Method and an apparatus for producing multi-level components by shock compression of powdered material

Abstract

The invention refers to a method and an apparatus for producing multi-level components with conform target density from powdered material. The powdered material is filled into a mould die, which includes a multiple of lower and upper relatively movable punches, and the filling height of the column over each punch is associated to the geometrical levels of the final component. The material is optionally pre-compacted by individual static pressure acting on each punch and is compressed by at least one shock or impact device from at least one direction. Compensating adjustments for powder flow between columns and for density gradients are made during the pre-compression and shock compression.

Description

TECHNICAL FIELD [0001] The invention concerns a method and an apparatus for producing multi-level or stepped components compressed to higher densities through a shock (impact) compression, or a combination of a static compaction and shock compression. [0002] At compaction of powdered material to higher densities of final component shapes, including steps or multi-levels with axial pressing techniques, consideration must be taken into account that the fill volume for each level or step is relatively different. Because of powder material's tendency to compact in vertical columns and generate little hydrodynamic flow, the column for each of the component levels must be compensated for a filling volume corresponding to the final level height and the target density of the component. Excessive density variations may result in crack initiation of the final component and distortion of the component during sintering. [0003] Patent SE-0200230-1 discloses an invention for producing a material ...

AI Technical Summary

Benefits of technology

[0028] i) Each punch may be subjected to an additional static pressure applied during the shock compression. This will enhance the acceleration displacement of the punch into the powder column below or above the punch press surface. Each punch may be individually controlled such that each punch is subjected to an individual pressure, i.e. a higher static pressure will enhance the ratio of densification of the powder column below or above the punch press surface. The static pressure may also be applied prior to and / or retained after the shock compression.

[0030] iii)The mass of the punches may be adjusted relatively to each other. A punch with a relatively higher mass will have a lower velocity and hence reduced energy compressing the powder column facing the punch press surface, resulting in a decreased density of the same powder column relative the powder column compressed with a punch of lower mass.

[0032] The lower punches will have specific lengths in relation to each other, with respect to the step heights that corresponds to respective associated steps of the lower side of the final body produced, so that the bases of each of the punches end exactly at the same plane, or are stacked onto each other in a manner that allows for solid mechanical contact between the punch bases. The upper punches will have specific lengths in relation to each other, with respect to the step heights that corresponds to respective associated steps of the upper side of the final body produced, so that the bases of each of the punches ends exactly at the same plane, and are stacked onto each other in a manner that allows for solid mechanical contact between the punch bases. This arrangement will allow for the exact equidistant displacement of the punches during the shock compression operation and the possible additional static press operation.

Problems solved by technology

Excessive density variations may result in crack initiation of the final component and distortion of the component during sintering.

These methods of correction of the filling height for each step in combination with a shock (impact) compression process will not be applicable for compensation of the density of each step, due to that the punches during the shock compression operation, with respect to fundamentals of impact mechanics, preferably can be managed with a relatively equidistant displacement of each of the lower punches, and / or a relative equidistant displacement of each of the upper punches.

Using the known technologies would render a varying target density of the material above each of the lower punch surfaces and initiated cracking.

However, this method refers to conventional powder press machines with a low press displacement velocity (static pressing).

Powder densification with methods and machines disclosed in the patents WO 9700751 and WO 0222289, machine solutions without apparatus and methods for individual punch control in press force and position for tool systems including two or more punches on either upper or lower side of the moulding die, where each punch corresponds to respective associated steps of the final material body produced, may therefore not be possible.

The said machines can therefore not produce multi-level components of a homogeneous target density throughout the stepped sections of the component, due to the lack of individual punch control and therefore compensation.

They have different degree of success because of technical limitations due to difficulty in compensation for density gradients.

One approach of producing multi-level components may be performed by stepped dies, slotted punches or fixed stepped punches, but they all result in heterogeneous densities and cracking.

However, the described approaches will give a heterogeneous density distribution in the different stepped sections of the final component and also render undesired powder flow between the powder columns above each of the lower punches.

Furthermore, it will be suffering from technical difficulties such as positioning the punches during filling, fixation of the punches before the shock compression stroke and retracting the punches after ejection.

Furthermore, these methods may also suffer from uncontrolled effects as a result from internal shock wave such as crack initiation.

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