Operaciones de conformado de metales. Metal Shaping

Hellow everybody , here we are going to explain in english , something about metal shaping and a little bit of english wheel. Here we go :

Metal shaping is an invaluable skill to have in hot rod fabrication. There are many specialized tools used in the forming process.

Shaping metal is basically as simple as shrinking or stretching it to achieve the required shape.
Before any metal can start forming, its good to know the exact shape of the piece one wishes to create. Bucks can be made using anything from styrofoam to plaster and anything between that a pattern can be pulled from. Below is a picture using "Burt" buck strips of metal and foil tape to create the shape required. Chicken wire was used to hold the metal strips in place in order to tack and tape them together. The buck was then slathered with bondo to check the actual shape and to pull the best possible pattern from

Once the buck is ready, a flexible shape pattern can then be made. The pattern starts with low stick masking tape. Plastic stretch wrap and transfer tape can also be used.

The low stick tape is then covered with fiberglass reinforced packing tape applied in two directions. This helps it maintain its shape when removed. Once the pattern is ready it is pulled off carefully and then the back is dusted with baby powder or similar item to stop it from sticking to itself. Reference marks can be added to the pattern before adding the packing tape. The pattern can also be cut into manageable sized pieces before removal from buck..


Primary metal forming processes

-Rolling.
-Forging.
-Extrusion.
-Tube and wire drawing.
-Deep drawing


 Rolling:

-Rolling is the most extensively used metal forming process and its share is roughly 90%

- The material to be rolled is drawn by means of friction into the two revolving roll gap

- The compressive forces applied by the rolls reduce the thickness of the material or changes its cross sectional area

- The geometry of the product depend on the contour of the roll gap

- Roll materials are cast iron, cast steel and forged steel because of high strength and wear resistance requirements

- Hot rolls are generally rough so that they can bite the work, and cold rolls are ground and polished for good finish


Extrusion

It is a relatively new process and its commercial exploitation started early in the nineteenth century with the extrusion of lead pipes. Extrusion of steels became possible only after 1930 when extrusion chambers could be designed to withstand high temperature and pressure.

In extrusion, the material is compressed in a chamber and the deformed material is forced to flow through the die. The die opening corresponds to the cross section of the required product.
It is basically a hot working process, however, for softer materials cold extrusion is also performed.

Forging:

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. Forged parts can range in weight from less than a kilogram to 580 metric tons. Forged parts usually require further processing to achieve a finished part.

Forging can produce a piece that is stronger than an equivalent cast or machined part. As the metal is shaped during the forging process, its internal grain deforms to follow the general shape of the part. As a result, the grain is continuous throughout the part, giving rise to a piece with improved strength characteristics

Tube and wire drawing.

The process of wire drawing involves the production of wire of close diameter and tolerance by drawing descaled hot-rolled rod through a die. The finished wire is coiled onto a motor driven block. The dies are manufactured from hard material e.g tungsten carbide. Diamonds dies are used for small diameter wire. Soap is used for lubrication. If large diameter reductions are required the rod is progressively drawn through several stages of dies and blocks.

Deep drawing

Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch.It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies. The flange region (sheet metal in the die shoulder area) experiences a radial drawing stress and a tangential compressive stress due to the material retention property. These compressive stresses (hoop stresses) result in flange wrinkles (wrinkles of the first order). Wrinkles can be prevented by using a blank holder, the function of which is to facilitate controlled material flow into the die radius.

English wheel


An English wheel (ewheel) can then be used to smooth out the lumps created from the stretching or shrinking processes. If too much pressure is exerted by the ewheel on areas that were shrunk, the material will start to stretch changing the shape. If too much pressure is exerted at the stretched areas, the metal will be stretched even more and change the shape. Picture of the ewheel below. This is a clone based on the Imperial Wheeling Machines brand.


A good quality wheel and anvils will greatly help in the wheeling process as the contact between the rollers and sheet will remain constant and give nice results.

Here we have a video that try to explain how we can use an english wheel: