DOG HOLE IN GEAR BLANK AND METHOD FOR ITS MANUFACTURING THEREOF INVOLVING FORGING PROCESS
Technical field of the invention:
Present invention relates to a new method for manufacturing Dog Hole, an auto component, wherein the said method essentially involve Dog Hole forging step in the process and therefore Dog Hole formation is achieved by forging only, without practicing conventional VMC operations previously being used.
Background and object of the present invention:
Dog Hole in the gear blank is a very important component, assembled in the motor-bike's engine transmission unit. Such Dog Hole components are conventionally in use and are being manufactured mainly through machining processes, wherein a number of VMC operations/milling operations are involved. Conventionally, for dog hole formation in the device machining processes are in practice and the application of single step forging process for the same purpose is no where in practice; mainly due to following reasons:
Technical complications in die designing for commercial production of dog Hole;
Non-achievement of ideal forging conditions for producing commercially acceptable dog Hole;
Various steps involved in the production of conventional Dog Hole component by conventional method can be understood by schematic flow chart of Figure 1. Details of the conventional process are mentioned in the following chart herein below:
Before dog hole formation the metal piece is subjected to preliminary treatment of hot forging (upsetting & forming, centre hole piercing) on horizontal hot former; followed by controlled cooling (continuous furnace/normalization). After that several machining and milling operations are performed towards Dog Hole formation and producing the finished product, namely deburring, hobbing, hardening (case carburizing), shot blasting, honing etc.
CONVENTIONAL PROCESS
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As the concerned auto component has to be assembled in the engine transmission system and has to perform without fail in very stressful high temperature environment, Dog Hole component must have very high stress bearing capacity, corrosion resistance, high temperature tolerance and very high structural strength.
The manufacturing process greatly affects the properties and performance of the said auto component and machining method of producing the said component, due to its limitations, does not help in improving the properties and strength of the final Dog Hole component.
Further the machining process involve substantial time, material loss, energy and other resources in the production of the Dog Hole component, making it a costly affair, which is not market friendly.
As the concerned component, Dog Hole, is an important component in auto industry, mainly in two-wheeler auto industry, and further in motor-cycle's engine transmission related industry, it becomes very vital to produce the component, Dog Hole in gear blank, through forging without involving various VMC operations.
The Dog Hole component, produced through present proposed process is much advanced in properties, mainly the structural strength, high stress tolerance, and performing well in high temperature environments.
The main object of the present invention is to propose a method for production of metallic auto component, Dog Hole in gear blank, wherein the said method essentially involve Dog Hole forging step in the process and therefore Dog Hole formation is achieved by forging only, without practicing conventional VMC operations previously being used.
Other main object of the present invention is to propose an auto component, Dog Hole in gear blank, wherein the Dog Hole formation is achieved in forging step, without involving VMC operations.
Another object of the present invention is to propose a suitable close die for the production of Dog Hole in gear blank, wherein the said die is provisioned towards directly creating Dog holes in forging step only, without involving Dog Hole milling (machining).
Another object of the present invention is to propose a method, involving a suitable die, for manufacturing Dog Hole components with different optional dimensions/diameters and optional number of holes of variable dimensions.
Statement of the present invention:
The present invention is intended to propose a method for production of metallic auto component, Dog Hole in gear blank, wherein the said method essentially involve Dog Hole forging step in the process and therefore Dog Hole formation is achieved by forging only, without practicing conventional VMC operations previously being used; and wherein the present invention is further intended to propose:
an auto component, Dog Hole in gear blank, wherein the Dog Hole formation is achieved in forging step, without involving VMC operations;
a suitable close die for the production of Dog Hole in gear blank, wherein the said die is provisioned towards directly creating Dog holes in forging step only, without involving Dog Hole milling (machining); and
a method, involving a suitable die, for manufacturing Dog Hole components with different optional dimensions/diameters and optional number of holes of variable dimensions.
Summary of the present invention:
The present invention is mainly related to the process of Dog Hole formation in forging without involving VMC/machining operations therein. Further, due to the proposed method of formation of Dog Hole in forging process, the final component obtained is much advanced in its structural strength and stress bearing capacity.
The piece of raw material (preferably SCM415HV) is initially subjected to preliminary treatment of hot forging (upsetting and forming) on horizontal hot former. After the Upset forging, the treated flattened metal piece (herein after referred as work piece) therein is subjected to annealing, wherein the said work piece is purposefully subjected to heat treatment in a condition where heating is done above the recrystallization temperature, maintaining a suitable temperature for pre-determined duration, followed by gradual and slow cooling, in such a manner that the said work piece undergoes changes in the properties such as strength and hardness. Furthermore, Annealing is used to induce ductility, soften material, relieve internal stresses, refine the internal structure by making it homogeneous, and improve cold working properties.
After the treatment of annealing, said work piece is subjected to the Dog Hole formation process by forging. During the forging process, desired number of holes of predetermined shape and size are created in the work piece; and the said work piece takes the final desired shape before sending for secondary operations applicable therein. A suitably designed die plays important role in this particular forging step towards Dog Hole formation and final shape creation therein.
The forged Dog Hole created work piece is then subjected drilling, which is a cutting process that uses a drill bit to cut or enlarge a hole in the solid material. The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the work piece, which forms chips at the cutting edge. Drilled holes are characterized by there sharp edges on the entrance side and the presence of burrs on the exit side.
After drilling step, the forged Dog Hole created work piece is subjected to other secondary operations towards producing a finished product with desired properties.
The shot blasting operation after the drilling step is performed mainly to smoothen and shape the rough surfaces of the work piece therein and to remove the surface contaminants. Usually a pressurized fluid, typically air, or a centrifugal wheel is used to propel the media.
The Dog Hole component takes its final shape during CNC milling stage, wherein certain milling operations are carried out, precisely controlled and automated via computer numerical control (CNC).
The process of manufacturing of the concerned auto component, Dog Hole in Gear Blank, mainly involves inventiveness in the above mentioned steps of the process. A chart to summarize the complete manufacturing process is shown herein below; wherein this chart includes in continuation the novel and herein proposed steps, namely annealing, Dog Hole forging, drilling, shot blasting and CNC machining:
NEW PROCESS
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Detailed description of the present invention:
Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: '"cold," "warm," or "hot" forging. There are several advantages of manufacturing an object through forging process. Some of the important advantages are as follows:
(A) Part Integrity:
(i) Structural strength: Forging also provides a degree of structural integrity that is unmatched by other metal working processes. Forging eliminates internal voids and gas pockets that can weaken metal parts. By dispersing segregation of alloys or non-metallic, forging provides superior chemical uniformity. Predictable structural integrity reduces part inspection requirements, simplifies heat treating and matching, and ensures optimum part performance under field-load conditions.
(ii) Directional strength: By mechanical deforming the heated metal under tight controlled condition, forging produces predictable and uniform grain size and flow characteristics. Forging stock is also typically pre-worked to refine the dendritic structure of the ingot and remove defects or porosity.
These qualities translate into superior metallurgical and mechanical qualities, and deliver increased directional strength in the final part.
(iii) Impact strength: Parts can also be forged to meet virtually any stress, load or impact requirement. Proper orientation of grain flow assures maximum impact strength and fatigue resistance. The high-strength properties of the forging process can be used to reduce sectional thickness and overall weight without compromising final part integrity.
(B) Grain Flow:
Through forging process directional alignment can deliberately be oriented in a direction requiring maximum strength. This also yields ductility and resistance to impact and fatigue.
Through casting process, no grain flow or directional strength is achieved.
During mechanical processing, the unidirectional grain flow has been cut when changing contour, exposing grain ends. This renders the material more liable to fatigue and more sensitive to stress corrosion cracking.
(C) Part Flexibility:
(i) Variety of sizes: Limited only to the largest ingot that can be cast, typically the forged component weights can run from a single pound to over 400,000 pounds.
(ii) Variety of shapes: Forging provides vast range for shape designing for a device, ranging from a bar, shaft and ring configurations to specialized shapes. These include multiple O.D./I.D. hollows, single and double hubs that approach closed die configurations, and unique, custom shapes produced by combining forging with secondary processes such as torch cutting, sawing and machining.
(iii) Metallurgical spectrum: Forgings can be produced from literally all ferrous and non-ferrous metals. The forging process itself can be adjusted through the selection of alloys, temperatures, working
methods and post-forming techniques to yield desired metallurgical properties.
(iv) Cost-effectiveness: Forging helps in directly producing the desired product, wherein it requires certain secondary operations only and therefore it provides possibility for achieving production of high quantity of components and thus is also very cost effective.
The present invention is an effort towards Dog Hole formation primarily through the forging process without involving VMC operations therein.
The piece of raw material (preferably SCM415HV) is initially subjected to preliminary treatment of hot forging (upsetting and forming) on horizontal hot former. After the Upset forging, the treated flattened metal piece (herein after referred as work piece) therein is subjected to annealing, wherein the said work piece is purposefully subjected to heat treatment in a condition where heating is done above the recrystallization temperature, maintaining a suitable temperature for pre-determined duration, followed by gradual and slow cooling, in such a manner that the said work piece undergoes changes in the properties such as strength and hardness. Furthermore, Annealing is used to induce ductility, soften material, relieve internal stresses, refine the internal structure by making it homogeneous, and improve cold working properties.
After the treatment of annealing, said work piece is subjected to the Dog Hole formation process by forging. During the forging process, desired number of holes of predetermined shape and size are created in the work piece; and the said work piece takes the final desired shape before sending for secondary operations applicable therein. A suitably designed die plays important role in this particular forging step towards Dog Hole formation and final shape creation therein.
The forged Dog Hole created work piece is then subjected drilling, which is a cutting process that uses a drill bit to cut or enlarge a hole in the solid material. The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the work piece, which forms chips at the cutting edge. Drilled holes are characterized by there sharp edges on the entrance side and the presence of burrs on the exit side.

The shot blasting operation after the drilling step is performed mainly to smoothen and shape the rough surfaces of the work piece therein and to remove the surface contaminants. Usually a pressurized fluid, typically air, or a centrifugal wheel is used to propel the media.
The Dog Hole component takes its final shape during CNC milling stage, wherein certain milling operations are carried out, precisely controlled and automated via computer numerical control (CNC).
Though the Dog Hole is formed in forging process, the said auto component requires certain more operations towards improving the properties and performance of the finished product therein. Therefore, after completing the steps like annealing, Dog Hole forging, drilling, shot blasting, and CNC machining one after another, other conventional secondary operations are conducted.
Actually due to treatments like annealing, forging and other subsequent machining operations on the work piece, its properties require to be supplemented towards enhancing structural strength, hardness, smoothness and stress tolerance therein. Further the surfaces of the work piece become rough, some where very sharp and full of burr.
Burrs in drilled holes cause fastener and material problems. Burrs cause more stress to be concentrated at the edges of holes, decreasing resistance to fracture and shortening fatigue life. They interfere with the seating of fasteners, causing damage to fastener or the assembly itself. Cracks caused by stress and strain can result in material failure. Burrs in holes also increase the risk of corrosion, which may be due to variations in the thickness of coatings on a rougher surface. Sharp corners tend to concentrate electrical charge, increasing the risk of static discharge. Burrs in moving parts increase unwanted friction and heat. Rough surfaces also result in problems with lubrication. As wear is increased at the interfaces of parts, it becomes necessary to replace them more frequently. Electrical charge buildup can cause corrosion.
Therefore the process of manufacturing of Dog Hole in Gear Blank, as proposed herein adopts the secondary processes like deburring, hobbing, hardening (case carborizing), shot blasting (hanger type), honing/hard bore turning, gear rolling (100%) and final inspection before oiling and packing. The main steps involved in the
present new process are high lighted in the schematic flow-chart of Figure 2(a), while the schematic flow-chart of Figure 2(b) highlights the secondary steps of the manufacturing process.
The scheme of the conventional process for preparation of the Dog Hole auto component is depicted in Figure 1.
Figure 3 represents the Dog Hole components, which are manufactured by the newly proposed method involving forging for Dog Hole formation without VMC operation. This dimension and shape of the depicted Dog Hole component is according to the requirement of a particular engine transmission assembly. Therefore newly manufactured components by proposed forging process herein, may appear alike the conventional such component, but it is far superior than the conventional Dog Hole components made by conventional machining method, mainly in terms of structural strength, stress tolerance, performance in high temperature environment and its working life span etc.

We claim:
1. Dog Hole in gear blank and a method for its manufacture wherein the said
method, wherein the said Dog Hole formation is achieved in forging stage
and wherein the said Dog Hole component is characterized by enhanced
structural strength, increased stress tolerance and enhanced working in
high temperature environment;
And wherein the said method is primarily characterized by following operations in a series:
Annealing, Dog Hole Forging, drilling, shot blasting and CNC machining.
2. Dog Hole in gear blank and a method for its manufacture, as claimed in claim 1, wherein the said method for manufacturing the Dog Hole component is primarily characterized by creation of Dog Hole component in forging operation without involving VMC machining operations.
3. Dog Hole in gear blank and a method for its manufacture, as claimed in claim 1, wherein the said forging operation towards producing the Dog Hole is performed using a suitable closed die.
4. Dog Hole in gear blank and a method for its manufacture, as claimed in claim 1, wherein the said Dog Hole in Gear Blank, optionally of different shape, size, dimension, teeth profile, surface pattern and configuration is manufactured by the said method involving Dog Hole forging step using a suitable closed die of corresponding shape, size, dimension, teeth profile, surface pattern and configuration therein.
5. Dog Hole in gear blank and a method for its manufacture, as claimed in claim 1, wherein the said method of manufacturing, apart from its essential steps of annealing, forging, drilling, shot blasting, and CNC machining, involves secondary operations, namely deburring, hobbing, hardening
(case carburizing), shot blasting (hanger type), honning/hard bore turning, and gear rolling.
6. Dog Hole in gear blank and a method for its manufacture, as claimed in
claim 1, wherein the said method of manufacturing is characterized by
manufacture of said Dog Hole components with different optional
dimensions/diameters and optional number of holes of variable
dimensions.
7. Dog Hole in gear blank and a method for its manufacture, substantially as
herein described and illustrated in the figures of the accompanying
drawings.