Press Forming Sequence to Prevent Sliding Marks on Cylindrical Walls
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Solution Overview
Problem
Conventional pressing machines form sliding contact marks on the outer surface of workpieces due to contact with the inner surface of the forming hole, resulting in poor appearance.
Innovation Solution
A pressing machine with a transfer device and a stripper mechanism that synchronizes the movement of the punch and knockout pin to restrict inward deformation and control the upward movement of the workpiece, preventing sliding contact marks by ensuring the workpiece is pushed into and out of the forming hole in a manner that minimizes contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the workpiece is pushed into the forming hole while the punch remains inserted, then the workpiece can be formed, but sliding contact marks are formed on the outer surface of the workpiece due to sliding contact with the inner surface of the forming hole
Solution Approach 1:
The punch is extracted from the workpiece before the workpiece is pushed into the forming hole. This preliminary action prevents the punch from being in contact with the workpiece during the pushing operation, thereby eliminating the source of sliding contact marks on the workpiece surface.
Solution Approach 2:
The punch is extracted (taken out) from the workpiece before the pushing operation. By removing the punch from the system during the critical pushing phase, the harmful sliding contact between the punch and workpiece surface is eliminated, preventing surface defects.
2Manufacturing precision
If the workpiece is pushed into the forming hole, then forming can be completed, but the workpiece may come into contact with the inner surface of the forming hole causing sliding contact marks
Solution Approach 1:
The stripper acts as an intermediary device that restricts the workpiece from contacting the inner surface of the forming hole during the pushing operation. By introducing this mediator, the harmful direct contact between the workpiece and forming hole surface is prevented, eliminating sliding contact marks.
Solution Approach 2:
The stripper is positioned and configured in advance to restrict workpiece movement before the pushing operation begins. This preliminary arrangement ensures that during the pushing phase, the workpiece cannot contact the forming hole inner surface, preventing surface defects.
3Manufacturing precision
If the punch remains inserted during the pushing operation, then forming control is maintained, but the workpiece surface quality deteriorates due to sliding contact
Solution Approach 1:
The forming process is segmented into distinct phases: first the punch forms the workpiece, then the punch is extracted, and finally the workpiece is pushed into the forming hole. By dividing the process into separate steps, the harmful sliding contact is eliminated while maintaining forming control in the first phase.
Solution Approach 2:
The punch extraction is performed as a preliminary action before the pushing operation. This sequencing ensures that the workpiece surface is protected from sliding contact marks while the forming control achieved by the punch is preserved in the earlier forming phase.
Data Source
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AI summary
Provided is a pressing machine and a press forming method in which sliding contact marks are hardly to be formed on a workpiece. A pressing machine (10) of the present disclosure includes a punch (20), which is in a state of being inserted into a cylindrical workpiece (90), enters a forming hole (50) of a die (41) to strip off or draw a cylindrical wall (91) of the workpiece (90) between the outer surface of the punch (20) and the inner surface of the forming hole (50). The pressing machine (10) includes a stripper (30) configured to come into contact with the workpiece (90) to retain the workpiece (90) within the forming hole (50) wherein the punch (20) moves toward the top dead center, and a knockout pin (55) configured to push the workpiece (90) out of the forming hole (50) after the punch (20) has come out of the workpiece (90).