Working in metal manufacturing uses a lot of machinery and metal shearing is one of them. Shearing, in fact, is often the first step in the process. Sizing your material into easy to handle and workable pieces. Metal shearing machines have been around in some form or another, for many years, and believe it or not, have not changed significantly throughout time.
The type of metal shearing machine you need will ultimately depend on what you need to use it for. They are rated by their ability to cut a certain thickness of steel to a certain length. However they vary in design and are equipped with different options for a varying degree of production requirements. s
Metal shearing is a term used in the metal fabrication process. It is a process used to trim unwanted material or trim sheet metal. It cuts a straight line and is used when you need to size a workpiece or prepare blanks for later metal processing such as CNC Punching.
The shearing process involves the use of a machine or tool to cut through sheet metal. These tools are designed to cut with extreme precision. Shearing doesn’t require the use of heat nor does it produce waste in the form of chips, or stray bits of metal. This makes it a popular choice for manufacturers as full material utilization is common.
The machine used holds the sheet metal in place with a series of pressurized clamps called ‘holddowns’ and then the blade from the top of the machine moves down across a lower blade to make a cut. The top blade and lower blade are not placed at the same position, yet are offset ever so slightly to avoid collision yet provide the cleanest possible sheared edge. The slight difference is called the blade clearance.
Usually, the lower blade stays still (fixed) while the upper blade is pushed down with a great deal of force. The upper blade is fixed at a slight angle to the lower blade. This angle allows the cut to be made from one end to another, instead of at once. It reduces the amount of force required to cut the metal.The blades themselves come in different qualities of tool steels for hardness, wear resistance or shock absorption.
Metal cutting shears come with different abilities for different materials. They are also far more technological advances, so they make work faster and are more productive.
The type, thickness and consistency of the materials you are shearing will greatly affect the recommended choice of shear you purchase. If you're shearing thin gage metals or light aluminum you might be fine with an air or electrically operated shear, whereas if you're shearing ¾” Plate with plasma cut holes throughout you may really need to consider a good mechanical shear for the shock absorption capabilities.
It's not only important to consider the type of material but also the structure of that material as Tread Plate, Expanded Metals, Perforated metal etc all shear differently than flat material of an equal make.
The quantity of parts you need to shear is almost as important as the type of material you are shearing. While a basic and inexpensive machine might be fine for low-volume intermittent use, a more sophisticated or robust machine would be required for the production duties of, say a steel service center.
Not only do the machines have a wide variation of designs but they also can be equipped with a large number of options including conveyor/stackers to bring the sheared material onto a stack on a pallet for quick removal. Other options can include high speed hydraulics or more accurate Front gauging options.
When you are selecting that shear one of the choices you have to make is the drive, or power systems behind it. Different drive systems are available to meet different demands of production and different cost structures.
Once you have decided on the drive type of the shear, you need to know what design style may be better suited for your needs. There are two basic design types of shears on the market (regardless if they are mechanically or hydraulically driven) and they are the Guillotine style or Swing Beam style. A guillotine design in a shear refers to the upper blade being driven directly downward by the drive mechanism whereas a swing beam pivots the upper blade forcing down the blade by using the power of leverage.
Guillotine style provides for a more robust, yet expensive shearing system whereas the Swing Beam style uses smaller drive (hydraulics) components due to the advantage of leverage it employs in the design.
Rake Angle is the angle the upper shearing blade is canted at in order to not engage too much material during the shearing process. The lower the rake angle the better quality the resulting sheared edge (including twist, bow and camber) yet the more robust and powerful the shear must be. Lower rake angles engage more blade in the material requiring more force (and thus more machine) to shear. Ideally the perfect shear would have a zero rake angle, however the forces required to shear even the thinnest of materials would be astronomical making the machine itself far too costly. Adjustable rake angles can allow for smaller shears to engage thicker materials but at a cost. As the rake angle increases the sheared edge quality, blade life and machine stress increase. Thin sheared strips can come off twisted or bowed as a result of heavy rake angles.
At Southern Fabricating Machinery Sales we have many options available in new and used shearing systems including shears from manual to mechanical driving methods. More importantly, we know shearing, the metals, the machines and the results they produce. We can work with you and your team and explain what makes one shear option better for your application then another. Contact us today for more information on shears available from Southern Fab.