Differentiation characteristics of the powder compaction technology for the application of
hydraulic, mechanical and hybrid-presses
The base differentiation characteristics for hydraulic, mechanical and hybrid-presses are deduced
- shape and size of compactions
the needed compaction force
from the accuracy of the compaction, which has to be ensured,
from the unit capacity per minute, which is to realize.
1. Hydraulic powder presses
The application advantages of the hydraulic powder presses are characterized by
- a big available range of compaction force up to 15,000 kN
a big number of eligible free programmable compaction axes, also in connection with
the attainability of variable kind of processes according to the ejection- (counter
compaction-) or die withdrawal method
the realization of a speed-proportional compaction process on base of cross section
related filling height allocations and –corrections
the possibility of an axle correlated decompression phase
Especially for compactions with multi subdivided cross sections a high constancy of the density
distribution can be ensured, which will lead after the sintering – and sizing process to the adherence of very small
tolerance ranges and a machining can be avoided through this oftentimes.
The possible strokes per minute conform to the size of the compactions and to the filling –and
compaction strokes, which has to be realized and the range is normally between 4….15 strokes per minute.
The disadvantage of the hydraulic powder presses are the big need of electrical power and the high
costs for investment.
2. Mechanical powder presses
The application of pure mechanical presses as cam- eccentric- or knuckle joint presses is limited by
compaction forces < 5000 kN, whereas the main applications are placed in the range < 2000 kN.
Mechanical powder presses are working mainly according to a die- withdrawal –method, because of the
fixed lower punch in the tooling a kinematic system of die-movement can be designed with lower dimensions.
The application of these powder presses is concerned to simple parts with small cross-sections
subdivisions, which are also limited in their dimensions.
For this reason it is possible to realize strokes per minute in a range of 12…40, but for very small
parts it is also possible to derive values up to 100 strokes per minute, excluding the view to round table
Adapter with spring-lifted tooling punches will be used for simple parts, which will reinforce in
the compaction position on mechanical fix points, but the number of such punches is limited.For higher quality
requirements hydraulic controllable axes will be used increasingly for the concerned tooling punches.
In comparison to eccentric presses knuckle joint presses ensures the advantage of a longer
compaction – and decompression phase, which will lead to a higher soft- compaction with better effects in
de-aerating and more favorable relaxation. The danger of cracks can be reduced therefore.
3. Hybrid powder presses
This kind of presses take in an intermediate position between the hydraulic and the pure mechanical
presses, what is particularly related to possible cross section shapes, sizes and strokes per minute.
Hybrid presses will be differed in machines, where the mechanical main movement of the upper punch
is connected with a hydraulic drive system. In this way you can use the advantages of the kinematic system as well
as the high flexibility of the hydraulic system.
Different function characteristics for the upper punch movement up to reverse operations can be
realized therefore, that means a specific adaptation on the requirements of the compactions is possible.
In the other case the hydraulic completion is concerned to the adapter system, while by using of
free programmable hydraulic pressing axes the higher accuracy requirements of the compactions can be ensured.
The base function is the mechanical upper punch movement of the press and all hydraulic axes in the
adapter will be forced to follow this function, that mean all compaction axes of the upper and lower punch system
will come into the compaction position in the same time.
If the die-movement is also designed and controlled by a hydraulic lower punch, 2-layer-systems from
different materials can be also compacted with such a hybrid press economically.
The precondition for all of the above mentioned 3 types of presses is the attainability of a nearly
equal filling, in order to ensure a high final accuracy of the compaction. This will be decisive influenced by the
kind and characteristics of the used powder and its ability to fill the die-cavity equally and completely, despite
of a complicated shape-design.
The attainability of an optimized compaction process of different compaction heights will lead only
in this case to success, when the filling density in all areas of the die-cavity is the same, independent from the
used type of press.
A limitation of the strokes per minute in depending of the kind of products is caused on this
Therefore the activities for the improvement of the conditions for using of the best powder and for
ensuring of the best filling must be pushed forward with the same intensity as it is necessary for the development
of the presses and tools to guarantee higher part’s accuracy.
Especially for the last the die-withdrawal-method will be the determined technology for mechanical
presses, but increasingly differentiated hydraulic lower punch drives as hybrid completion, which are related and
controlled to the mechanical upper punch movement, will come to a higher signification.
Quite apart from that for simple geometric shapes with a relative small size the pure mechanical
presses will dictate the outlook in the press-departments in the future, because of their high economy, less
investment costs and long living time.
In opposite to that the hydraulic presses will distinguish by a further procedural variability and
flexibility and on base of free programmable controlling-systems with a high accuracy in positioning under force
alternatively for the die- withdrawal- or ejection-method with assignable subdivisions of the lower – and
upper punches the hydraulic presses will be used advantageously in the future.