Views: 60 Author: Site Editor Publish Time: 2018-04-27 Origin: Site
As versatile as the ironworker is, it is still possible to purchase the wrong machine – or at least not the best one – for your application. Here are some reasons why careful examination of these factors will prevent that from happening.
An ironworker can be an important and versatile machine in a metal fabrication shop. Ironworking is quite often the first step in the manufacturing process, and one ironworker can typically provide enough fabricated material to keep up to seven welders or assemblers busy.
Since its invention in the late 1800s, the ironworker’s main strength has been its ability to perform a variety of operations. For example, it can punch a range of materials with punches of various sizes and shapes; it can shear rod, flat bar, angle and channel; it can notch angle iron, pipe, channel and flat bar. That’s not all. Many ironworkers are available with special tooling to bend, stamp and form, too. But as versatile as the ironworker is, however, it is possible to purchase the wrong machine – or at least not the best machine – for your specific application. When investing in an ironworker, you must examine several important factors to insure that you purchase the correct equipment: its capacity, versatility, safety features, and quality.
The material thickness you process will indicate what size of ironworker you require. An ironworker punches material ranging from light gauge sheet metal to plate as thick as 1¼ in. Ironworkers are typically rated by tonnage at the punch station. A 50 ton ironworker should punch a 1¼ in hole in ½ in material; a 60 ton machine should punch a one inch hole in ¾ in material; an 80 ton machine should punch a one inch hole in one inch material; and a 150 ton machine should punch a one inch hole in one inch material.
The first step, then, is to determine the maximum material thickness so you can establish the tonnage range needed for your punching application. Examine the steel rack and the products that you are fabricating. Determine the maximum hole diameter to be punched, the maximum thickness of the material to be punched, and the maximum thickness and width of the channel, angle, and rod to be sheared or bent.
The material or part width plays a part in your equipment selection. The throat depth of an ironworker punch station should be greater than half of the part or material width. Material length, however, really is not an issue since an ironworker can process almost any material or part length. Because many different types of steel and ranges of hardness in mild steel exist, it is advisable to get a machine that is at least 20 percent larger than you think your everyday use requires. This cushion will help you avoid getting a machine that is too small. Most machines are rated for material with tensile strengths between 60,000 lb and 65,000 lb.
Many mild steels have tensile strengths between 50,000 lb and 70,000 lb or higher, and your machine may not have the power to punch the material at the higher end of the hardness values. When punching hard steel (such as stainless steel) it is better to increase the estimated tonnage by 50 percent, depending on the grade of steel.
Beware! Not all tons are created equal. A metric ton actually is heavier than a U.S. ton (2,200 lb vs. 2,000 lb). A machine rated for metric tons should be able to punch a larger hole than a machine rated on the same number of U.S. tons.
For example, 80 tons of pressure by U.S. standards can punch a one inch hole through one inch material; 80 metric tons should be able to punch a 1-3/32 in hole though the same material thickness.
Be sure to compare the rating of the machine, not only in tons, but also in the diameter of the hole and thickness of material it can punch. Ironworker tonnage ratings can vary from manufacturer to manufacturer.
ASSESSING VERSATILITY NEEDS
All ironworkers are equipped with flat bar shears. The main differences between flat bar shear stations are the length and the approach of the blade to the metal. Some ironworkers use a guillotine, or fixed-rake-angle shear, and others use a scissors-type shear
The advantage of the fixed-rake-angle shear is that the angle of the blade as it approaches the work remains constant throughout the cut, sometimes offering larger capacity without increasing machine tonnage. The disadvantage is that without the ability to vary the rake angle, the distortion of the drop piece will remain the same throughout the cut.
The advantage of a scissors-type shear is that it can vary the rake angle of the blade. Thicker material is cut closer to the pivot point. Thinner material is cut farther from the pivot point, where the rake angle of the blade is flatter, thereby minimizing distortion. Scissors machines typically have a longer flat bar shear, some up to 24 in long.
On some ironworkers, the rake angle of the bar shear blade is adjusted by inserting and removing wedge-shaped shims above the shear blade. This may require substantial mechanical ability and substantial time. Also, if the shims are not adjusted each time material thickness changes, the machine could be damaged. Ironworkers are available with different designs to enhance versatility. For example, the stations on some machines are permanently built in. These machines offer punching stations, angle shears, rod shears, notchers, and short flat bar shears. If you are a structural steel fabricator, you may prefer these machines because the stations cover the majority of the materials you process and do
not require tooling changes.
If you are a general welding, fabrication, maintenance, and structural steel fabricator who does not know what a customer will bring in the door tomorrow, you may want an ironworker that offers the capability to adapt to all customer needs. Tabletop tooling concepts, which provide a wider variety of tooling, may suit your needs. In addition to angle shears, rod shears, notchers and flat bar shears, tabletop ironworkers offer options such as larger press brake bending attachments, tube shears, channel shears, pipe notchers, V notchers, picket tools, square tube shears and a variety of special tooling. Although these machines can use a larger variety of tooling than those with built-in stations, time is required to switch from one operation to the next.
ADDRESSING SAFETY ISSUES
Safety is an important factor when choosing an ironworker. Be sure to choose an ironworker that meets ANSI B 11-5 standards. Examine the guarding. Be sure it can be adjusted down to within ¼ in from the top of the material to be punched and to the bottom of the guard to stripper (this is an ANSI standard). This will prevent operators from placing any part of their bodies between the material being punched and the stripping mechanism. All other stations should offer complete safeguarding as well.
For productivity as well as safety, the machine you choose should offer an infinitely adjustable stroke control to minimize machine movement, decrease the number of pinch points and increase strokes per minute and production. This is especially important in bending applications and for special tooling for which the upstroke must be adjusted in addition to the downstroke.
Electric stroke controls offer advantages over mechanical linkage controls. Electric stroke controls have quicker cycle times and more precise stopping because they use switches that send signals to the control valve almost instantly.
Machines that use mechanical linkage stroke controls must be in motion to cause the linkage to close the control valve. As the valve closes, the machine slows down and is more difficult to regulate.
Safety instructions should include proper alignment of the punch and dies. Because punches are usually hardened to 58 Rockwell, the punch will not bend as it collides with a die. If it is out of alignment, it is more likely to flake or even explode, causing serious harm to the operator. The preferred and most widely used method of aligning the punch and die is similar to the way punch presses have been aligned for many years. This is done by bringing the punch ram to the bottom of the stroke and installing the punch and dies with the stroke down. This way, the punch already has been entered into the die, the alignment can be checked and guards may be replaced without machine movement.
In trying to determine equipment quality, consider the size of the pivot points and beam strength of the steel that is under pressure. Since your ironworker produces many tons of force, the force must be generated and transferred through the pivot points as well as the beam. Another good indicator of quality is how much shock is produced when the ironworker punches. Excess shock, which can be identified by a loud popping or banging noise as the punch goes through the material, could indicate the beam or side frame is stretching and snapping back into place. Continued shock can cause welds to break, as well as other failures. Higher-quality machines control this by increasing side frame, beam, and pin size.
The hydraulic system also should be a consideration. You are buying the machine for the tons of pressure it produces, not for the motor’s horsepower rating. Some ironworkers are designed (through mechanical advantages) to produce more tonnage with less horsepower, thus making the machine more efficient. Machines with higher-horsepower motors usually operate at a higher hydraulic pressure, or pounds per square inch, and this increased pressure can produce more wear on hoses, pumps, and valves.
The final key in selecting an ironworker is support. An ironworker is a piece of equipment that is made to last for many years; this means it is important to be able to get additional optional tooling or special built tooling as well as replacement parts for the machine and support from the manufacturer for many years to come.
Remember that an ironworker purchase should be a well-informed and comfortable decision. Consider its ease of operation, ease of financing, and ease of delivery. Determine if a component or fully integrated ironworker is the right fit for you. Evaluate your financing options – you may be able to finance directly through the manufacturer – and know where the machine is being manufactured and where it ships from, as well as how long it will take to get it up and running in your fab shop. Before purchasing an ironworker, take the time to analyze your needs and carefully assess the features available. It will be time well spent.