Press to Position or to Pressure?

Application & Machine Considerations

Most applications, such as ferrous alloys and copper/bronze alloys, use the press to position procedure in the manufacturing of precision netshape and near-netshape components.  This greatly reduces the need for further processing expense.

Machine considerations for pressing to a position are very standard.  All powder compaction presses are originally designed to press to a position. 

 

Mechanical Presses: Top ram adjustment setting & bottom ram adjustable stops to manage positional repeatability. (standard)

Hydraulic Presses:  Linear transducers and feedback to the HMI for setup and repeatability.  (standard)

Servo Presses:  Linear transducers and feedback to the HMI for setup and repeatability.  (standard)

Mechanical Presses:   Top ram cylinder in the head where the operator can set a pressure relief to collapse the cylinder when the set force is reached.  (additional equipment option)

Hydraulic Presses:  Pressure transducers and feedback to the HMI for setup and repeatability.  (additional programming to include pressure feedback)

Servo Presses:  Pressure transducers and feedback to the HMI for setup and repeatability.  Motor and drive selection can change if your application requires pressing to pressure.  (additional programming to include pressure feedback and potential change in drive specification)

Proximity Sensor

Pressing to Position 

        

Certain applications in powder compaction require the press to press to a position.  This requires that the press tool members move to a preset position to compact the powder contained in the die. 

 

Control Scheme

Simple press designs utilize adjustable position micro switches or proximity sensors, while modern press control systems use linear position transducers control movement to pre-programmed tool positions.  Very precise positioning of independent tool levels can be programmed and easily controlled to repeat within linear 0.0005 inches (0.013mm) – at production type velocities.  With slight velocity reduction, even tighter precision is possible – as low as 0.0003 inches (0.009mm).

Linear position transducer

Pressing to Pressure   

  

Other powder compaction processes make it necessary to utilize pressing to a set pressure.  

 

Control Scheme

Operation is very similar to that of pressing to position.  The desired pressure limit is preset by the press operator. In older and simple presses this is accomplished by adjusting pressure relief valves. Modern and more sophisticated presses utilize pre-programmed feedback from pressure transducers or load cells. Position control is still utilized for precise die filling and ejection movements. Typical repeatability for pressure-to-pressure machines is +/- 1 ton to  +/- ½ ton depending on the size of the machine. 

load  cell

pressure transducer

Application & Machine Considerations

Pressing to pressure is ideal for products where density is more critical than position (similar to isostatic pressing).  The pressure control affords the ability to manage uniform shrinkage or uniform porosity in the compacted components.  

 

Many ceramic, tungsten carbide, polymer, molybdenum and diamond abrasive material applications utilize this process to provide unique and consistent properties -- repeatable with precision. 

 

When selecting a machine to press to pressure it is important that the following are taken into consideration:  

 

 

 

For more information on these options and others, please contact Gasbarre Press Group

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DuBois, Pennsylvania 15801

814.371.3015

press-sales@gasbarre.com