Mandrel Rod Retaining Stroke Reduction in Tube Rolling Mills
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Solution Overview
Problem
The existing methods for handling mandrel bars in seamless pipe rolling mills result in reduced productivity due to the need for the mandrel bar retaining device to move during the main time of the machine cycle, leading to longer cycle frequencies and temperature loss in the rolled product.
Innovation Solution
A device with a retaining unit that shortens the working stroke of the mandrel bar, allowing it to be pre-threaded during non-productive machine cycle time, reducing cycle time and minimizing temperature loss, and includes a fixing unit that temporarily holds the mandrel bar at the rear end for efficient insertion and withdrawal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the mandrel bar is threaded into the tube blank on the rolling line during the main cycle time, then the mandrel bar can be properly positioned for rolling, but the cycle frequency is reduced and productivity decreases
Solution Approach 1:
The mandrel bar is pre-threaded into the tube blank during the non-productive time before the rolling process starts. The retaining device is positioned and ready to hold the mandrel bar at the engagement point before rolling begins, so that when the rolling process starts, the mandrel bar is already in its final position and does not need to be moved during the main cycle time.
2Ease of operation
If the mandrel bar retaining device moves during the main time of the machine cycle, then the mandrel bar can be inserted and withdrawn, but the cycle time increases and productivity is reduced
Solution Approach 1:
The retaining device is positioned in advance at the engagement point and is ready to hold the mandrel bar before the rolling process starts. The device performs the insertion and positioning actions during the non-productive setup time, so that during the main rolling cycle, no movement of the retaining device is needed.
Solution Approach 2:
The mandrel bar handling operations (insertion, positioning, and initial holding) are extracted from the main rolling cycle and performed separately during the non-productive time. This separates the mandrel bar preparation operations from the rolling operations, allowing them to be completed before the rolling process begins.
3Loss of time
If the mandrel bar is pre-threaded next to the rolling line, then the cycle time is reduced, but temperature loss of the rolled product occurs due to longer contact time
Solution Approach 1:
Instead of pre-threading the mandrel bar in a separate location next to the rolling line (which increases contact time), the mandrel bar is threaded directly into the tube blank at the rolling line position. This changes the spatial dimension of the operation, allowing the mandrel bar to be inserted at the exact location where it is needed, minimizing unnecessary contact time and temperature loss.
4Loss of time
If the working stroke of the mandrel bar is shortened, then the cycle time is reduced and productivity increases, but the mandrel bar may not be fully inserted into the tube blank
Solution Approach 1:
The mandrel bar is pre-positioned and pre-threaded into the tube blank during the non-productive time before rolling begins. The retaining device is positioned at the engagement point and ready to hold the mandrel bar in its final position. This preliminary positioning ensures that when the rolling process starts, the mandrel bar is already fully inserted to the correct depth, eliminating the need for a long working stroke during the rolling cycle.
Data Source
Figure 1
Figure 2-1~2h
Figure 2-2~2n
AI summary
Device (10) for handling mandrel rods (3) in a rolling plant (1) that has a rolling mill (20) for rolling seamless tubes (2'), the device (10) comprising: a push pointer (11) which is designed to move a mandrel rod (3) situated in a rolling line (L) in a rolling direction (R) such that the mandrel rod (3), starting from an initial state, can be pushed into a tube blank (2) situated upstream of the mandrel rod (3) in the rolling direction (R); a retaining device (12) having a fixing unit (12a) that is movable along the rolling line (L) and is designed to temporarily hold the mandrel rod (3) at an action point (3c) in the region of the rear end (3b) of the mandrel rod (3) and to carry out a working stroke, starting from a starting position (xA), in the rolling direction (R) and counter to the rolling direction (R), as a result of which the mandrel rod (3) can be inserted into the rolling mill (20) in the rolling direction (R) and pulled out of the rolling mill (20) counter to the rolling direction (R) by the retaining device (12); characterised in that the retaining device (12) is configured such that the starting position (xA) of the fixing unit (12a) in the initial state is between the two ends (3a, 3b) of the mandrel rod (3).