Types of Forming Machines
Forming machines fabricate specific configurations out of long metal strips, most commonly coiled steel. The process is accomplished by power feeding the metal through a series of fixed rollers, each one incrementally shaping the strip into a finished profile.
It’s an adjustable and energy efficient process that produces a precise, uniform part. It also supports a wide variety of profiles and lengths.
Die and Punch
Punches come in various shapes and can perform a number of functions including punching holes, cutting blanks and piercing workpiece materials. They are used to make a variety of shaped holes in a workpiece that is commonly a metal or plastic in sheet form. These tools encounter both compressive and tensile forces during the punching process which cause the workpiece material to fracture and create a hole. To maximize punch life they must be designed to withstand both stresses and have the proper characteristics. This can be achieved by using a combination of a proper fit between the punch and die, a blend radius on the tip to reduce stress concentration in critical areas and having the correct sizing for the tool to minimize friction and allow the material to flow during the process.
The die, also called the bolster plate, is the side of the press that receives the punch and must be made of high quality tool steel. A standard die may be a blanking or piercing die with the blanking punch producing either a profiled slug for further working and the piercing punch creating a hole for insertion of the finished part. Nested type dies are also available which combines both these functions in one unit.
PVD coatings can improve die and punch performance by providing a slick barrier to protect the tool from wear and an increased coefficient of friction that allows the material to flow during deformation. Coatings can also resist “material pickup,” tiny pieces of the workpiece that adhere to the tool and can cause galling and scoring.
Roll Forming
Roll forming uses long coils of metal that are fed into the machine and progressively bent through a series of rollers, adding shape to the cross section. The process allows for strict tolerances and enables high volumes of parts to be produced with a single set of tools. Punching and notching are also possible in-line, reducing the need for secondary operations.
Can be used with a wide range of materials, including a variety of ferrous and non-ferrous metals. Can be used to shape complex and intricate cross sections. Forming Machine Can reduce manufacturing costs by avoiding additional machining and assembly steps. Can produce complex, accurate shapes that would be difficult or impossible to fabricate in other ways. Can accommodate a broad spectrum of part dimensions, from very short to extremely tall.
Allows for inline processes, such as punching, notching and cutting. Can be used to produce multiple lengths of the same profile with a single set of tools, lowering cost per piece.
Ensures quality by eliminating the need to precut the material. Reduces end flare, a form of springback, by controlling it in the roll forming process. Can be used on heavy gauge and high-strength materials, as the leading and trailing edges of the material are held in each bending station, unlike in a precut process.
Wire Drawing
When a wire is drawn, it is reduced from a larger diameter to a smaller one. It is also called cold working because heat is not used to aid the deformation of the metal.
A drawing machine requires the appropriate dies, wire and lubrication to be successful. It can be either a wet or dry process depending on the type of lubrication used. The dies should be properly annealed and pickled to remove oxidation.
The lubricant in a drawing machine is typically a beeswax or paraffin type. It is essential that the lubrication is well maintained to prevent surface flaws. Insufficient lubrication will result in poor die appearance and surface markings such as scuffs or die imprints. In addition, improper lubrication can encourage uneven deformation which will result in warping.
When the dies are in a drawing mode they must have an approach angle which ranges from 6 to 20 degrees. The die’s entrance cone should be bell-shaped and open to provide sufficient channeling for lubricant. It should also have a back relief to strengthen the exit point of the nib, prevent breakage and improve heat transport away from the metal forming zone.
A wire drawing machine requires a capstan or capstans that are specially designed and manufactured for the application. They must be able to run true, rotate evenly and be sized for the specific application and material.
Tube Drawing
In tube drawing, tubes with larger diameters are drawn through a die to reduce the outside (OD) and inside diameters. The process creates precise geometric results and increases important material properties such as yield strength and tensile strength. Tube drawing can be performed using various methods including cold drawing, expansion drawing and plug drawing.
FEM analysis of the expansion and plug drawing Forming Machine factory processes was carried out to investigate the forming characteristics and deformation mechanism. The analysis and experimental results were in good agreement. The results showed that the expansion drawing process is effective in producing thin-walled tubes. The results also indicated that the forming radius, r, and the height of the ribs were dependent on the OD and wall thickness of the tube.
The cold drawing process involves a lot of plastic deformation, which can lead to lattice distortion and increase internal energy. This can cause a large amount of stress to the metal and result in defects such as sunburst cracking. In addition, it can decrease ductility and strength. To minimize these problems, a tube drawing machine can be fitted with a chatter detection system. These systems detect vibrations in real time and convert them into a speed-reduction recommendation for the machine operator. This can help prevent chatter before it causes lasting damage to the tube and can increase machine efficiency.
