Method and device for controlling a press based on wedge drive tool spring condition

A method for monitoring and assessing a position Pi of a work slide of a wedge drive tool in a press, without a position sensor, comprising the steps of:

• actuating a slide bed of the wedge drive tool from an end position (XE) back to a starting position (XA) of the work slide;
• using a gas pressure spring, arranged in the wedge drive tool, to actuate the slide bed;
• opening the press from a lower press position to an upper press position;
• indirectly detecting the position of the slide;
• and
• detecting and evaluating at least the restoring force of the spring, further comprising the following steps:
• a) Detecting the restoring force Fm (t) of the gas pressure spring at at least one point in time t, that is either at or after the beginning of the respective opening process of the press where the slide, actuated by the gas pressure spring, moves along a path x from its end position (XE) back to its starting position (XA);
• b) Determining, by an electronic evaluation unit, whether the restoring force Fm (t) is equal to, greater or smaller than a specified target restoring force Fs (x), that the restoring force at the location x of the slide corresponds to;
• and
• c) Determining the respective condition value Z (x, t) at the point in time t, which represents a permissible or impermissible position Pi of the wedge drive tool at position x between the starting position XA and end position XE, where
• Z
• ⁡
• (
• x
• ,
• t
• )
• =
• {
• P
• i
• ⁢
• ⁢
• impermissible
• ,
• Fm
• ⁡
• (
• x
• )
• <
• Fs
• ⁡
• (
• x
• )
• P
• i
• ⁢
• ⁢
• permissible
• ,
• Fm
• ⁡
• (
• x
• )
• ≥
• Fs
• ⁡
• (
• x
• )
• d) Generating an action that stops the press if the condition value is found to be impermissible.