Sheet Metal Processes

The main feature of sheet metal is its ability to be formed and shaped by a variety of processes. Each process does something different to the metal giving it a different shape or size.

Brackets

Sheet metal brackets and other engineering components can be readily punched and laser cut from well nested sheets in low to medium volume. Our experienced CAD Engineers can nest components to optimal effect, carefully adjusting the space between components as well as the sheet edge, based on years of experience which saved time and money. Engineering components can also be punched with holes and squares where required.

Blanking

High volume blanking of components such as washers, spacers, shims and general punched parts can be undertaken quickly and effeciently. Using customer containers we can supply high volume parts by weight ready for production management systems such as Kanban or direct line side supply.

CAM

Computer-aided manufacturing (CAM) is the use of computer-based software tools that assist engineers and machinists in manufacturing or prototyping product components. CAM is a programming tool that allows you to make 3D models using computer-aided design (CAD). CAM was first used in 1971 for car body design and tooling.

Deep Drawing

Deep Drawing is a type of Drawing process where the depth of the part is more than half its diameter. Deep drawing is used for making automotive fuel tanks, kitchen sinks, 2 piece aluminum cans, etc. Deep drawing is generally done in multiple steps called draw reductions. The greater the depth, the increased number of reductions required. Deep drawing may also be accomplished with fewer reductions by heating the workpiece, used in sink manufacture for example.

In many cases, special material that has been rolled at the steel mill in both directions can aid in the deep drawing process. Material that has been rolled in both directions has a more uniform grain structure and is referred to as "draw quality" material. Draw quality material will often improve deep drawing (limiting tearing).

Drawing

Drawing forms sheet metal into cylindrical or box shaped parts by using a punch which presses the blank into a die cavity. Drawing process can also be utilized to create arbitrary shapes with the help of soft punch.

Drilling

A tool can be used to drill holes by pecking to let the swarf out. Using a special tapping tool and the ability to control the exact rotational position of the tool with the depth of cut, it can be used to cut screw threads.

Laser Cutting

CNC laser involves moving a lens assembly carrying a beam of laser light over the surface of the metal. Oxygen or nitrogen or air is fed through the same nozzle from which the laser beam exits. The metal is heated and then burnt by the laser beam, cutting the metal sheet. The quality of the edge can be mirror smooth, and a precision of around 0.1mm can be obtained. Cutting speeds on thin (1.2mm) sheet can be as high as 25m a minute. Most of the laser cutting systems use a CO2 based laser source with a wavelength of around 10um; some more recent systems use a YAG based laser with a wavelength of around 1um.

Linishing

The operation of polishing as carried out on a linisher. This machine is designed for the polishing of flat objects and carries a flat revolving cloth belt whose surface is impregnated with a suitable abrasive material.

Press Brake Forming

This is a form of bending, used for long and thin sheet metal parts. The machine that bends the metal is called a press brake. The lower part of the press contains a V shaped groove. This is called the die. The upper part of the press contains a punch that will press the sheet metal down into the v shaped die, causing it to bend. There are several techniques used here, but the most common modern method is "air bending". Here, the die has a sharper angle than the required bend (typically 85 degrees for a 90 degree bend) and the upper tool is precisely controlled in its stroke to push the metal down the required amount to bend it through 90 degrees. Typically, a general purpose machine has a bending force available of around 25 tonnes per metre of length. The opening width of the lower die is typically 8 to 10 times the thickness of the metal to be bent (for example, 5mm material could be bent in a 40mm die) the inner radius of the bend formed in the metal is determined not by the radius of the upper tool, but by the lower die width. Typically, the inner radius is equal to 1/6th of the V width used in the forming process.

The press usually has some sort of back gauge to position depth of the bend along the workpiece. The backgauge can be computer controlled to allow the operator to make a series of bends in a component to a high degree of accuracy. Simple machines control only the backstop, more advanced machines control the position and angle of the stop, its height and the position of the two reference pegs used to locate the material. The machine can also record the exact position and pressure required for each bending operation to allow the operator to achieve a perfect 90 degree bend across a variety of operations on the part.

Punching

Punching is performed by moving the sheet of metal between the top and bottom tools of a punch. The top tool (punch) mates with the bottom tool (die), cutting a simple shape (e.g. a square, circle, or hexagon) from the sheet. An area can be cut out by making several hundred small square cuts around the perimeter. A punch is less flexible than a laser for cutting compound shapes, but faster for repetitive shapes (for example, the grille of an air-conditioning unit). A typical CNC punch has a choice of up to 60 tools in a "turret" that can be rotated to bring any tool to the active punching position. A modern CNC punch can take 600 blows per minute.

A typical component (such as the side of a computer case) can be cut to high precision from a blank sheet in under 15 seconds by either a punch or a laser CNC machine.

Roll Forming

A continuous bending operation for producing open profiles or welded tubes with long lengths or in large quantities,

Individual metal articles, such as steel girders or wrought iron gates, can be hot-dip galvanized by a process called batch galvanizing. Other modern techniques have largely replaced hot-dip for these sorts of roles. This includes electrogalvanizing, which deposits the layer of zinc from an aqueous electrolyte by electroplating, forming a thinner and much stronger bond.

Roll-forming or Rollforming is a continuous bending operation in which a long strip of metal (typically coiled steel) is passed through consecutive sets of rolls, or stands, each performing only an incremental part of the bend, until the desired cross-section profile is obtained. Roll-forming is ideal for producing parts with long lengths or in large quantities.

Roll-forming lines can be set up with multiple configurations to punch and cut off parts in a continuous operation. For cutting a part to length, the lines can be set up to use a pre-cut die where a single blank runs through the roll mill, or a post-cut die where the profile is cutoff after the roll forming process. Features may be added in a hole, notch, embossment, or shear form by punching in a roll-forming line. These part features can be done in a pre-punch application (before roll-forming starts), in a mid-line punching application (in the middle of a roll-forming line/process) or a post punching application (after roll-forming is done). Some roll-forming lines incorporate only one of the above punch or cutoff applications others incorporate some or all of the applications in one line.

Roll Forming Variation

A variety of cross-section profiles can be produced, but each profile requires a carefully crafted set of roll-tools. Design of the rolls starts with a flower pattern, which is the sequence of profile cross-sections, one for each stand of rolls. The roll contours are then derived from the profile contours. Because of the high cost of the roll sets, simulation is often used to validate the designed rolls and optimize the forming process to minimize the number of stands and material stresses in the final product.

Spinning

Spinning is used to make axis-symmetric parts by applying a work piece to a rotating mandrel with the help of rollers or rigid tools. Spinning is used to make rocket motor casings and missile nose cones and satellite dishes for example.

Stretching

Stretching is a process where sheet metal is clamped around its edges and stretched over a die or form block. This process is mainly used for the manufacture of aircraft wings, automotive door and window panels. Stretching tools are very useful such as a kindilan.