As with all manufacturing processes, advances in technology have revolutionised the forging industry. The principles of the stamping process has changed little over the  years but the design of dies and die-sinking process have benefited enormously from the new technologies which has enabled the industry to improve quality and dimensional accuracy and extend the forging process to modern high-strength materials.

W H Tildesley has ensured that it is at the very forefront of these advances with state of the art computer modelling and die-sinking facilities, a purpose-built in-house machine shop and cutting edge internet based material procurement system.

Cad/Cam engineering | I.T. systems | Co-ordinate measurement | The process

CAD/CAM engineering

Computer Aided Design and Computer Aided Manufacture combined with Forging Simulation software speeds up both the design feasibility and die production processes. Rapid production of dies using high-speed milling technology that can run 24hrs a day means that the conventional myth that forging tooling is slow to produce or prohibitively expensive is no longer the case. In extreme cases dies have been manufactured and forgings produced in a matter of days.

Forging Simulation

WHT has the latest technology in this field. The simulation software uses finite element analysis and the stability of the automatic meshing and re-meshing enables use to simulate geometrically complex parts in both 2D and 3D. It also shows grain-flow and is able to predict common forging defects such as cracking and underfill. He end result is the most economic utilisation of material and optimum strength and integrity of the forging itself.

The simulation is used for:-

• The prediction of grain flow: analysis of contact distance to the dies, analysis of the velocities and displacements.

• The prediction of defects in the part: folds, cracks and underfill.

• The accurate analysis of the final geometry: spring back, die deformation.

• The analysis of the part through the whole forging process:  temperature distribution, stress and residual stress evolution, strain distribution and fibering evolution.

• The optimisation of the forging sequence: stage number reduction, reduction of material weight.

• The optimisation of die life: stress prediction within the tool, abrasive wear prediction and temperature evolution.

• Forging plant selection: forging load prediction and hammer deflection prediction.

All this means that the tooling is manufactured quickly and ‘right first time’, reducing expensive development costs at the initial forging stage and saving time and cost.

High-Speed Die production

One of the biggest advances in machining technology has been the development of high-speed ceramic-coated cutting tools that can machine hardened die-steel. This not only reduces lead-time by not having to have dies heat-treated after manufacture but also eliminates the risk of distortion that take place when heat treating complex die shapes. More recent developments in cutter-tool design and cutter-path software also mean that dies can be produced with a ready-to-use finish that does not require hand polishing before going into the hammer. Again a double benefit saving both time and cost.

Further advances in communication technology in the last few years have also rapidly increased response time, particularly in the international marketplace. The interchange of complex CAD files between WHT and our customers takes valuable time out of the design and approval processes and allows customers to see digital models of their components for evaluation.

Material Procurement 
The pattern of small and medium batch forging and the permutations of materials creates a dizzying level of quotation and purchasing activity which used to involve e-mails, faxes and telephone calls. Chasing down the offers and matching them to the quotations then working out the best offer from the differing formats usually took several days. Now WHT has a fantastic web-based solution that covers all those jobs. Our Materials Controller can ‘go out to tender’ at the press of a button each time we require materials for a specific customer part. Suppliers can login to their own area and submit quotations according to the specification required. Comparison of specifications and prices is quick and accurate and once the winning quotation is chosen a request for order is generated in the administration office.

It has major benefits for our suppliers since they receive an e-mail notification whenever a new requirement is created and each supplier has their own archive that shows their hit-rate in winning orders. The system has cut out a huge amount of non-value-adding activity for both WHT and our suppliers. It saves valuable lead-time in getting materials and provides greater accuracy in getting the right grades and sizes when placing orders. It also means we can be confident that we are getting the best deal for our customers.


Co-ordinate measurement 
Reflecting the shift into higher precision forgings and finished machined components, WHT now uses a Faro Portable Coordinate Measuring Machine (CMM) for all critical dimensional checking. The Faro is one of a versatile new breed of CMM that offers great flexibility in application. It serves both our quality department in checking forgings and machined parts, and our tool room in monitoring die production and condition.

The forging process is unique in its ability to transform standard sections of high strength steels and alloys into complex shapes, many of which are hard to measure across blend radii, draft angles and non-symmetrical features.  In this mode it is invaluable in producing 1st-off sample reports and reverse-engineering of legacy parts where no drawings exist.
However, in addition to basic coordinate measurement of key dimensions from datum lines the machine boasts powerful software capability that can marry-up with WHT’s existing 3-D CAD modelling system. Once programmed-in, a single touch of its probe on any part of a component or die cavity will register whether or not it is in tolerance of the original design. It is also portable enough to be used to check tooling parts whilst they are on machines without taking them out of their fixtures and to check cutter profiles on CNC machines etc.

With the move into precision machining of finished forgings and turned automotive parts the CMM has shown its true versatility in ensuring dimensional accuracy and in producing Initial Sample Inpection Reports (ISIRs) and First Article Inpection Reports (FAIRs.) It is clear that this technology is now a vital tool in WHT’s pursuit of world-class performance in precision components.

 

THE FORGING PROCESS 
Forging is suitable for one-offs and low volume production as well as mass production runs.

The drop forging process is particularly used in safety critic applications. At low volumes forging provides an alternative to machining, where as at high volumes it competes with casting.

Quality
By its very nature, forging improves grain structure in the finished part. Metal billets go through plastic deformation as they’re forged and as a result the metal grains align in the direction of flow. This characteristic produces exceptional strength to weight properties and reduces stress concentrations that tend to occur in corners and fillets. Parts can be machined post-forging with no loss of quality, because there are no voids or porosity in the finished article. The tolerances range from 1 mm in small parts up to 5 mm in large parts, but vary according to requirements, because reducing tolerances increases costs. Forging is often combined with machining for improved accuracy. Cold coining or sizing in house can also close tolerances and reduce the need to machine some parts.

Design Opportunities
This process is suitable for low volume production as well as one-offs. This is because it produces parts with superior strength to weight properties that cannot be manufactured in any other way. Small volumes can be machined from solid, but they will have to compensate for reduced strength brought about by random grain alignment. Undercuts are not possible in forging, however, it is possible to form undercuts and form joints with secondary forging operations. These processes can be used to make a huge range of component sizes and geometries. Drop forgings can weigh as little as 0.5 kg or as much as 50 kg.

WHT's Engineers can often assist in the design feasibility of customer's components and we would be delighted to discuss your particular requirement.

Design Considerations
Designing for forging must take into account many factors that affect design, including partition line, draft angles, ribs, radii and fillets. Parts are formed by hammering, or pressing, which can produce surprisingly deep protrusions, up to 6 times the thickness of material. Draft angles can be minimised and even eliminated by clever design, especially in ductile materials like aluminium and brass. Radii, however, are very important because they encourage the flow of metal and reduce tool wear. Minimum radius increases with depth of protrusion.

Compatible Materials
Most ferrous metals can be forged, including carbon, alloy, super alloy and stainless steels. Non-ferrous metals including aluminium, brass, copper and titanium are also suitable.

Costs
There is no doubt that new technologies have made the forging process affordable for small and medium batches to a level that was once inconceivable. Closed die forging tools typically last between 5000 and 7000 cycles in more common carbon materials but can be as low as 100 cycles where very complex shapes are required in high-strength super-alloys. Die life expectancies are greatly reduced by sharp corners, material forgeability and very close tolerances. Some of these limitations can be offset by incorporating multiple impressions into the die design or by pre-forming the metal billet before putting it into the dies. Forging cycle times are rapid: a typical forging is often complete within 10-30 seconds. However some complex shapes require complex procedures where the level of skill and experience of the Stamper plays a key part.

Environmental Impacts

A Forge is a relatively dangerous process to work and health and safety is maintained by operator training, controlled production procedures and involvement of the workforce.

The forging process provides optimum use of materials with little waste. All trimmed flash and off cuts are recycled and of course all metal components can be recycled at the end of their life-cycle.