EP3310508A1

EP3310508A1 - Method and device for producing mould material moulds for the casting of metals

Info

Publication number: EP3310508A1
Application number: EP16731979.7A
Authority: EP
Inventors: Frank Iburg
Original assignee: Kuenkel Wagner Germany GmbH
Current assignee: Kuenkel Wagner Germany GmbH
Priority date: 2015-06-17
Filing date: 2016-06-15
Publication date: 2018-04-25
Anticipated expiration: 2036-06-15
Also published as: WO2016203394A1; DE102015109805A1; EA035330B1; US20190193144A1; CN108200764B; CN108200764A; EA201792461A1; UA123500C2; EP3310508B1

Abstract

The aim of the invention is to produce improved moulds for the casting of metals without increasing the complexity of production. By "improved" it is meant that the mould, consisting of the mould material, permanently has a surface of uniform hardness, even in the event of a change or variation in the quality of at least one of a plurality of properties of the mould material. Also disclosed is the production of a mould material mould for a cast having minimum strength for the casting of metals. A granular mould substance is poured into a mould box (40) as a mould material (41). The mould substance (41) is compacted in the mould box (40) in a mould system above a pattern (44) which stands on a pattern plate (46). In a first step, the mould box (40) is moved by a press device (1) across a first distance to stop against a frame (13) of a press head (10). In a second step, the pattern plate (46) is moved by the press device (1) across a second distance (s₁, s₂) into an end position in order to harden or compact (create) the mould material mould. A length of the second distance (s₁,s₂) is preferably automatically changed in accordance with the mould material, or the second distance (s₁,s₂) is changed as a result of a change in at least one property of the non-compacted mould material (41) and in accordance with a force determined at the end of a previous hardening or compacting of the mould material of the previous mould (100,102;102'). The proposed mould machine operates in the manner of a hardness control (strength control) of the mould material (41) in the compacted mould.

Description

METHOD AND DEVICE FOR MANUFACTURING MOLDED SHAPES FOR METAL CASTING

This disclosure (and claims) relate to a method of making a

Shaped form with a predetermined or predefinable minimum strength for metal casting. In this case, a molding material is entered in a molding box and the

Mold material compacted in the mold box. The compaction takes place according to the invention in two steps, a first step in which the molding box is moved over a first path to a stop with a pressing head and a second step in which the molding material is moved over a second path to an end position and thereby further compressed. A length of the second path is dependent on a nature of the molding material.

Moldings or molding materials that are used in the production of form molds for metal casting, have on the side of the force introduction after the

Compaction a higher dimensional stability, than on the - the introduction of force

away - side. The differences in the dimensional stability are proportional to the forces acting on the respective areas. This effect is due to the fact that the forces are transferred from the force-introducing side at the angle of repose of the molded material to be compacted. That is, the forces are proportionally based on lateral boundaries by friction, for example on a mold box wall or on upright or upstanding model contours.

This unequal effect of the forces leads to a different compression of the molding material in the molding box. This in turn results in an inconsistent strength of the molding material. In order to reduce or even compensate for these differences in the molding compound, various precompression processes have been developed since the 1960s. Thereby, the compaction differences between the molding material molding side into which the force is introduced and the opposite side were reduced. As a result, the average dimensional stability of the molding material shape is improved.

The quality improvement of the molding material forms achieved by the densification, that is, the resulting better compaction of the material in areas away from the introduction of force, but have not led to a konsta nten dimensional stability or quality of the molding materials, which is desirable to durable products of high quality to produce with a small scrap.

DE 44 25 334 C2 (DIS, Dansk I ndustrie), there column 1, lines 38 to 45, would like the

Make the surface of the mold hard enough. It is not called the force, but the pressure, which nevertheless means power for the same area. This proposal in the state However, the technique does not work with a molding box and a model plate arranged therein (on which the model stands and which is moved opposite the molding box), but with the compaction of poured sand into a molding chamber, there column 2, lines 29 to 39 there pressing plates 3, 8 has a model 4, 5 on its surface, which are laterally moved toward each other, so that the filled molding sand in the

Forming chamber is compressed and the desired molding (casting) is formed.

DE 602 17 205 T2 (Sintokogio) has a similar task, deals with the properties of the foundry sand and has recognized that different mold sands have different properties and therefore compensation regulations are required to the uniform height of the sand mold circumscribed in paragraph [06] reach, under best compression conditions. The best possible paraphrase can be found there in the sequence of paragraphs [042] to [045]. However, a pressure sensor is only mentioned in paragraph [69] and it has the task between the first phase of compression (the primary compression referred to in paragraph [042]) and the second phase of compression

Compaction (referred to in paragraph [043] secondary compaction) to distinguish what is found there in claim 5. The pressure sensor causes switching from primary compression to secondary compression.

There is a need for a method of making molded metal casting molds that compacts more uniformly, thereby improving the dimensional stability of the molding material mold. This achieves - more effectively than before - a consistently high quality of cast metal products and reduces the number of damaged molding materials (and castings). There is still a need for a plant for the production of

Forming molds with - in the long term - consistent quality of the molds.

The object of the invention (s) is to produce better molds for metal casting and not to increase the complexity of the production. "Better" can be rewritten so that it is permanently, even with change or change of quality, at least one of several properties of the molding material, an equally hard on the surface form of the molding material.

This object is achieved by the method (claim 1 or 20), but also with the device (claim 15). These are integrated here holistically.

The claimed two-stage method (claim 26) has a first step and a second step and for the second step there is a second path which is set according to the third feature, respectively, is changed. A change is required when a property of the sand changes. Does not change anything on the sand, no control intervention is provided. This is the so-called "steady state" of the given controlled system. A measurement of a preceding compression operation has an influence on the next compression operation (or one of the following compression operations).

The claimed inventions (claim 1, 20, 26) work as a working method in each case completely different than the prior art. A different setpoint is provided, namely the force determined for the quality and hardness of the shape of a previous impression, and it paves the way for subsequent impressions given prior to raising the model plate as a second distance.

The second distance is set or the person skilled in the art would say "is set" (according to claim 15), when the molding box abuts the top of the pressing head. Then there is virtually no further upward movement for the bottom-pressing device. Then, the movement is performed (second step in claim 1), (only) the model plate is further moved upwards by the pressing device, the molding box itself can not be moved further, but the model plate is moved a second distance to have a target , namely the lower edge of the molding box.

This second distance (claim 1, last feature) is adjusted depending on a force. This force is representative of the hardness of the mold on the surface and is used by the invention as a reference variable, from which the necessary path in the second impression results. In itself, it is a strength or hardness control of

Sand surface over a specification of the model hub as a higher-level control. This is not achieved according to the invention in the same process, but with a time delay after the end of the previous impression. DE 602 17 205 T2 shows a box which requires a position control. DE 44 25 334 C2 discloses no box, so there is not the criterion of the position to be reached relative to the box here.

In the example, this is very clear ... two equal paths, in the example S2 of about 5mm, with two different compression curves (force-displacement characteristics of the two different sands) provide a very different force. Thus, they also provide very different strength, e.g. the right image of Figure 8a. The invention will readjust here, and this difference control shows in the example the figure 8 in the right picture. The path will be adjusted in such a way that at the end of the way the power is best achieved.

The route guidance therefore has a dual aspect, a force must be achieved, and this force must be achieved at a time when the model plate reaches the bottom edge of the molding box. In addition, this must be carried out with repeated accuracy. If the person skilled in the art understands the problem differently and starts from different sands which have a different path-force characteristic, the invention results in the necessity of changing the path so that the force (hardness or strength) at the end of the compaction is appropriate. If the skilled person worked differently and regulated only one force, the path would not be correct if he assumed changes in the properties of the under-compacted molding material (molding sand). According to the invention both objectives are achieved and as a basis the invention uses the or one of the preceding measurements of the force at the end of the associated compression.

Result oriented can be said that the power can be too high, if the

Lower edge of the molding box is reached. Then it is useless, even a longer concern of this force on a timer to DE 602 17 205 T2 would improve nothing. However, if the force is too low, because the sand was too compact, it is at the end of the

(assuming fixed) Hubes the potential strength of the sand surface not yet maxed out.

Thus, the invention can be viewed from several directions, and it is not obvious from the prior art if the prior art also orientates the matching of the pattern plate to the bottom or bottom of the molding box as the end of its process. For the production of a reasonable or useful form, this is absolutely necessary, but how this need is achieved according to the invention is different, and indeed fundamentally different from the way DE 602 17 205 T2 proposes to do so.

Embodiments of the claimed basic inventions are covered by the subclaims. They can be combined in a technologically meaningful way. The description, in particular in conjunction with the drawing, additionally characterizes and explains the invention.

In the granular, flowable molding material (also molding sand, molding material, later simplifying "molding material"), from which the molding material forms are produced for metal casting, it is usually Betonit bonded molding materials, also called "sand". The molding material is used repeatedly in a cycle, whereby the starting material may be formed over time with, for example, core or green sand (new sand), from the insert core (s) for the castings to be produced, and fines such as crushed sand grains. not in one

mixed deterministically. This mixture of pure molding material, green sand or used core sand and fines alters the property of the molding material.

The molding material can also have a different particle size distribution, which has an immediate effect on how much force has to be applied to the To compress molding material to a target value. In practice, the molding material properties of a material batch are determined using a standard test. In this test, a standard container is filled with material and compacted by means of a punch with a predetermined force. The penetration depth of the punch into the standard container is measured when the predetermined force is reached.

The measured value, that is the distance that the plunger penetrates into the standard container, is the value that is set in prior art systems as a constant value for the recompression of the molding material molds made from the material of the one material batch.

It is not considered that the force curve over the path is not a constant, but changes depending on the specific properties of the molding material of each mold shape. FIG. 1 shows the result of several measurements of

Molding material of a material batch. It is easy to see that with a given force of 3,000N, with which the punch is pressed into the standard container, the penetration depth of the punch into the standard container varies between approx. 12 mm and more than 50 mm.

An invention relates to the method for producing a molding material for metal casting with a predetermined minimum strength of the mold.

In the process, molding material (granular molding material) is filled in a molding box and the material in the molding box is compacted in a molding line. The compaction takes place in two steps.

In a first step, the molding box with the filled molding material is moved by a pressing device over a first path for abutment against a pressing head. The pressing head is usually arranged above the molding box, so that the molding box is pressed from below against the pressing head.

The pressing head may have a punch or multi-punch, which protrudes from the pressing head in the direction of the molding box. The ram or ram will hold in a predetermined position during the first step and, in that position, will penetrate into the molding material previously filled in the molding box during the first step. Less preferably, the stamp or the multi-stamp can be actively pressed in the direction of the mold box during the first step.

In a second step, the model plate with the model (for stationary

Mold box) by the pressing device over a second distance in an end position for hardening or compaction (creation) of the molding material moves. In this case, the second distance is varied depending on the nature of the molding material, in particular for each mold box preferably adjusted automatically depending on the composition of the molding material. Preferably, the new setting of the current process of compaction results from the measurement of the force of the previous one

Compression process.

This means that for each (coming) molding material form an individual, from the

Determined composition of the molding material dependent second path and this second distance is set individually on the molding plant for each next Formstoffform. Also included is the case that between two or more molding material forms, the second distance does not have to be adjusted because the molding material for the two or more consecutive shapes has an identical or at least substantially equal composition. But the process also has the ability to

Adjustment of the path (to be driven stroke of the punch) to cause, if there is a deviation in at least one property of the molding material. This is the meaning of a regulation that only intervenes when an adjustment is required, ie a control difference was measured.

The regulation thus achieves both, the adjustment of the force at the end of the compaction, which force determines the quality of the form (its hardness at the surface). And the hub, which is necessary to reach the lower edge of the molding box, at least in

Essentially with a maximum tolerance of ± 5% of the height of the mold box (as the best possible comparative measure).

At the end of the hardening or compaction need not rewrite any time. It can span a time range which extends from the time of the end of the compression on reaching the lower edge of the molding box to at most the duration of the molding cycle or sampling clock of the control (T) (claim 12). In this area, no or no noticeable change in the shape hardness occurs; A measurement of the force of compaction can therefore take place immediately when the force is still applied (end of compaction) or lie a little later, be determined with a different measuring device, which determines the hardness at the surface, but before the next pressing ( Compression). Leaving the control more time, so takes more molded molding boxes between measurement of the mold hardness and adjustment of the distance s purchase, the scheme is still functional, has only an internal inserted runtime (a dead time in the sense of regulation). In the example, the strength is measured on the first compacted mold, but only used as a controlled variable for the fourth mold to be compacted. There are two molded boxes between measuring and changing the distance for the upcoming compression (box 4 is measured, boxes 3 and 2 in between, box 1 is being compacted and this is the measurement of box 4 and its Formstoffform used). Then box 3 is measured and affects box 0, etc. In the ESB of this regulation, such a dead time affects in a first approximation as a PTI element, ie a delay, which does not allow to regulate as directly as an action of the measured value used immediately after the impression (box 1 to box 0) and the control error on the compression of the following measurement process, however, this type of control is still functional.

During the second step, the punch or punch of the punch may be held or moved as described in the first step. After completion of the second step, which heals after completion of a pressing stroke of the pressing device, the punch or the multi-punch can be pressed with an increased pressure in the molding material.

The fact that this refers to a first route and a second route means that the molding box first moves over the first route, at the end of the first route

Stroke stopped and then the model plate is moved for the second distance.

Preferably, it may be that the molding box in a continuous movement passes through the first path and the second path. In this case, the setting of the second path can be done before the movement of the model plate respectively the second movement of the pressing device starts and / or while the molding box moves along the first path.

The compression of the molding material by the pressing device and / or the pressing head can be determined or measured in particular by means of at least one sensor or a pressure sensor. The sensor may be located in or near a shape-critical region of the molding material mold. The sensor may, for example, be part of the molding box, in particular integrated into an inner wall of the molding box so that it immediately detects the pressure transferred to the molding material at this point or in this area. For larger castings or castings with complicated geometry, multiple sensors may be present at appropriate critical locations.

The or a sensor may alternatively be an optical sensor which measures the densification of the molding material in a region within the molding material; For example, a laser sensor, whose penetration depth is adjustable in the material.

Finally, one or the sensor may be a sonic pulse sensor, such as sonar, that detects a degree of material compaction in the molding material molding or a portion of the molding compound by means of sound waves. Measured by the pressure sensor, introduced into the molding compound force is converted into a signal that is fed via cable or cable-free control. The control can be a central control of the molding plant, preferably a local control with which the received signals can be processed faster than in the standard controls of the molding plants, some of which are already 30 years old.

The controller may have a storage medium in which a setpoint or limit values of a setpoint range for the measured introduced force are stored. A stored in the controller, for example, in a computer program can

Have algorithm with which the value received from the sensor with the setpoint or the limits in the storage medium compared and a possible deviation of the measured actual value of the predetermined setpoint or desired range can be determined.

The one mentioned in the previous section also applies - mutatis mutandis - to the case where the sensor is the optical or the sound-pulse sensor. Even in these cases, a setpoint or a setpoint range with clearly defined

Limit values in the control respectively the storage medium can be stored as comparison values for the current actual value measurement.

If a deviation between the currently measured actual value and the stored nominal or limit value is detected, this deviation can be determined by an algorithm

Correction value can be calculated. This correction value can then be converted into a signal

be converted and the signal can be sent to an actuator of the molding plant, which changes a length of the second path, that is, the second

Distance extended or shortened.

In this case, the second path can be adjusted independently of the size of the deviation by a predetermined path length, for example 0.5mm, 1mm, 1.5mm or any other distance. That is, the actuating signal gives only one direction of an adjusting movement of the actuator and possibly a number of necessary

Path length change steps, but not an absolute value of the

Path length change.

Alternatively, the controller may determine the path length change depending on the calculated correction value, that is, the actuating signal in this case indicates a direction of the adjusting movement of the actuator and a measure of the adjusting movement of the actuator. The predetermined setpoint or setpoint range may be a value entered by an operator into the controller or a corrected value set by the controller during production or production for the controller

Form of molding material was determined, which was produced immediately before the current measurement.

The latter means that at the start of the production of the molding material forms, that is, before the beginning of the compression of the first molding material of a production, a setpoint is entered into the controller. This setpoint is then compared in the control with the actual measured value of the first molding material form and possibly corrected. The measured actual value or the corrected value calculated by the controller then serve as the actual value of the second molding material of the same production as a predetermined target value, etc. The measured actual value or the value then serves for the nth molding material of the current production the controller calculates the correction value for the n-th molding material shape as the nominal value with which the actual value measurement of the n-th molding material mold is compared.

Finally, the correction value can also be determined from information about the molding material for the molding material currently to be produced. To obtain this information, for example, the molding material can be scanned during filling in the molding box, so that a minimum, average and maximum grain size of the molding material and their volume fraction can be determined in the molding material. From this information, supplemented by further information such as temperature, humidity, etc. of the molding material, then a force can be calculated, which is necessary in order to produce a molding material form with a predetermined strength.

Values such as the temperature and the humidity can also be included in the calculation if, as described above, the registered force is determined by means of a sensor.

Another invention relates to a molding machine for casting molds from a granular molding material (molding material), for example, concrete-bonded molding sand, for metal casting.

The molding equipment comprises a linearly movable pressing device for applying pressure to the resulting molding material or mold, comprising a molding box for receiving the mold and a filling frame for receiving an upper portion of molding material for the mold. The molding plant further comprises a pressing head with at least one

Shaping stamp, which may comprise a decoupled from the drive of the pressing device drive. The pressing head is disposed in a closing direction of the pressing device before (usually below) the molding box and is not moved by the pressing device. That is to say, when closing (the beginning of compacting), the pressing device closes the (filled) molding box, move the filling frame, the plate carrier together with the model resting on the press head. When the filling frame reaches the frame of the press head, the molding box remains stationary. Then the model plate with the model is moved relative to the mold box until it reaches its bottom edge. That is a necessary condition, at least this must be essentially fulfilled. The molding material should be flush with the lower edge of the molding box.

The pressing head comprises at least one, preferably a plurality of forming dies distributed on the inner surface of the molding box, the at least one forming punch being fixed in position relative to the molding box, or the forming punch being actively pressed by a drive into the molding material for the mold to be compacted the molding box is moved against the pressing head and / or after the molding box comes into abutment with the pressing head. Preferably, the pressing head comprises more than one forming die, wherein the plurality of forming dies can form a multi-stamp.

The molding installation further comprises an actuator coupled to the pressing device or the molding box with a linear drive which is decoupled from a drive of the pressing device. The possible effective directions of the linear drive of the actuator and the drive of the pressing device can be rectified. The fact that the linear drive of the actuator is decoupled from the drive of the pressing device, means in particular that the actuator relative to the pressing device linear in and against the possible

Movement direction of the pressing device can be moved.

A controller sets a distance (si) between the pressing device (2) and the molding box via the actuator when the molding box is in abutment against the pressing head or a frame of the pressing head. This "if" is not in the sense of a temporal assignment in the claimed molding machine to read (claim 15). It is the possibility to have this setting when the compaction is done afterwards. The change can also be made by the concern with the press head or a frame of the press head, it can be adjusted even at the first stroke, so has a whole temporal range, only a structural end, to which it should be adjusted as late as possible To have an effect.

An adjustment of the actuator can be between 20mm and 100mm, preferably the adjustment is between 30mm and 90mm, more preferably between 40mm and 80mm. The adjustment depends on the height of the molding box or the size of the filler or of the mold to be produced with the casting. The adjustment can also be larger or smaller than the preferred adjustment. By the adjustment of the actuator, a total travel distance is changed, which the pressing device when manufacturing the mold from a starting position in which the molding box is not in abutment with the pressing head, in an end position, where the

Pressing process for the production of the mold is completed, travels. By the actuator, the total travel distance of the pressing device or the total stroke of a printing cylinder of the pressing device can be extended or shortened.

Furthermore, the system comprises at least one force sensor, one of the

Pressing device and / or the pressing head in the molding material registered or applied to the molding material force measures. Instead of or in addition to the force sensor, an optical sensor or a sonic pulse sensor can also be used to measure the densification of the molding material in an area below the surface. Reference is made to the comments on the procedure.

Finally, the system comprises a controller, wherein the control is signal-technically connected at least to the sensor and the actuator. The controller automatically adjusts the distance between the sensor based on the signal from the sensor

Pressing device and molding box respectively a bottom of the molding box. This setting can be started before the start of the movement of the pressing device and must be completed at the latest, just before the molding box comes into contact with the pressing head.

The control can be a central control of the molding plant, but it is preferably a separate control with extremely short control times.

The molding machine may have other features that - mutatis mutandis - the

Description of the method can be taken. It applies in principle that all features of the process can also be read on the system, and vice versa, all the features of the system to the process.

Embodiments of the invention are illustrated by way of example and not in a manner in which limitations of the drawings are or are read into the claims. Like reference numerals in the figures indicate similar elements.

FIG. 1 shows a graphical representation of results of several

Samples of a material batch with a given force

were condensed.

FIG. 2 shows a graph of the achieved compaction in FIG

Dependence on a fixed stroke.

FIG. 3 shows a relationship in a graphical representation

between dimensional stability and the applied pressing force.

FIG. 4 shows a section of a graphic in an enlargement

Representation of a target area for the dimensional stability.

FIG. 5 shows a detail of a molding installation 1 with force sensors 30, 30 '.

FIG. 6 shows a detail of another molding installation in which the force

at the end of the previous one (e.g.

previous) compression process is measured differently.

FIG. 7 illustrates a controller 102 or 102 'with sampling clock T. Am

At the end of the previous compression process, a force (the

Compaction). The controller 102 then changes for the

following compression process, the distance s ₀ to Si (or from Si to s ₂₎ , the distance to the model plate 46, the lower edge of the

Mold box 40 reached. This also (indirectly) the stroke of the second section of the pressing process is changed. This is due to the (determined, ie measured or from other values, for example pressure calculated) differential resistance between the setpoint and actual value, which the controller 102 or 102 'feeds. That is the rule difference of

Subtractor 99.

Figure 8 shows a control process in which the controller 102 in the controller

100 reduces the path s for the next impression, in this case because the force F (applied by the lift cylinder a press) on

End of the previous impression was too high.

FIG. 8a shows an end of the impression with the path s returned

a force F _s0 . Left the starting position, right the end position at

Reaching the lower edge 40a of the molding box 40. The (changed) force-displacement characteristic of an altered molding material results in the same path s in a different force F. Figure 8b shows the beginning of the impression with the not yet laid back

Way s without force. On the left the starting position, on the right the same position

(Enlarged). The (exact) force-displacement characteristics of the

compacting molding material 41 is still unknown.

FIG. 9 shows isolated force-displacement characteristics of two molding materials A

and B, or a molding material 41 which has changed in the course of use with an inherent property. In addition to a compressibility take the fines fraction and the

Grain size distribution significant influence on the force-displacement characteristic of one or two to be compared molding materials.

Shown is an equal path s for both sands A, B. However, one is

Difference of almost 2 times the received power (or

Firmness) on the ordinate - what a difference. If it is possible to increase the way for the sand B, it is possible

give it as great a hardness as they do for sand A

has been achieved.

FIG. 1 shows the standard container already mentioned, which can be filled with a sample of a molding material. The molding material is intended to be compacted in a molding line into a molding material mold for a metal casting. After filling into the standard container, the molding material can be compacted by means of a punch. The punch is connected to a hydraulic cylinder, for example, which presses the punch with an adjustable force in the standard container. When the punch has been pushed into the standard container with the specified force, the penetration depth of the punch into the standard container can be measured.

This measurable value is representative of the compaction behavior of the material in the standard container, is considered in the prior art as representative of the compaction behavior of an entire batch. The value of the measurement is used to set a distance or a stroke for the recompression on a pressing device for producing a molding material. With this adjustment of the re-compaction, an entire batch of the molding material is then processed in a molding installation in the prior art.

The graphical representation next to the standard container shows by way of example the result of pressing operations with several material samples of a single batch of corresponding molding material with an equal force. In the table, the force acting on the punch is applied to the depth of penetration of the punch in the standard container. The measurement results show that the molding material of a batch is not nearly homogeneous, but that with a compression of the samples with identical force, the penetration depth of the punch S in the standard container B is between about 12mm and about 50mm.

FIG. 2 likewise shows a graphic representation, as has already been conveyed with FIG. Arrows represent plastically that at a fixed stroke (distance), depending on the composition or property of the molding material, the granular molding material is compacted with a force of a minimum of about 1700N and a maximum of about 2400N. That is, the molding materials made with these materials under identical pressure have very different strengths, which is detrimental to smooth production, for example, can lead to increased rejects.

FIG. 3 shows in a further graphical representation that in the case of the molding material forms the achievable strength of the mold is compressed directly (substantially linearly) from the force input into the molding material at the end of the compression process or from the force with which the molding material is compressed at the end of the compression process, depends.

In order to demonstrate the relationship shown in the graph between the dimensional stability and the force introduced into the molding material at the end of the stroke or the path, numerous samples of a molding material with three different

Final forces condensed. As a result, it could be proved that a correlation between the dimensional stability and the force introduced into the molding material can be reproduced by a linear function with sufficient precision.

FIG. 4 shows an enlarged detail of a graphical representation with a target region for a desired dimensional stability of a molding material. The target area is limited by a lower limit F ^ n and an upper limit F _max . That is, a force at the end of the stroke must have been achieved so that a curve in a graph showing the strength over a distance (from FIG. 2) that lies within the target range at the end of the stroke. This range can be a hysteresis, or only have a value as a "switching value" that reaches or at least a little bit

should be exceeded.

In the diagram section of Figure 4 is a curve I can be seen, which increases up to a maximum value l _max and then falls again. At point l _max , the greatest strength is achieved for a given force input. The maximum value l _max is clearly not within the target range. To compress the same material so far that the force reaches the target range, it is only possible to change the manipulated variable "force". This requires that the entry of force must be increased. The result of the force increase is curve II whose maximum value II _{max is} now within the target range.

It can additionally be seen from FIG. 4 that an increase in the force or the force input can be achieved via a change in the stroke or the distance which is predetermined by the actuator of the molding installation (not shown). Compared to the previously set stroke, the distance (which the stroke covers) has been reduced.

The stamp (the pressing device) thus sets a different path, nevertheless the end of this changed path is still the lower edge of the molding box. But the force at the end of the changed path is different, in such a way that it corresponds to the target value, which is representative of the hardness of the surface (mostly on the surface)

Surface of the model).

FIG. 5 shows an exemplary construction of a pressing device 1 of a molding installation in which a molding material 41 can be compacted to form a molding material.

Shown is in a vertical longitudinal section, a pressing device 1 a molding plant for the production of form material forms or molds for metal casting. The

Pressing device comprises a lifting cylinder 2, which with an adjustable pressure in

Arrow direction can be moved. To lower the lifting cylinder 2, this can simply be switched powerless, which he preferably moves back alone by its own weight in a starting position. The lifting cylinder 2 may be a cylinder which can be acted upon with oil or air. Instead of the lifting cylinder 2, a linear drive can be used, for example, a rack which can be moved linearly by a gear drive.

The lifting cylinder 2 is connected via a connecting device 3 with the underside of a

Mold box 40 connected. The molding box 40 comprises a filling frame 42. In the following, the molding box 40 and the filling frame 42 are subsumed under the term "raised molding box" 40. The molding box 40 is filled with a molding material 41. Above the mold box, a press head 10 is arranged with a multi-stamp 11. From the press head 10 protrudes in the direction of the mold box 40 from a stop 13, which is a movement of the

Form box 40 limited in the arrow direction.

The connecting device 3 comprises an actuator 20 with a drive 21 and a support cylinder 22, in which the actuator 20 can at least partially retract when the lifting cylinder 2 moves to its final position. The drive 21 is decoupled from the drive of the lifting cylinder 2. With the actuator 20, a distance between the top of the

Lifting cylinder 2 (or the model carrier 46) and the bottom or lower edge 40 a of Mold box 40 (the model plate with the model standing on it to specify the cavity of the molding material form) are enlarged or reduced.

In the embodiment, the set distance Si. The distance can be minimum zero. A maximum value is determined by the structural design of the actuator 20.

In the molding box 40, two sensors 30 are arranged in this embodiment, which measure one of the lifting cylinder 2 and / or the pressing head 10 acting on the mold material 41 force. The force measured by the sensors 30 is applied to a

Control 100 headed. The controller 100 comprises a storage medium 101, in which a predetermined strength value is stored for the molded material form to be produced, or limit values are stored within which a desired strength value lies (controlled variable or target variable).

A microprocessor 102 as a control device (also called controller 102) functions as a "control or regulation" (a functionally adapted technical program or more such modules as a controller), with a measured by the sensor 30 strength value held in the memory 101 or separately predetermined strength value can be compared.

If a deviation is detected (as a control difference), a correction value can be calculated, which is output as a signal to the actuator 20. The signal causes activation of the drive 21, which can move the actuator 20 from its position to another position. The position Si is considered from a control point of view changed into a second position (or a second distance) s ₂ .

A working cycle of the pressing device 1 of the molding plant can, for example, proceed as follows ...

The filled with molding material 41 molding box 40 is in the

Pressing device 1 entered.

• The support cylinders 22 of the actuator 20 are in the calculated

Position moved out and in the extended position

locked.

The lifting cylinder 2 moves with the molding box 40 in the direction of

Press boss 10 until the molding box 40 abuts against the stop 13.

In this case, the multi-stamp 11 in the mold material 41

pressed.

• The lifting cylinder 2 continues to drive up and overcomes the

Actuator 20 set distance Si. • The multi-stamp 11 are pressed further into the mold material 41.

• The multi-stamps 11 press with defined pressing pressure.

• The lifting cylinder 2 and the Vielstempel 11 return to their respective

Starting position back.

• The molding box 40 is removed.

FIG. 6 shows an exemplary construction of a pressing device 1 'of a comparable molding installation, in which a molding material 41 is compacted to form a molding material, but the control system and its measured values work differently.

The force is not measured here on the model, but calculated on the pressure P of the lower ram from the control 90 (determined). The determination is made via a proportional factor (force per area is pressure). The setting of the changed distance s ₂ after the measurement of the force F ₂ (in the previous compression process) is carried out as a distance of the model plate to the lower edge 40a of the molding box 40. It may be an Ace to the previous setting. So s ₂ = Si + As, where As can also be negative.

Even at the end of the compression of this process, the model plate is at the level of the lower edge of the molding box. But the force at this time has a different value, due to the adjustment of the distance to s ₂ , where the punch traveled a different stroke.

The determined force F ₂ is passed to a controller 100 '. This controller 100 'comprises a memory 101' in which a predetermined strength value is stored for the molding material to be produced, or limit values are stored within which a desired strength value lies (controlled variable or target variable). A microprocessor or an ASIC 102 'as a control device (also called controller 102') functions as a "control or regulation" (here also a functionally adapted technical program or several such modules as a controller), with the determined strength value with the held in the memory 101 ' or separately given strength value can be compared, so that there is a control difference. From this, the controller calculates a manipulated variable change As.

The controller in this case reduces the path for the next impression by As, because the force has been too high. In the other case, if the determined force was too small (and thus the desired strength was too low), the path is increased by As. At the end of the previous or previous compaction process, the force is determined which, at the end of the stroke s, presses the model into the foundry sand. The cycle of compression is T. For each T there is a strength value in the form of the (measured or determined) force at the end of a molding process (as a compression process). This is deducted from the setpoint w, so that a control difference at the subtractor 99 results, cf. Figure 7. With the

Control deviation Δw is set via the controller 102 or 102 ', which may be a proportional controller, the new s ₂ or (general) s, with i = 1 to n.

The controller changes the distance s ₀ , Si, s ₂ until the model plate 46 reaches the lower edge 40 a of the molding box 40. This also (indirectly) changes the stroke of the second section of a Twinpress compaction. This due to the differential resistance between the setpoint and actual value, which feeds the controller 102.

Figures 8a and 8b are self-explanatory in the process. They show the beginning of the second compression, ie the approach of the model carrier 46 to the lower edge of the molding box 40, and the end in Figure 8a, in which this lower edge is reached and the resulting force at F is _{thus shown} in the diagram. Another molding material would have reached only the force (and strength), which shows the underlying curve as reached.

FIG. 9 illustrates the force-displacement characteristic of two "sands" (molding materials). Two curves with not the same force-displacement characteristic illustrate the very different force obtained (dimensional stability) for the same distance s. The same path is marked by arrows of the same length, which give distinctly different forces (shown on the ordinate on the left), about 1.5 kN and about 2.8 kN (sand A).

If the force is to remain the same despite an even creeping change in the force-displacement characteristic at the end of a respective compression process, the path can be adapted. Exactly this way is the solution with the force control and the path change in the second compression process (the second stroke), and since the end of the second stroke is mandatory, namely the lower edge 40a of the molding box 40, the stroke to be covered must be changed by the As described above become.

Thus, the result can be explained scientifically, an interposition of a regulated changed route reaches both the constant force, which the

Shape stability as constant rewrites, and the target point of the upward movement, the process technology for the reuse of the mold half 41 (then compressed) is fixed. Reference number (excerpt)

1 pressing device

2 lifting cylinders

3 connection device

10 press head

11 multi-stamp

13 stop

20 actuator

21 drive

22 support cylinders

30 sensor

40 shape box

41 molding material

42 filling frame

44 model

46 Model plate or model carrier

100 control

101 storage medium

102 computer programmed as a controller

51 distance (way or distance)

52 distance (way or distance)

53 distance (way or distance)

I measurement curve

l _max curve maximum

II trace

II _max curve maximum

Claims

Claims ...

1. A method for producing a molding material form for a casting with a

Minimum strength for metal casting, where

a granular molding material is introduced as molding material (41) into a molding box (40),

the molding material (41) in the molding box (40) is compacted in a molding line above a model (44) resting on a mold

Model plate (46) stands, wherein

in a first step, the molding box (40) is moved by a pressing device (1) over a first path for abutment against a frame (13) of a pressing head (10);

in a second step, the model plate (46) of the pressing device (1) over a second distance (si, s ₂ ) in one

End position for hardening or compaction (preparation) of the

Molding material shape is moved;

and thereby the second distance (si, s ₂ ) is changed in response to a detected force at the end of a previous hardening or compaction of the molding material of a previous form

(100, 102; 102 ') as a result of a change in at least one property of the un-compacted molding material (41);

or

a length of the second path (s _!, s ₂ ) as a function of the molding material (41) is preferably changed automatically.

2. The method of claim 1, wherein in the compaction of the molding material (41) by the pressing device (1) and / or the pressing head (10) introduced into the molding material (41) force is determined or measured by a sensor (30), especially at the end of the compression process.

3. The method according to the preceding claim, wherein the introduced force is determined or measured by the sensor (30) and passed to a control device (100), wherein in a memory (101) of the controller (100), a desired value or limits of a target range for the introduced force is predetermined, and the measured value is compared with the desired value or the limit values.

4. A method according to claim 3, wherein a deviation from a comparator provided in the controller (100) is detected, and as a result the second distance (si, s ₂ ) is changed (As).

5. The method according to the preceding claim 3 or 4, wherein a program from the detected deviation calculates a correction value, the correction value is converted by the controller (100) into a signal and the signal is output to an actuator (20) having a length changed the second route.

6. The method according to any one of the two preceding claims, wherein it is in the

stored value is a predetermined or predetermined value.

7. The method according to any one of the preceding claims, wherein the determined force value has been detected by the sensor (30) in the compression of a previous Formstoffform, in particular the Formstoffform, which was created immediately before the current compression with subsequent measurement.

8. The method according to any one of the preceding claims, wherein the comparison value was determined in the preparation of the previous Formstoffform (90), in particular immediately before the current compression.

9. The method according to any one of the preceding claims, wherein the change in the length of the path in dependence on the calculated correction value is determined, in particular the path is reduced, if the detected force was too large.

10. The method according to the preceding claim 3 or 4, wherein from the detected

Deviation a correction value is determined, which is in particular proportional to deviation, and the correction value is converted by the controller (100) into a signal, which signal is output to an actuator (20) which varies a length of the second path;

the deviation

a failure to reach the target range, ie outside the

Target range is;

is below a target value of the force as a setpoint;

or

exceeding a target value of the force as a setpoint. Method according to one of the preceding claims, wherein a detected deviation of measured (30) or determined force at the end of the current compression operation to desired force as a representative of the strength causes a control sense as follows;

if the measured force is too big, the second distance will be

(si, s ₂ ) reduced; or

If the measured force is too small, the second distance becomes

(si, s ₂ ) enlarged;

in particular in each case proportional to the previously detected deviation.

Method according to one of the preceding claims, wherein at the end of the hardening or compression covers a time range from the end of the compression when reaching the lower edge (40a) of the molding box (40) to at most the duration of the shaping clock or sampling clock of the control (T ) is sufficient, since in this area no or no noticeable change in the shape hardness occurs.

Method according to one of the preceding claims, wherein the change in the distance of the model plate (46) from a lower edge of the molding box (40) compensates for or compensates for an altered force-displacement characteristic of the currently compacted molding material (41) Force-displacement characteristic of more than one compression process previously compressed molding material (41), although it should be the same molding material.

Method according to one of the preceding claims, wherein with the change in the distance of the model plate (46) from a lower edge of the mold box (40) for the force-displacement characteristic of the currently compressed molding material (41), the force-displacement characteristic of the above, that is used directly in the previous compression process.

15. Molding system for casting molds for metal casting, the plant comprising ...

a linearly movable pressing device (2) for applying pressure to the resulting shape, with a model (44) and a model of this

carrying model plate (46), a molding box (40) for the mold

and a filling frame (42) for receiving an upper portion of

Molding material (41) for the mold,

a press head (10) with at least one shaping punch (11),

a coupled to the pressing device (2) or the molding box (40)

Actuator (20) with a linear drive, by a drive of the

Pressing device (2) is decoupled,

a force sensor (30,90) for measuring one of the pressing device

(2) or the press head (10) in the molding material (41) registered or

on this exerted force;

a controller (100,102), wherein with the controller (100) via the

Actuator (20) a distance (si) between the pressing device (2) and the

Mold box (40) is adjustable when the molding box (40) on the

Press head (10) or a frame (3) of the pressing head rests.

16. molding plant according to the preceding claim with one of the elements of claims 2 to 14 without their reference back to claim 1.

17. Molding plant according to the preceding claim 15, wherein the pressing head (10) has a plurality of parallel forming punches (11).

A molding line according to claim 15, wherein the adjustment of the distance (s 1) is made before the pattern plate (46) is movable upwardly from the pressing device (2).

19. Device according to one of the preceding claims 15 to 18, wherein the

Force sensor (30) is formed so that it detects a force value in the compression of a previous Formstoffform, in particular the molding material form, which was created immediately before the current compression.

20. A method for producing a force-controlled molding material, suitable for a metal casting, the molding material form with a predetermined or predetermined

Minimum strength at least the surface thereof, which receives the metal casting, wherein

a compactable molding material (41) is filled in a stack of boxes with a molding box (40);

the molding material (41) in the stack of boxes above a

Model (44) resting on a pattern plate (46) initially spaced (si) from a lower edge of the

Mold box (40), wherein

the box stack with the model plate of one

Pressing device (1) is moved over a first distance to the initial compression of the molding material (41);

an altered second distance (s ₂ ) depending on

a detected or determined force (F ₂ ) at the end of a compression process of one of the preceding

Compaction processes instead of the first distance is set;

the model plate (46) of the pressing device (1) relative to

Shaped box (40) over the changed second distance (s ₂ )

into an end position for the second compaction and creation

the molding material shape is moved.

21. The method of claim 20, wherein the molding material is a mold half.

22. The method of claim 20, wherein the second distance (s ₂ ) for the following compression process in dependence on the detected or determined force (F ₂ ) is changed at the end of the temporally preceding compression process.

23. The method according to claim 20, with one of the elements of claims 2 to 14 without their reference back to claim 1.

24. The method of claim 20, wherein the pressing head (10) comprises a plurality of

Form stamps (11).

The method of claim 20, wherein the initial adjustment of the distance (si) has occurred before the model plate (46) is movable upwardly from the pressing device (2).

26. A method for producing a molding material for a casting with a

Minimum strength for metal casting, where

the molding material (41) in the molding box (40) in one

Forming system above a model (44) is compressed, which stands on a model plate (46), wherein

in a second step, the model plate (46) relative to the molding box (40) from the pressing device (1) via a second

Distance (si, s ₂ ) in an end position for hardening or

Compression (creation) of the molding material shape is moved; And thereby

the second distance (s _!, s ₂ ) depending on one

determined force at the end of a previous hardening or compression of the molding material of a previous form is changed (100,102; 102 '), as a result of a change in at least one property of the un-compacted molding material (41).

27. The method of claim 1, wherein in the compression of the molding material (41) by the pressing device (1) and / or the pressing head (10) introduced into the mold material (41) force determined by a sensor (30), in particular is measured , in particular at the end of the compression process.

28. The method according to claim 27, wherein the introduced force is determined or measured by the sensor (30) and passed to a control device (100), wherein in a memory (101) of the controller (100) a desired value or limits of a target range for the introduced force is predetermined, and the measured value is compared with the desired value or the limit values.

29. The method of claim 26, wherein from the detected deviation a

Correction value is calculated, the correction value is converted by the controller (100) into a signal and the signal is output to an actuator (20) which changes a length of the second distance (s ₂ ). Method according to one of claims 26 to 29, wherein a detected deviation of measured (30) or determined force at the end of a current

Compaction process to desired force as a representative of strength causes a sense of control as follows ...

if the measured force is too big, the second distance will be

(si, s ₂ ) reduced; or

If the measured force is too small, the second distance becomes

(si, s ₂ ) enlarged.

The method of claim 30, wherein the second distance is changed in each case proport previously detected deviation.