Mandrel Reverse Motion in Tube Rolling Mill
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Solution Overview
Problem
Existing tube rolling processes with mandrels face challenges such as uneven temperature distribution, reduced productivity, and difficulties in rolling short or thin-walled tubes due to mandrel acceleration and extraction methods, which affect dimensional quality and stability.
Innovation Solution
A process and plant design where the mandrel is inserted in-line but moves opposite to the rolling direction, eliminating the need for an extracting rolling mill, allowing for reverse mandrel insertion and extraction, and utilizing rotating arms for efficient conveyor operations to reduce cycle times and improve tube cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mandrel moves freely with the tube during rolling (floating mandrel), then high productivity is achieved with very short cycle times, but the mandrel acceleration causes compression states that lead to dimensional quality defects and uneven temperature distribution along the tube
Solution Approach 1:
The patent inverts the conventional mandrel motion direction by making the mandrel move in the opposite direction to the tube rolling direction. This reverse motion prevents mandrel acceleration and the associated compression states that cause dimensional defects, while still enabling high productivity through coordinated reverse movement and extraction at the inlet side
2Manufacturing precision
If the mandrel is retained and fed at controlled speed during rolling, then dimensional quality is improved, but the tube cooling remains uneven because the head part remains hot longer while the rear part is cooled by mandrel contact
Solution Approach 1:
By reversing the mandrel motion direction, the patent changes which tube portions contact the mandrel during rolling. The reverse motion ensures more uniform thermal contact along the tube length, preventing the head portion from remaining excessively hot while the rear is over-cooled, thus improving temperature uniformity
3Ease of operation
If an extracting device is used to pull the tube forward while the mandrel is blocked for extraction, then the mandrel can be extracted from the tube, but the cycle times become longer and productivity decreases to 2 tubes per minute
Solution Approach 1:
The patent eliminates the need for a separate extracting device by inverting the extraction location to the inlet side of the rolling mill. The mandrel is extracted in reverse direction at the inlet side where the tube enters, allowing simultaneous tube rolling and mandrel extraction, thus maintaining high productivity without requiring additional extracting equipment
Solution Approach 2:
The patent extracts the mandrel from the tube at the inlet side rather than requiring a downstream extracting device. This early extraction at the entry point eliminates the need for separate extraction equipment and reduces cycle time by allowing continuous operation
4Productivity
If the mandrel conveyor work travel is reduced by reversing mandrel insertion, then productivity is enhanced and cycle times are reduced, but the process complexity increases with reverse insertion requirements
Solution Approach 1:
The patent simplifies the overall system by inverting the mandrel insertion and extraction sequence. Although individual steps require reverse motion coordination, the elimination of the extracting device and reduction in mandrel conveyor travel distance result in net lower complexity and improved productivity
Data Source
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AI summary
A tube rolling plant (R) with multi-stand rolling mill having two or more rollers, for implementing a mandrel rolling process with controlled speed has a mandrel (31) which is inserted into the hollow body (39) from the frontal opening thereof by passing it first through the rolling mill (5). An opposite movement (L3) with respect to the rolling direction is imparted to the mandrel (31) by means of the hooking device (61) when rolling the hollow body (39) and the rear end of the rolled tube (42) is extracted at the end of the rolling operation.