Rule-based DFM analysis for forging . Forging is the deformation of a metal that is controlled into a specific form by compressive force. The process of forging back to 8000 BC. and evolved from a simple blacksmithing manual art. Then as now, a series of hammer press punches do the forming or forging parts. Modern forging uses a hammer-driven or pressed impact machine that damages the piece-work by controlled pressure. The forging process is superior in casting because the molded parts have denser microstructure, clearer grain patterns, and less porosity, making them much more powerful than casting. All metals and alloys can be forged, but each will have a rank of forging ability from high to low or poor. Factors involved are material composition, crystal structure and mechanical properties all of which are considered in the temperature range. The wider the temperature range, the higher the rank of the forging ability. Most forging is done on heated parts of the work. "Cold forging" can occur at room temperature. The most fabricated materials are aluminum, copper, and magnesium. The lower rating is applied to various steel, nickel, and titanium alloys. The temperature of hot forging ranges from 93 Â ° C (200 Â ° F) to 1650 Â ° C (3000 Â ° F) for fireproof metal.
Here is a Rule-based DFM analysis for the Forging process. These rules can be included at the design stage to improve process efficiency. DFM refers to the design for manufacturability.
Video Rule based DFM analysis for forging
Forging type
Open the forging die
In the open die forge the cylinder billet becomes annoyingly annoyed between a flat dead pair or platens. With fringe homogeneous deformation, the height of the cylinder decreases and its diameter increases. Forging shafts, discs, rings etc. are performed using open forgings technique. Square cast ingots are converted into a round shape with this process. Open die forging is classified into three main types, namely, cogging, fullering and edging.
Hang up hook
It is also known as forging forging. Impressions made in a dead pair. These impressions are transferred to the workpiece during deformation. A small gap between a mold called a flash ditch is provided so that excess metal can flow into the gutter and form a flash. Flash has got a very important role during the deformation of the working parts inside the dead cavity. Due to the long and high thickness ratio of the flash ditch, the friction in the gap is very high. Because of this the material in the flash slot is subjected to high pressure. There is a high resistance to flow. This in turn promotes effective filling of the dead cavities. In hot forging, flash cools faster because of its smaller size. This increases the resistance of the flash material to the deformation resistance. As a result, most workpieces are forced to damage and fill the dead cavities more effectively - even the intricate part of the dead cavity is filled.
Maps Rule based DFM analysis for forging
Hot forging
The heat forging is defined as the metal work above the recrystallization temperature. The main advantage of heat forging is that the metal undergoes a deformation of the strain hardening effect negated by the recrystallization process.
Benefits
- Decrease in yield strength, therefore it is easier to work and requires less energy (style)
- Improved toughness
- Increased temperature increases diffusion which can eliminate or reduce chemical inhomogeneity
- The pores can reduce their size or close completely during the deformation
- In steel, FCC austenite is weak, ductile, and defective, not a strong BCC ferrite at lower temperatures
Losses
- Unwanted reaction between metal and surrounding atmosphere
- Tolerance is less precise due to thermal and curved contractions of uneven cooling
- Grain structures can vary across metals for various reasons
Cold forging
Cold forging is defined as metal work under recrystallization temperature, but usually around room temperature.
Benefits
- No need for heating
- Better final surface
- Superior dimension control
- Better reproducibility and exchange
- The directional property can be imparted into the metal
- Contamination issues are minimized
Losses
- Higher power required
- Heavier and stronger equipment and more powerful tools are required
- Less brittle metals
- Metal surfaces should be clean and scale-free
- Intermediate anneal may be necessary to compensate for the loss of ductility that accompanies strain hardening
- The given directional property can damage
- Undesirable residual stress can be generated
Category tolerance
Group 1
(see Table 2.1 and Table 2.2):
a) Tolerance length, width and height. b) Incompatibility of tolerance. c) The remaining tolerance (and trimmed flat) tolerance. d) Billing Tolerance.
Group 2
(see Table 2.3 and Table 2.4): Tolerance of thickness. Tolerance of ejector marks.
Group 3
(Table 2.5.jpg and Table 2.6): Flat and flat tolerance. Tolerance for center-to-center dimensions.
Group 4
Tolerance of fillet radius and edges (see Table 2.7). Burr Tolerance (see Table 2.7). Surface tolerance. Tolerance on the surface of the draft angle. Tolerance of eccentricity to deep holes. Eccentricity tolerance for pierced holes. Tolerance on the concentric boss. Tolerance for non-accumulated supplies. Tolerance for deformation of shaved edges.
Form deviation
Tolerance for length, width, height, and thickness includes IL only dimension dimensions, but also deviation of form which: a) Out of the round, b) Deviation from cylindricality c) Deviation from parallelism, and cl) Other deviation from contours specified. Such deviations do not exceed the limits given by tolerance. Their extreme case III can cover all areas of tolerance unless the other is approved between the supplier and the buyer. Where the form deviation restriction has been approved, this should be noted in the figure.
Design procedure
Information required by forger
In order to help the forging supplier to utilize his experience for the best effect, both in designing die and tools and in establishing the forging inspection procedure, rt is in the interests of the buyer to supply the following
Information: a) Drawing machine complete; b) Details and dimensions of machining location (prior notice should be given for subsequent changes in these location points) c) Other relevant information on machining operations and component functions.
Get started
It is recommended that the drop drawing which then must be filed for counterfeiters should prepare for buyers for approval, and, if necessary, for joint consultation.
In the case where the buyer wishes to prepare his own forged image, there is no need that the finished machine component image and any other information mentioned above be available to the supplier.
Indication dimensions in image
It is important to note that, with the exception of the circular draft surface the tolerances shown in this standard become only for the dimensions specifically shown in the agreed forging drawings.
For this reason, the method for showing dimensions in forging withdrawal has an important mastery on the control dimensions of forging.
Tolerance for dimensions not shown in the forging images can not be taken from the standard but can be determined, if necessary, only by calculations based on the dimensions and tolerances that have been shown in the approved forging image.
Image tolerance indication
All forging images must be supported, 'Tolerance in accordance with IS: 3469 (Part II) -1974 unless otherwise stated
For the correct support of forging images, the following form of tolerance presenuation on the foot of the image is recommended:
Category: 1. Length and overall diameter 2. Width 3. Height 4. Not suitable 5. Time flash and trimmed flat 6. Thickness 7. Sharpness 8. Flattened 9. Radius edge and edge 10. Surface
Any tolerance that applies only to certain dimensions must be shown in the image to the particular dimension in question. Tolerance of ejector sign and beep tolerance should be shown on the wrought image against a particular location. The special tolerance agreed between the buyer and the supplier should be clearly indicated on the forging drawing and shall, to the extent possible, be incorporated to the particular dimension concerned.
Importance of image
Images of counterfeit parts that have been received by the buyer are valid documents for the inspection of forged parts. This image is also the only valid document for tolerance on the remaining parts of the forgings that are not worked
Process
There are different types of forging processes available, but they can be grouped into three main classes: 1. Withdrawn: increase in length, declining section 2. Surprise: Length decreases, cross section increases 3. Squeezed in closed compression die: generate flo multidirectional 4. The general forging process includes: roll forging, swaging, cogging, open-die forging, forging forging, press forging, auto hot and irritating forging.
Open-die drop-hammer forge
Open-die forging is also known as smith forging. In the open-die forge the hammer down and change the shape of the workpiece, which is placed on a stationary grounding. Open-die forging gets its name from the fact that dies (the work surface of a workshop contracting workpiece) do not close the workpiece, allowing it to flow except when contacted by the dies. Therefore, operators need to direct and position the workpiece to get the desired shape. The dice is usually flat-shaped but may have a special shaped surface for special operations; for example, the dice may have a round, concave, or convex surface or be a tool for forming a hole or a cutting tool. Open-die forge yourself for short walks and is appropriate for artwork and customs. Another open forging moment is used for rough form ingots to prepare it for further surgery. It can also direct the grain to increase the strength in the required direction.
Redemption drop-hammer impression-off
Forging forging is also called wrought-forging. In die-cast metal work is placed in dice that resembles a mold, which is attached to the runway. Usually a dead hammer is also formed. The hammer is then dropped on the workpiece, causing the metal to flow and filling the dead cavities. Hammers generally contact with workpieces on a millisecond scale. Depending on the size and complexity of the hammer part can be dropped several times in a row. Excess metal is squeezed out of dead cavities; this is called flash. Flash cools faster than the rest of the material; This cool metal is stronger than the metal in it that helps prevent more flashes from forming. It also forces the metal to completely fill the dead cavity. After forging the flash trimmed.
In commercial molds, workpiece forging is usually moved through a series of holes in the mold to get from the bar to the final shape. The first impression is used to distribute the metal into a rough shape according to the later hole requirements; This impression is called the impression creeping, swinging, or bending. The following cavities are called blocking cavities in which workpieces work into more and more like end products. These stages usually implant workpiece will be curved and large fillet. The final shape is forged in the final impression cavity or finisher. If there is only a short section to do, it may be more economical for die not to have a final impression cavity and more precisely the final feature engine.
Forging molds has been further improved in recent years through increased automation which includes induction heating, mechanical feeding, positioning and manipulation, and direct heat treatment of parts after forging.
One variation of forging-forging mold is called forging without flash, or forging the right forging. In this type of forging, the cavities die completely closed, which makes the workpiece of the flash formation. The main advantage to this process is that less metal is lost to flash. Flash can reach 20 to 45% of the starting material. The disadvantages of this process include: additional costs due to more complex die designs, better lubrication requirements, and better placement of workpieces.
There are other variations of part formations that integrate forging molds. One method combines casting preform forging of molten metal. The foundry is then removed after cooling to solid state, but when it is still hot. It was then finished in one dead cavity. The flash is trimmed and then quenched to room temperature to harden the part.
Other variations follow the same process described above, except that the preform is produced by metal droplets spraying deposition into collector shaped (similar to osprey process).
Forging-off forging has a high initial cost due to the creation of dies and the design required to make the cavity die. However, it has a low reoccurring cost for each part, so the forging becomes more economical with more volume. This is one of the main reasons for counterfeiting that is often used in the automotive industry and tools. The forgery of other reasons common in industrial sectors is that forging generally has about 20% higher strength to weight ratio compared to cast parts or machinery of the same material.
Print design and die-casting tool
Forging dies are usually made of high alloy steel or tools. Dies should be impact resistant, wear-resistant, maintain strength at high temperatures, and have the ability to withstand fast warming and cooling cycles. To produce a better, more economical die the following rules should be followed:
1. Dead must part with one flat area if possible, Otherwise, the dividing plan should follow the contours of the part. 2. The dividing surface shall be a plane through the forging center and not near the top or bottom edge. 3. An adequate draft must be provided; a good guide of at least 3 Â ° for aluminum and 5 Â ° to 7 Â ° for steel 4. Useful fillets and radii should be used 5. Ribs should be low and wide 6. Various parts must be balanced to avoid extreme differences in metal streams 7. Full gain must be taken from the fiver flow line 8. Dimensional tolerances should not be closer than required Dimensional tolerances of the steel parts produced using the mold forgings mold method are described in the table below. It should be noted that the dimensions in all areas of influence are influenced by the closure of the dies, and therefore depend on the wear life and the final flash thickness. The dimensions that are fully contained in one segment or half off can be maintained at a much greater accuracy. Lubricants are always used in forging to reduce friction and wear. It is also used as a thermal barrier to limit heat transfer from workpiece to die. Eventually the lubricant acts as a parting compound to prevent any part from sticking to one of the dies.
Push for
Press forging is a variation of forging. Unlike drop-hammer forging, press forges work slowly by applying pressure or continuous strength. The amount of dead time in contact with the workpiece is measured in seconds (compared to the milliseconds of the drop-hammer forges). The main advantage of press forging, compared with forging, is its ability to change the shape of a complete workpiece.
Drop-hammer forging usually only damages the surface of the workpiece in contact with hammer and anvil; the inside of the workpiece will remain relatively not perform well. There are some disadvantages to this process, most of which come from workpieces that come into contact with the dead for long periods of time. The workpiece will cool down faster because it contacts the workpiece; dies drastically move more heat from the surrounding atmosphere. As the object cools, it becomes stronger and less brittle, which can cause cracks if deformation continues. Therefore, heated dies are typically used to reduce heat loss, increase surface flow, and enable the production of finer detail and closer tolerance. The workpiece may also need to be reheated.
Forging press can be used to perform all kinds of forging, including forging die and forging mold. Forging impresion-die presses usually require less draft than forging drop and have better dimensional accuracy. In addition, press forgings can often be done in one dies closure, allowing for easy automation.
Forging upset
Forging ups increase the diameter of the workpiece by compressing its length. Based on the number of pieces produced this is the most widely used forging process. Forging ups are usually done in a special high-speed machine; the machine is usually set to work in the horizontal plane to facilitate the rapid exchange of workpiece from one station to the next. Early workpieces are usually wire or rod, but some machines can accept bars up to 25 cm (10 inches) in diameter. Standard interference machines use separate prints that contain many cavities. The dice is open enough to allow the workpiece to move from one cavity to the next; die then close and post tool, or ram, then move longitudinally against the bar, annoying him into the cavity. If all the cavities are used on each cycle then the finished parts will be produced with each cycle, which is why the process is ideal for mass production.
Some examples of common components generated using annoying forging processes are engine valves, couplings, bolts, screws, and other fasteners.
The following three rules must be followed when designing the part to be forged:
1. Unsupported metal lengths that may be damaged in a single blow without harming shall be limited to three times the diameter of the bar. 2. The stock length greater than three times the diameter may be disrupted successfully provided the fault diameter is not more than 1.5 times the stock diameter. 3. In error requires a stock length of more than three times the diameter of the stock, and where the cavity diameter is not more than 1.5 times the stock diameter, the length of the unsupported metal outside the dice surface should not exceed the diameter of the bar.
Automatic hot forging
The automatic heat forging process involves grinding steel rods (usually 7 m or 24 ft) to one end of the machine at room temperature and hot forging products emerging from the other end. It all happened very quickly; small parts can be made at a rate of 180 parts per minute (ppm) and larger can be made at a rate of 90 ppm. The parts can be solid or hollow, round or symmetrical, up to 6 kg (12 lbs), and up to 18 cm (7 inches) in diameter. The main advantages to this process are the high level of output and the ability to receive low-cost materials. A little labor is required to operate the machine. No flash is produced so material savings are between 20 - 30% compared to conventional forging. The end product is consistent 1050 ° C (1900 ° F) so that air cooling will produce parts that are still easily machinable (the advantage is the lack of annealing required after forging). Tolerance is usually  ± 0.3 mm ( ± 0.012 inch), the surface is clean, and the draft angle is 0.5 to 1  °. The life tool is almost double the conventional wrought because the contact time is in the order of 6/100 seconds.
The downside of this process can only be done on the part and the smaller symmetric cost; the initial investment could be more than $ 10 million, there is a large amount needed to justify this process. The process starts by heating the bars up to 1200 to 1300 ° C (2200 to 2350 ° F) in less than 60 seconds using high power induction coils. Then descaled with a roller, sheared to empty, and transferred several consecutive forming stages, where it was tempered, preformed, finely forged, and pierced (if necessary). This process can also be paired with high-speed cold forming operations. Generally, cold forming operations will perform the finishing stage so that cold working benefits can be utilized, while maintaining high speed of automatic heat forging.
Examples of parts made by this process are: wheel hub bearings, transmission gears, tapered roller bearings, stainless steel clutch couplings, and neck rings for LP gas cylinders. Manual transmission gear is an example of automatic heat forging which is used in conjunction with cold work.
Roll wound
Roll forging is a process in which the stock bar is round or flat decreases in thickness and increases in length. Roll forging is done using two cylindrical or semi-cylindrical rolls, each containing or more of a groove. A bar is inserted into the scroll and when pressed stop rotating the roll and the bar is getting shaped as it is rolled out of the machine.
The workpiece is then moved to the next set of plots or rotated and reinserted into the same groove. This continues until the desired shape and size are achieved. The advantage of this process is that there is no flash and embed the favorable grain structure into the workpiece. Examples of products produced using this method include axle, taper lever and leaf springs.
Near-net shape and form-closeing
This process is also known as precision forging. This process was developed to minimize the costs and waste associated with mail forging operations. Therefore, the final product of precision forging requires little or no final machining. Cost savings are derived from the use of fewer materials, and thus less scrap, decreased overall energy used, and reduction or removal of machinery. Precision forging also requires less or draft, 1 Â ° to 0 Â °. The decline of this process is cost, therefore only implemented if significant cost reductions can be achieved.
Tools
The most common thoughts of wrought equipment are hammers and grounding. The principles behind hammers and grounding are still used today in hammer equipment. The principle behind the machine is very simple, lift the hammer and then drop it or push it to the workpiece, which rests on the ground. The main variation between the drop-hammer is the way the hammer is powered; the most common air and vapor hammers. Drop-hammers usually operate in a vertical position. The main reason for this is because the excess energy (energy that is not used to change the shape of the workpiece) that is not released due to heat or sound needs to be transmitted to the foundation. In addition, a large machine base is needed to absorb the impact. To address some of the drawbacks of drop-hammer machines or counterblow counters are used. In counterblow machines both hammer and moving pads and workpieces are held between them. Here the excess energy becomes backward. This allows the machine to work horizontally and consists of a smaller base. Other advantages include less noise, heat and vibration. It also produces distinctly different flow patterns. Both of these machines can be used for open or closed die forging. A forging press, often simply called the press, is used to forge the press.
There are two main types: mechanical and hydraulic suppression.
Mechanically suppress the function by using cams, crank or switch off to produce presets (predetermined forces at specific locations in strokes) and reproducible strokes. Due to the nature of the different types of system styles are available at different stroke positions. Mechanical suppression is faster than the hydraulic counterpart (up to 50 times per minute). Their capacities range from 3 to 160 MN (300 to 18,000 tons). Hydraulic press using fluid pressure and piston to produce force. The advantage of a hydraulic press over a press machine is its flexibility and greater capacity. The disadvantages are they are slower, bigger and more expensive to operate. Forging, forging and forging are all using special machines.
Note
References
Source of the article : Wikipedia
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