DD289722A5 - PROCESS FOR PRE-SETTING A FLUIDICALLY WORKED LOW HOLDER - Google Patents

Abstract

The invention relates to a method for presetting a fluidically operated hold-down device, in particular for deep-drawing processes, during which the hold-down force is automatically varied during the presetting process. According to the invention, the blank holder is driven onto the workpiece with little force at the beginning of presetting. With the onset of first-order wrinkles, the hold-down force is slightly increased over the sum of the force components resulting from the tangential compressive stresses prevailing in the instantaneous form. This hold-down force is stored and thus forms a new Ausgangsgesesetz for the next Voreinstellprozesz. This control process is repeated finite times until an optimal hold-down force is achieved. Fig. 2 {deep drawing; Down device; Clamping force; Preset; Wrinkling; tangential compressive stresses; Control process}

Description

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Field of application of the invention

The invention relates to a method for presetting a fluidically operated hold-down device, in particular for deep-drawing processes, wherein the hold-down force is automatically varied during the pre-setting process.

Characteristic of the known state of the art

The presetting of fluidically operated hold-downs is still done manually by the press and Einrichtpersonai. Through approximate calculation and experience, a hold-down force is selected at the beginning of the presetting process. After the first deep-drawing process, an evaluation of the drawn workpiece takes place. If this wrinkling found on the flange, so there is an increase and found cracks reducing the hold-down force.

This presetting process is repeated until low-quality workpieces are deep-drawn.

A disadvantage of this method used in practice is that the Voreinstellprozeß done manually and subjectively shaped and requires a lot of time.

Object of the invention

The object of the invention is to overcome the listed deficiencies.

Explanation of the essence of the invention

The invention has for its object to provide a method for automatically presetting the optimal hold-down force during deep drawing.

According to the invention this object is achieved in that at the beginning of presetting the hold-down low force on the workpiece and increases with the onset of wrinkles first order, the hold-down force slightly above the sum of the force components, resulting from the prevailing in the instantaneous tangential compressive stresses becomes. The amount of this hold-down force is stored. ind forms a new starting variable for the next presetting process. This control process is repeated finite times until the optimal hold-down force is achieved. The detection of first-order wrinkles takes place, for example, by sensors which detect a change in distance between the hold-down device and the deep-drawing ring. An electronic evaluation unit takes over the evaluation of the signals and the regulation of the hold-down force during the Voreinstellprozesses corresponding to the distance between hold-down and deep-drawing ring and thus according to the wrinkling.

With this inventive solution, it is now possible to automate the presetting process for determining the optimum hold-down force.

Ausführi'ngsbelsplel

The invention will be explained with reference to an embodiment niher

 Show it

Fig. 1: Schematic representation of a tool for thermoforming with integrated optical fibers for a

Distance measurement for controlling the hold-down force, Fig. 2: Representation of the sum of the force components F ₅ , resulting from the tangential compressive stresses a ₀ and the hold-down force F _n as a function of Voreinstellhübe

The tool shown in FIG. 1 for deep-drawing cup-shaped sheet metal parts consists of the deep-drawing die 1, the deep-drawing ring 2, the downholder 3 equipped with optical waveguides 4 and the optical system 5. Outside the tool are arranged a radiation source 6, the opto-electronic receiving transducer 7, the miniature computer 8, the Y-coupler 10, the hydraulic cylinder 11, the pressure generator 12, the oil reservoir 13 and the proportional pressure relief valve 14. In Fig. 2 is the curve of the sum of the force components F, resulting from the tangential compressive stresses O ₀ , in the Ziehteilflansch and de, hold-down force F _{n shown} as a function of the preset strokes. At the beginning of the presetting process (stroke 1), the hold-down device F _n moves onto the inserted sheet metal blank 15 with a small force F _n . Since F _n <F _s , first-order wrinkles develop in the drawn part flange. Thus, the distance a increases between hold-down and deep-drawing ring. Thus, a process control signal 9 to increase the hold-down force F _n to a value slightly above the sum of the force components Fs, resulting from the tangential compressive stresses a ₀ , output. This hold-down force forms the new output variable for the next presetting process (FIG. 2, stroke 2 and stroke 3). The control process is repeated until wrinkling (F _n > F ₅ ) fails (stroke 4).

The detection of Abstandos a and thus the detection of wrinkles occurs in the embodiment by the arranged in the hold-3 optical waveguide 4 (Fig. 1). Those emitted by the radiation source 6, e.g. an infrared emitter diode, coupled via the Y-coupler 10 in the optical waveguide 4 radiation is diffusely reflected by the deep-drawing ring 2 corresponding to the distance a. The reflected radiation is fed back into the optical waveguide at a defined proportion corresponding to the distance a and fed via the Y-coupler 10 to an optoelectronic receiving transducer 7. The electrical signal generated by the optoelectronic receiving transducer 7 is further processed in the small computer 8 and output to the hydraulic unit 11 ... 14.

Instead of optical fibers also other, z. B. inductive or capacitive sensors, find the distance measurement application.

Claims (1)

Method for presetting a fluidically operated blank holder, in particular for deep-drawing processes, characterized in that - ascends the workpiece with little force at the beginning of presetting the hold-down device, with the onset of first-order wrinkles, the hold-down force is slightly increased over the sum of the force components resulting from the tangential compressive stresses prevailing in the instantaneous form, - The amount of hold-down force is stored and so for the next Voreinstellprozeß forms a current output and - That this control process repeated finite times.