Machining fixture production

• US 10,025,288 B2
• Filed: 04/10/2015
• Issued: 07/17/2018
• Est. Priority Date: 04/24/2014
• Status: Active Grant

• Current Assignee: BAE Systems Plc
• Original Assignee: BAE Systems Plc
• Inventors: Bickerstaff, John, Wilson, David Mark
• Primary Examiner(s): Pan, Yuhui R
• Application Number:
  US15/304,658
• Publication Number:
  US 20170045875A1
• Time in Patent Office: 1,194 Days
• CPC Class Codes: B64F 5/10 Manufacturing or assembling aircraft, e.g. jigs therefor
• CPC Class Codes: G05B 19/402 characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position G05B19/19 takes precedence
• CPC Class Codes: G05B 19/4099 Surface or curve machining, making 3D objects, e.g. desktop manufacturing
• CPC Class Codes: G05B 2219/35025 Design and manufacture jig
• CPC Class Codes: G05B 2219/35218 From cad data derive fixture configuration and assembly program
• CPC Class Codes: G05B 2219/37221 Probe fixture to know datum points
• CPC Class Codes: G05B 2219/49007 Making, forming 3-D object, model, surface

Abstract

Disclosed is a method of producing a machining fixture for fixedly holding a workpiece during machining of that workpiece. The method comprises: providing an initial machining fixture comprising a plurality of receiving elements for receiving the workpiece to be machined; determining a datum, the datum being dependent upon the relative positions of the receiving elements; determining positions and orientations of one or more reference surfaces with respect to the datum; measuring the surface of the initial machining fixture with respect to the datum; and, thereafter, controlling machining apparatus with respect to the datum to machine the initial machining fixture to form the one or more reference surfaces, thereby producing the machining fixture.

Claims

1. A method of producing a machining fixture for fixedly holding a workpiece during machining of that workpiece to form a predetermined object, and for machining the predetermined object from the workpiece, the method comprising:

providing an initial machining fixture comprising a plurality of receiving elements for receiving the workpiece to be machined;

determining a datum, the datum being dependent upon relative positions of the receiving elements;

determining positions and orientations of one or more reference surfaces of the machining fixture with respect to the datum, each of the reference surface of the machining fixture being associated with an object feature of the predetermined object that is to be produced;

measuring a surface of the initial machining fixture with respect to the datum; and

thereafter, controlling machining apparatus with respect to the datum to machine the initial machining fixture to form the one or more reference surfaces, thereby producing the machining fixture;

providing the workpiece to be machined, the workpiece comprising a plurality of attachment features;

attaching the workpiece to the machining fixture by attaching the receiving elements of the machining fixture to the attachment features of the workpiece; and

thereafter, performing, using the machining apparatus a machining operation to machine the workpiece so as to produce the predetermined object,

wherein said machining of the workpiece comprises, for each reference surface;

locating at least part of the machining apparatus against that reference surface; and

controlling the machining apparatus to move away from that reference surface with respect to the datum to machine the workpiece so as to form the object feature associated with that reference surface.

2. The method according to claim 1, wherein the machining fixture is an airframe component machining fixture configured for fixedly holding the workpiece during a process of producing an airframe component from that workpiece.

3. The method according to claim 1, wherein:

the method further comprises providing a first digital model of the predetermined object to be produced from the workpiece using the machining fixture; and

the step of determining positions and orientations of one or more reference surfaces of the machining fixture comprises;

using the first digital model, identifying one or more features of the object; and

for each identified feature, determining a position and orientation of a reference surface of the machining fixture relative to the datum.

4. The method according to claim 3, wherein:

the machining fixture is an airframe component machining fixture configured for fixedly holding the workpiece during a process of producing an airframe component from that workpiece; and

each object feature is a landing for receiving a further airframe component during an airframe assembly process.

5. The method according to claim 1, wherein the method further comprises,

providing a first digital model of the predetermined object to be produced from the workpiece using the machining fixture;

and

using the first digital model and the determined positions and orientations of the one or more reference surfaces of the machining fixture, determining a second digital model, the second digital model being a model of the machining fixture specifying the positions and orientations of the reference surfaces of the machining fixture; and

the step of controlling machining apparatus with respect to the datum to machine the initial machining fixture to form the one or more reference surfaces is performed using the second digital model.

6. The method according to claim 1, wherein the step of determining the datum comprises:

measuring the relative positions of the receiving elements on the initial machining fixture; and

using the measurements of the relative positions of the receiving elements, calculating the datum.

7. The method according to claim 1, wherein:

relative positions of the attachment features of the workpiece to be machined are dependent upon the relative positions of the receiving elements; and

the step of determining the datum comprises;

measuring the relative positions of the attachment features on the workpiece; and

using the measurements of the relative positions of the attachment features, calculating the datum.

8. The method according to claim 1, wherein the predetermined object is an airframe component selected from the group of airframe components consisting of a frame and a longeron.

9. The process according to claim 1, wherein:

the predetermined object is an airframe component selected from the group of airframe components consisting of a frame and a longeron; and

each of the object features is a landing for receiving a further airframe component during an airframe assembly process.

10. An apparatus for producing a machining fixture for fixedly holding a workpiece during machining of that workpiece to form a predetermined object, the machining fixture being formed from an initial machining fixture comprising a plurality of receiving elements for receiving the workpiece to be machined, the workpiece comprising a plurality of attachment features, the apparatus comprising:

one or more processors configured to;

determine a datum, the datum being dependent upon relative positions of the receiving elements; and

determine positions and orientations of one or more reference surfaces with respect to the datum;

measuring apparatus configured to measure a surface of the initial machining fixture with respect to the datum; and

machining apparatus configured to be controlled with respect to the datum so as to machine the initial machining fixture to form the one or more reference surfaces, thereby producing the machining fixture;

upon attachment of the workpiece to the machining fixture by attaching the receiving elements of the machining fixture to the attachment features of the workpiece, the machining apparatus being further configured to perform a machining operation to machine the workpiece so as to produce the predetermined object, wherein said machining of the workpiece comprises, for each reference surface;

locating at least part of the machining apparatus against that reference surface; and

controlling the machining apparatus to move away from that reference surface with respect to the datum to machine the workpiece so as to form the object feature associated with that reference surface.

11. The apparatus of claim 10, wherein the machining fixture comprises a rigid base portion, and the receiving elements extend from an upper surface of the base portion.

12. The apparatus of claim 11, wherein the reference surfaces are formed from sacrificial blocks attached to the base portion.