| dc.description.abstract | This Master thesis consists of a literature review on surface integrity after milling with ceramic tools in nickel‐based super alloys. Examples of turning and milling with carbide tools have also been included, due to little literature on the above. The effect of cutting fluids in ceramic milling operations, and the effect of high pressure cooling in turning operations have been reviewed. Last the possibilities of using a Finite Element Analysis (FEM) program, to study the effect of high pressure cooling in turning operations have been reviewed.
There have been done machining tests with two different milling cutters on NTNU (32 and 63 mmcutters). One of the tests was not successful (32 mm cutter), while the other (63 mm) showed a large improvement potential for Volvo Aero Norway (VAN). In a comparative analysis of tool life, VAN’s existing tool supplier showed better results than two other tool supplier companies. Regrinded tools,gave an equivalent or marginally worse tool life.
The effect of cutting fluids in ceramic milling operations was studied. The use of flood cooling gave a non acceptable tool life, while use of Minimum Quantity Lubrication (MQL), (application of pure cutting fluid with a flow rate of 20 – 90 ml/h) gave a marginally worse tool life.
Surface integrity after ceramic milling was studied in a separate experiment. The work piece was cut up in pieces, and polished so the thickness of the deformed layer could be studied in a microscope(30 – 60 μm). This experiment was repeated with a lower radial cut and the use of MQL, this resulted in a thinner deformed layer (9 – 13 μm), unfortunately this was not within VAN’s 5 μm requirement.
The improvement potential in today’s ceramic milling operations was calculated during two machining tests at VAN. When the cutting speed and feed was increased (from Vc(nom) = 1100 to 1283 m/min, and from fz = 0.08 to 0.10 mm/tooth), the productivity increased by 46 %. Since the tool life was the same, a cost saving of 23 and 25 % can be achieved for the 80 and 63 mm cutter respectively. If the machining centre had coped with the increased spindle load, the recommended parameters from the NTNU tests could have been used (Vc(nom) = 1283 m/min, fz = 0.16 mm/tooth).This would have increased the total productivity with 133 % and a cost saving of 50 and 58 %.
An economic analysis show that VAN can reduce costs if they regrind used ceramic inserts in USA, but that they must incorporate a insert size in between of their two current sized, to get an acceptable cost saving. The large cost saving potential found in the fall project (Barstad, 2009), has disappeared due to VAN’s exceptionally negotiation of the purchase price of ceramic inserts (47 ‐ 64 % reduction).
The literature review reveal that no realistic FEM models of the effect of high pressure cooling in turning operations exists. Therefore it was only performed a simple FEM analysis of turning with ceramic tools in a nickel‐based super alloy. A low cutting speed (10 m/min) had to be used, since the program did not accept high cutting speeds (300 m/min) in this alloy.
In connection with the project presentation at VAN, a movie regarding milling with ceramic tools, and a Power Point Presentation was made. | nb_NO |
