Different sections of the forming mandrel are designed with different cross-sectional dimensions to address local variations in elastic recovery. The first section with larger cross-section compensates for greater elastic recovery in that region, while the second section with smaller cross-section maintains the cavity opening dimensions where less recovery occurs.
2Strength
If additional components are attached to the outside of the hollow body wall for fixation, then the hollow body can be securely fixed, but the cavity cross-section narrows further, exacerbating the insertion difficulty
Solution Approach 1:
The forming mandrel is designed in advance with expanded cross-sectional sections that pre-compensate for the dimensional reduction caused by subsequent component attachment and elastic recovery. This preliminary dimensional adjustment ensures that the cavity remains accessible for counterpart insertion even after additional components are attached for fixation.
3Manufacturing precision
If the forming die moves along the hollow body wall with a forming motion, then the wall profile is produced by plasticizing the material, but uneven elastic recovery occurs along the length of the hollow body wall
Solution Approach 1:
The forming mandrel is divided into multiple sections with different cross-sectional dimensions corresponding to different regions of the hollow body wall. This segmentation allows each region to be formed with appropriate dimensional compensation for its specific elastic recovery characteristics, ensuring more uniform cavity cross-section along the entire length.
Solution Approach 2:
The cross-sectional dimensions of the forming mandrel are varied along its length to match the varying elastic recovery characteristics of different hollow body wall regions. By changing the mandrel parameters (cross-sectional area) along its length, the process compensates for uneven material recovery and achieves more uniform cavity dimensions.
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
Ensures a uniform cavity cross-section after forming, facilitating the insertion of a counterpart and accommodating additional components, thereby enhancing the functionality and compatibility of the formed hollow body.
Implementation Method 1
the wall profile on the inside of the hollow body wall is produced by plasticizing material of the hollow body wall due to the forming motion of the forming die and by mapping the forming mandrel profile on the inside of the hollow body wall as the wall profile
Implementation Method 2
a material-related elastic recovery of the hollow body wall that is uneven along its length and occurs automatically when the forming mandrel is removed from the interior of the hollow body after the forming process is complete
Data Source
Figure 1~3
Figure 4~5
Figure 6(1)~6(2)
AI summary
To create a wall profile on an inner side of a plastically deformable hollow body wall (2) of a hollow body (1), a forming mandrel (8) is arranged inside a cavity (3) of the hollow body (1) such that the forming mandrel (8) extends at the level of a first longitudinal section (l1) of the hollow body wall (2) with a cross-sectionally expanded mandrel section (12) which has a shaping mandrel profile section as well as a cross-sectional excess compared to a cross-sectionally reduced mandrel section (14) which extends at the level of a second longitudinal section (l2) of the hollow body wall (2) following the first longitudinal section (l1) of the hollow body wall (2) and has a further shaping mandrel profile section. A forming die (9) is moved with a forming motion relative to the hollow body wall (2) and relative to the cross-section enlarged mandrel section (12) and relative to the cross-section reduced mandrel section (14) of the forming mandrel (8).A mechanical arrangement is designed to carry out the above procedure.