What Is Involved in Metal Fabrication?
Metal fabrication is the process of constructing machines and/or structures from raw materials such as iron, steel, and copper. Metal fabrication companies specialize in this value adding process of production. Actions in fabrication may include cutting, bending, welding, blacksmithing and/or assembling. Contractors and equipment manufacturers might create such products as hand railings, stairs and structural frames for buildings.
Metal fabrication specialists use materials like plate metal, pre-formed and expanded metal, welding wire, fittings and castings. Beginning with these raw materials, they cut them to the correct size using tools like a special band saw or cutting torches.
Metal is then formed using dies. Tube bending machines and rolling machines may be used to bend metal or make round sections of metal. Metal parts may be welded together, cooled, sand blasted, and painted.
Other metal fabrication may require specialized, specific processes including: punching, welding, forging, casting, brazing, shearing, drawing and spinning or even electrical and hydraulics services. Construction companies often outsource metal fabrication to an enterprise that specializes in such work. Metal fabrication businesses are sometimes called fab shops or machine shops.
What Is a Corrective Action?
Corrective actions are taken in the metal fabrication industry to detect a non-conformity, as well as to ensure that undesirable situations are corrected. Examples of corrective actions include maintenance performed for corrosion, misalignment of parts, physical damage, faulty construction, incorrect assembly,or cracks.
How Is Quality Assurance Carried Out?
The final product is thoroughly inspected before it is shipped off to the client. The quality inspectors are looking for flaws in the product. They may do this assessment through non-destructive testing. This involves testing of materials for surface or internal flaws or metallurgical condition. Non-destructive testing is performed without affecting the integrity of the material or its suitability for use.
Non-destructive testing methods may include:
- Visual Inspection (VT) - This is the most common test method. The quality assurance specialist looks at the surface of the part being inspected. Visual inspection involves the visual observation of the surface of a manufactured object. The specialist is looking for the presence of surface discontinuities. Visual inspection may be enhanced by using optical instruments including magnifying glasses, mirrors, borescopes, charge-coupled devices (CCDs) and computer-assisted remote viewing.
- Magnetic Particle Testing - This process utilizes one or more magnetic fields to locate surface and near-surface non-conformities in iron-based materials. This may be done with either a permanent magnet or an electromagnet. Here’s how it works: When the magnetic field encounters a non-conformity, it shows up in the surface where very fine coloured ferromagnetic particles are applied to the surface. Anomalies produce a visible indication on the surface of the part.
- Liquid Penetrant Testing (PT) - When a highly fluid liquid (the penetrant) is applied to the surface of a part, it will penetrate into fissures and voids open to the surface. Penetrant testing can be performed on magnetic and non-magnetic materials. It does not work well on porous metals. When performing a PT inspection, the surface being tested must be clean and free of foreign materials or liquids. The part is inspected visually, using a black light for fluorescent penetrants.
- Radiographic Testing (RT) - Industrial radiography exposes the test object to radiation which passes through the object being inspected. X-rays are used for less dense materials like: aluminum, while gamma radiation is used, and for thicker or denser materials.
- Acoustic Emissions Testing (AE) - Acoustic emission testing applies a localized external force like an abrupt mechanical load or rapid temperature or pressure change to the part being tested. Stress waves then turn generate short-lived, high frequency elastic waves on the part surface. These are detected by sensors attached to the surface. Multiple sensors generate data can be evaluated to locate discontinuities.
- Guided Wave Testing (GW) - This test for piping use controlled excitation of one or more ultrasonic waveforms. These travel along the length of the pipe. Guided wave testing is looking for changes in the pipe stiffness or cross sectional area. GW testing can inspect the pipe wall volume over long distances without having to remove coatings or insulation. It can locate both inner and outer discontinuities.
While destructive testing methods exist, these are more costly and time consuming and are used only if discontinuities cannot be detected via non-destructive testing methods.
Why Are Corrective Actions in the Metal Fabrication Industry So Important?
When parts do not function properly, systems cease to work, which causes a loss in revenue. Moreover, non-conformity of parts may result in worker injury or death. Corrective actions pinpoint non-functioning parts or systems. Corrective actions provide a plan for making adjustments to faulty parts, shoddy workmanship and/or incorrect assembly so that machinery is cost effective and safe.