EP1199150A2 - Method and apparatus to determine parameters for pressing articles of complexe construction - Google Patents

Abstract

The pressing appliance comprises pressure rams which move to and fro in one pressing direction. The movement of the rams is measured. The density and or height of a pressed part is/are measured to determine the parameters of the pressed parts. A calculator assesses the die-fill for a next pressing-test. The initial material for pressing is in granular or powder form.

Description

The invention relates to a method for determining from pressing parameters to pressing complex structures Compacts with the generic features of the claim 1 and a device for performing such Process.

In general, the state of one or more segments constructed part, pressed from powdered raw materials by specifying the dimensions and densities of individual Segment sections indicated by this. A in Fig. 1st Pressed part shown, hereinafter also as a compact referred to, for example, consists of three segments, the one each as part of a powder pressing process decisive segment height hsi with i = 1, 2 or 3 as well have a segment density ρi per segment. In the case of Fig. 1 pellet shown do not start all three Segment sections on the same basic level, so that at corresponding calculations also the distances x1 or x3 from a support surface or a basic level are. To simplify the ones explained below Principles, however, a compact is considered below, in which all three segment sections S1, S2 and S3 differ from extend from a basic level upwards like this 2A can be seen.

As can be seen from FIG. 2B, there is an exemplary one Press device for pressing powdered raw materials to such compacts 9 in particular from a Stamp guide 1, in which in particular a main stamp 2, hereinafter also referred to as the upper bear, up and down to be led. On the underside there are 2 pistons 3, 4 on the upper bear and 5 attached, which are used to actuate individual stamps, hereinafter also referred to as segment stamps 6, 7 and 8, serve. The segment stamp 6, 7 and 8 can by means of Pistons 3, 4 and 5, each relative to the main stamp 2 and be moved down. The segment stamps 6, 7 and 8 are in a press form, which here for the graphic Simplification identical to stamp guide 1 is adopted. The mold is used to hold one to be pressed granular or powdery base material and closes down with a bottom 10. With usual presses is usually instead of one Bottom 10 a comparable press ram arrangement, on the from below with a main stamp and / or one Large number of individual segment stamps a pressing force in the direction the press shape can be exercised. In the case of Fig. 2B position shown is the arrangement in the Press position with lowered main stamp 2 and lowered Segment stamps 6, 7 and 8. The compact 9 takes the Form of the compact shown in Fig. 2A.

In order to achieve the required segment densities ρ1, ρ2 in the compact 9 and ρ3 of the individual segment sections S1, S2 and S3 must reach before the pressing process compared to Press volume significantly larger volume of powder in the respective sub-segments S1, S2 and S3 are filled. Usually the ratio of filling volume to pressed volume for powdery raw materials between 1.8 and 2.3. After filling the powdered Base material is a pressing force on the upper bears 2 Compacting the powdery base material from one appropriately trained pressing device applied. The Shaping of the compact 9 is carried out by the Oberbären 2 independently movable segment stamps 6, 7 and 8, which are relative to the main press movement of the upper bear or Move main stamp 2.

The exact densities and heights of the individual segment sections To be able to achieve S1, S2 and S3 of the compact 9 are Main stamp 2 and the segment stamps 6, 7 and 8 with Position measuring systems 11 - 14 equipped, the position of the Capture upper bears 2 or stamps 6 - 8. A problem with such pressing devices is that such Position measuring systems 11 - 14 not directly at the plate ends or Stamp ends can be attached, but more or less far away at the beginning or top of the plate Stamps 2, 6 - 8 are arranged.

The arrangement of the path measuring systems does not have any effect later pressing operations, this arrangement is problematic however for determining the required pressing parameters. Due to the high pressures that are used to press the Powdery raw materials are used in the Also press the individual main and segment stamps 2, 6 - 8 compressed. Usual deflections of these components Press are in the mm range, while the Accuracy requirements for the compacts in the 0.01 mm range lie.

The usual procedure for setting height and Density values of the individual segment sections S1, S2, S3 of a Presslings 9 comprises a large number, usually clearly more than 15 iterative approximate pressing tests. In one or After several initial pressing tests, a compact 9 is first made manufactured with a density that allows the compact 9 to touch and measure. Then try with iterative pressing tests the required part height hs1, hs2 and set hs3. After reaching the required Part heights the required press position or Press height e.g. defined and set by fixed stops.

After setting or running in the required Part heights hs1 - hs3 are usually combined with another Numerous iterative pressing tests optimized the part density. By feeding or removing powdery raw material the density can be increased or be reduced.

If, for example, the density in segment hs1 is determined by the increased filling of powder increases, so the springs associated plate or the associated segment stamp 6 at Press in more due to the increased pressing force. consequently the local part height hs1 of the segment section changes S1. In addition, the entire press device also springs due to the press force difference different, which also affects the Segment heights hs2, hs3 of the segment sections S2 and S3 as well transfers ρ2 or ρ3 to their densities. Hence, too the values of the segment sections that are actually not affected S2 and S3 are reset accordingly if in the Area of segment section S1 changes in parameters required are. In other words at any position and / or change in density in a segment section Si this via appropriate interactions Changes in the parameters of the remaining segment sections Si.

For illustration purposes, a height h _OB from a basic level to the path measuring system 11 of the main stamp 2 is shown in FIG. 2B, which allows the movement of the main stamp 2 in the upward and downward direction to be traced. The problem is, as stated, the section of the main punch 2, which lies in the upward or downward direction between the path measuring system 11 and the lower edge of the main punch 2, since this section of the main punch 2 is compressed differently when a first pressing pressure is applied than when a first one is applied in addition various second press pressure. The same applies to the measuring sections of the individual plates or arrangements of pistons 3, 4, 5 with segment stamps 6, 7 and 8, where the measuring sections h1, h2 and h3 each only the distance between an upper piston edge and the corresponding path measuring systems 12 - 14 detect, but not, depending on the pressing pressure, different degrees of deformation of the sections between the path measuring systems 12 - 14 and the corresponding lower edges of the segment punches 6 - 8. These sections, which cannot be clearly measured with regard to the compression, are outlined in FIG. 2B by spring symbols c _OB , c1 - c3 ,

The object of the invention is to provide a method for Determining press parameters for pressing complex structures Propose compacts where the number of Press attempts is reduced.

This task is accomplished by a method for determining Pressing parameters for pressing complex compacts, especially powder metallurgical or ceramic Compacts, with the features of claims 1 and 2 solved. Advantageously, an automated Device with the features of claim 6 automatically perform such a procedure.

Advantageous configurations are the subject of dependent Claims.

Fig. 1

einen komplex aufgebauten Pressling mit mehreren Segmentabschnitten unterschiedlicher Höhe;

Fig. 2A

ein Beispiel für einen vereinfacht aufgebauten Pressling mit mehreren unterschiedlich hohen Segmentabschnitten;

Fig. 2B

eine Pressenanordnung zum Pressen eines pulverförmigen Grundstoffes zu einem Pressling und

Fig. 3

ein Ablaufdiagramm für ein Pressverfahren gemäß dem bevorzugten Ausführungsbeispiel.

An embodiment is explained below with reference to the drawing. Show it:

Fig. 1

a complex compact with several segment sections of different heights;

Figure 2A

an example of a simplified compact with several different high segment sections;

Figure 2B

a press arrangement for pressing a powdery base material to a compact and

Fig. 3

a flowchart for a pressing process according to the preferred embodiment.

As can be seen from the flow chart of FIG. 3, there is a preferred method for determining press parameters for pressing complex compacts, in particular ceramic compacts preferably made of granules or powdery raw materials from two process stages. In a first stage of the process, essentially only the density of the individual segment sections Powder removal or powder feed optimized Adjustment of the height neglected. Only in one second step after retracting the target or Target densities an adjustment of the desired heights of the individual segment sections.

If the parameters for a new compact 9 or the production of a compact 9 are to be carried out in a new press, powder with a powder height H _powder with approximately twice the desired target height is placed in the mold 1 before the pressing dies 2, 6-8 H _If the compact section S1 - S3 is filled. Then press punches 2, 6 - 8 are attached and the filled powder is pressed. For an automated algorithm, a variable for describing the height of the last filled powder level H _{PowderAlt is assigned} to the value of the previous powder level H _powder before the pressing for each segment i.

After pressing, the density ρi for the individual Pellet segments Si determined here with i = 1 - 3.

In a next step, the measured density value ρ _{measurement is} compared with the target value for the density ρ _target . If the measured value for the density ρ _measurement and the target value for the density ρ _{target differ} for one or all of the segment sections Si, the press mold is again filled with powder. The product from the old powder height H _PulverAlt and the quotient of the target density value ρ _setpoint and the measured density value ρ _measured for the individual segments to determine the new powder height H _PulverNeu is determined i. After the powder has been filled in, it is pressed again, the individual press punches 2, 6 - 8 each being moved to the previous height h _OB , h1 - h3, so that the individual height values h _OB , h1 - h3 on the press are kept constant , The height values on the compact usually change. For an automated algorithm, the variable for the old powder level H _{PulverAlt is assigned} with the now used powder level H _PulverNeu . The method then goes back to determining the density values ρi for the compact segments Si.

As soon as the query ascertains that the target density values ρ _target and the measurement density values ρ _{measurement are} identical or differ from one another only within permissible tolerances, the method proceeds to the next method step. First, the individual heights hsi for the individual compact segments Si are determined. If these measured height values hsi, _measurement for the compact segments Si do not match the target height values hsi, _target , the mold is again filled with powder in order to carry out a further pressing test. The new powder height H _PulverNeu determined time by the product of the old powder height H recently used _PulverAlt and the quotient of the nominal height hsi, _Soll and the measured height hsi, _measured for the individual segments Si. Then the filled powder is pressed with a constant pressing pressure or constant pressing force compared to the last pressing step. In an automated procedure, the tag for the most recently used powder height H _PulverAlt is again filled with the last-used height value H _PulverNeu. The process sequence for determining the individual heights hsi then goes back for the compact segments Si.

If the comparison of the target heights hsi, _target and the measuring heights hsi, _{mess shows} Si identity for all pellet segments or a deviation within permissible tolerance limits, the required pressing parameters are determined and the process can be completed.

In the first test attempts, the total number so far from generally well over 15 press tests to 3 to 4 Press attempts can be reduced. With the proposed Process is exploited that the entire press including the segment stamps 6 - 8 and the main stamp 2 after the first press attempts to determine the individual Segment section densities ρ1 - ρ3 in a sprung Condition. After reaching the target densities for the Individual segment heights can be the heights for each Sub-segments independently with no effect on each other can be calculated and set using the second formula. In the Rule is just one step to calculate all of them Partial heights required if the densities for the individual segment sections were determined and retracted. Ideally, with the appropriate knowledge of Parameters for certain powders to be pressed and Parameters for the behavior of the individual press elements an even more optimized determination of the press parameters can take place than in the experiments carried out so far.

While only one in FIG. 2B for the convenience of explanation Press shown with stamps above the mold is, have conventional presses for the production of complex Compacts also below the mold form on. The proposed procedure is of course also with such press arrangements can be used.

The procedure is suitably equipped Device with a pressing device with a variety of Press punches (2, 6 - 8) which move forward and in one pressing direction are movable back, distance measuring devices (11 - 14) for Measure the movements of the punches (2, 6 - 8), one Pellet parameter determining device for determining Density and / or height parameters (ρ1 - ρ3, hs1-hs3) of one Presslings (9) and a calculation device for calculating one level for the next one Press test can be partially or fully automated.

Claims (7)

Method for determining press parameters for pressing compacts from a base material to be pressed, in which
the height of a test compact is only set after a target density has been reached. Method for determining press parameters for pressing compacts (9) from a base material to be pressed, with the steps: Pressing a test compact (9) and as long as a measurement density (ρ _measurement ) lies outside a tolerance measure of a target density (ρ _target ), manufacture a further test compact (9) with a new level of pressed material (H _powder new), then Determine the compact height (hsi) and compare it with a _target height (hsi, _target ) and as long as the _nominal height (hsi, _nominal ) and measuring height (hsi, _measuring ) do not deviate within a tolerance, press again with a new material height (H _powder new) with constant pressing force. The method of claim 1 or 2, wherein
determining the new Pressguthöhe (H _PulverNeu) when determining the compact density as the product of the previous Pressguthöhe (H _PulverAlt) by the quotient of nominal density (ρ _Soll) and measured density (ρ _measurement) and again presses with constant pressing height (h _OB, h1 - h3 ) he follows. A method according to any preceding claim, in which
takes place, determining the new Pressguthöhe (H _PulverNeu) after reaching the target density (ρ _Soll) as product of the Pressguthöhe recently used (H _PulverAlt) by the quotient of nominal height (hsi, _Soll) and measured height (hsi, _Mess). A method according to any preceding claim, in which
the comparative measurements, comparisons and redeterminations for different segments (S1 - S3) of complex compacts (9) are carried out for each segment (S1 - S3). Device for the automated determination of press parameters for pressing compacts from a material to be pressed a pressing device with a plurality of pressing rams (2, 6 - 8) which can be moved back and forth in a pressing direction, Position measuring devices (11 - 14) for measuring the movements of the punches (2, 6 - 8), a compact parameter determination device for determining density and / or height parameters (ρ1 - ρ3, hs1-hs3) of a compact (9) and a calculation device for calculating a level of the material to be pressed for a next pressing attempt, wherein the pressing tests are carried out with a method according to any one of the preceding claims. Method or device according to the preceding Claim in which the base material to be pressed or Pessgut is a granular or powdery material.

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