Numerically controlled cutting method

• US 4,559,601 A
• Filed: 12/01/1982
• Issued: 12/17/1985
• Est. Priority Date: 04/04/1981
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Seki, Masaki, Tanaka, Kunio, Kishi, Hajimu
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): MACDONALD, ALLEN R
• Application Number:
  US06/451,145
• Time in Patent Office: 1,112 Days
• Field of Search: 364/168, 364/169, 364/170, 364/474, 364/475, 318/570, 318/572, 318/573, 219/69 W
• US Class Current: 700/187
• CPC Class Codes: B23H 7/06 Control of the travel curve of the relative movement between electrode and workpiece
• CPC Class Codes: G05B 19/41 characterised by interpolation, e.g. the computation of intermediate points between programmed end points to define the path to be followed and the rate of travel along that path G05B19/25, G05B19/31, G05B19/37, G05B19/39, G05B19/40 take precedence
• CPC Class Codes: G05B 2219/35151 Modeling geometric, generation or forming of curved surface
• CPC Class Codes: G05B 2219/49243 5-D
• CPC Class Codes: G05B 2219/50334 Tool offset, diameter correction
• CPC Class Codes: G05B 2219/50336 Tool, probe offset for curves, surfaces, contouring

Abstract

There is disclosed a numerically controlled cutting method of cutting a curved surface SF generated by interconnecting corresponding points mi, ni (i=1, 2, . . . ) on two curved lines CV1, CV2 with a cutter BT of a milling machine having simultaneously controlled five axes or a wire electrode of a wire-cut electric discharge cutting machine. According to the numerically controlled cutting method, curve information specifying the two curved lines CV1, CV2, information on tool radius or wire radius, information on the direction of tool or wire compensation, and division information for dividing the curved lines are supplied as inputs. Using the above items of information an offset position at dividing points mi, ni, which are next to dividing points mi-1, ni-1 at which the cutter BT or wire is currently positioned, is determined. The cutter BT or wire is then moved to the offset position to cut the curved surface SF.

Claims

1. A numerically controlled cutting method of cutting a curved surface which is generated by interconnecting corresponding points on two curved lines, comprising the steps of:

supplying as inputs curve information specifying the two curved lines, information on the shape of a cutter such as cutter radius, information on the direction of cutter radius compensation, and division information for dividing the curved lines;

dividing the curved lines based on said division information to determine dividing points mi, ni (i=1, 2, . . . );

determining the vectors of normals in said direction of cutter radius compensation at the dividing point mi on one of the curved lines and at the corresponding dividing point ni on the other curved line, and computing cutter compensation positions mi'"'"', ni'"'"' corresponding to the dividing points mi, ni upon cutter position compensation along the directions of the normals using said information on the shape of the cutter;

computing a cutter axis direction (I, J, K) from said cutter compensation positions mi'"'"', ni'"'"';

computing movement data on control axes of a numerically controlled machine tool using coordinates (X, Y, Z) of the cutter compensation position ni'"'"' and said cutter axis direction (I, J, K); and

moving the cutter relative to a workpiece based on said movement data on the control axes to cut the curved surface.

2. A numerically controlled cutting method according to claim 1, wherein said moving the cutter relative to the workpiece comprises the step of computing movement data x, y, z along orthogonal coordinate axes and movement data b, c, in vertical and horizontal directions of rotation, out of said movement data on the control axes, according to the following equations:

##EQU8## where l is the length of the cutter.

3. A numerically controlled cutting method of cutting a curved surface which is generated by interconnecting corresponding points on two curved lines, comprising the steps of:

supplying as inputs curve information specifying the two curved lines, information on wire radius including an electric discharge gap in wire-cut electric-discharge cutting, information on the direction of wire compensation, and division information for dividing the curved lines;

dividing the curved lines based on said division information and computing dividing points mi, ni (i=1, 2, . . . );

computing the vectors of normals in said direction of wire compensation at the dividing point mi on one of the curved lines and at the other dividing point ni corresponding to the dividing point mi, and computing wire compensation positions mi'"'"', ni'"'"' corresponding to the dividing points mi, ni upon wire position compensation in the directions of the normals using said information on the wire radius;

computing the direction of the wire axis from said wire compensation positions mi'"'"', ni'"'"';

computing the positions of points mi" (u, v), ni" (x, y) corresponding to the wire compensation positions mi'"'"', ni'"'"' and lying on planes parallel to a table for placing a workpiece thereon, using said direction of the wire axis, said wire compensation positions; and

driving the table in the directions of X, Y based on x, y and driving the wire in the directions of U, V based on u, v to cut the workpiece along the curved surface.

4. A numerically controlled cutting method according to claim 3, wherein said computing the positions of said points mi", ni" comprises the step of computing the coordinates (u, v), (x, y) of said points mi", ni" according to the following equations:

space="preserve" listing-type="equation">u=Sx t·

I

space="preserve" listing-type="equation">v=Sy t·

J

space="preserve" listing-type="equation">x=Sx'"'"' t'"'"'·

I

space="preserve" listing-type="equation">y=Sy'"'"' t'"'"'·

j

where t=(d-Sz)/K, t'"'"'=(d'"'"'-Sz'"'"')/K, and d, d'"'"' are coordinates on the Z-axis of said dividing points mi, ni.

5. A numerically controlled cutting method for taper cutting a workpiece along a predetermined curved surface, which intersects a first plane on a first side of the workpiece along a first curved line and which intersects a second plane on a second side of the workpiece and parallel to the first plane along a second curved line, using an elongated cutter having an axis, said method comprising the steps of:

dividing the first curved line into segments which intersect each other at dividing points mi (i=1, 2, . . . ) and dividing the second curved line into corresponding segments which intersect each other at corresponding dividing points ni (i=1, 2, . . . );

for each pair of dividing points mi, ni, determining a corresponding pair of cutter compensation positions mi'"'"', ni'"'"' lying in a plane which is substantially normal to said predetermined curve and which passes through the dividing points mi and ni, the compensation positions mi'"'"', ni'"'"' being spaced apart from the dividing points mi, ni so as to lie on the axis of said cutter when the dividing points mi, ni lie substantially on the periphery of said cutter;

when the axis of the cutter passes through the compensation positions mi-1'"'"', ni-1'"'"', moving the cutter with respect to the workpiece so as to bring the axis of the cutter to a position passing through the compensation positions mi'"'"', ni'"'"'; and

repeatedly moving the cutter with respect to the workpiece until the predetermined curved surface is cut.

6. The method of claim 5, wherein said cutter is a milling cutter and wherein the step of moving the cutter with respect to the workpiece so as to bring the axis of the cutter to a position passing through the compensation positions mi'"'"', ni'"'"' comprises the steps of determining a cutter axis direction parallel to a line running through mi'"'"' and ni'"'"' and moving the cutter with respect to the workpiece until a predetermined point on the axis of the cutter substantially coincides with one of mi'"'"' and ni'"'"' and the axis of the cutter lies substantially parallel to the line running through mi'"'"' and ni'"'"'.

7. The method of claim 5, wherein said cutter is the wire electrode of a wire-cut electric discharge machine having a movably mounted wire guide and wherein the step of determining a pair of cutter compensation positions mi'"'"', ni'"'"' additionally comprises the step of finding the points Pc and Pc'"'"' which lie along a line running through mi'"'"' and ni'"'"' and which lie respectively on said first and second planes.