Small sheet metal components can be de-burred cleansed in a barrel which is called barrel de-burring or rumbling. The components are put into a barrel with small ceramic stones and allowed to roll against each other to remove the sharp edges on the outer profile and around any holes and cut outs that have been pierced. This process is particularly suited to parts that are to be treated in someway e.g. zinc plating or powder coating as the barrelling process will remove any protective surface finish already on the sheet e.g. galvatite or zintec.
Tumble finishing, also known as tumbling or rumbling, is a technique for smoothing and polishing a rough surface on relatively small parts. In the field of metalworking, a similar process called barreling, or barrel finishing, works upon the same principles.
Sheet metal flange operations are usually much simpler than draw operations. Often, part flanges are made in dies that are accomplishing other operations, too. Engineers bear in mind that dies, and their components, are costly. Rather than building one die that’ll perform a flange operation, and another die to achieve hole piercing, the two dies could be combined into one, whenever allowable or possible. Part conditions dictate what different operations can be performed in the same die.
the metre scale is generally used for measuring length while other tools are used for specific applications
marking on sheet metal is generally accomplished by scriber
layout is drawn after taking into account of the dimensions of the piece required thoroughly
Hand cutting process is done after carefully measuring and marking the sheet generally performed with the Snip the type of tool used also depends upon the gauge or thickness of sheet
Shearing is a process for cutting sheet metal to size out of a larger stock such as roll stock. Shears are used as the preliminary step in preparing stock for stamping processes, or smaller blanks for CNC presses.
Sheet-Metal Forming Processes include rolling, drawing etc
The term metal forming stands for shaping andor bending of sheet metal in three
dimensions in order to give it the desired shape and size of the final product. For this,
metal is either required to be stretched or shrunk in all directions or may need a
combination of both. Best example of this operation can be seen if one observes the
traditional metal workers manufacturing cooking utensils of brass out of blanks by hand
hammering and shaping them into different shapes and sizes with out any joint. For
producing hallow shapes through hand forming the centre of the metal has to be thinned
or the edges have to be thickened. The former will involve sinking and hallowing work
while latter will need raising of edges. Both hammers and mallets of different shapes are
used in this operation according to whether the metal has to be stretched needing a solid
blow, formed (needing an elastic blow by a mallet or a soft hammer) or sunk (requiring a
Edge Forming and Wiring
The edges of sheet metal products are formed (or folded) to ensure safety of hands, while
handling these products, and to provide stiffness to the products in order that L!ey will
retain their shapes during handling, i.e. will not get buckled or compressed by simple
hand or fingure pressure during handling. When still stronger edges are needed they are
reinforced by inserting a metal wire or rod and then forming the edge by curling the edge
of the sheet metal around it. This not only increases stiffness of the joint but also
improves its appearance.
It is the process of forming edges of the sheet metal using various tools such as hemming.
Machine Shearing *
It is done by means of shearing machines. These machines can be hand operated (bench
type) or Guillotine shears. The former is used for smaller and thinner sheets while the
latter for larger and thicker ones. Other types of shearing machines are the rotary shears
for continuous cutting along a straight line.
Several means are used for joining sheet metal parts together or securing them to other
metallic or non-metallic bodies. In case of very large size parts, specially when they are
to be fastened to other metallic or large non-metallic bodies, screwed fastening can be
used. Sheet metal parts can also be joined by riveting, welding, brazing and adhesives,
self tapping screws are more popular screwed fastners in sheet metal work. However, still
the most commonly used methods are joining the sheet metal parts by means of folded
joints or self securing joints, followed by soldering and adhesive joining.
They are used for soldering work and consist of a forged piece of copper joined to
an iron with a wooden handle. These are also called soldering coppers. They are
made in various shapes and sizes.
It is the operation of cutting circular blanks or curved contours with the help of a circle
cutting machine. It is also a continuous cutting operation.
Piercing is the operation of cutting internal features (holes or slots) in stock. Piercing can also be combined with other operations such as lance and form (to make a small feature such as tab), pierce and extrude (to make an extruded hole). All these operations can be combined with blankingBlanking is a cutting process in which a piece of sheet metal is removed from a larger piece of stock by applying a great enough shearing force. In this process, the piece removed, called the blank, is not scrap but rather the desired part. Blanking can be used to cutout parts in almost any 2D shape, but is most commonly used to cut workpieces with simple geometries that will be further shaped in subsequent processes. Often times multiple sheets are blanked in a single operation. Final parts that are produced using blanking include gears, jewelry, and watch or clock components. Blanked parts typically require secondary finishing to smooth out burrs along the bottom edge.
The blanking process requires a blanking press, sheet metal stock, blanking punch, and blanking die. The sheet metal stock is placed over the die in the blanking press. The die, instead of having a cavity, has a cutout in the shape of the desired part and must be custom made unless a standard shape is being formed. Above the sheet, resides the blanking punch which is a tool in the shape of the desired part. Both the die and punch are typically made from tool steel or carbide. The hydraulic press drives the punch downward at high speed into the sheet. A small clearance, typically 10-20% of the material thickness, exists between the punch and die. When the punch impacts the sheet, the metal in this clearance quickly bends and then fractures. The blank which has been sheared from the stock now falls freely into the gap in the die. This process is extremely fast, with some blanking presses capable of performing over 1000 strokes per minute.
Fine blanking is a specialized type of blanking in which the blank is sheared from the sheet stock by applying 3 separate forces. This technique produces a part with better flatness, a smoother edge with minimal burrs, and tolerances as tight as ±0.0003. As a result, high quality parts can be blanked that do not require any secondary operations. However, the additional equipment and tooling does add to the initial cost and makes fine blanking better suited to high volume production. Parts made with fine blanking include automotive parts, electronic components, cutlery, and power tools.
Most of the equipment and setup for fine blanking is similar to conventional blanking. The sheet stock is still placed over a blanking die inside a hydraulic press and a blanking punch will impact the sheet to remove the blank. As mentioned above, this is done by the application of 3 forces. The first is a downward holding force applied to the top of the sheet. A clamping system holds a guide plate tightly against the sheet and is held in place with an impingement ring, sometimes called a stinger, that surrounds the perimeter of the blanking location. The second force is applied underneath the sheet, directly opposite the punch, by a “cushion”. This cushion provides a counterforce during the blanking process and later ejects the blank. These two forces reduce bending of the sheet and improve the flatness of the blank. The final force is provided by the blanking punch impacting the sheet and shearing the blank into the die opening. In fine blanking, the clearance between the punch and the die is smaller, around 0.001 inches, and the blanking is performed at slower speeds. As a result, instead of the material fracturing to free the blank, the blank flows and is extruded from the sheet, providing a smoother edge.
Punching is a cutting process in which material is removed from a piece of sheet metal by applying a great enough shearing force. Punching is very similar to blanking except that the removed material, called the slug, is scrap and leaves behind the desired internal feature in the sheet, such as a hole or slot. Punching can be used to produce holes and cutouts of various shapes and sizes. The most common punched holes are simple geometric shapes (circle, square, rectangle, etc.) or combinations thereof. The edges of these punched features will have some burrs from being sheared but are of fairly good quality. Secondary finishing operations are typically performed to attain smoother edges.
The punching process requires a punch press, sheet metal stock, punch, and die. The sheet metal stock is positioned between the punch and die inside the punch press. The die, located underneath the sheet, has a cutout in the shape of the desired feature. Above the sheet, the press holds the punch, which is a tool in the shape of the desired feature. Punches and dies of standard shapes are typically used, but custom tooling can be made for punching complex shapes. This tooling, whether standard or custom, is usually made from tool steel or carbide. The punch press drives the punch downward at high speed through the sheet and into the die below. There is a small clearance between the edge of the punch and the die, causing the material to quickly bend and fracture. The slug that is punched out of the sheet falls freely through the tapered opening in the die. This process can be performed on a manual punch press, but today computer numerical controlled (CNC) punch presses are most common. A CNC punch press can be hydraulically, pneumatically, or electrically powered and deliver around 600 punches per minute. Also, many CNC punch presses utilize a turret that can hold up to 100 different punches which are rotated into position when needed.
A typical punching operation is one in which a cylindrical punch tool pierces the sheet metal, forming a single hole. However, a variety of operations are possible to form different features. These operations include the following:
Piercing – The typical punching operation, in which a cylindrical punch pierces a hole into the sheet.
Slotting – A punching operation that forms rectangular holes in the sheet. Sometimes described as piercing despite the different shape.
Perforating – Punching a close arrangement of a large number of holes in a single operation.
Notching – Punching the edge of a sheet, forming a notch in the shape of a portion of the punch.
Nibbling – Punching a series of small overlapping slits or holes along a path to cutout a larger contoured shape. This eliminates the need for a custom punch and die but will require secondary operations to improve the accuracy and finish of the feature.
Lancing – Creating a partial cut in the sheet, so that no material is removed. The material is left attached to be bent and form a shape, such as a tab, vent, or louver.
Slitting – Cutting straight lines in the sheet. No scrap material is produced.
Parting – Separating a part from the remaining sheet, by punching away the material between parts.
Cutoff – Separating a part from the remaining sheet, without producing any scrap. The punch will produce a cut line that may be straight, angled, or curved.
Trimming – Punching away excess material from the perimeter of a part, such as trimming the flange from a drawn cup.
Shaving – Shearing away minimal material from the edges of a feature or part, using a small die clearance. Used to improve accuracy or finish. Tolerances of ±0.001 inches are possible.
Dinking – A specialized form of piercing used for punching soft metals. A hollow punch, called a dinking die, with beveled, sharpened edges presses the sheet into a block of wood or soft metal.