Movable Die Contact Control for Accurate Hot Press Forming
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Solution Overview
Problem
Conventional hot press forming methods struggle to achieve both shape accuracy and productivity, as they often result in defects due to uneven cooling rates and prolonged bottom-dead-center holding times.
Innovation Solution
A hot press apparatus with a movable die part that alternates between abutting and retracting from the metal sheet during the bottom-dead-center holding period, allowing for controlled cooling rates and reduced holding time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the formed product is kept in the die until uniform temperature is reached, then shape accuracy is improved, but productivity deteriorates due to prolonged bottom-dead-center holding period
Solution Approach 1:
The die surface structure is made dynamic by providing movable die parts that can switch between contact and non-contact states with the formed product during the bottom-dead-center holding period. This allows the cooling conditions to change dynamically, enabling both rapid cooling (for productivity) and uniform temperature distribution (for shape accuracy) at different time points within the holding period.
Solution Approach 2:
The movable die parts are controlled to periodically contact and separate from the formed product during the bottom-dead-center holding period. This periodic action creates alternating periods of rapid cooling and reduced cooling, allowing the system to achieve both productivity (through overall rapid cooling) and shape accuracy (through periodic uniform cooling phases).
2Strength
If a gap is kept between the die and the formed product to reduce cooling rate, then local strength is improved, but shape accuracy deteriorates due to thermal contraction defects
Solution Approach 1:
The gap between the die and formed product is made dynamic through movable die parts that can adjust their position. During certain phases of the bottom-dead-center holding period, the movable parts contact the formed product for rapid cooling and strength enhancement. During other phases, they separate to create gaps that allow more uniform cooling and reduce thermal contraction defects, thereby achieving both local strength improvement and shape accuracy.
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
This approach ensures shape accuracy of the formed product with a property distribution while minimizing the bottom-dead-center holding time, thereby enhancing productivity and reducing defects.
Implementation Method 1
a bottom-dead-center holding period for which the first die part and the second die part are at a bottom-dead center includes an abutment period for which the movable die part abuts the metal sheet and a non-abutment period for which the movable die part does not abut the metal sheet
Implementation Method 2
as these portions experience thermal contraction during cooling, the formed product may develop defects of shape. Further, if there are large temperature differences within the formed product when the formed product is removed from the die, the formed product may deform due to thermal contraction
Data Source
AI summary
A hot press apparatus includes a first die part 2 and a second die part 3, and a control unit 9. At least one of the first and second die parts 2 and 3 includes a recess 3a in the surface facing the other die part in the direction of pressing. A movable die part 4 is provided in the recess 3a. The control unit 9 controls the movable die part 4 such that the bottom-dead-center holding period, for which the first and second die parts 2 and 3 are at the bottom-dead center, includes an abutment period for which the movable die part 4 abuts the metal sheet B and a non-abutment period for which the movable die part does not abut the metal sheet B.