An Overview of the Milling Machine, Its Processes, and Components

The process in which allows the creation of the variety of features on a part from cutting the unwanted material, such process is known as “Milling Process”. Milling is an important form of machining. Milling process requires tools like a milling machine, workpiece, cutter, and fixture. The workpiece is a pre-shaped material that joins to the fixture, attached to a platform on the milling machine. Along with this, there is a fixation of a cutter in the milling machine, the cutting tool has sharp teeth that rotate at high speed. The machine cuts away the material from the workpiece in the form of small chips by feeding the workpiece into the rotating cutter that allows the creation of desired shape.

As far as the construction of the machine is concerned, the parts of the milling machine are not axially symmetric; they have many features, such as slots, holes, pockets, and three-dimensional contours. Some parts can be completely fabricated by the help of milling process; as components of these parts are used in limited quantity, like prototypes, custom designer fasteners or brackets. One of the most common applications of milling is the fabrication of tooling for other processes. For example, milling the three-dimensional molds. The parts manufactured by using a different process applies to add or refines features of these parts by using milling as a secondary process. The milling process can offer high tolerance and surface finish. Therefore, for that reason milling is an ideal for adding precise features to a part whose basic shape has already been formed.

Components of Milling Machine

Milling machines can be available in several of sizes and designs. However, they have the same components that enable the work performed on three-dimensional that is about the tool. The components of the milling machine include the following sub-parts:

• The base is a simple platform that provides support to the machine, normally fixed on the ground surface. A column attached to the base connects to the other components.
• A table has “T” shaped slots along its surface. The milled workpiece is mounted onto the table surface.  The workpiece can be joined in a fixture called a vise. The vise has fixation into the T-slots, or they can be clamped directly into these slots.
• The saddle is a platform that provides support to the table and allows its longitudinal motion. The saddle is also able to move and provide the horizontal motion of the workpiece in the Y-direction by sliding along another platform.
• There is another platform that supports to saddle and table is called “Knee.”

All of the above-given components of milling machine can operate on both orientations either in vertical or horizontal which allows the creation of two distinct form of the milling machine. Horizontal milling machine sometimes called arbor milling because horizontal milling machine uses a cutter that is mounted on a horizontal shaft, which is called an arbor. On the other hand, a vertical milling machine orients the cutter vertically. It has cutter fixed inside a piece, which is called collet, and then it is attached to a spindle that is orients vertically. The spindle is located inside the milling head, which attaches to the column. On the vertical milling machine, all the milling operations performed to remove the material by using both the bottom and sides of the cutter.

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Pressure Testing: Purpose, Regulation Requirements and Its Risk Factors

Pressure Testing has a great importance among industrial processes, as it is a non-destructive test that verifies the system’s integrity of pressure shell on new or old installed tools and equipment; this mechanism also has the ability to detect tightness of a system against leakage.

Pressure Testing has equally importance in the fabrication process, and it is a last physical quality test that performs in a controlled environment. Most of the piping codes require this test, to ensure that repaired or a new piping system is capable to maintain its safety against rated pressure and leakage. 

Most of the regulatory and enforcement agencies compliance to piping codes that mandates for the construction of the system. Nowadays, Pressure testing is mainly preferred due to good safety considerations, whether Pressure Testing is legally backed or not, it serves constructively by protecting works and public.

Pressure Testing establishes a pressure rating for required components. It may also be used to establish a safe rating by calculating various special systems. Before start-up of new systems, Pressure Testing is performed to confirm the integrity of vessels and to obtain relevant certification.

Regulation Requirements for Pressure Test

Pressure Testing is also demanded by the regulation requirements. The important points of these regulation requirements are given below:

• By using the hydrostatic method, all the pressure piping leak tests must be conducted.
• A pressure piping system will not test at a temperature that is colder than its minimum allowed temperature.
• When conducting a Pressure Test, a contractor must considered the ductile-to-brittle transition temperature and the possibility of brittle fracture.

The biggest advantage of Pressure Testing is that it can be performed at low working pressure. The fatal disadvantage of pressure testing, exposure to aged equipment with poor toughness could result in the brittle fracture.

From the above discussion, it can be concluded that the pressure test procedure confirms safety. The purpose of such procedure is to ensure pressure tests are conducted safely and effectively. They apply to mechanics, supervisors, inspectors and subcontractors responsible for pressure tests. Pressure tests are performed to verify the reliability, and leak tightness of pressure systems. A pressure test is required for a new pressure system before use or an existing pressure system after repair or alteration.

Understanding The ASME Standards

ASME (American Society of Mechanical Engineers) is technological association that maintains standardization of equipments for the industries of processing & mining, which involves with items like pressure vessel, boiler and inspection piping. The role of the society is to maintain checks and balances for industrial inspection by the help of volunteer engineers, which are entitled to monitor about predefined aspects of standard for manufacturers and operators operating those mechanical equipments in machining shop. Manufacturers tend to acquire ASME U-Stamp certification, so they could reveal to their consumers about the maintenance of standards while using modern equipment, and they can acquire their services without any hassle. Moreover, it further reflects that firm endows a healthy reputation among industry wide professionals, and certification has bound the company to adopt standards of optimal safety in the production of their products or services.

The certification of ASME U-Stamp also assures that manufacturing company is using pressure vessels and boilers in the synthesis of industrial process are not threat to life. Such kind of industrial apparatus contains excessive pressure & elemental wear and tear, so their usage needs to adopt those standards and protocols of certification, useful in reducing the aspect of malfunction & optimization of productive efficiency of equipment. The welding or other technical equipments that use pressure vessels and machinery must be capable of regular refurbishments, repairs and parts replaceable.

Maintenance Of Quality Assurance:
To achieve optimal operation of welding, there is more than one factor that supervises the whole process from preliminary point to production of product. To get into the listing of certified welding shops, the two levels i.e. machine operation refurbishment and repair must be adopted for future mechanical upgradation of apparatus, so manufacturers or retailers of such an equipment caters to include reusability factor in the machinery. For that sake, pressure vessel manufacturer as well as engineering board of ASME U-Stamp certification inspects the equipment for optimal output.

Generally, physical magnitudes of industrial equipment aren’t small, the large welding machineries comprise of small components which need to be refurbished during different phases of production. Having engineered at component level enables these machines to undergo raw and hard materials in rough condition. The process of excavation and production demands different mechanisms, capacities and orientations. The mechanical operation of these large machines may get damaged during completion of required processes, so machining and repair at component level becomes more easy. Concisely, certification benchmarks ASME U Stamp companies for optimal function of equipment involved in the industrial synthesis.

The achievement of ASME U-Stamp Certification doesn’t involve complex procedure, the inspection to monitor about standards is conducted by respective field experts. The professionals and engineers constituting this association, utilize their skills to prove durability and capability in technology related industrial processes involved in machining shop. Maintaining these procedures for machinery ensures continuity in production and optimal return of investment for the costs along with safety measures for workers.

Oxy-Fuel Welding (OFW)

Oxy Fuel Welding (OFW) is a metal joining process, used to join metal end pieces by heating. This process is commonly used to join mild steel. Oxy-Fuel welding is also called oxyacetylene welding because in this process mixture of acetylene and oxygen burns at intense flame of 3500^oC. Oxyacetylene gas welding consists of a group of welding processes, which joins different type of metals by heating them whether it is used with gas flame or without filler metal. When the gas flame combined with metal, it melts the surface to molten form, by allowing the welding process to take place. Oxy-Fuel welding can be used for shaping metal, cutting and brazing of metals. Oxy-fuel welding is mostly used for prefabrication of tubes, steel sheets and plates.

Oxy-FuelWelding process includes welding operations that make use of oxygen, which can also be combined with fuel gas as a heating medium. In this process, gas, fuel and oxygen are mixed in a mixing chamber with proper proportion that also a part of the welding assembly. This welding process involves a filler metal and the melting of the base metal, which can be used by means of the flame produced at the tip of welding torch.

Oxy-Fuel Welding Processes

There are following three processes that involves in Oxy-Fuel Welding.

• Oxy-acetylene welding
• Oxy-hydrogen welding,
• Pressure gas welding.

Oxy Fuel welding also known as air acetylene welding because of its industrial significance, in which combustion of air and acetylene heat is obtained. Welding with Methyl acetone- propadiene gas (MAPP gas) also uses same procedure like Oxy-fuel welding.

Advantages of OFW

There are following given advantages of oxy Fuel welding:

• A welder can control temperature of weld zone, heat input and the oxidizing or reducing potential of the welding environment that controls the welding process.
• Welding process also controls the shape, weld bead size and weld puddle viscosity as it independently adds a filler metal of the welding heat source.
• Oxy Fuel Welding is used for welding of tubes, thin sheets and small diameter of pipe.
• OFW is also used to repair welding joints, welds of thick sections. However, its repair work is not very economical, so its use is not feasible at commercial level.

Oxy fuel welding process is used in welding shops, it is mostly used for torch brazing, soldering, and many other types of operations, where its heat transfer rates and flame characteristics are not the same like that of welding.

Inspection Overview Of Pressure Vessel

Simply, a pressure vessel appears as a storage container, fabricated to accumulate pressure more than 15 p.s.i.g. In several inspections of pressure vessels at workplaces, usually numerous cracks and damages are observed on their surface. Such cracks and damages on the surface of pressure vessel result in the form raptures & leakages, even they can be risky to health and safety measures in workplace due to air poisoning, suffocation, explosion and fire. In severe case, damages in vessel can result fatal and can bring harm to ecology and property assets. Therefore, to ensure safety & health of workers, the design, manufacture, operation and maintenance of pressure vessel should be according to designated procedures & standards.

Below, the techniques & technologies handy in pressure vessel repair after inspection, by preventing premature failure and shutdown of facility:

Inspection Techniques Of Pressure Vessel:
To ensure safe operation of pressure vessel, online inspection is in the benefit of plant processing as well as surrounding environment. To find out the thickness of vessel surface, ultrasonic testing is widely conducted over industrial level. The purpose of such testing is to check regularly the thickness of metal of suspected areas with necessary equipment, if thickness of surface reaches at minimum allowable limit, then precautionary measures should be taken in order to keep plant working.

Notably, the other inspection techniques incorporate designing & maintenance of pressure relief valves along with installation of corrosion coupons & sentinel holes.

Real Time Example:
A. J. Warner, a senior engineer, who works for a refinery plant in Texas, quotes an example "Consider, for example, that a key Gulf coast refinery develops a serious problem in a pressure vessel. This will likely cause a shutdown of that unit, lasting anywhere from one day to several weeks or longer. This causes a disruption or shortage in the supply of gasoline to the market, which will drive up the cost at the pump. Therefore, it is in the best interest of everyone that pressure vessel technology remains a key focus area for the refining industry and beyond."

Keeping it in same way, Millennium Industries, a pressure vessel manufacturer at industrial scale maintains health and safety measures at its facility. Company aims to provide those industrial solutions, which have less affect over environment, impact over employees’ health, control risk factors and safe work practices.

Hydraulic Pumps

Hydraulic pump is a mechanical device which is used to converts the mechanical power of the system into hydraulic energy. To overcome the pressure which is induced by the load hydraulic pump generates high power flow.

A hydraulic pump performs basic two functions when it operates:

• A mechanical action which creates a vacuum at the pump inlet, it permits atmospheric pressure to force liquid from the reservoir into the inlet line to the pump.

• The second function which is performed its mechanical action that delivers liquid to the pump outlet and then forces it into the hydraulic system.

Why we need Hydraulic Pumps?

We need hydraulic pumps because they are the main sources of power for different dynamic machines. Hydraulic pumps have the power to push large amount of oil through the hydraulic motors and cylinders. In returns, the pump converts the mechanical work of energy into the hydro static energy.

Principle on which Hydraulic pumps operates

According to the displacement principle the hydraulic pump operates. In this principle the existed mechanically sealed chambers in the pump may involves. The purpose of these chambers is to transport the fluid from suction port (inlet) of the pump to the pressure port (outlet). These sealed chambers also ensure that no direct connection between the inlet and outlet port of the pump. This is the main reason that these pump suitable to operate at very high pressure and they are also ideal for Hydraulic systems. The mechanism of pump is shown in the figure below:

Mechanism of a pump

Types of Hydraulic Pumps

Depending on their different functional and other system requirements such as range of pressure or flow, operating medium, type of drive etc. hydraulic pumps are manufactured. Hydraulic pumps may have large range of design principle and configurations. All pumps can’t fully meet the requirements of the system. So for that reason different types of hydraulic pumps exists which are given below:

Hydraulic Gear Pumps

External gear pump

Internal gear pump

Gear ring pump

Screw spindle pump

Hydraulic Vane Pumps

Single chamber vane pump

Double chamber vane pump

Hydraulic Piston Pumps

Axial piston pump

Radial piston pump

Uses of Hydraulic Pumps

Hydraulic pumps are used in hydraulic machines. While selecting a hydraulic pump it must have good frequency, pressure and temperature capabilities. Hydraulic pumps are used to do different type of works such as open, close, lower and to lift components.They are also used in field services like machining and assortment of construction

A pump produces liquid flow or movement which is necessary for the development of pressure. This is a function of resistance to fluid flow in the system. For example, the pressure of the fluid at the pump outlet is zero for a pump not connected to a system (load). Further, to overcome the resistance of the load, pressure will rise to the level for a pump delivering into the system.

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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.