Micromachining aerofoil components

• US 6,611,731 B2
• Filed: 07/22/2002
• Issued: 08/26/2003
• Est. Priority Date: 12/13/1999
• Status: Expired due to Term

• Current Assignee: Winbro Group Technologies Ltd. (Quaser Machine Tools, Inc.)
• Original Assignee: M&J Technologies Company Limited
• Inventors: Duffin, Jason E.
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): KOSOWSKI, ALEXANDER J
• Application Number:
  US10/200,619
• Publication Number:
  US 20030004606A1
• Time in Patent Office: 400 Days
• Field of Search: 700/192, 700/193, 700/187, 219/121.7, 219/121.71
• US Class Current: 700/187
• CPC Class Codes: B23B 2250/12 Cooling and lubrication
• CPC Class Codes: B23B 39/00 General-purpose boring or drilling machines or devices; Sets of boring and/or drilling machines
• CPC Class Codes: B23B 51/011 Micro drills
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 2219/45139 Laser drilling
• CPC Class Codes: G05B 2219/50294 Tool offset length by going to a reference and recording distance

Abstract

The method is suitable for the micromachining of accurately aligned holes in the aerofoil surface of a component such as a jet engine turbine blade or vane which comprises a ground anchorage portion and a cast aerofoil portion. The method uses a micromachining apparatus which is pre-programmed to machine holes in the aerofoil surface when that surface is in a predefined reference position and orientation in the apparatus. Initially the component is mounted in the micromachining apparatus by means of its anchorage portion. At least one probe is then moved into contact with the surface of the cast aerofoil portion to derive the positions of selected points on that aerofoil portion. From the derived position data, angular and linear offset data may be calculated to define the deviation of that cast aerofoil portion from the reference position and orientation defined in the computer memory of the micromachining apparatus. That angular and linear offset data is applied to the computer program resident in the micromachining apparatus to control the movement of the drilling head relative to the aerofoil surface and to machine the air holes in the aerofoil surface without having to remove the component from the apparatus.

Claims

1. A method for micromachining the aerofoil surfaces of a component which comprises a ground anchorage portion and a cast aerofoil portion, which method comprises:

mounting the component in a micromachining apparatus by means of its anchorage portion, the micromachining apparatus having a computer memory storing data defining a single predefined reference position and a single predefined reference orientation of the aerofoil surface in the apparatus, and data relating to the position and orientation of holes to be machined in the aerofoil surface relative to that predefined reference position and orientation;

deriving the positions of selected points on that aerofoil portion;

calculating, from the derived position data, linear and angular offset data to define the deviation of that cast aerofoil portion from the predefined reference position and orientation; and

applying that linear and angular offset data to a computer program resident in the micromachining apparatus to control the movement of a drilling head relative to the aerofoil surface and accurately to machine air holes in the aerofoil surface even when the component is mounted in the micromachining apparatus with the aerofoil portion located other than in its reference position and orientation.

2. A method according to claim 1, wherein the or each probe is mounted on a movable platform and the positions of the selected points are derived by using at least one probe mounted on the movable platform on which the drilling head is mounted.

3. A method according to claim 1, wherein the derived position data are obtained from at least six probe measurements:

four being the positions of two pairs of associated tangent points of which each pair defines a point at which an outer curved edge of the aerofoil surface would touch tangentially two straight lines drawn in space with a known angle between them; and

two being the positions of points at which mutually perpendicularly aligned probes touch the aerofoil and anchorage portions of the component.

4. A method according to claim 2, wherein, the derived position data are obtained from at least six probe measurements:

four being the positions of two pairs of associated tangent points of which each pair defines a point at which an outer curved edge of the aerofoil surface would touch tangentially two straight lines drawn in space with a known angle between them; and

two being the positions of points at which mutually perpendicularly aligned probes touch the aerofoil and anchorage portions of the component.

5. The method according to claim 1, wherein the micromachining apparatus comprises a machining device selected from the group consisting of a laser head, an electrochemical machining head, an electrical discharge machining head and a water jet drill.

6. The method according to claim 1, wherein the micromachining apparatus comprises at least two machining devices selected from the group consisting of a laser head, an electrochemical machining head, an electrical discharge machining head and a water jet drill.