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CAD CAM Industries

J.D. Whelan

CAD/CAM having a revolutionary impact on forgings industry

As is the case with so much technology in the 1980s, forging technology is undergoing a rapid transformation. The driving forces are the usual customer demands for lower costs, higher quality, and greater customer responsiveness. Many of the solutions that are being investigated have a double-barrelled effect. That is, often solving a quality problem leads inevitably to better customer responsiveness. The introduction of a new technology or methodology to solve one problem tends to impact on all of them. This article will touch on the major technical changes that are occurring and attempt to put them into perspective.

Forging customers in general are making renewed demands on their suppliers. In the area of quality many customers are no longer satisfied to accept the assurances of their suppliers regarding the effectiveness of their final inspection procedures. Instead, they are demanding that their suppliers institute meaningful statistical process control (SPC) procedures throughout their whole facilities. Their expected end result is that their suppliers will do a reduced level of final inspection, and that the customer will do no incoming inspection, other than for a statistical sampling. A rejection in the statistical sampling rejects the whole lot that it represents.

Rather, in-process SPC controls the process so that there are no deviations to be found later. They are found as they are created and rejected on the spot. Or, it is recognized that the process is out of control and the process is shut until the cause of the deviations is identified and corrected. This can be thought of as building a fence at the edge of the cliff, rather than having an ambulance standing by waiting for casualties at the bottom.

Pratt & Whitney division, East Hartford, Conn., of United Technologies Corp. has recognized the importance of SPC and makes a program available to its suppliers. The firm not only asks its suppliers to implement SPC but also offers a set program complete with training if required.

In the area of customer responsiveness, inventory control and the worldwide competitive climate that exists for all engine builders places a premium on fast delivery and rapid response to the call for schedule changes. At the Medium Gas Turbine division of General Electric Co. a senior executive has remarked that their inventory thrust is away from "just-in-case' toward "just-in-time'. He added that they are looking for suppliers who are prepared to respond to schedules that may change at will. Their customers demand it, and so they must require it of their suppliers. The implications for the superalloy forging supplier are clear. Be prepared for smaller order quantities delivered with less lead time. In return there may be more room for multi-year sourcing, but that's no promise.

Superalloy customers are demanding and expecting higher quality, greater flexibility in scheduling, and along with all of that, they are placing a great deal of pressure on lower prices. It is the classic case of wanting more for less. The only meaningful response for forging suppliers is to improve their technology dramatically. There is little room left for choice. And as one last parting shot, users of superalloy forgings are still looking for improved overall performance; longer fatigue lives, lighter weights, greater strengths, and so on. The growing trend toward worldwide competition is hastening the technology transformation in the U.S. forging industry.

The emergence of computer-aided design and computer-aided manufacturing (CAD/CAM) systems along with the introduction of low cost microprocessor controls is having a revolutionary impact on the forging industry. The incentives for the forgers of superalloys to introduce this technology are very strong. The acceptance of this new technology along with the increasing supply of engineers who know how to integrate computers, engineers, operators, equipment and processes into one unified approach to the design and production of high quality forgings at the lowest possible cost is remarkable.

CAD/CAM systems can be used to coordinate the complete process of design and manufacture of forgings including the important technical consultation phase with the end customer. The following outline is a view of how CAD/CAM systems will be working in the not-too-distant future. A customer will send an inquiry to his supplier by simultaneously contacting the appropriate sales department personnel and also downloading his technical requirements to the supplier's engineering department via their CAD/ CAM systems.

The supplier will have his own decisions to make regarding how far he carries his design at this inquiry stage. But assuming he ultimately receives the order for the job in question whatever level of design work he did is now readily available to use in the final design phase. There is no reason to lose any engineering effort between the estimating phase and the final engineering phase. The forging outline will be determined on the CAD/CAM system and using this design and with very little additional effort the process for die design, forging parameters, and numerical control (n/c) machining also will be finalized. If required, consultation with the customer at the design phase can take place via the CAD/CAM system.

One of the frustrations of engineers and metallurgists through the years has been the difficulty of ensuring that their design ideas get carried out in the shop exactly as they had envisioned them when they developed the process. The addition of micro-processor controls to the equipment in the shops and the linking of these computer controls to the CAD/CAM system is closing the process control loop in many forge shops. The kinds of machines that can be linked, and the way that they are linked to the CAD/CAM system, is limited only by the imaginations of the managers and engineers in the industry. This author is aware of machine shops (for both production forgings and forging dies), forging presses, and furnaces for heating and heat treating that are being fitted with micro-processors and then being linked to CAD/CAM systems either for direct down-loads or for control via tapes or cassettes, depending on the needs and limitations of the shops involved.

The Air Force is sponsoring a computer-aided engineering project to evaluate a number of forging parameters. A computer model will be developed to integrate experience-based knowledge with the existing finite-element analysis program. The object will be to develop parameters which will lead to a capability to do computer modelling of forging and/or extrusion parameters such as material plasticity and lubrication characteristics, which in turn lead to the development of particular properties or metallurgical structures.

It is also of interest to develop computer models of how the metal flows in a particular die set to determine in advance of an actual trial whether the dies will fill properly. All of this will aid in the proper design of forging sequences, die designs, temperatures, and lubricants to yield the desired shape, properties and structures the first time. Again, the beneficiaries are better quality, faster reaction times, and thereby lower costs. None of this is possible without the computer-based technology which is developing in the industry.

Key changes occurring on the presses themselves involve more and more hot die and isothermal forging. Of course, for some time now powder alloy forgings have been produced on isothermal presses using thorium dispersed molybdenum (TZM) dies. The thrust is for more and more alloys to be forged isothermally or on hot dies, where the forgings are run on dies that are not TZM but are run at temperatures well above traditional die temperatures. Die materials include a variety of superalloys, either cast or wrought. The objective is to eliminate cracking completely and to produce a forging which is as close to the customer's final shape as possible, without the high cost of TZM dies and the slower run rates experienced on isothermal presses. Close tolerances also are required to optimize the effectiveness of the increasingly automated machine shops that the forgings move into.

Die change times have for years been a driving force to keep forging run sizes high. When a large piece of equipment is down for several hours to make a die change, it is imperative that a sizeable number of forgings be run to amortize the set up cost over. More and more we are hearing about presses being installed with automated die change systems. Many companies are looking at existing equipment and doing retrofits. The driving force for this change comes from the high cost of inventories and the fact that customers are increasingly saying that they want to change schedules at will, and take only small quantities of forgings at a time.

The future for superalloy disk producers might include isothermally forging disks complete with integral blades. Work has been going on in this area for a number of years. Of course, the incentive for the engine manufacturer is the high cost of machining and the assembly cost associated with fitting disks with blades. The designer is relieved of the problems associated with possible failure in the blade roots.

Certainly, there is any number of new things going on in the forging industry. However, these are some of the most significant technological developments that are shaping the forging of superalloys in the 1980s.

Photo: The future for superalloy disk producers might include isothermally forging disks complete with integral blades.