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Drawing press with individually controlled centre sleeves

instead of a common die cushion plate that acts as a sheet metal support for the centre sleeve during the drawing process, each individual centre sleeve on this press configuration is equipped with a differential cylinder.

 

On the condition that the sheet-metal support ring is unstable, this arrangement facilitates controlling the individual forces on the corresponding centre sleeve as a function of ram travel.

 

This technology is already known and is also in use.

 

Under normal operating conditions, not all centre sleeves are used at the same time, relative to the table bed bores. The bores in the table bed are arranged in a grid pattern so that the individual tools can be selected relative to the grid pattern with the corresponding centre sleeves.

 

Drawing operations:

Depending on the press size and tool, approximately 4 to 12 centre sleeves are actively used in normal drawing operations. These considerations and prerequisites were taken into account for the subsequent analysis. For cost reasons, 6 proportional valves, Y1 to Y6, were installed in this press. This means that 6 different control circuits can be used in drawing operations. Up to 4 centre sleeve cylinders can be connected in parallel to each control circuit.

 

All hydraulic connections of the center sleep cylinders are routed to the manifold rail X1 and X2. The connections between AY, BY and X are established with couplings and hoses. Since the setup process to another tool necessitates a different assignment of the centre sleeves, the manifold block X, AY and BY is arranged to the left and right of the side column.

 

A user-friendly chart is used to quickly activate the individual centre sleeves by engaging the corresponding couplings. The individual control valves Y are represented in various colours in the menu diagramme of the PC control. Using the touchscreen, control valves Y1 can be programmatically assigned to the individual centre sleeves. The same applies accordingly to the other valves.

The overall representation of the table bed with the activated centre sleeves then provides a user-friendly, colour-coded rendering.

 

Material flow measurement provides expanded options for drawing process:

IFUM, Hanover, has developed a sensor that can be installed into the drawing ring. Using this sensor, material flow can be measured during the drawing process in the X and Y axis relative to a unit of time. This facilitates conclusions to be drawn about the hold-down force.

The DUNKES press in combination with the press control has already been prepared such that the following drawing operations can be executed:

  • Counterforce of the individual centre sleeves based on the programme selection, as a function of the ram travel,

alternatively

  • counter holding force of the individual centre sleeves during the drawing process as a function of the material flow measurement. 

The sensors and a supplemental control from IFUM must be incorporated if the intent is to integrate the material flow measurement.

Schematic representation of the centre sleeve pattern in combination with the control valves
Control inputs for the individual centre sleeve cylinders
Sensor-based control for the material flow measurement