Fine blanking

Fine blanking is a fully automated precision metalworking process. It is a form of precision metal stamping in which extremely tight tolerances can be held, and usually additional machining steps can be avoided post-production. Materials that can be fine blanked include carbon steels, alloy and stainless steels, as well as soft non ferrous alloys like aluminum, brass or copper.

Overview

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 die 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 [cite news | first= | last= | coauthors= | title=Fineblanking 101, Partech | date=2004-09-20 | publisher= | url =http://www.partechfineblanking.com/fineblanking101.htm | work = | pages = | accessdate = 2008-04-18 | language = ] . 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 .5-13mm [cite book | last = Kalpakjian | first = Serope | authorlink = | coauthors = Schmid, Steven R. | title = Manufacturing Engineering and Technology | publisher = Pearson Prentice Hall | date = 2006 | location = Upper Saddle River, NJ | pages = 429 | url = | doi = | id = | isbn = 0-13-148965-8 ] . Currently parts as thick as 19mm can be cut using fine blanking [ cite web|url=http://www.fineblanking.org/overview/history.html |title=Fineblanking |accessdate=2008-04-18 |last=Precision Resource ] . Tolerances between ±.0003"-.002" are possible based on material thickness & tensile strength, and part layout [ cite web|url=http://www.mpi-int.com/guidelines.pdf |title=guidelines |accessdate=2008-04-18 |last=MPI International, Inc. |format=PDF ] .

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 [cite book | last = Bralla | first = James G. | authorlink = | coauthors = | title = Design for Manufacturability Handbook | publisher = McGraw-Hill | date = 1999 | location = New York, New York | pages =3.47-3.48 | url = | doi = | id = | isbn = 0-07-007139-X ] . Some combinations may require progressive fine blanking operations, in which multiple operations are performed at the same pressing station however.

Advantages

*excellent dimensional control, accuracy, and repeatability through a production run.
*excellent part flatness is retained.
*straight, superior finished edges to other metal stamping processes.
*smaller holes possible relative to thickness of material [ cite web|url=http://www.fineblanking.org/overview/benefits.html |title=Fineblanking |accessdate=2008-04-18 |last=Precision Resource ] .
*little need to machine details.
*multiple features can be added simultaneously in 1 operation [ cite web|url=http://www.fineblanking.org/overview/benefits.html |title=Fineblanking |accessdate=2008-04-18 |last=Precision Resource ] .
*more economical for large production runs than traditional operations when additional machining cost and time are factored in (between 1000-20000 parts minimum, depending on secondary machining operations [cite book | last = Bralla | first = James G. | authorlink = | coauthors = | title = Design for Manufacturability Handbook | publisher = McGraw-Hill | date = 1999 | location = New York, New York | pages = 3.49-3.50 | url = | doi = | id = | isbn = 0-07-007139-X ] ).

Disadvantages

*slightly higher tooling cost when compared to traditional punching operations.
*slightly slower than traditional punching operations.

References