| When it comes to metal fabrication equipment, you | | | | neutral axis of the section and the furthest distance on |
| may have heard of an angle roll bending machine. | | | | the section from that neutral axis. In symmetric |
| Some may refer to it as a section bending machine, | | | | sections bending about the neutral axis both ways will |
| but its purpose is still the same - form raw pieces of | | | | give the same section modulus, however in non |
| metal into desired shapes and sizes. | | | | symmetric sections, the section moduli are different for |
| If you have ever seen an angle roll bending machine, | | | | calculations of leg in and leg out bending. |
| you would agree that most are constructed in a | | | | Depending on the design of the machine, each |
| vertical steel frame. It is common that the bending | | | | machine will have a certain capacity of bending. Thus |
| portion of the machine is located on one side, with the | | | | the pressure exerted on the machine members will |
| power and drive of the machine on the opposite side. | | | | dictate the limit, before rendering the deflections the |
| This writing is intended to educate and help the | | | | members sustain unacceptable or the wear and tear |
| purchaser of Angle Bending Machines to ask the right | | | | caused on the machine would be excessive. This limit |
| questions when considering a purchase. | | | | is what is specified as W or S (Section Modulus |
| Power source: | | | | Capacity) in in3 or cm3. |
| Small units are powered by an electric motor with a | | | | In general catalogs and brochures describing section |
| reducer. The power transmission is accomplished by | | | | bending machines would give the maximum section |
| gear trains and or chains / sprockets combinations. | | | | sizes a machine can bend of each type of structural |
| These are units used in small job shops and rod iron | | | | or bar section. With a minimum diameter the machine |
| fabricating establishments. The new generation of the | | | | can bend them to. By rule of thumb and practice it has |
| section bending machines is powered by hydraulic | | | | been established that the minimum diameter of bars, |
| systems. These are used for bending from the | | | | tubes and pipes is ten times the height of the leg or |
| smallest bars to very large wide flanged structural | | | | the dimension taken in the radial direction. For the rest |
| beams. | | | | of the sections it is approximately 11 to 12 times the |
| The large hydraulic units have a double pump hydraulic | | | | height of the section or the leg. |
| system, with one providing the flow for the rotation of | | | | When a section dimension and thickness is not |
| the rolls and the other for the extension and retraction | | | | mentioned on the capacity charts, the user either |
| of hydraulic cylinders attached to arms carrying the | | | | needs to calculate the section modulus of the section |
| bending rolls. | | | | and if this is less than the Section modulus capacity of |
| Some designs use one main hydraulic motor, usually | | | | the machine, he/ she will be in the safe zone and no |
| mounted to an epicyclical in-line reduction gear, which | | | | damage will come to the machine. If in doubt it would |
| imparts rotation to all three rolls. Another variation is | | | | behoove the user to contact the manufacturer for |
| each roll having its individual hydraulic motor/ reduction | | | | professional advice. |
| box combination directly driving it. | | | | Controls: |
| The Bending Process: | | | | Section bending machines have become sophisticated |
| There are some terms used in the industry describing | | | | and are using NC and CNC to bend complicated |
| the capacities of Section Bending Machines and the | | | | forms. These controls have canned programs for |
| process used, which the purchaser should become | | | | standard sections and they use teach mode where by |
| familiar with. | | | | the operator can produce the part manually and the |
| Square and rectangular rods, round rods, square and | | | | machine keeps track of all the steps he/ she uses to |
| rectangular tubing, round tubing, standard pipe, equal leg | | | | accomplish the job. Then the program is memorized |
| and unequal leg angles, "C" and "MC" channel, "S" and | | | | and archived for continuous use. |
| "WF" beams, "T" bars ...these are sections which can | | | | The new controls can even collect their own section |
| be rolled on section bending machines. | | | | characteristic data, by bending a piece of the section |
| "Leg out" means the leg of a section, like in angles will | | | | at different settings. The radius produced at a certain |
| stick outward from the ring formed in a radial direction. | | | | setting is input into the program and by taking three |
| "Leg in" means the leg of a section, like in angles will | | | | readings, the program surmises the reaction of the |
| stick inward from the ring formed in a radial direction | | | | section to bending forces; then uses the information |
| toward the center of the ring. "Leg out" is also known | | | | when the program parameters are entered and the |
| as "Easy way" and "Leg in "Hard way" There are | | | | part is run...at first trial the machine would produce a |
| exceptions to this terminology when it comes to | | | | near perfect part. With small adjustments, what used |
| channels, whereby one can bend a channel leg in, leg | | | | to take hours of testing, experimenting and developing |
| out and the hard way when bent on its side. | | | | is cut down drastically. |
| Bending of round sections, pipes and round tubing | | | | Controllers have large memory capacity and many job |
| require special tooling other than what is usually | | | | programs are stored and recalled easily. Most units |
| provided standard with section bending machines. In | | | | have RS232 communication capability and lately USB |
| special cases with square and rectangular tubing | | | | ports have been appearing on most of them. There |
| where the wall thickness is low...the manufacturer | | | | are many operating systems used on these |
| should be consulted as to whether special all section | | | | controllers...some are still using DOS, some use |
| enveloping tooling is required to avoid the section from | | | | Windows and even Linux, while some have proprietary |
| collapsing under the bending forces. | | | | operating systems. |
| Bending Channels, S beams and WF beams the hard | | | | Observation: |
| way, present a special challenge because the force of | | | | With each passing day, technology is improving, and |
| bending would sometimes collapse the web connecting | | | | this is no different for angle roll bending machines. |
| the flanges. Most manufacturers of heavy section | | | | Computers and engineers are largely responsible for |
| bending machines offer what is called a "Traction | | | | section bending machine construction, and this allows |
| Tool", which holds the section back and supports the | | | | for more precise equipment. Some inexperienced |
| web so as to avoid collapse. | | | | shoppers may jump at a machine with greater |
| Machine Capacity: | | | | horsepower or even one that weighs more. Do not be |
| Each section has what is known as a "Section | | | | fooled; instead consider these things when buying: |
| Modulus". This value is a measure of the resistance a | | | | reliability and durability of materials used in the |
| section displays to bending. It is the quotient of the | | | | machine's construction, solid design, and of course |
| sections Moment of Inertia about the axis passing | | | | ease of maintenance. |
| through its center of gravity, which coincides with the | | | | |