How to Buy Forgings
When the decision is made to buy a forging, the purchaser must have some general knowledge in order to make the best purchase possible. Understanding exactly what you need to look for in a supplier, what material is desired along with your own knowledge about the forging process will ensure you get the best bang for your buck. Going in blind could cost your company more money, produce unsatisfactory components and lead to a grueling buying experience. We will be discussing in this 2 part series the best way to go about purchasing a forging of any kind.
Communication and Cooperation.
Buyers and producers of forgings need to work closely to ensure the buyer receives the best product at the best possible price. As advancements in forging methods and materials continue to improve the process, collaboration is more crucial than ever before. By being aware of these advancements and working closely with the forger, the engineer or purchaser can ensure delivery of high-quality products while keeping the ever important cost low.
Even with its long history and the countless technological advancements over recent years, forging still involves a great deal of artistry and hands on work. Even if a product designer or industrial buyer is knowledgeable about shaping metals, there is much to be gained by bringing the forger into the design and specification phases of product development.
Once it has been decided that a product or component requires the strength, toughness, dimensional accuracy and overall integrity of a forging, the question remains which forging process would be the best. Some of these forging processes include open die, impression die, ring rolling and so on. Often this is a straightforward decision based on part size, configuration and quantity required.
The buyer should have a clear understanding of what their component specifically requires and ensure their needs can be met by individual forgers. Here are some points to consider when choosing a forger.
-Does the forger have experience in applications similar to the one being considered?
-Is design assistance offered?
-Does the forger have the equipment required to produce your part?
-Is the forger able to provide related services like heat treating, machining and testing?
-Is the forger accustomed to producing the volume required?
-Does the company specialize in long runs, short runs or quick delivery?
-Is the forger capable of producing nonstandard alloys, specs & sizes?
Answering these questions is key to finding the qualified forger to meet your needs.
An experienced and capable forging engineer should be able to make design suggestions with purchasers best interests in mind. They should be able to simplify processing, reduce required machining and ensure the speed of the delivery. It might be possible to achieve the high-level performance benefits of a forging without significantly increasing material or production costs over those associated with other processes.
It is important to get the forger involved in the early stages of the design process. The benefits might vary depending on the complexity of the part and the forging process used. For example, impression die forgings may benefit more dramatically than open die products. But again, this is exactly why it is important to consult with the forger to completely understand the benefits and which forging process to choose.
Make sure you clearly express how the desired forging will be used, the operating environment and critical mechanical properties. The forger needs to clearly understand the service stresses like load-bearing, power transmitting, impact, hydraulic pressure, operating temperatures, corrosive condition and the stress locations. This will help the engineer design and pass on suggestions to improve the overall product while reducing manufacturing costs.
7 Main Design Points
1) Material Selection – It is vital that the purchaser specifies realistic property levels required by the application. The best price while having an acceptable component is only possible when tensile, hardness, impact and other mechanical properties are realistically based on the service requirements of the component being forged. Then once the requirements are established, the forger can select the best material for optimum performance, forgeability, heat treatability, machineability and cost.
2) Part Configuration – Sometimes a forger is able to make slight changes in a part’s shape which will simplify forging requirements, reduce die costs and speed up production with no loss in part performance. The forging engineer will look at its tooling and processing requirements and see where they can reduce draft angles or sharper radii without affecting part function. Often a simpler die can be used or the parting line can be adjusted to allow the use of a flat top die which will produce a more affordable part.
3) Dimensional Tolerances – Producing as-forged shapes to tight tolerances is more achievable than ever as companies strive to develop their net- and near-net-shape forging capabilities. Still, there is considerable cost involved in holding tight as-forged tolerances. A wise buyer will see if the forger could help evaluate the trade-offs between reduced machining and increasing die and processing costs.
For open die forging, nearly all forgings will require some machining. Determining where and how much machining stock “envelope” should be specified and the complex decision is best made together with the forger. All tolerances that are set should be included along with all dimensions of the part drawing that is given to the forging engineer. Based on this information, their experience and the supplier a forger can accept or request modifications to the specifications for the most cost-effective production method.
4) Applying Guidelines – There is a system that was developed that act as dimensional tolerance guidelines that set limits on size, length, width and thickness, die match and straightness. Guidelines for impression die applications can be found in the Forging Industry Association’s Tolerances for Impression Die Forging, Hammer, Press and Upsetter.
Standards are also in place that applies to material considerations like chemistry, strength, ductility, impact resistance, conductivity, soundness and grain flow. Unless there is a specific reason to choose a certain material or tighter tolerance controls it would be best to follow established standards to avoid additional costs.
5) Surface Finishing – Most forging companies have machining capabilities and some even offer finishing services. More customers are asking forgers to also do finishing machining to isolate responsibility and cut costs. The added responsibility gives the forger more flexibility which can result in savings for the buyer. The forger, with drawings that show the finished dimensions and tolerances, can design the ideal forging around the finished part. The largest benefit is that the machining envelope can sometimes be reduced which will save on material and machining time.
6) Inspection & Testing – The only tests that are needed will be ones that establish the mechanical properties and quality required for reliable performance. This will help keep costs low while also ensuring the part performs as needed because any additional tests will increase the cost. Non-destructive testing like ultrasonic and magnetic particle inspects have become increasingly important for critical service applications like generator or turbine rotor shafts. These tests are expensive and time-consuming so they should only be used when absolutely necessary. Statistical process/quality control techniques are being used in many forge shops and these capabilities could reduce the need for costly testing on individual forgings.
7) Delivery – This step is not necessarily important in the early stages but could be a helpful when speaking about volume and shipping schedules . These factors could help the forger provide a better service in the long run. Production-run setup and material acquisition requirements will also need to be taken into consideration by the forger. Reductions in material and production costs are able to be made through advanced planning.
How to Buy Forgings Part II
When buying forgings it is extremely important you as a purchaser are knowledgeable about the different aspects of the forgings process to ensure you get exactly what you need. Not only can knowledge about the forgings process lead acquiring the best component possible, you could also save money at the same time.
This is the second of a two part series “How To Buy Forgings”. Part I is available above.
In Part I we discussed what to look for in a forger, the importance of communication & collaboration between forger and purchaser and steps to follow throughout the design process.
In Part II we will be discussing the advancing of forging technology and processes and a new direction the industry Is heading towards.
Forgings are a well-established industry but recent advancements in technology have made their way into these forging plant’s hands. New techniques and capabilities have led to more options when it comes to the forging of a product for buyers as well as the forger. It will be important for a buyer to keep up-to-date with the latest developments surrounding forging and material capabilities. This goes back to Part I where it is important to choose a forging company that will assist and communicate throughout the early stages of the design process. A forging engineer would be able to help you through the advanced processes and explain which may be best for your unique forging request. It is also important to communicate effectively with each forger because the capabilities and technologies can vary from one forging plant to another.
Here are some areas where technology has transformed the forging process:
1) Net Shape Forgings
Net-Shape Forging has the potential to dramatically reduce finishing costs after the forging process is complete. Machining time will be reduced and there will be less stock from the machining process after forging. Not all forgers offer this kind of forging option so it is vital that you understand the capabilities of the forger you have chosen. However, the earlier the forger is involved with the design process the more likely near-net shapes can be achieved.
2) Micro alloyed Steels
For use in forging crankshafts, connecting rods, front axles for trucks and other large critical components, micro alloyed steels can be used to reduce the need for heat treatment after forging. Small additions of vanadium, columbium and other ingredients can be used to strengthen plain carbon grades of steel. Still an emerging technology, many forgers may not have the capability but for certain components it may be the ideal option. The costs associated with heat treatment have the potential to be eliminated. It is important to ensure that the micro alloyed steel still meets the performance properties to suit the application of the component.
Computer controlled design capabilities are having a dramatic effect on many industries including forging plants. Quoting, die design, production, billet handling and presses, to heat treating and machining, computing power is affecting the forging process from the ground up. It is extremely efficient to use this software throughout the design and production process. Files and changes can be shared in real-time to every party involved. These developments have created a much more cohesive forging experience for both the buyer and forger.
Forging: A Service Industry
The forging industry has been moving away from antiquated business models and looking for their place in the 21st century global market. The custom forge plant is essentially a service organization that wants to deliver the buyer the best product at the best possible price. One of the most important aspects of the service forgers produce is their assistance and expertise. A service oriented forger will make sure to take the time to assist in any design and developmental steps to offer the buyer the best forging options to fit their specific needs.
As business become better communications, it is vital to reach out to different forgers and chose the one that is most likely to assist and communicate freely every step of the way. Competition throughout the global marketplace gives buyer the ability to ensure they receive the highest level of service possible. If they are not satisfied with the service they are receiving, there is an entire world of forgers out there that are willing to provide the service they need.
As materials and process technologies advance, the buyer must have the forger involved in the decisions that will affect the cost and performance of the part. Through close collaboration between forgers and buyers you can get the most out of recent forging industry innovations and help ensure you receive the best possible component while keeping costs at a minimum.
Throughout this two part service we dove into the forging process head first. There are finer complexities which a 2,000 word write up can explain, but this should serve as a starting point for buyers who are looking for a forger. Knowing what to look for in a forger, making a point to communicate and collaborate freely, including the forging in on the design process are some key places to focus on when beginning the buying process. Furthermore, an understanding of how technology has transformed the forging industry could be the difference between the right component at the right price or an expensive mistake. It is also to ensure your forger is providing the most comprehensive service possible to make sure the correct processes are used to create your unique component. Buying a forging is not always the simplest process, but if you follow these steps you can be sure your experience will be as smooth as possible.
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