Metal Fabrication: Its Processes & Applications

A process in which metal structure undergoes the cutting, bending and assembling processes is known as Metal Fabrication.

Processes of Metal Fabrication

Now we will discuss one by one of each process in detail:

Cutting

Metal cutting is done with the help of different automated and manual tools such as saw, chisel or shear. It also includes process of torching that completes by use of torches and via Computer Numerical Controls (CNC) cutters.

Bending

Metal bending is done with the help of manual or powered hammering. It can also be done with the use of pressure brakes. Most of the CNC-Controlled backgauges utilize hard stops to position cut parts, in order to place bend lines in the correct position. As technology is getting advance, now there are several offline programming software, which can configured to make program for any CNC controlled press brakes machines.

Assembling

The process of assembling joins the pieces of metals through welding and binding with adhesive materials. Sometimes, metal bends appear in the form of crimped seam. For fabrication, structural steel and metal sheets are the usual starting materials.
These materials are mostly present along with welding wire, flux and fasteners that can be used to join the pieces. Human labor and automation manufacturing processes are commonly used products of fabrication, and the shop that specializes in these types of metalwork is called Fabrication Shop.
Most of the end products are not classified as fabrication, either they have similar shape and function. The end products of metalworking, such as machining, metal stamping, forging and casting are not classified as fabrication.

Difference between Fabrication Shop and Machine Shop

Fabrication work overlaps with various metal working specialties. Machine and fabricationshops have overlapping capabilities, but in conceptual manner, fabrication and machine shops are different from each other. In fabrication shop, manufacture deals with metal preparation and assembling processes. Whereas, machine shop enables cutting of metals, but they mostly deal with the parts of machining on different machine tools. Most of the companies, involves in both types of activities that includes in fabrication and machine work.

Practical Applications of Fabrication Work

Blacksmithing Process is the core of fabrication work.  From different aspects, welders, boilermaker, millwrights is also included in fabrication work.

Metal fabrication is one of most the important process in field installations. It involves in the construction of machines as well as structures made from different types of raw material. Fabrication shop may involve in most of the processes like welding, cutting, forming and machining. These large fabrication shops offer additional value to their customers by limiting the need for purchasing personnel to locate multiple vendors for different services.

Shielded Metal Arc Welding (SMAW)

SMAW is a process of welding that uses a fragile electrode coated in flux. SMAW have many names this process is also known as stick welding, Manual Arc Welding or flux shielded arc welding. In SMAW process as the weld is laid, the external coating of flux on electrode disintegrates, providing a layer of slag and a shielding gas. These elements protect the weld area from infectivity until the area cools. The external flux coating also performs more functions such as it provides control bead shape or arc stability.

Equipment & Operation for SMAW

The following equipment and operations are necessary for SMAW process.

• Welding power source
•  Electrode holder
• Ground clamp
• Welding cables and connectors
• Accessory equipment (It includes wire brush, chipping hammer)
• Protective equipment (It includes gloves, helmet etc.)

Welding Power Sources

Shielded Metal Arc Welding circuit we can use either Direct Current (DC) or either Alternating Current. In some specific cases, the power source must use constant current type. In this type, power source will deliver relative welding current or constant amperage. As it will remains constant so the weld beads which are produced will be uniform in shape and size.

Electrode Holder

The use of electrode holder is to connect different welding cables and ducts to the electrode. Electrode holder is available in different sizes and capacities. The purpose of insulated handle is to guide electrode over the weld joints.

Ground Clamp

The purpose of the ground clamp is to connect the ground cable to the work piece. A good ground clamp having the characteristics of carrying more electric current without overheating.

Welding cables and connectors

Electrode cable and ground cable plays an important role in the SMAW circuit. So different welding cables and connectors are also necessary components for the SMAW circuit.

Coated Electrodes

In Shielded Metal Arc Welding various types of coated electrodes are used. For different types of welding specific electrodes are used according to their types. For example, electrodes used for low allows and stainless steels will quite different from the coated electrodes which are used for mild or carbon steel.

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Safety Practices For Fabrication Shop Work

Fires blown up due to welding are avoidable, if workers follow those safeguards & practices prescribed by workshop administration before stepping into it, then precious lives could be saved from loss. 1.4% residential fires & 10% commercial fires reported in Irving – Texas due to welding accidents in 2002. Negligence in preventive measures give rise to such incidents, workers could overcome them by adopting prescribed standards of protection.

It is necessary for welders whether they are professional or unprofessional to know about potential threat of catching fire on fabrication shop, as work at high currents during make and break of connections.

Must do Checkups:
First thing first, before getting into work you should examine:

• Equipment’s health, 
• Working & surrounding area, 
• Available items to minimize hazards and 
• Measures that can ensure safety.

Checking of Equipment:
In order to avoid any accidents, the installation of the welding equipment should be done by qualified technicians, which can ensure about the connectivity as well as operation of apparatus according to manufacturer’s instructions. However, installed equipment correct operation i.e. cable, electrode holder and coupling devices is verified at welder’s end, he should be competent enough to identify, recover or report about the defects. The welder should make sure each time he uses the equipment, the external connections are clean & tight, clamp of wire has firm grip to grab the workpiece and appropriate distance between welding point & workpiece.

Reduction of Electric Shock Risk:
In arc welding, the major hazard that you might come across is the arc radiation and electric shock, it may occur due to appearance with live parts i.e. electrodes and workpiece of welding circuit. Certified welding shops use proper safety & protection system, as voltage seepage during rainy season increases as compared to normal.

More than One Welding Operations at One Workpiece:
There is a huge risk of electric shock when more than one workpieces have physical or electrical connection. Complete isolation of workpieces should be observed, else it will increase the probability of electrocuted in case of simultaneous connection.

Outdoor Working:
While working outdoor welding repair the possibility of moisture increases, it also increases voltage leakage. In such case, system requires sufficient level of waterproofing, for enclosures the ingress protection (IP) codes should be:

• IP 23 protection against water spray <60 degrees from vertical
• IP 24 protection against water spray from any direction

In case of rainfall, welder, equipment & workpiece should have complete protection from moisture.

Some Safety Practices to Avoid Tragic Situations:
The safety practices are as follows:

• The welders should takeoff ornaments like rings and metallic straps before getting started with work.
• The clothing like gloves, boots & overalls should be used to protect from electric shock.
• The external connection of the welding apparatus should be checked on daily basis, whether connections clean and fixed or not.
• The electrode of manual metal arc welding (MMAW) should have insulation for protection, to change the electrode.
• High frequency (HF) can make welder feel electric shock, HF could affect even through small hole in glove.

What Is CNC Machine, Types & Troubleshooting?

The word CNC is the derivation of NC meaning ‘Numerical Control’, whereas CNC means ‘Computer Numerical Control’. Obviously, CNC is numerically controlled device attached with the element of digital computing. In order to do so, machine tools are controlled by means of computer instructions, which are predetermined to perform each function of machine. Punched Tape is the clear example of machined controlled by computing device.

Overview:
Both NC & CNC enables greater ratio of productivity for tools of machine, as they are automatically controllable and require less human intervention. Before the innovation of CNC, Hydraulic Tracer Systems were less capable of automation element, due to the usage of hydraulics in cutting tools of lathe & template of mill. Moreover, such systems require taper attachments, which were used for many manual lathes indifferently capable of hydraulic tracer, as tracer had greater capability for the elaboration of templates rather than simple tapers.

Classification of CNC Machines:
As CNC involves usage of computers, so it increases the no. of machines, which could be brought under such classification.

• Retrofitted Machines – The machines that don’t have CNC installed by default or during manufacture.
• Custom Built Machines – The custom-built machines to perform CNC operation.

Types of CNC Machines:
Here we will mention some of the widely used at industrial level:

Milling Machine:
Milling Machine is used to cut different materials driven by computer controls, which translates programs containing instructions in the form of digits and letters to move the spindle of machine at specified dimensions. The standard programming language of all CNC machines is G code, while some manufacturers use customized propriety languages, which are simpler than standard language & easy in transfer.

Lathe Machine:
Lathe is a retrofitted CNC machine mostly used for cutting metal objects rotating with a fast speed. Basic feature of Lathe Machines is that they are capable to cut the metal by the help of indexable tools & drills with extreme precision in a quick manner that is not possible on manual lathes. Usually machine comprise of twelve tool holders, along with coolant pumps that cut down on tool wear. The field installation & control specification of Lathe Machine is similar to Milling Machine as it allows G code as well as proprietary programming language.

Troubleshooting of CNC Machine:
To troubleshoot a CNC machine, here are the key steps to follow:

• Environmental Issue: The issue may arise due to increase in temperature. Temperature of machining shop should be maintained with respective measures.
• Mechanical Issue: The problem may exist in flatbed guideway, ballscrews, & spindles that affect the tools and job under machine.
• Electrical Issue: At major level, it could be heating of cable, or it could be at miniature level that could be traced by trained CNC engineer through milling machine schematics.