Apparatus and method of carrying out a melting and casting operation

Abstract

The invention concerns an apparatus 1 for carrying out a melting and casting operation in the fine casting art comprising a melting crucible 2 for receiving melting charge, a heating device 3 for heating the melting charge in the melting crucible 2 , and a pyrometer 8 for ascertaining the temperature of the melting charge. In order to improve the quality of the products manufactured with such an operation the invention provides that the apparatus 1 is provided with a control device 4 for controlling the melting and casting operation in dependence on the ascertained melting charge temperature, wherein the control device 4 has a database 16 with a plurality of selectable, respectively melting charge material-specific parameter sets PS1, PS2, PS3 each with one or more parameters for configuring the pyrometer 8.

1 . Apparatus for carrying out a melting and casting operation in the fine casting art, in particular the dental art, comprising 
 a melting crucible ( 2 ) for receiving melting charge,    a heating device ( 3 ) for heating the melting charge in the melting crucible ( 2 ), and    a pyrometer ( 8 ) for ascertaining the temperature of the melting charge,    characterised by    a control device ( 4 ) for controlling the melting and casting operation in dependence on the ascertained melting charge temperature,    wherein the control device ( 4 ) has a database ( 16 ) with a plurality of selectable, respectively melting charge material-specific parameter sets (PS1, PS2, PS3) each with one or more parameters for configuring the pyrometer ( 8 ).    
     
     
         2 . Apparatus as set forth in  claim 1  characterised in that each parameter set (PS1, PS2, PS3) has one or more parameters for controlling the melting and casting operation in dependence on the melting charge material.  
     
     
         3 . Apparatus as set forth in  claim 1  or  claim 2  characterised in that the control device ( 4 ) has an input unit ( 14 ) for the input of melting charge identification for the selection of a parameter set (PS1, PS2, PS3).  
     
     
         4 . Apparatus as set forth in one of the preceding claims characterised in that the pyrometer ( 8 ) is a quotient pyrometer.  
     
     
         5 . Apparatus as set forth in one of the preceding claims characterised in that one or more sensors ( 9 ) of the pyrometer ( 8 ) can be directed by means of an optical system ( 11 ) directly on to at least one partial region of the melting crucible ( 2 ).  
     
     
         6 . Apparatus as set forth in one of claims  1  through  4  characterised in that the sensor or sensors ( 9 ) of the pyrometer ( 8 ) is/are connected to the connected optical system ( 11 ) by way of an optical waveguide ( 10 ) which can be directed on to at least one partial region of the melting crucible ( 2 ).  
     
     
         7 . Apparatus as set forth in one of the preceding claims characterised in that the control device ( 4 ) has a communication interface for supplementing and/or updating the data base ( 16 ), parameter sets (PS1, PS2, PS3), parameters and/or control programs and/or for reading out protocols of a melting and casting operation and/or parameters.  
     
     
         8 . Apparatus as set forth in one of the preceding claims characterised in that associated with each melting charge identification is its own parameter set (PS1, PS2, PS3).  
     
     
         9 . Apparatus as set forth in one of claims  1  through  7  characterised in that associated with a respective group of a plurality of melting charge identifications of a melting charge family, in particular an alloy family, having substantially identical or similar melting and casting properties, is an individual parameter set.  
     
     
         10 . Apparatus as set forth in one of the preceding claims characterised in that the heating device ( 3 ) is adapted by the control device ( 4 ) in such a way that a predetermined temperature of the molten material is kept substantially constant.  
     
     
         11 . Apparatus as set forth in one of the preceding claims characterised in that the heating device ( 3 ) is controllable by the control device ( 4 ) in such a way that the heating power of the heating device ( 3 ) is reduced when a predetermined temperature of the molten material is reached.  
     
     
         12 . Apparatus as set forth in one of the preceding claims characterised in that the control device ( 4 ) is so designed that it selects a parameter in dependence on the melting charge temperature pattern ascertained during a melting operation, in particular the ascertained solidus temperature and/or the ascertained liquidus temperature.  
     
     
         13 . Apparatus as set forth in one of the preceding claims characterised in that the control device ( 4 ) is operable in a pyrometer calibration mode in which the control means sets calibration parameters for calibrating the pyrometer in dependence on the temperature pattern ascertained with a predetermined reference melting charge, in particular the solidus-liquidus temperature characteristic.  
     
     
         14 . Apparatus as set forth in one of the preceding claims characterised in that the control device ( 4 ) is operable in a testing mode in which the control means checks the pyrometer ( 8 ) on the basis of the temperature pattern ascertained with a predetermined reference melting charge, in particular the solidus-liquidus temperature characteristic.  
     
     
         15 . Apparatus as set forth in  claim 13  or  claim 14  characterised in that the reference melting charge is a pure metal, in particular pure copper.  
     
     
         16 . Apparatus as set forth in one of the preceding claims characterised in that the control device ( 4 ) controls the melting and casting operation in dependence on the presence or the absence of an auxiliary means ( 17 ) which can be arranged in the region of the melting crucible, in particular a graphite insert, for assisting with the heating operation.  
     
     
         17 . Apparatus as set forth in  claim 16  characterised in that the ascertained melting charge temperature is reduced by a temperature difference value T 0  when the auxiliary means ( 17 ) is present.  
     
     
         18 . Apparatus as set forth in  claim 17  characterised in that the temperature difference value T 0  is ascertained from the casting temperature T G  approximately in accordance with the following equation:  
         T   0 =(( T   o   −T   G )/( T   o   −T   u ))* T   const.    
       wherein T o  is an upper temperature value in the range of between 1300° C. and 1600° C., in particular 1400° C., T u  is a lower temperature value in the range of between 800° C. and 1100° C., in particular 1000° C., and T const.  is a temperature constant in the range of between 50° C. and 250° C., in particular between 80° C. and 180° C., in particular 100° C.  
     
     
         19 . Apparatus as set forth in one of claims  16  through  18  characterised in that a given moment in time during the melting and casting operation is displaced by a compensating time duration t v  when the auxiliary means ( 17 ) is present.  
     
     
         20 . Apparatus as set forth in claim.  19  characterised in that the compensating time duration t v  is ascertained from the casting temperature T G  approximately in accordance with the following equation:  
         t   v =(( T   o   −T   G )/( T   o   −T   u ))* t   const.    
       wherein T o  is an upper temperature value in the range of between 1300° C. and 1600° C., in particular 1400° C., T u  is a lower temperature value in the range of between 800° C. and 1100° C., in particular 1000° C., and t const.  is a time constant in the range of between 10 seconds and 120 seconds, in particular 60 seconds.  
     
     
         21 . A method of carrying out a melting and casting operation in the fine casting art, in particular the dental art, in particular with a casting apparatus ( 1 ) as set forth in one of claims  1  through  20 , comprising the following steps: 
 introducing melting charge into a melting crucible ( 2 ),  
 heating the melting charge by means of a heating device ( 3 ), and  
 ascertaining the temperature of the melting charge by means of a pyrometer ( 8 ),  
 characterised by  
 controlling the melting and casting operation in dependence on the ascertained melting charge temperature,  
 wherein one of a plurality of melting charge material-specific parameter sets (PS1, PS2, PS3) is selected from a database ( 16 ) in dependence on the introduced melting charge and the pyrometer ( 8 ) is configured by means of one or more parameters of the selected parameter set (PS1, PS2, PS3).  
 
     
     
         22 . A method as set forth in  claim 21  characterised in that the melting and casting operation is controlled by means of one or more material-specific parameters of the selected parameter set (PS1, PS2, PS3).  
     
     
         23 . A method as set forth in  claim 21  or  claim 22  characterised in that a parameter set is selected on the basis of a melting charge identification inputted by means of an input unit.  
     
     
         24 . A method as set forth in one of claims  21  through  23  characterised in that the temperature of the molten material is kept substantially constant at a predetermined temperature for a predetermined period of time.  
     
     
         25 . A method as set forth in one of claims  21  through  24  characterised in that the heating power of the heating device ( 3 ) is reduced when a predetermined temperature of the molten material is reached.  
     
     
         26 . A method as set forth in one of claims  21  through  25  characterised in that a parameter set is selected on the basis of a melting charge temperature pattern ascertained during a melting operation, in particular the ascertained solidus temperature and/or the ascertained liquidus temperature.  
     
     
         27 . A method as set forth in one of claims  21  through  25  characterised in that a melting operation is implemented with a reference melting charge and a temperature pattern, in particular the solidus-liquidus temperature characteristic, is ascertained and compared to a reference characteristic, stored in the database ( 16 ), of the reference melting charge and the pyrometer ( 8 ) is calibrated and/or checked by means of the comparison result.