Recently, I was assisting an automotive Original Equipment Manufacturer (OEM) in Pune that was facing an increase in the input cost of raw material for transmission gear blanks. Their traditional closed-die forging method of forging was not only wasteful of expensive chrome-moly steel with a flash that was about 25% loss but also the procurement department could not cope with the squeezed margins while engineering was not giving into the metallurgy to alter it.
The solution came not through renegotiating steel supplier contracts that was the procurement department's idea but through the re-assessment of the forming process itself that the operations department and the production planning suggested. By changing the critical parts to precision forging, they were able to cut the flash loss to under 5% and they almost totally did away the rough machinning after finishing. Truly speaking, it was one of those moments in industrial sourcing where a simple change of approach led to the resolution of the problem that was costing the customer several million rupees.
For those of you who are dealing with procurement, supply chain or component engineering for highly stressed applications, mastering the art of precision forging is more than an operational move, it is the very heartbeat of keeping and defending a healthy margin.
What Is Precision Forging? (Beyond the Textbook Definition)
We can pass over the boring textbook stuff for now. Conventionally, one takes a metal billet that is preheated, places it between a pair of dies, and then it is forged by hammering the metal into the dies until it fits the cavity. Engineers intentionally overprovide with material to ensure that the die cavity fills completely.
This surplus material is deliberately allowed to escape the confines of the cavities via a small gap along the perimeter. The metal which forms the excess material is later trimmed at a secondary operation.
It has its uses. There is no doubt about it. But it also results to a lot of waste.
Net-shape or near-net-shape forging, a synonym of precision forging, totally changes this formula. Precision forging is a flashing forging process in which the metal parts are so close to the finished size and shape that they do not require substantial machining or any machining at all after the forming. It is a flashless or near-flashless closed-die forging process.
The key here is that, instead of using machines in a subsequent process, you simply have to decide exactly what is the shape, you cut the bar to the right size with a hacksaw, and then you can roll the billet on to the die by a press.
Feature | Conventional Closed-Die Forging | Precision Forging |
Flash Generation | Significant (15% to 30% material loss) | Zero to minimal (< 5% loss) |
Dimensional Tolerances | Coarse ($\pm 0.5\text{ mm}$ to $\pm 1.5\text{ mm}$) | Tight ($\pm 0.05\text{ mm}$ to $\pm 0.2\text{ mm}$) |
Secondary Machining | Heavy roughing and finishing required | Light finishing or direct assembly |
Initial Tooling Cost | Moderate | High (requires high-rigidity dies) |
Material Utilization | Low to moderate | Up to 95%+ |
The analogy could be like this: Rather than first putting a metal into a shape close to the final one and then machining to the required size and form, you calculate the volume of the starting billet, you have the precise control of thermal expansion and deformation of the metal at different times under controlled pressure within a die.
The Metallurgy of Net-Shape Geometry
What is the reason that the microscopic crystal structure or the grain of a metal is so vital here? When a part is cut by an ordinary milling machine, the direction of the machining cut is across the flow lines of micrograins which are a part of the grain structure of the metal. It is similar to a sawing of a piece of wood across the grains; you produce a stress area and also a weakening of the structure.
On the other hand, in the case of precision forging, the directional grains flow of the metal is actually molded into the geometry of the finished part.
Since the metal flows into the details without the flow being stopped:
- The fatigue strength is significantly enhanced it is at least 20% (in some cases more than 30%) better when compared to the strength of a equivalent machine-made product.
- Impact toughness gets a big leap in quality which results in the component being able to withstand many hundreds/cyclings without breaking.
- Porosities and air pockets are squeezed out under very high pressing forces from all directions which leads to complete elimination of them.
Precision forging ensures structural reliability for such parts like critical automotive powertrains, aerospace brackets, or high-pressure valve internals of Indian industrial hubs.
How the reduction of Material Waste contributes to a better Bottom-Line ROI
Procurement people do their job only based on one word MONEY. Let us understand the same.
About half of the total cost for a manufactured article is due to the raw material cost. Imagine what happens when you procure expensive high-alloy steel, titanium, or nickel-based superalloys. Each kilogram that goes to the shop floor as the waste is an agony!
Major Procurement Message: There is an exponential increase in material savings through net-shape technologies. Lower quantities of raw material mean less freight expense, no capital involved in inventory for scrapped material, and less energy spent on producing finished parts.
Consider an example of Indian pump and valve component sourcing
- Raw Billet Input: For valve body forging to a certain dimension, one needs only 12 kg of billet.
- Flash & Trim Scrap: 3 kg of the initial material is lost as flash。
- Rough Machining Waste: After the first stages of turning/milling the swarf produced is 2.5 kg。
- Final Weight:5 kg。
Basically, you get away with paying for only 6.5 kg of premium product even if you get charged for the full 12 kg!
The leftover material, if of sufficient value, is sold as scrap for a price that may only amount to a fraction of what you paid for the material of original quality, a prime mill certified stock.
An optimized use of material becomes possible with an expert forging procedure where the initial billet could be reduced from a typical weight of around 12 kg to approximately 7 kg using advanced technology. There should be no flash scrap and machining chip generation less than 1 kg. With these changes your material usage will jump from about 54% to over 92%.
If you extrapolate this change into 100, 000 units being manufactured yearly, then the financial implications would be nothing less than enormous.
Engineering Factors That Enable: But Is "Net-Shape" Even a Feasible Option?
This seems quite simple if looked at from a drawing, isn't it? The less the metal and the harder the squeezing, the more efficient the process.
But... it's not exactly.
Getting a consistent part shape requires a whole chain of engineering controls. One deviation in one area will result in incomplete die filling or broken/damaged tooling.
1. Ultra-accurate control of input billet volume
Excess metal cannot find any hiding place in flashless forging. If you bring more metal than required, die pressures will increase very sharply and it might even result in the destruction of the press tools. If you are short by just a bit, then the cavity will remain unfilled. In such an environment, having precision cutting tools or machines for parts along with accurate mass sort is a must.
- Advanced Die Design and Thermal Management
Precision forging dies are highly intricate products in engineering industry. They are made to endure great mechanical forces under repeated load cycles and at the same time maintain the die size without deformation due to repeated heating and cooling. At present, tool room departments make use of simulation software (Finite Element Analysis) in the tooling planning process in order to get accurate simulation results related to how metal will flow within the die, die deflections during a forging operation, etc.
3. Lubrication and Surface Coatings
The occurrence of metal-to-metal friction at high temperatures has two major consequences: first, one type of deformation called galling is induced and second the unequal friction prevents the plasticized metal from going into the cavity of the die or thin walls where forging is very difficult. This is where high performance lubricants (graphite-free) and also ceramic die layering or coatings become the solution.
Top 10 Factors for Sourcing Teams in the Indian Market
After going to multiple sites and meeting a number of suppliers of forging companies located near big cities and even remote places such as Rajkot, Belagavi, Pune, and the NCR region, you will need very clear questions in the list of items to be considered for distinguishing real capabilities of net shape forging from those of standard ones.
Tooling Investment vs. Production Volume
Reality check: the net-shape processes tooling cost is much higher than the standard closed dies set-ups initially. This is because the dies have to be machined to a very tight tolerance, have to be made of higher grade tool steels, H13 or the so-called super premium powder metallurgy steels, and will need a range of coatings.
- Small volumes: Below 1000 units/year: The amortization cost of your tooling will likely be greater than your savings in raw materials unless the materials are quite exotic like Titanium or Inconel.
- Highly produced items: More than 10, 000 pieces a year: Since tooling expenses are very easily paid for you'll be able to capture material savings and reduced CNC cycle times to boost your profit margin quickly.
Supplier's Quality Infrastructure
It is not just checking the tonnage of the presses in their factory when you visit your suppliers, the one major thing you need to inspect is the overall systems and control they have around their production processes:
- Before heating, do they have automatic billet weighing?
- Besides that, how about the kinds of temperature sensing equipment, i.e. multi-frequency optical pyrometers, to monitor what the induction of heat doing?
- The fact is, do they have the necessary hardware such as in-house CMM and 3D optical scanning to quickly carryout die-wear analysis?
The Road to Sustainability and Energy Efficiency
One of the most important issues to be considered in supply chain management all over the world is the calculation of the carbon footprint that is caused.
Every time when a ton of steel is created, transported, heated, machined, and remelted, it is a source of considerable carbon emissions. A simple fact is that net-shape forging not only minimizes the material that is needed but it also eliminates the work done during the hours the CNC is operated at the highest power consumption. Therefore, net-shape manufacturing has the ability of directly cutting Scope 1 and Scope 2 emissions in the entire supplier network.
It appears, at least to me, that once ESG compliance becomes a required rule for all foreign and Indian big companies who have international export markets as well, the fact that a vendor is willing to provide the proof of how the energy used for every part of the product is reduced will turn from being one of the nice to have options into an obligation for vendor choice.
Whether your main focus is preserving margins in the face of rising raw material costs, unearthing bottleneck machining processes, or even improving the functionality of the part under extreme usage situations, net-shape component production is one of the most effective avenues industrial leaders can leverage nowadays in their quest to bring down the total cost of their operations.
Do you evaluate forged components for your products for materials efficiency at your current stage? If so, could you tell me the particular shapes and materials which are costing you the most problems from the perspective of cost?
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