The next speaker on this subject was K. Dawson of the Caterpillar Tractor Company, who reported on computer— aided design of track link forging dies and tooling. Cater— pillar began manufacturing track links in 1972. They now make 5 million track links per year, according to Mr. Daw- son, ranging from less than six pounds to over 30 pounds in weight. In the manufacturing process, steel bars are unloaded,    stored,    and    supplied    from    storage    to  an

VOL.  2,  NO.  2,  JANUARY 1982 89

unscrambler, from where they are fed one at a time to the shears. Sheared billets are sent to the heating station  and from there to the press, where the hot billets are first busted into squares, forged (blocker followed by finisher), trimmed of flash, and hot pierced to generate bolt holes.  The forged links are then sent on to various measuring machines for inspection. Mr. Dawson observed that die sinking is an important activity for Caterpillar since they  sink  over 1600 die impressions per  year.  To make the most  productive  use of their EDM electrodes, a new electrode is used  first  to finish one impression and then to rough another impression before being resharpened. The computer-aided design pro- cess at Caterpillar begins with the forge designer reviewing the forging drawing against the backdrop of the data base created by the engineering  department.  The  designer  calls up the materials file, selects a shrink factor, and proceeds with the design of tooling. He works to a l : 1 scale during design; drawings can be subsequently generated to any de- sired scale. Stress analysis and load estimation are  then done, based on past experience rather than by computer modeling of the forging process, and the right size die block and  press  are  selected.

The end product of the CAD exercise is a  set  of  die sinking model drawings allowing for shrink. This is accom- plished within 15 pct of the time previously required, while providing drawings of improved quality and which  are easier for the patternmaker to read. Furthermore, the entire design can be easily mirror-imaged to transform a right-hand link design into a left-hand one, or to transform the design from male to female details. Mr. Dawson noted,  in regard to the learning curve associated with the new practice, that whereas the first computer-aided design for a complex die would require considerably more time than required for the traditional design procedure, the second time  a  similar  die had to be designed,  it  would  take but  half  as much  time as in conventional designing. CAD is thus very useful when a company works with a family of parts (for example, track links of various sizes) rather than with a single product of its kind. CAD is also particularly advantageous when major design changes are sought, requiring repeated corrections in a number of components. Mr. Dawson concluded his talk by remarking that the Caterpillar Tractor Company would be going  in  for  a  new  CAD  system  at  an  estimated  cost    of

$900,000.

The final presentation on computer aids, given by C.F. Billhardt of Battelle-Columbus Laboratories, described the tailoring of a commercial CAD/CAM system to include forging load and stress analysis simulation for closed-die forging. The approach described by Mr. Billhardt uses a Computervision CAD/CAM system to generate geometric descriptions of different sections of a forging on a real-time basis. The “slab method” is used, in conjunction with appro- priate material and interfacial data, to estimate the total forg-

90         VOL.  2,  NO.  2,  JANUARY  1982