DETAILED INFORMATION ON HOW FINE BLANKING WORKS
Fine blanking produces stamped parts with a clean, 100% sheared edge. This edge is the result of special tooling and a special press. To understand why this is necessary, we need to first look at the reasons why a part fractures and then how the Fine blanking Process works to overcome these conditions.
1.) Tool Clearance
In conventional stamping, clearances run 10-20% the thickness of the material. This allows the stress to be relieved by fracturing. In fine blanking, clearances run from .0001" to .0003", which does not produce fracturing.
2.) Material Movement to Relieve Stress
In conventional stamping the material will bend away from the punch, causing the part to fracture.In Fine blanking, the material is held in constraint In many situations, "impingement" is added to the clamp action to stop material from flowing away from the punch. The final element is counter force. An additional die element is added which mirrors the shape of the punch. Pressure is applied to this element throughout the process. This keeps the part from bowing away from the punch resulting in an extremely flat piece.
Fine blanking
Typical fine blanking press cross section figure
Fine blanking is a specialized form of blanking where there is no fracture zone when shearing. This is achieved by compressing the whole part and then an upper and lower punch extract the blank. This allows the process to hold very tight tolerances, and perhaps eliminate secondary operations.
Materials that can be fine blanked include aluminium,brass,copper and carbon,alloy and stainless steels. Fine blanking presses are similar to other metal stamping presses, but they have a few critical additional parts.
A typical compound fine blanking press includes a hardened punch (male), the hardened blanking die (female), and a guide plate of similar shape/size to the blanking die. The guide plate is the first applied to the material, impinging the material with a sharp protrusion or stinger around the perimeter of the die opening. Next a counter pressure is applied opposite the punch, and finally the die punch forces the material through the die opening. Since the guide plate holds the material so tightly, and since the counter pressure is applied, the material is cut in a manner more like extrusion than typical punching.
Mechanical properties of the cut benefit similarly with a hardened layer at the cut edge from the cold working of the part Because the material is so tightly held and controlled in this setup, part flatness remains very true, distortion is nearly eliminated, and edge burr is minimal.
Clearances between the die and punch are generally around 1% of the cut material thickness, which typically varies between 0.5–13 mm (0.020–0.51 in). Currently parts as thick as 19 mm (0.75 in) can be cut using fine blanking. Tolerances between ±0.0003–0.002 in (0.0076–0.051 mm) are possible based on material thickness & tensile strength, and part layout.With standard compound fine blanking processes, multiple parts can often be completed in a single operation. Parts can be pierced,partially pierced, offset (up to 75°), embossed, or coined, often in a single operation. Some combinations may require progressive fine blanking operations, in which multiple operations are performed at the same pressing station.
Advantages & disadvantages
The advantages of fine blanking are:
1)excellent dimensional control, accuracy, and repeatability through a production run.
2)excellent part flatness is retained.
straight, superior finished edges to other metal stamping processes.
3)smaller holes possible relative to thickness of material
little need to machine details.
4)multiple features can be added simultaneously in 1 operationmore economical for large production runs than traditional operations when additional machining cost and time are factored in (1000–20000 parts minimum, depending on secondary machining operations)
The disadvantages are:
1)slightly higher tooling cost when compared to traditional punching operations.
2)slightly slower than traditional punching operations.
Fine blanking produces stamped parts with a clean, 100% sheared edge. This edge is the result of special tooling and a special press. To understand why this is necessary, we need to first look at the reasons why a part fractures and then how the Fine blanking Process works to overcome these conditions.
1.) Tool Clearance
In conventional stamping, clearances run 10-20% the thickness of the material. This allows the stress to be relieved by fracturing. In fine blanking, clearances run from .0001" to .0003", which does not produce fracturing.
2.) Material Movement to Relieve Stress
In conventional stamping the material will bend away from the punch, causing the part to fracture.In Fine blanking, the material is held in constraint In many situations, "impingement" is added to the clamp action to stop material from flowing away from the punch. The final element is counter force. An additional die element is added which mirrors the shape of the punch. Pressure is applied to this element throughout the process. This keeps the part from bowing away from the punch resulting in an extremely flat piece.
Fine blanking
Typical fine blanking press cross section figure
Fine blanking is a specialized form of blanking where there is no fracture zone when shearing. This is achieved by compressing the whole part and then an upper and lower punch extract the blank. This allows the process to hold very tight tolerances, and perhaps eliminate secondary operations.
Materials that can be fine blanked include aluminium,brass,copper and carbon,alloy and stainless steels. Fine blanking presses are similar to other metal stamping presses, but they have a few critical additional parts.
A typical compound fine blanking press includes a hardened punch (male), the hardened blanking die (female), and a guide plate of similar shape/size to the blanking die. The guide plate is the first applied to the material, impinging the material with a sharp protrusion or stinger around the perimeter of the die opening. Next a counter pressure is applied opposite the punch, and finally the die punch forces the material through the die opening. Since the guide plate holds the material so tightly, and since the counter pressure is applied, the material is cut in a manner more like extrusion than typical punching.
Mechanical properties of the cut benefit similarly with a hardened layer at the cut edge from the cold working of the part Because the material is so tightly held and controlled in this setup, part flatness remains very true, distortion is nearly eliminated, and edge burr is minimal.
Clearances between the die and punch are generally around 1% of the cut material thickness, which typically varies between 0.5–13 mm (0.020–0.51 in). Currently parts as thick as 19 mm (0.75 in) can be cut using fine blanking. Tolerances between ±0.0003–0.002 in (0.0076–0.051 mm) are possible based on material thickness & tensile strength, and part layout.With standard compound fine blanking processes, multiple parts can often be completed in a single operation. Parts can be pierced,partially pierced, offset (up to 75°), embossed, or coined, often in a single operation. Some combinations may require progressive fine blanking operations, in which multiple operations are performed at the same pressing station.
Advantages & disadvantages
The advantages of fine blanking are:
1)excellent dimensional control, accuracy, and repeatability through a production run.
2)excellent part flatness is retained.
straight, superior finished edges to other metal stamping processes.
3)smaller holes possible relative to thickness of material
little need to machine details.
4)multiple features can be added simultaneously in 1 operationmore economical for large production runs than traditional operations when additional machining cost and time are factored in (1000–20000 parts minimum, depending on secondary machining operations)
The disadvantages are:
1)slightly higher tooling cost when compared to traditional punching operations.
2)slightly slower than traditional punching operations.
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