May 5, 2014

Press Hardening Processes: New concepts for Loading and Unloading Parts

The aim is to reduce the time required to transfer the part all along the Press Hardening Process

Fagor Arrasate event: Press Hardening Processes: New concepts for  Loading and Unloading Parts

This has been called press hardening,  hot forming, hot stamping, etc. and in any event refers to a technology centred on transforming the metallographic characteristics of steel sheeting (22MnB5) while simultaneously forming the sheeting. For this process, metal sheeting is first heated to temperatures around 900ºC to obtain its complete austenite transformation and is then transferred to a forming station (press + die) where the part is simultaneously cooled with the die closed.

Starting from the generic configuration of the cell around the press, the first point to analyze in each step is the relative position of the furnace centring table and the press itself. Depending on the different factors, the press may be configured in alignment with the furnace itself or at 90º in relation to the furnace centring table, in a perpendicular position.

The first transfer type for loading and unloading the press used commercial robots. This has the advantage of using widely tested equipment which works even in adverse conditions (e.g. forging). Furthermore, both engineering and maintenance teams are familiar with the characteristics so during the installation design phase, both the use and the maintenance can easily be industrialized.

The search for greater cadences requires the implementation of more complex robotic systems (e.g. doubles) or other totally different transfer systems.

As the result of an optimum configuration of press-furnace it is possible to reduce the movement to a main linear transfer movement between both elements and a secondary up-down movement for pick-up. The Fagor  LR3120 Feeder also has the advantage of having a telescopic arm on its main movement, where not only are the speeds of the main action amplified but the collision issues are also minimized as it manages to make clamp holder gripper reach the end positions at both ends of the travel. High speeds are achieved with these feeder systems.

Contrary to classic cold stamping transfer systems with two lateral bars along both sides of the die, Hotteknik integrates the transfer systems of four separate units with divided bars facilitating independent control of loading and unloading which particularly optimizes the overlapping between both operations and the press itself.

Although the features of the components are vital for the final results, special attention must be paid to synchronization of relative movements when talking about cadence. If we seek to optimize the entire transfer system in conjunction with the hydraulic press, the press must have a control system in closed cycle enabling us to guarantee its position at all times. Otherwise, we will be forced to increase the safety margins of the relative movements in detriment to the efficiency of the entire unit.