Mandrel Rod Handling With In-Line Pre-Threading for Faster Tube Rolling
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Solution Overview
Problem
The existing mandrel rod handling systems in seamless tube rolling mills require significant axial stroke for the mandrel rod retaining device, which limits cycle frequency and productivity, and can result in temperature loss of the rolled product due to prolonged contact with the mandrel rod.
Innovation Solution
A device comprising an inserter and a retaining device with a movable fixing unit that temporarily holds the mandrel rod, allowing it to be pre-threaded into the tube blank within the auxiliary time of the machine cycle, thereby reducing cycle time and increasing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mandrel rod is threaded into the tube blank in the rolling line using a conventional retaining device, then the mandrel rod can be properly inserted and retained, but the axial stroke required is too long which reduces cycle frequency and productivity
Solution Approach 1:
The mandrel rod is pre-threaded into the tube blank before the tube blank enters the rolling mill, during the auxiliary time of the machine cycle. This preliminary action allows the main retaining device to have a shorter axial stroke since it only needs to retain the already-inserted mandrel rod, not thread it from scratch. The pre-threading operation prepares the mandrel rod in advance, separating the threading function from the retaining function.
Solution Approach 2:
The mandrel rod handling process is divided into two separate functions: (1) pre-threading the mandrel rod into the tube blank during auxiliary time, and (2) retaining the mandrel rod during the main rolling operation. This segmentation allows each function to be optimized independently - the pre-threading can occur during non-critical time periods while the retaining device focuses solely on holding the mandrel rod with minimal stroke.
2Productivity
If the mandrel rod is pre-threaded next to the rolling line, then the axial stroke of the retaining device is reduced, but temperature loss of the rolled product occurs due to longer contact time with the mandrel rod
Solution Approach 1:
Instead of pre-threading the mandrel rod beside the rolling line (lateral positioning), the invention performs the pre-threading operation within the rolling line itself, utilizing the longitudinal dimension of the rolling process. The mandrel rod is fed and threaded into the tube blank at a position downstream of the tube blank entry point, allowing the tube blank to already be in the rolling line when mandrel insertion occurs. This dimensional change reduces both the contact time before rolling begins and the distance the mandrel rod must travel outside the rolling line.
3Reliability
If the mandrel rod is threaded into the tube blank during the main time of the machine cycle, then proper insertion is achieved, but the cycle frequency is reduced due to the time required for the retaining device to retract and reposition
Solution Approach 1:
The mandrel rod is pre-threaded into the tube blank during the auxiliary time period, which is the time when the tube blank is being positioned and prepared for rolling but before the main rolling operation begins. This preliminary threading action completes the mandrel insertion before the critical rolling cycle starts, so the retaining device does not need to perform time-consuming retraction and repositioning operations during the main machine cycle. The auxiliary time is utilized efficiently to prepare the mandrel rod insertion in advance.
Data Source
AI summary
A device for handling mandrel rods in a rolling plant for rolling seamless tubes comprises an inserter. The inserter moves a mandrel rod in a rolling direction such that the mandrel rod, starting from an initial state, is pushed into a tube blank situated upstream of the mandrel rod. A retaining device has a fixing unit that is movable along the rolling line and is designed to temporarily hold the mandrel rod at an action point at a rear end of the mandrel rod and to carry out a working stroke. The mandrel rod can be inserted into the rolling mill in the rolling direction and pulled out of the rolling mill counter to the rolling direction by the retaining device. The retaining device is designed such that the starting position of the fixing unit lies between the two ends of the mandrel rod in the initial state.