Turning to the subject of the Battelle—Eaton program on spiral bevel gears, Mr. Sabroff noted that their emphasis was on developing and implementing CAD/CAM tech— nology for this application, rather than on precision forging process development. The target component was a ring gear of 10 inch diameter, 12 inch face-width, 10 deg taper angle, and having 39 teeth. The work involved computer-aided design of the forging dies and the generation of a program for cutting the EDM electrodes. In addition, consideration was given to a flexible CAD/CAM system for use in a forge shop for batch manufacturing of a family of spiral bevel gears. Forging trials conducted at Eaton involved a 3000—ton forging press in which the ring gear target component was precision-forged (0.007 inch machining envelope) at l5OO ° to 2000 °F. Preforms were box-heated in a gas-fired fur- nace, under a reducing atmosphere, to the required initial temperature. Die materials were primarily H11 and H 13 grades of hot-work die steel. Since only 20 sets of gears were made, with the objective of proving out the CAD/CAM techniques used, die life data were not available on this particular component. However, Eaton’s experience with essentially similar pans led Mr. Sabroff to predict a die life of 3,000 to 10,000 parts.

The next CAD/CAM presentation was shared by R.A. White  and M.  Yu of Red Oak Forge Company.  Mr.  White

J.  APPLIED  METALWORKING

described Red Oak Forge as a nonunion plant staffed exclu- sively with salaried employees (no time clocks). The plant features 1600-ton and 2500-ton mechanical presses, semi- automated lines, and 55 employees including a CAD/CAM staff of six. Their CAD/CAM hardware comprises a com- puter, plotter, two CRT terminals, tablet, light pen, control panel, and the work station. Mr. White advocated the pur- chase of software first, followed by the hardware necessary to meet the company’s needs. Red Oak Forge employs an ANVIL-4000 software package which uses Fortran  VII and is capable of generating, manipulating, and analyzing both 2D and 3D geometries, as well as mechanical drafting , NC tape generation, parts classification, and file and informa— tion managment. The procedure for NC involves input of the part geometry into the computer, tape production, fabri- cation of a Fiberboard/plastic model, review by the customer, NC tape editing, and EDM electrode manufacture on an NC machine. (This procedure, which took three to four weeks by the traditional aproach, can be presently completed in six to eight hours and is targeted eventually for four hours.) Simultaneously, forging and preform drawings are printed by the plotter and sent to the customer for approval. Next, the design of the various items of tooling, including block- ers, finishers, and trim tools, is undertaken. This involves geometrical simulation of each die in the computer and validation of the EDM electrode shape. Finally, the  die cavity is made using an EDM machine  and/or  a CNC mill- ing machine.

The end results of the computerized process are high— quality dies and forgings, excellent consistency, good nesting,  and  low  mismatch   between   the   forging   and the trim tools. The drafting capability of their plotter auto- matically provides them with four views (with provision for countless more), in addition to which they can visualize all the milling cutter paths three—dimensionally. According to Mr.   White,   the   cost   of   the   system   was approximately

$300,000, including purchased hardware and software, installation, and staff training. It normally takes their staff less than three months to become productive on the CAD/CAM system, he added. His  coauthor,  Mr.  Yu , followed with a presentation of the different geometrical elements (fishbelly, semicircle, semiellipse, and quarter ellipse) into which the forging and preform geometries can be broken down. This aids in the selection of the correct preform volume. Allowances are made for flash loss based on the degree of complexity  of the   forging.