Method and device for producing a die-cast part

Abstract

A method is provided for producing a die-cast part by means of a die-casting die, wherein air contained in the die-casting die is sucked out. A moisture contained in the air that is sucked out is measured. In the method, the moisture is measured while the air is sucked out. A device for producing a die-cast part, which device has a diecasting die, a suction apparatus for sucking out air present in the die-casting die, at least one sensor for detecting the moisture in the air that is sucked out, and a control apparatus for controlling the device, is designed to perform the method.

Claims

1. A method for producing a diecast part, comprising: extracting air that is contained in a diecasting mold by suction through a first suction line and a second suction line; measuring a level of humidity contained in the extracted air with a sensor enclosed in a sensor structure, wherein the level of humidity in the extracted air is measured while the air is being extracted, the sensor structure is attached directly to a vacuum block, without a valve interposed between the sensor structure and the vacuum block.

2. The method according to claim 1, wherein a temperature and/or a pressure of the extracted air are also measured.

3. The method according to claim 2, wherein process parameters of the method are controlled in an open-loop and/or closed-loop manner based on measured properties of the extracted air.

4. The method according to claim 3, wherein a defined measuring time is fixed for the measurement, the measuring time being less than 10 seconds.

5. The method according to claim 3, wherein the measuring of the level of humidity is performed continuously.

6. The method according to claim 5, wherein a moisture sensor configured to sense the measured property/properties is cleaned between two measuring times at least once within a casting cycle, the moisture sensor being sprayed with a cleaning agent and, after the spraying, being blasted with compressed air.

7. The method according to claim 6, wherein the extracting is performed by connecting to a vacuum source.

8. The method according to claim 1, wherein the sensor has a response time of less than 1 second, and a measurement is fully completed within 1 second.

9. The method according to claim 1, wherein the sensor structure includes a housing with an inspection glass, so as to also permit effective visual inspection of a level of fouling.

10. An apparatus for producing a diecast part, comprising: a first suction line; a second suction line; a diecasting mold; an extraction device configured to extract air by suction and being located outside the diecasting mold; a moisture sensor that is part of a sensor structure and that is configured to sense a level of humidity of extracted air in only one out of the first and second suction lines; and a control device configured to control the apparatus, wherein the moisture sensor structure is attached directly to a vacuum block, without a valve interposed between the sensor structure and the vacuum block.

11. The apparatus according to claim 10, wherein the moisture sensor has a response time of less than 1 second.

12. The apparatus according to claim 11, wherein the moisture sensor is configured to sense a relative humidity and a temperature.

13. The apparatus according to claim 12, further comprising: a protective cap that is provided in the moisture sensor, the protective cap being optimized for incident flow.

14. The apparatus according to claim 13, wherein the moisture sensor is installed in a housing with an inspection window.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic overview illustration of a die-casting installation, for the purpose of illustrating an exemplary embodiment of the present invention; and

(2) FIG. 2 is a schematic partially sectional illustration of a sensor arrangement, for the purpose of illustrating a design variant.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) Preferred exemplary embodiments and design variants will be explained in detail below on the basis of the appended drawings. It is self-evident that the drawings are purely schematic and may illustrate features in enlarged form, or so as to be highlighted in some other way, for the purposes of illustrating the invention, without this being intended to constitute an accurate scale of the proportions.

(4) FIG. 1 schematically illustrates a die-casting installation with elements of relevance for the understanding of the invention. Certain elements that are necessary or expedient for the operation of a die-casting installation have been omitted in order to simplify the illustration. The die-casting installation described here is an apparatus within the context of the invention.

(5) As per the illustration in FIG. 1, a die-casting installation has a die-casting mold 1, a shot part 2 with a piston 3, a vacuum distributor 4, and a vacuum source 5. In the figure, only the fixed side of the die-casting mold 1 is illustrated, and only the piston 3 and various measurement instruments of the shot part 2 are schematically illustrated. It is self-evident that the die-casting mold 1 may have further parts such as removable and closable mold parts (movable side), connections, measurement devices, a cleaning device, release agent applicator, blowing-out measures and the like. The piston 3 of the shot part 2 may also be understood to be part of, or may be integrated in, the movable side of the die-casting mold 1. The shot part 2 may also be formed as the sole physical part of the movable side of the die-casting mold 1.

(6) By way of the shot part 2 or the piston 3, a liquid metal can be injected into the mold, which liquid metal remains in the mold under pressure until it solidifies in order to form a workpiece. As has already been described above, the workpiece is removed from the mold after solidifying, and the mold is then cleaned, wetted with a release agent, and possibly blown clean using compressed air. After subsequent closure of the mold, the latter is evacuated in order to reduce the residual humidity content, and the next injection is performed to produce the next workpiece.

(7) To evacuate the mold 1, the mold is connected to a vacuum distributor 4, which in turn is connected at a primary side to a vacuum source 5. The evacuation system is of secondary construction, symbolized in the figure by I, II. In strand I, the vacuum distributor 4 is connected at the primary side via a vacuum line 6 to the vacuum source 5. A valve 7 for controlling a connection state is arranged in the vacuum line 6. Furthermore, a separator 8 is arranged in the vacuum line 6 in order to move humidity from the air that is drawn-in. In the same way, in strand II, a vacuum line 9, in which a valve 10 and a separator 11 are arranged, is provided for connecting the vacuum distributor 4 to the vacuum source 5. The vacuum source 5 may, for example, be a vacuum tank (not illustrated in any more detail) which is evacuated by way of a vacuum pump (not illustrated in any more detail) to ambient air in order to maintain a predetermined negative pressure. Alternatively, a vacuum pump (not illustrated in any more detail) may be provided for each strand I, II. The valves 7, 10 and the vacuum source 5 are connected to an installation controller for controlling the connection state of the vacuum lines 6, 9 and the negative pressure provided by the vacuum source 5.

(8) At the secondary side, the vacuum distributor 4 is, in strand I, connected via a vacuum line 12 to a vacuum block 13, which in turn is attached to the die-casting mold 1. Furthermore, two signal lines, specifically a control line 14 and a measurement line 15, extend from the vacuum distributor 4, which signal lines are likewise connected to the vacuum block 13. In the same way, strand II is constructed at the secondary side by a vacuum line 16, a vacuum block 17, a control line 18 and a measurement line 19. Two cable holders 20, 21 are provided for gathering and supporting the lines 12, 14-16, 18 and 19. The cable holders 20, 21 may also be configured as connector panels, which the lines 12, 14-16, 18 and 19 each run into at the distributor side and at the mold side such that, in the event of local repositioning of the die-casting arrangement 1, 2 or of the primary-side vacuum arrangement 4-10, or in the event of exchange of the mold 1 for a different mold, the mold-side or distributor-side connections do not have to be released, and thus mechanical loading, sealing problems or loosening of the connections at the mold 1 and/or at the vacuum distributor 4 can be avoided.

(9) A humidity sensor 22 is provided in the secondary-side vacuum line 16 of the strand II. The humidity sensor 22 is designed for measuring a relative humidity content in the air that is extracted by suction via the vacuum line 16. It is advantageously also possible for the sensor to be set up for measuring a temperature of the air that is extracted by suction via the vacuum line 16. Using the parameters of relative humidity rH and temperature T, it is, for example, also possible to calculate the absolute humidity.

(10) Furthermore, in each case one pressure gauge 23, 24 for the measurement of the respective pressure is arranged in the measurement lines 15, 19.

(11) Further measurement technology is provided in the shot part 2. Here, a position encoder 25 outputs an advancement travel s of the piston 3, and two pressure gauges 26, 27 output a pressure in an annular chamber 3a and in a metal chamber 3b, respectively, of the piston 3.

(12) The humidity sensor 22, the pressure gauges 23, 24, 26, 27 and the position encoder 25 are connected via signal lines (not shown any more detail) to an interface 28, which in turn is coupled to a monitor 29 for the monitoring of the operating parameters.

(13) The distributor 4 and the interface 28 are connected to the installation controller. The installation controller controls and/or regulates operating parameters such as piston pressure, metal temperature, vacuum pressure, etc. The interface 28 and/or the monitor 29 may have input elements (not illustrated in any more detail) such as switches, keyboards, mouse pointers, etc., in order to enable an operator to input and/or manipulate preset values. By means of an incorporation of the humidity sensor 22, the installation controller may also be configured to perform an automatic process termination beyond a certain threshold value. The threshold value may, for example, be predefined so as to specify a threshold beyond which a residual humidity content in the mold is so high that unacceptably high losses in quality are to be expected owing to shrinkage cavity formation or porosity in the cast part.

(14) A humidity and temperature sensor which is commercially available under the designation CON-HYTELOG-USB has, for example, proven to be suitable as the humidity sensor 22. This sensor has a precision NTC for temperature detection and a capacitive polymer sensor, with long-term stability, for the measurement of the relative humidity, and is produced in various configurations. In a first configuration, the sensor has a measurement range for the relative humidity of 10 to 95% with a typical accuracy of 3% and a measurement range of 20 to +60 C. for the temperature. In a second configuration, a measurement range for the relative humidity of 0 to 100% is attained, with a typical accuracy of 2%, and the measurement range for the temperature is 40 to +80 C. For both configurations, the resolution for the relative humidity is typically 0.01%, and for the temperature, the resolution is 0.01 K and the accuracy is 0.5K between 0 and +40 C. The sensor has a USB plug connector for direct connection to a PC, wherein the supply of power is likewise realized via the USB connection. For communication with the sensor, COM port emulation is provided. Further details regarding the characteristics and the control of the sensor can be gathered, for example, from a product datasheet available at http://www.produktinfo.conrad.com/datenblaetter/175000-199999/183018-da-01-de-FEUCHTE_TEMP_MESSFUEHLER_EDELSTAHL_USB.pdf (accessed on 08.10.2012).

(15) A particular advantage of the humidity sensor has proven to be the response behavior, which has a response time of less than 1 second. In this case, a response time is understood to mean the time that elapses until the sensor, in the event of a change in ambient parameters, exhibits a preferably stable change in output that can be evaluated for control and/or regulation purposes in the context of the evacuation of a die-casting installation according to the present invention.

(16) In the case of a sensor of the type being used in a humidity measurement system at the die-casting mold, immediate, very sensitive detection of residual humidity content is possible. In this way, such process disruptions can be reacted to immediately. This results in a reduction in the reject rate owing to shorter feedback times, and in improved quality of the die-cast parts. Furthermore, pore-sensitive processes such as LOS can be made more easily possible.

(17) The use of two vacuum lines (or suction lines) 12, 16 has the further advantage, aside from increased fail-safety, that the suction power in the first vacuum strand I and in the second vacuum strand II can be controlled and/or regulated differently. For example, the first vacuum strand I can be configured for a maximum suction power in order to be able to evacuate the mold 1 as rapidly as possible. By contrast, the second vacuum strand II may be configured for the most distinct and fast-responding measurement possible.

(18) FIG. 2 shows, in a schematic, partially sectional illustration, an arrangement of a temperature sensor 22 with a sensor housing in a modification of the exemplary embodiment of FIG. 1.

(19) In the present design variant, a sensor housing 30 is provided, which is attached directly to the vacuum block 17 of the second vacuum strand II (cf. FIG. 1) of the die-casting mold 1 (cf. FIG. 1). More precisely, a face side 30a of the sensor housing 30 is connected via a short line piece 16a of the secondary-side vacuum line 16 of the second vacuum strand II (cf. FIG. 1) to a vacuum port (not illustrated in any more detail) of the vacuum block 17. Connected to an opposite face side 30b is a line piece 16b which leads to the mold-side cable holder 21 (cf. FIG. 1) and which forms a piece of the secondary-side vacuum line 16 of the second vacuum strand II (cf. FIG. 1).

(20) In a side wall 30c there is provided a screw-in piece 31 through which the humidity sensor 22 can be inserted into an interior space of the sensor housing 30. More precisely, the humidity sensor 22 has a sensor tube 22a and a handle 22b, wherein a connection part 22c is provided on a rear end of the handle 22b. On a forward end of the sensor tube 22a there is arranged a tip 22d with an opening 22e, wherein the sensors themselves of the humidity sensor 22 are accessible to ambient air via the opening 22e. The humidity sensor 22 is inserted through the screw-in piece 31 such that the sensor tube 22a bears against a seal 31a of the screw-in piece 31 in a circumferential direction, and the tip 22d projects fully into the interior space of the sensor housing 30.

(21) On a second side wall 30d of the sensor housing 30, a cleaning nozzle 32 is screwed in such that a jet of a cleaning medium CM reaches the tip 22d of the humidity sensor 22. The release agent vapor from the casting mold (mold 1) leaves behind waxy residues during series operation, which residues are removed again by means of water, if appropriate with the addition of further synthetic and/or natural chemicals.

(22) For the purposes of this description, cleaning medium is understood to encompass both water on its own and with the addition of further chemicals. This process, too, must take place very rapidly in order that the cleaning medium does not disrupt the measurement. The cleaning nozzle 32 is supplied with cleaning medium 36 from a CM reservoir 37 via a CM line 33 in which a CM pump 34 and a CM valve 35 are arranged. The cleaning medium 36 in the CM reservoir 37 may, as mentioned above, be water on its own or water with further added chemicals.

(23) Also screwed onto the second side wall 30d of the sensor housing 30 is a blowing-clean nozzle 38, which is likewise directed toward the tip 22d of the humidity sensor 22. By way of the blowing-clean nozzle 38, the tip 22d of the humidity sensor 22 can, after the cleaning process, be blown clean using compressed air CA in order to minimize disruption of the measurement acquisition by the cleaning medium CM. The blowing-clean nozzle 38 is supplied with compressed air from a pressure accumulator 41 via a CA line 39 in which a CA valve 40 is situated. The pressure accumulator 41 is supplied with compressed ambient air 43 by a compressor, and is kept at a predetermined positive pressure. An arrangement for regulating the positive pressure is not illustrated in any more detail in the figure and may be readily realized in one form or another by a person skilled in the art depending on requirements.

(24) An inspection window 44 is arranged in a third side wall 30e of the sensor housing 30. The inspection window 44 enables an operator to observe the sensor 22 which is exposed to the exit air 45 from the die-casting mold 45, and to react to any fouling or other undesired events.

(25) For completeness, it is pointed out that the connection part 22c which is provided on the handle 22b of the humidity sensor 22 can, during operation, be coupled to a plug connector 46a of a connecting line 46, which in turn can be coupled to the interface 28 (cf. FIG. 1).

(26) During the use of the illustrated arrangement, after the conclusion of a casting cycle, upon the starting of the vacuum device in the vacuum line 16 the residual humidity is measured. The measurement is performed directly at the mold 1, and the measurement duration is approximately 1 second. The short measurement time is advantageous because the results are available immediately, and the next casting cycle can be immediately interrupted if the measurement result is not in order. Subsequently, within a cycle, the measurement sensor is cleaned again using cleaning medium CM and compressed air CA.

(27) Here, an advantage is realized in relation to conventional systems which operate using sensors with a longer response time. Such sensors can provide reliable results only under steady-state conditions, such that it is necessary to form a reference chamber in which an uninterrupted measurement can be performed over 10 to 30 seconds. Since the reference chamber must be realized in a suction line, no further evacuation, and thus also no further shot, can be performed during said time.

(28) The present invention has been described above on the basis of a preferred exemplary embodiment and a number of modifications and variants, and has been illustrated by way of an example and schematically in the figures. The invention is not restricted to the exemplary embodiments illustrated and described, because these serve merely for illustrating and explaining the concept of the invention. Modifications and enhancements within the scope of expert knowledge and capabilities are encompassed by the scope of the present invention, at any rate insofar as they fall within the wording or the equivalent use of the subject matter of the appended claims.

(29) Alternatively, it is for example possible to use sensors even with a response time of longer than 1 second. In this case, it is possible to obtain evaluable results if the response behavior is compensated mathematically. For example, in the event of a change of the measurement output, the further progression of the measurement output can be inferred already at an early point-in-time from the first-order and higher-order derivatives. Also, in this way, it is possible within certain limits to approximate to a quasi-continuous measurement, which makes it possible to identify deviations from normal behavior, in particular in relation to reference measurements, at an early point-in-time. At any rate, a measurement time should be less than 10 seconds, preferably considerably less than 10 seconds, in order to be able to optimally utilize the advantages of the arrangement according to the invention and the method according to the invention.

(30) In a design variant which is not illustrated in any greater detail, the tip 22d of the humidity sensor 22 is covered by a protective hood which is optimized with regard to an optimum incident flow of the exit air for the measurement. The protective hood may, for example, be pre-integrated in a side wall of the sensor housing 30, or may be capable of being retroactively installed through an opening of the inspection window 44.

(31) In a further modification, it is for example possible for the short line piece 16a to be reduced to a screw-in connector which is screwed into the face wall 30a of the sensor housing 30 and by which the sensor housing 30 as a whole can be screwed onto the vacuum block 17. Proceeding yet further, the vacuum block 17 may be integrated with the sensor housing 30, which further simplifies the construction.

(32) In a design variant which is not illustrated in any greater detail, a mixing device may be provided for the admixing of a chemical from a further reservoir into the CM line 33 (cf. FIG. 2).

(33) The line 46 may also be attached directly to the handle 22b without a plug-type connection.

(34) The invention is also applicable to installations with only one vacuum line or suction line.

LIST OF REFERENCE SIGNS

(35) 1 Die-casting mold (fixed side) 2 Shot part 3 Injection cylinder 3a Annular chamber 3b Metal chamber 4 Vacuum distributor 5 Vacuum source 6 Vacuum line (primary I) 7 Vacuum valve (primary I) 8 Separator (primary I) 9 Vacuum line (primary II) 10 Vacuum valve (primary II) 11 Separator (primary II) 12 Vacuum line (secondary I) 13 Vacuum block (secondary I) 14 Control line (secondary I) 15 Measurement line 16 Vacuum line (secondary II) 16a Short piece 16b Piece 17 Vacuum block (secondary II) 18 Control line (secondary II) 19 Measurement line (secondary II) 20 Cable holder (distributor side) 21 Cable holder (mold side) 22 Humidity sensor 22a Sensor tube 22b Handle 22c Connection part 22d Tip 22e Opening 23 Pressure gauge (secondary I) 24 Pressure gauge (secondary II) 25 Position encoder (shot part) 26 Pressure gauge (annular chamber) 27 Pressure gauge (metal chamber) 28 Interface 29 Monitor 30 Sensor housing 30a, 30b End wall 30c, 30d, 30e Side wall 31 Screw-in piece 31a Seal 32 Cleaning nozzle 33 CM line 34 CM pump 35 CM valve 36 CM reservoir 37 Cleaning medium (CM) 38 Discharge nozzle 39 CA line 40 CA valve 41 Pressure accumulator 42 Compressor 43 Ambient air 44 Inspection window 45 Exit air 46 Measurement line 46a Plug connector rH Relative humidity in % s Travel I First vacuum strand II Second vacuum strand COM (Serial) communication interface CA Compressed air PC Personal Computer (workstation computer) CM Cleaning medium T Temperature USB Universal Serial Bus

(36) The above list of reference signs and symbols is an integral part of the description.

(37) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.