Method for producing foundry casting molds

Abstract

A method for producing casting molds, such as cores or core assemblies used in foundry practice, wherein molding material, preferably molding sand, is injected or shot into a molding chamber via a gaseous flow medium, preferably air, under a predeterminable pressure. The shot and resulting solidified mold is deaerated, then the tool is opened, and the solidified mold is removed. The shooting process and/or deaeration process are controlled via detected and, if need be, prepared process parameters according to a predeterminable specification.

Description

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation of international application PCT/DE00/03870 filed Nov. 3, 2000, and designating the U.S.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a method for producing casting molds, such as cores or core assemblies used in foundry practice, wherein molding material, preferably molding sand is injected or shot via a gaseous flow medium, preferably via air, under a predeterminable pressure, into a molding chamber. The shot and resulting solidified mold is then deaerated, the tool is opened, and the shot mold is removed after opening the tool.

[0003] Quite generally, the invention relates to the field of foundry practice. For casting shaped parts of any type, foundry cores or foundry molds are generally made as separate parts, combined, and joined together to form a casting mold or a core assembly. Thereafter, these core assemblies are filled with molten metal for producing, for example, a metallic workpiece. In series production, the core assemblies to be filled with molten metal pass one after the other through the production line.

[0004] Core and shell shooting machines of the above type have been known from practice for decades. Only as an example, one may refer to DE 31 48 461 C1, which discloses a core and shell shooting machine.

[0005] Until now, production of ready-to-pour shells or core assemblies has occurred from a control device or control panel, wherein production is predetermined by a constant control. In the case of a change in the production sequence or in the case of a change in individual production steps or production stations, it has been necessary to change or adjust the control. An automatic monitoring or even adjustment of the production process, in particular the actual shooting operation, via deaeration, until the removal of the shot core, has been absent.

[0006] In the shooting of casting molds, it is possible that on the one hand during the actual shooting operation, and on the other hand during the deaeration and subsequent opening of the mold, very crucial problems arise, which counteract an optimization of the production process. Thus, for example, individual shooting nozzles and/or deaeration nozzles may clog with core sand, so that a longer process duration or an inadequate outcome of the production process is bound to result. Tool wear or damage to the tool likewise counteract an optimal production outcome. A too rapid deaeration of the shooting hood after the shooting operation could cause sand to whirl up or flow back, thereby negatively affecting on the one hand the outcome of the production and on the other hand the production quality, in particular, however, also the cycle time.

[0007] DE 44 22 353 C2 discloses a method for producing casting molds or parts of such molds, wherein the injecting or shooting operation is terminated at a time, which is a function of the pressure in the molding chamber. Specifically, in the cited art the injecting operation is terminated, when the pressure in the molding chamber has passed through a maximum. Accordingly, the maximum pressure is an indication for terminating the injecting operation. Further parameters are not considered in the art.

[0008] In practice, however, the method disclosed in DE 44 22 353 C2 is problematic, since only a pressure maximum is detected. For example, if a pressure maximum develops in the case of increasingly clogging nozzles, the injecting operation is ended, without an adequate shaping having been able to take place. In the end, the known method involves a control, with the parameter used for the control being the pressure maximum within the molding chamber.

[0009] It is therefore an object of the present invention to further develop a method of the described general type, so that for the quality assurance, a monitoring of the process occurs with simple means.

SUMMARY OF THE INVENTION

[0010] The method of the present invention accomplishes the foregoing object in that the shooting process and/or the deaeration process are controlled in response to at least one process parameter that is detected and compared in accordance with a predeterminable specification. Contrary to the general state of the art, no control will occur upon detection of a maximum pressure. Instead, an adjustment is made, which is based on process parameters according to any predeterminable specification. Affected are at least the processes of the actual shooting and deaeration before removing the shot and solidified mold. The goal of such an adjustment is the reduction of the cycle time, the automation of the production process, as well as the detection of defects or imperfections via conclusions from the process parameters and the cycle times resulting therefrom.

[0011] Specifically, it would be possible to base the adjustment on individual process parameters, predeterminable combinations of the process parameters, or algorithms on the basis of the process parameters. Furthermore, it would be possible to predetermine for the respective process step or process, i.e. for the actual shooting and/or for the deaeration, a maximum process duration as special process parameters. Should a longer process duration result or be computed based on the other process parameters, one would be able to infer a defect, for example, clogged nozzles, imperfections on the tool, or the like. What matters in the end are the detected parameters, which allow to draw the different conclusions as to the quality of the production and/or the condition of the tool.

[0012] At this point, it should be especially emphasized that it is possible to detect as a process parameter the pressure, which builds up or prevails in the entire system during the shooting. Specifically, it may be the pressure in the shooting air reservoir, in the sand hopper, in the tool, in the lines, or elsewhere in the system. Contrary to a control upon reaching a predetermined or predeterminable maximum pressure, one could use here as a basis a pressure progression in a regular shooting process, which is used to compare the actual pressure progression over the shooting process. Should the actual pressure progression deviate from the predetermined pressure progression, it would be possible to lengthen or shorten the duration of the shooting process via a corresponding adjustment, namely depending on the kind and amount of the deviation.

[0013] As an alternative or in addition to the detection of the pressure or pressure progression, it would be possible to detect as a further process parameter during the shooting, the volume flow or air flow in the entire system, for example, in the tool. Likewise in this instance, it would be possible to take a progression of the volume flow or air flow extending over the entire shooting process as a basis for a reference input, so that in the case of a deviation from desired values, an adjustment is made, which lastly becomes effective on the time characteristic and/or the required pressure. An increasing clogging of the shooting nozzles could be counteracted, at least within a certain scope, by a pressure increase.

[0014] It is likewise possible to detect as a process parameter the quantity of sand that is injected into the tool. This may occur, for example, via a weight loss in the supply container or via a weight increase in the tool or molding chamber. It would be possible to end the shooting process based on a plurality of process parameters, namely while taking into account the concrete sequence of the process parameters over the production process.

[0015] It is likewise possible to adjust the course of the deaeration process and, if need be, the time of opening the tool via detected and, if need be, prepared process parameters, namely similarly to the case of the actual shooting process. During the deaeration of the tool, it would be possible to detect as a process parameter the pressure progression inside the tool, and to compare it with a predetermined pressure progression in the case of an ideally completed deaeration.

[0016] Furthermore, it is possible to detect as process parameter during the deaeration of the tool, the air flow, in particular the amount of air flowing out of the tool. As soon as a predeterminable quantity of air has escaped, it will be possible to open the tool, with this procedure being dependent on the inner volume of the tool.

[0017] Within the scope of an especially advantageous development of the method according to the invention, a preferably electromagnetically operating air bleed valve is activated in such a manner that, while avoiding sudden changes of pressure, the pressure prevailing in the tool drops gradually. A linear pressure drop has shown to be especially advantageous for purposes of effectively avoiding that sand particles are entrained toward the air bleed valve or backward into the shooting nozzles. It is here intended to effectively avoid clogging by entrained sand particles.

[0018] Furthermore, it would be possible to compare the individual production steps or processes and/or the detected and/or determined process parameters with an optimal curve of the process sequence, preferably via a graph that can be shown on a display. Within the scope of such a development, it is possible to perform an optical comparison with reference to two curves. In this process, an operator may intervene interactively by adjustment, namely based on the comparison or possible deviations. Likewise possible is an automatic adaptation in the case of corresponding deviations. Such an adaptation is regularly effective on the time characteristic of the process.

[0019] As earlier mentioned, it would be possible to determine the ideal process duration based on the detected and/or determined process parameters. In this process, attempts are made to minimize the cycle time. For example, one could thus predetermine that upon exceeding a predeterminable cycle time, maintenance is performed or a tool exchange occurs.

[0020] In any case, it is basically possible that based on the detected and/or determined process parameters, the respective process is monitored with respect to possible imperfections or defects on the tool or on the machine itself. Lastly, there exists the possibility of drawing conclusions via the determined and, if need be, prepared process parameters, as to the quality of the production and/or the condition of the tool or the machine. Using the detected and/or determined process parameters as a basis, it also possible to define, for example, the ideal time for an automatic tool change, so that a least possible cycle time is realizable with an always functioning tool. It is likewise possible to compute the optimal maintenance interval based on the detected and/or determined process parameters, so that also to this extent, it is possible to realize a minimization of the cycle time, primarily, however, also a minimization of unnecessary repair work because of a regular and adequate maintenance.

[0021] Finally, it should be expressly stated that the foregoing description of the preferred embodiments of the invention does not limit the invention beyond the claims.

Claims

1. A method for producing casting molds adapted for use in foundry practice, comprising the steps of

shooting a molding material via a gaseous flow medium under a predeterminable pressure into a molding chamber,

causing the molding material to solidify in the molding chamber and form a solidified mold,

deaerating the solidified mold,

opening the molding chamber,

removing the solidified mold from the opened molding chamber, and

controlling the shooting step and/or the deaeration step in response to at least one detected process parameter compared to a predeterminable specification.

2. The method of claim 1 wherein the controlling step is based on individual process parameters, predeterminable combinations of the process parameters, or algorithms on the basis of the process parameters.

3. The method of claim 1 wherein a maximum process duration is predetermined as the process parameter.

4. The method of claim 1 wherein the pressure, which builds up or prevails during the shooting step in the system is detected as the process parameter.

5. The method of claim 1 wherein during the shooting step, the volume, flow or the air flow at desired places in the system is detected as the process parameter.

6. The method of claim 1 wherein during the shooting step the quantity of the injected molding material is detected as the process parameter.

7. The method of claim 1 wherein the duration of the deaeration step and/or the time of opening the molding chamber are adjusted via the detected and/or a prepared process parameter.

8. The method of claim 1 wherein during the deaeration step, the pressure progression within the molding chamber is detected as the process parameter.

9. The method of claim 1 wherein during the deaeration step the air flow leaving the molding chamber is detected as the process parameter.

10. The method of claim 1 wherein during the deaeration step an electromagnetically operating air bleed valve is activated in such a manner that the pressure prevailing in the molding chamber drops, while avoiding sudden pressure changes.

11. The method of claim 1 wherein the controlling step includes comparing the detected process parameter with an optimal curve of a process sequence via a graph that can be shown on a display.

12. The method of claim 11 wherein the controlling step further includes influencing the individual process steps interactively or automatically, using as a basis the comparison or possible deviations thereof.

13. The method of claim 1 wherein the ideal process duration is determined, using as a basis the detected and/or determined process parameters.

14. The method of claim 1 wherein the respective process steps are monitored for possible imperfections or defects, using as a basis the detected and/or determined process parameters.

15. The method of claim 1 wherein the time for an automatic tool change is defined, using as a basis the detected and/or determined process parameters.

16. The method of claim 1 wherein the maintenance interval is computed, using as a basis the detected and/or determined process parameters.