DE2400791A1 - DEVICE AND METHOD FOR FILLING PRESS DIE - Google Patents

Description

GERMAN GOLD AND SILVER SCHEIDEAITSTALT VORIiAIS ROESSLER 6000 - Prankfurt am Main, Weißfrauenstrasse 9

Apparatus and method for filling press dies.

The invention relates to a device and a method for the metered pulling of press dies with press granulate sinterable, powdery metallic or non-metallic, in particular inorganic substances with a uniform filling density, which are subjected to a sintering treatment after compaction in which a volume contraction (shrinkage) occurs due to physical and / or chemical reactions. The device works with a die chamber opening arranged on a press table via a die chamber opening Filling slide. It is used in particular to fill pressing tools for the production of in relation to Their surface is very thin, e.g. rectangular or round plates or rings of a few tenths of a millimeter up to a few millimeters thick; these compacts can be provided with holes.

The compacts are made of various types of ceramic mass, e.g. silicate or oxide ceramics as well as perrites or titanates and for ceramic capacitors, supports for electronic components of the micro-Ködul technology (substrates), for potentiometer carriers, insulating parts in electron tubes as well as for wall and floor panels used. The invention seeks to improve the accuracy of shape such as squareness or roundness as well as the dimensional accuracy of the finished parts.

Depending on how a press die is filled, a distinction is made between undosed and metered pressing. With undosed Pressing, excess molding compound is poured into the die. During compression, the amount not required for filling is used pressed out between the parts forming the press tool. The molding compound must therefore flow sufficiently under pressure, which is the case with clay-containing ceramic mass is achieved by means of a relatively high water content; one also speaks of IT compression molding.

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ORIGINAL INSPECTED

240079T

Press granules with a lower moisture content, which in ceramics are referred to as semi-moist or dry press masses, do not have these good flow properties. Uichttonhaltige Masses, such as pure oxide powder, are partly in spite of added organic or inorganic lubricants completely unplastic. Undosed filling of press dies is not possible here or only in exceptional cases. Dosing A quantity of pressed granulate can be done by weighing or measuring a certain volume. After filling into the Die, the material is compressed between an upper and a lower press ram and the compact is then ejected. The processes of filling the die, compressing and ejecting are predominantly carried out in practice by automatic presses executed. In principle, these work as follows: By lowering the lower stack or lifting the die with the upper punch removed v / is a filling space formed? its depth is in one predetermined ratio to the desired press thickness, taking into account the compression properties of the Preßgraiiulats (Fill factor). Then a container (filling slide) filled with the granulate and open at the bottom is pushed over the die opening (Forward movement), whereby the granules fall into the die. The filling slide is then back to the starting position withdrawn (backward movement) ·. The die opening is filled to the brim. So takes place with the filling slide a volumetric metering of the pressed granulate subsequently the upper punch is retracted into the die and the molding powder is compressed to the intended thickness. The pressing force can be transmitted mechanically or hydraulically and the compression either only from above or only from below or also at the same time or from above and below, one after the other. During the next work cycle, either the lower punch goes up or the die is moved downwards until the lower punch is flush with the upper edge of the die, with the compact upwards is expelled. The upper punch can be lifted off before this process or during the ejection. Before the Return the machine to the machine by moving the lower punch down

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Filling position moves, or during this process, the filling slide, which is moving forwards to fill again, hits the Away over the die the compact to the front, where it is gripped by a suitable device and transported on.

The compact obtained has a bulk density (weight / volume) which is below the density of the individual pellets from which the granulate is built up. The degree of this compression depends on numerous factors, for example on the size distribution of the powder, the friction conditions in the press granulate influenced by binding agents and lubricants and the friction conditions in the press tool, which depend on the type of granulate, the geometry of the tool, its Material, its surface properties and finally the applied pressure can be determined. The degree of compaction is given either as an absolute value (p / cm ⁵ ) or as a percentage of the theoretical density. The latter values are mostly between 50 and 80 fo.

If the compact is then subjected to a heat treatment at such high Subjected to temperatures that physical and / or chemical processes take place between the pressed grains, an approach takes place the grains together. Depending on the composition, the refractory components may be embedded in a glassy matrix or recrystallizations in solid Phase. In any case, this results in a reduction in volume. This contraction, also known as wastage, depends on a particular person Material and certain sintering conditions essentially depend on the density of the compact.

As the theoretical consideration shows, the linear shrinkage S (length after sintering minus length before sintering / length before sintering) with the compact density, Jp according to the relation

S = I--,

(1 - a)

Ss

together, where fs is the final density and a is the volatile binder fraction, with an isotropic, ie in

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- 4 the same shrinkage behavior is assumed in all directions.

The shrinkage is related to the compression density in such a way that that it is the lower, the more the compact was compressed and vice versa. He is in the construction of the press tool to take into account by correspondingly changed tool dimensions compared to the nominal dimensions. The one for a ceramic The dimensional accuracy that can be achieved for molded bodies depends on the shrinkage or the compression density.

The compacted density should now not only remain constant within a series of compacts, but initially also within of a single pressed part. Namely, if there are different compression densities in a single pressed part, because of the inevitably associated shrinkage, deviations from the original g-eometric shape (warpage) or mechanical stresses, which can lead to cracks. The manufacturer of ceramic moldings must therefore ensure uniform compression density at all points of the pressed part. There are a number of options that can be used individually or together, such as pressing technology favorable design of the molded body, press ram subdivisions in the case of uneven porous body cross-sections, use of free-flowing ones Granulate, absorbent filling of the die and promotion of the Riesein by shaking. Despite the application of this known per se Measures for a uniform die filling, it turns out that pressed parts that are very thin compared to their area show a change in their geometric shape during sintering. The conditions during the filling process are shown below using the • the accompanying Figures 1 to "3 explained. The filling of a die with a fill factor of 2.5: 1, whose length to thickness is in the ratio of 20: 1.

Figure 1 shows the press table 1 from above with the press tool inserted, wherein the die opening 2 is covered by the filling slide 3, which is designed as an open box.

According to FIG. 2, the filling slide shown in a side section is shown except for the part that has sunk into the die opening,

509629 / (HOS - 5 -

_ 5 - '

fully filled with the pressed granulate 4. The filling slide of the known devices for pulling press dies takes thus always a multiple of a die filling; he will only moved forward to the filling position. Each of the filling slide removed amount of granules is by means of a (not shown) storage container in the rear position of the Filling slide refilled to the previous filling level. This gate container cannot be moved behind the die opening arranged above the rear position of the filling carriage. It is open towards this, with its lower opening through a filling slide in the opposite direction to the material transport lengthening slide can be closed during the transport of the material.

Each time the filling slide moves back, the upper punch emerges (not shown) into the die 5 filled with granulate 4 and compresses this, e.g. in a ratio of 2.5: 1, down to the dashed line. Then the upper punch is lifted up and the lower punch 6 pushes the compact out of the Die.

After ejection, the compact has practically the same size and square shape as the die opening. After sintering if it turns out, however, that the plate has changed its shape has, as shown in Figure 3, become trapezoidal. The rear edge c - d of FIG. 1 in relation to the filling direction is has become longer than the front edge a - b, as shown in exaggerated form in the figure mentioned.

The surprising appearance of the uneven shrinkage of a body of geometrically simple form could not be observed when the die was evenly filled by hand with a weighed amount of granules. It was therefore to be assumed that the uneven Shrinkage with different densities in the compact is related to uneven filling of the die.

S09829 / 040S

2Ä00791

It is true. Constructions have been proposed which are intended to eliminate the uneven filling. Most frequently the method of overcrowding is used, in which the lower punch is first lowered deeper than necessary and only then raised into the desired position, with part of the molding powder being ejected again and stripped from the filling carriage will. Satisfactory uniformity of the filling is not achieved with this method either.

The subject matter of the invention is a device for the metered filling of press dies with granules made of sinterable material Volume contraction of sintering powder with a uniform filling density with a filling slide which can be displaced on a press table via a die chamber opening arranged in its plate and one immovable behind the die opening above the rearward position of the filling slide arranged granulate storage container, whose lower opening through one of the filling slide opposite to the direction of material transport lengthening slide can be closed during the material transport. The device is characterized in that the filling slide takes up the filling volume of the die chamber and with its rear boundary is displaceable over the front boundary of the die opening.

The inventive idea, which unexpectedly a reproducible Allows completely uniform die filling, so it consists in the filling slide before moving back into the starting position to be completely emptied over the die,

According to a modification of the device according to the invention Between the filling slide and the press table, a die chamber opening that covers the die chamber opening and can be pulled out against the direction of material transport Plate arranged. This construction is bad for bad guys Granules advantageous, wel they an absorbent filling with the precisely measured filling amount while achieving a uniform Fill density enables.

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Another object of the invention is a method for the metered filling of press matrices with granules of sinterable, Powder sintering with volume contraction in a uniform filling density, which is characterized in that one the die chamber is limited to its filling volume Total amount of tolumen of granules supplied.

In a variant of this procedure, one can see its advantages with the practicalities of the absorbent filling by moving the filling slide over the closed by the TJnterstempel and advances the die chamber opening covered by a plate until the two openings are on top of each other and then lowering the lower punch after pulling out the plate to the rear.

The invention is illustrated in the following on the basis of further figures attached drawing explained in more detail.

According to FIGS. 4 a to c, a filling slide 8 which takes up exactly the filling volume of the die is in its rear Position arranged under the storage container 7. In the position shown in Figure 4a, the carriage 8 is with granules filled from the storage container. During the forward movement according to FIG. 4 b, the pressed granulate falls into the die opening and is completely emptied in the foremost position according to Figure 4c. In this position the filling slide is over the die chamber opening pushed out by means of the slide 9 which extends the filling carriage in the opposite direction to the material transport. Hur "that's how it will be the desired uniform filling of the die is achieved.

In exceptional cases, e.g. with poorly flowing, sticky granules a thin sheet metal plate 10 is attached according to Figure 5 a between the movable filling carriage 8 and the die, which the Filling slide opening initially closes downwards. When the slide with its opening over the filling opening of the die is pushed, the plate 10 is pulled back so far that

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. ■ 2400731

until the filling openings on top of each other are free. The next Lowering the ünterstempeis is in the filling position then the granulate is sucked into the die (Pig, 5b). The emptied Filling carriage 8 is then pushed back into the rear starting position for renewed filling.

With the device according to the invention and the procedure described automatic loading of press dies without the disadvantages described above after sintering the compacts recognizable uneven shrinkage can be carried out.

It can be assumed that the known filling devices for press dies work unsatisfactorily for the following reason: If a filling slide, which takes up the multiple volume of the die chamber, is partially emptied and withdrawn after the die chamber has been filled, the front inner edge of the filling slide strips off the granulate above the die. In this case, an increase in pressure initially occurs in the front part of the filling carriage as a result of the damming effect of the granulate set in motion, which is indicated in FIG. 6 by the solid arrow. This increase in pressure is propagated in the granulate, this being pressed in the direction of the dashed arrow against the rear edge of the die opening, which prevents further backward movement of the granulate. As a result, the die filling is compressed more at this rear point. This is indicated in FIG. 7 by the increasingly greater density of the puncturing towards the rear. The resulting denser filling leads during the pressing process to a greater pressing density, which during sintering results in a greater pressing density. low shrinkage, so that the square compact is a trapezoidal, sintered molded part. Just by "driving over" the die chamber opening with the filling slide of the known device, as is carried out according to a feature of the invention, no improvement can be achieved here.

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Claims (4)

Claims Device for the metered filling of press dies with Granules of sinterable powder sintering with volume contraction in a uniform filling density with a on a press table via a die chamber opening arranged in its plate and one immovably arranged behind the die opening above the rearward position of the filling carriage It holds granulate storage, the lower opening of which is extended by an The slide can be closed during the transport of the material, characterized in that the filling slide is just that Filling volume of the die chamber r-takes and with his rear limit is displaceable over the front limit of the die opening away. 2. Apparatus according to claim 1, characterized in that . between the filling slide and the press table there is a die pad it is arranged to cover the opening and pull out the plate against the direction of material transport. 3. Method for the metered filling of press dies with granules made of sinterable material that sintered with volume contraction Powder with a uniform filling density, characterized in that the die chamber is filled with one in each case limited volume of granules completely supplied. 4. The method according to claim 3, characterized in that one the filling slide via the die chamber opening which is closed by the lower punch and covered by a plate so far forward until the two openings are on top of each other and then after pulling backwards, the plate lowers the lower punch. . PT- / no. Kr-IS
7.1.1974 4101 KK 509829 / Ö4QS , ⁴⁰ ·. ■ Empty them 11 β