Abstract:
A method for the manufacture of components composed of difficult-to-cut materials for gas turbines, in particular for manufacturing integrally bladed rotors for gas turbine aircraft engines, by producing recesses with one or more side walls, the recesses forming flow channels and the side walls forming blade surfaces, whereby material in the region of the flow channels is removed by a drilling process, and after the drilling process is finished the remaining material in the region of said flow channels is removed by a milling process. The unique combination of a drilling process followed by a milling process completing the material removal reduces significantly the manufacturing time.

Description:
This application claims the priority of European patent application 03 017 126.8, filed Jul. 29, 2003, the disclosure of which is expressly incorporated by reference herein. 
   FIELD OF THE INVENTION 
   The present invention relates to a method for the manufacture of components composed of difficult-to-cut materials for gas turbines, especially for aircrafts engines, by producing recesses with one or more side walls, in particular for manufacturing integrally bladed rotors for gas turbines, the recesses forming flow channels and the side walls forming blade surfaces. 
   BACKGROUND AND PRIOR ART 
   Integrally bladed rotors for gas turbines are often called “blisks” or “blings”, depending on the cross-sectional shape of the rotor. A disk-shaped rotor having integrated blades is called “blisk” (bladed disk), a ring-shaped rotor having integrated blades is called “bling” (bladed ring). 
   Several methods for the manufacture of integrally bladed rotors are known from the prior art. These methods include milling methods as well as chemical or electrochemical discharge methods to remove material from between the side walls defining the flow channels. E.g. a milling method for the manufacture of integrally bladed rotors is disclosed in the U.S. Pat. No. 6,077,002. All manufacturing methods known from the prior art are time consuming and result in an expensive manufacturing of integrally bladed rotors. 
   It is an object of the present invention to provide a method for the manufacture of especially integrally bladed rotors which allows to significantly reduce the material removal time. 
   SUMMARY OF THE INVENTION 
   The present invention provides a method for the manufacture of components composed of difficult-to-cut materials for gas turbines, especially for aircrafts engines, by producing recesses with one or more side walls, in particular for manufacturing integrally bladed rotors for gas turbines, the recesses forming flow channels and the side walls forming blade surfaces, whereby contours of said recesses are defined by defining contours of said side-walls and/or contours of said flow channels, whereby material in the region of said flow channels is removed by a drilling process, and whereby after the drilling process is finished the removal of material in the region of said flow channels is completed by a milling process. The unique combination of a drilling process followed by a milling process completing the material removal reduces significantly the manufacturing time and results in a less expensive manufacturing of integrally bladed rotors. 
   In accordance with a preferred embodiment of the present invention the drilling process is performed in a way that a drilling tool removes material in a flow wise direction of each flow channel, whereby the axis of the drill-holes is approximately in parallel to the flow direction through the flow channel to be manufactured. For each flow channel at least one center line of the flow channel will be calculated from the contours of the side-walls defining said flow channel. The drilling process is performed in a way that the axis of each drill-hole is approximately in parallel to the or each center line of the flow channel to be manufactured, whereby an intake-opening of each drill-hole is located adjacent to the leading-edges of the side-walls defining the flow channel to be manufactured, and whereby the outlet-opening of each drill-hole is located adjacent to the trailing-edges of the side-walls defining the flow channel to be manufactured. 
   In accordance with an alternative preferred embodiment of the present invention the drilling process is performed in a way that a drilling tool removes material in an across flow direction of each flow channel, whereby the axis of the drill-holes is approximately perpendicular to the flow direction through the flow channel to be manufactured. The drilling tool removes material by drilling pocket-like drill-holes starting from the outside diameter of the rotor in a radial direction towards a platform of said rotor. 
   For both above-mentioned preferred embodiments, after the drilling process is finished the removal of material in the region of said flow channels is completed by a milling process, whereby a milling tool removes the material remaining after the drilling process in the region of said flow channels. 
   Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1 : is a radial view of an integrally bladed rotor showing three blades in a cross-section in a first radial height; 
       FIG. 2 : is a radial view of the integrally bladed rotor according to  FIG. 1  showing the three blades in a cross-section in a second radial height; 
       FIG. 3 : is a radial view of the integrally bladed rotor according to  FIG. 1  illustrating a first step of the manufacturing method according to a first embodiment of the invention; 
       FIG. 4 : is an axial view of the integrally bladed rotor according to  FIGS. 1 and 3  illustrating a second step of the manufacturing method according to the first embodiment of the invention; 
       FIG. 5 : is a radial view of the integrally bladed rotor according to  FIGS. 1 ,  3  and  4  illustrating a third step of the manufacturing method according to the first embodiment of the invention; 
       FIG. 6 : shows a first alternative to the second step of the manufacturing method illustrated in  FIG. 4  according to another embodiment of the invention; and 
       FIG. 7 : shows a second alternative to the second step of the manufacturing method illustrated in  FIG. 4  according to another embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIGS. 1 and 2  show the radial view of a component to be manufactured, here by way of example, in form of an integrally bladed rotor  10  for a gas turbine. The present invention relates to a unique method for the manufacturing of such an integrally bladed rotor  10  composed of difficult-to-cut materials like nickel alloys or titanium alloys. Such integrally bladed rotors  10  are manufactured by producing recesses  11  between two opposite side-walls  12 ,  13 , whereby the two opposite side-walls  12 ,  13  are part of two adjacent blades  14 . The side-walls  12 ,  13  form blade surfaces and the recesses  11  form flow channels located between the individual blades  14 . 
     FIGS. 1 and 2  show the blades  14  in a cross-sectional view, whereby the radial heights of the cross-sections differ from each other. For that, it can be taken from  FIGS. 1 and 2  that the contours of the side-walls  12  and  13  are a function of the radial position within said side-walls  12 ,  13 . 
   In accordance with the present invention, the recesses  11  between the blades  14  are produced by removing material in the region of said recesses  11  or said flow channels by a drilling process, whereby after the drilling process is finished, the removal of the material in the region of said recesses  11  or flow channels is completed by a milling process. According to the invention, the removal of the material in the region of the channels  11  is a combination of a drilling process and a milling process, whereby the milling process takes place after the drilling process is finished. 
   A first preferred embodiment of the method according to the present invention will now be described in greater detail with reference to  FIGS. 1 to 5 . According to this first preferred embodiment of the invention, the drilling process is performed in a way that the material is removed in a flow wise direction of each flow channel or recess  11 . 
   Prior to the drilling process in flow wise direction, a surface  15  perpendicular to the drilling direction is produced by removing material on one side of the rotor  10  as indicated by the arrow  16  in  FIG. 3 . The surface  15  perpendicular to the direction of the drilling process provides a good drilling quality and a reliable drilling process. 
   After the surface  15  has been produced, a drilling tool (not shown) removes material by drilling drill-holes  17 ,  18  and  19  into the material (see  FIG. 4 ). The drilling of the drill-holes  17 ,  18  and  19  is started at the surface  15 , which is located in the region of the leading-edges  20  of the side-walls  12  and  13  defining the flow channel to be manufactured, whereby the drilling of the drill-holes  17 ,  18  and  19  continues in the flow wise direction of the flow channel to be manufactured and is determined in the region of the trailing-edges  21  of said side-walls  12 ,  13 . 
   In order to determine the drilling-direction for the drilling process or the axis of each drill-hole  17 ,  18  and  19  at least one center line for each recess  11  or flow channel will be calculated from the contours of the opposite side-walls  12 ,  13  defining the recess or flow channel to be manufactured. The center lines  22  calculated from the contours of the side-walls  12 ,  13  are shown in  FIGS. 1 and 2 . These center lines  22  are defined by two points  23  and  24 , whereby the first point  23  is defined by the half distance between the leading-edges  20  of the side-walls  12 ,  13 , and whereby the second point  24  is defined by the half distance between the trailing-edges  21  of said side-walls  12 ,  13 . This is shown in  FIG. 2 . These two points  23  and  24  define exactly the direction of the center lines  22 , whereby the direction of the center lines  22  is a function of the radial position or radial height within the side-walls  12 ,  13 . 
   Starting in the region of the leading-edges  20  of the opposite side-walls  12  and  13 , an intake opening of the drill-hole  17 ,  18  or  19  will be drilled, the drilling process will be continued in the direction of the corresponding center line  22  defining the axis of the drill-hole  17 ,  18  or  19 , and in the region of the trailing-edges  21  of the opposite side-walls  12 ,  13  an outlet opening of the drill-hole  17 ,  18  or  19  will be drilled. 
   As shown in  FIG. 4 , a plurality of drill-holes  17 ,  18  and  19  will be drilled in the region of one recess  11 . The size of the drill-holes  17 ,  18  and  19 , the pattern of the drill-holes  17 ,  18  and  19 , and the axis (angle) of the drill-holes  17 ,  18  and  19  depend on their radial height and is determined by the contours of the recesses  11  or the contours of the side-walls  12 ,  13  of the blades  14 . In the drawing of  FIG. 4  the cross-sectional size of the drill-holes  17 ,  18  and  19  is the same. However, as shown in  FIG. 6 , the cross-sectional size of the drill-holes can of course differ from each other. As shown in  FIG. 6 , four drill-holes  25 ,  26 ,  27  and  28  will be drilled between two opposite side-walls  12 ,  13  of two adjacent blades  14 . The cross-sectional size of the drill-holes  25 ,  26 ,  27  and  28  is a function of the contour or shape of the side-walls  12 ,  13 , whereby the shape is a function of the radial position within said side-walls  12 ,  13 . The drill-hole  25  located adjacent to an inner surface  29  or platform of the rotor  10  comprises the smallest diameter because of the fact, that the side-walls  12 ,  13  have a smaller distance from each other in the region of said inner surface  29  than in regions with increasing radial distance from said inner surface  29 . 
   After the drilling process by drilling drill-holes in a flow wise direction of each flow channel or recess  11  has been finished, the removal of the material in the region of said recesses  11  is completed by a milling process. This is shown in  FIG. 5 .  FIG. 5  illustrates a milling tool  30  and the movement of said milling tool  30  by the line  31 . The milling tool  31  is operated in a way, that the axis of the milling tool  30  is approximately oriented in radial direction of the rotor  10 . Details of the milling process itself are known to the person skilled in the art. 
   The uniqueness of the manufacturing method as described above is the combination of a drilling process and a milling process. The milling process takes place after the drilling process has been finished. In connection with the drilling process, the size of the drill-holes and the pattern of the drill-holes and the axis of the drill-holes is determined from the contours defining the recesses to be manufactured. After these parameters of the drilling process have been determined, the drill-holes are drilled preferably in the flow wise direction for all recesses forming the flow channels. After the drill-holes have been drilled, a milling process will be performed to complete the removal of the materials. 
   In contrary to the method described above, it is also possible that the drilling process is performed in a way that a drilling tool removes material in an across flow direction of each flow channel. This is shown in  FIG. 7 .  FIG. 7  shows a radial view of an integrally bladed rotor  10  with three drill-holes  32 ,  33  and  34  drilled into the material between two adjacent blades  14 . The axis of the drill-holes  32 ,  33  and  34  is approximately in radial direction of the rotor meaning that the axis of the drill-holes  32 ,  33  and  34  is approximately perpendicular to the flow direction through the flow channels or recesses  11  to be manufactured. A drilling tool removes material by drilling pocket-like drill-holes  32 ,  33  and  34  starting from the outside diameter of the rotor in a radial direction towards the platform or inner surface of said rotor. The remaining process is the same as described above in connection with the first preferred embodiment of the invention. 
   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.