Ultrasonic Machining Process Guidelines

You must have done different machining processes like cutting, drilling, milling, knurling etc. and would have got acknowledged with lots of machining skills. In my previous article on machining processes I have mentioned its advantages over casting process and with appropriate accuracy machining process can be used for variety of engineering materials.

Apart from much advantages of conventional machining process there are many demerits like hard and brittle materials are not suitable for machining and even casted products can’t be machined easily.

Hence engineers developed modern machining process like ultrasonic machining (USM) and many more like that to overcome the disadvantages of machining process which I’ll discuss later.

The reason behind the replacement of the process is that unconventional process are far better than the conventional machining process from many aspects like dimensional accuracy, surface finishing, less time consuming, large production, efficiency and harder and brittle material can be easily machined.

Look being a mechanical engineer you have to find the new ways like using ultrasonic machining process etc. to raise the production rate when the demand is more than the supply. And to have better production rate you have to certainly think of using the modern machining process or find alternatives otherwise you won’t survive in the industry.

But you have to keep in mind the minimum cost that can be spent on adopting new technologies to enhance production rate. Skilled Engineers and researcher are masters in these and hence they always try to modify the conventional machining process to get better results and did a great job of developing unconventional machining processes which I am going to discuss below.

Before going to the deep discussion in the topic ultrasonic machining process let tell you some important reasons of adopting modern or unconventional machining process and the process that are involved within it.

Why Modern Machining Process

With rapid growth in the demand of harder and brittle material for various manufacturing products led to the development machining of harder and brittle material from time to time. This is because these materials are very difficult to machine through conventional means and hence required a stronger and convenient machining process that can overcome all the disadvantages of the conventional machining process.

For machining harder tool and brittle materials a much stronger tool is required which could be very uneconomical and simultaneously accuracy, surface finish and huge efficiency could not be achieved.

And with the advancement of machining technology and adopting modern machining processes all of the above problems are resolved and working tremendously with high production rate and low investment cost.

Not only this with modern machining processes like ultrasonic machining, the properties of the materials like chemical inertness, grin structure, physical properties, conductivity etc remains same throughout the process which is plus point of the unconventional process.

As I said many application demand tight tolerances, intricate shape and size with additive features like dimensional accuracy, surface finish and higher reliability which are not fulfilled by the conventional forming and sintering processes.

You might be thinking if there is problem in the tool then why not use the hardest material (Diamond) of the earth as machining tool. This is because it very costly and simultaneously cannot be harnessed in intricate shape and sizes. And more important it is very time consuming which doubles the investment cost.

Common Modern Machining Processes

• Abrasive Jet Machining (AJM)
• Chemical Machining (CHM)
• Electrochemical Grinding (ECG)
• Electric Discharge Machining (EDM)
• Ion Beam Machining (IBM)
• Laser Beam Machining (LBM)
• Plasma Arc Machining (PAM)
• Ultrasonic Machining (USM)
• Water Jet Machining (WJM)

Why Ultrasonic Machining

Ultrasonic machining process is none conducting (Heat and Electricity), none chemical machining process which doesn’t have any effect on the chemical and physical properties and also the grain structure remains same throughout the process.

This additive feature adds value to ultrasonic machining process over other and most important part is that it can machine harder material with dimensional accuracy and perfect surface finish. The cost of the production is also under control. The production rate can also be increased whenever needed.

Ultrasonic machining process is material removal process and can be used for both conductive and non conductive materials. As I said it can machine much harder material almost more 40RHC, hence it also called as ultrasonic impact grinding or vibration cutting and can be used for wide variety of materials with additive features.

You would have heard of LASER, which is also used in modern machining process but it has some disadvantage like heating effect of laser machining changes the grain structure. Hence it is has limited material choice. Although it has tremendous advantage like higher production rate, higher accuracy and surface finish.

EDM is also unconventional process and has wide variety of intricate shapes and size but it is limited to conductive material only and material which is not conductive would not be machined.

 All these demerits of different modern machining process gives higher ranking to ultrasonic machining process as it can machine hard and brittle material and can be conductive or non conductive.

Working of Ultrasonic Machining

In ultrasonic machining process an ultrasonic transducer is used to generate ultrasonic waves of frequency higher than 20KHz. And this frequency is given to the horn and tool assembly resulting in continuous impacting on the workpiece with that frequency.

Actually a low frequency electrical signal is made to fall through the ultrasonic transducer producing higher frequency mechanical vibration waves. And after that this mechanical vibration is given to the tool in a fixed direction or it is unidirectional.

The amplitude of the mechanical vibration produced in the tool is kept low almost 0.02mm and continuously hammers the work piece with the given frequency. Ultrasonic machining tool is made up of soft materials and hence some time static load acting in downward direction is given to compress it against the workpiece.

During the impaction of the tool to the workpiece slurry containing abrasive particles is allowed to pass through the gap between the tool and the workpiece. The slurry is made up of abrasive materials suspended in a liquid and made to fall in the cutting zone under pressure.

Some commonly and mostly used abrasive materials are like carbide, silicon carbide, diamond, born carbide and alumina with the chemical added. The abrasive materials both acts as a tool and workpiece which reduces the chance of surface damage.

As I said abrasive is made to fall in the cutting zone which acquires the area gap between the tool and workpiece. The vibration tool impacts the abrasive material which ultimately impacts the worpiece and a reverse image of the tool is imprinted on the workpiece.

You know that ultrasonic machining process is a material removal process and can be categorized in three categories as per mechanism. The first one is hammering of the abrasive materials on the workpiece, the second one is cavitation due to erosion and chemical effect and the third one is micro chiping due to the sliding of the abrasive materials over the workpiece.

The rate of material removal process in ultrasonic machining process depends on many factors like physical properties of the materials, size and shape of the abrasive grains used in the slurry, process parameters, frequency, amplitude etc.

All the above factors play a major roll for material removal in ultrasonic machining and thus have significant effect on the surface roughness and dimensional accuracy. If the material is too hard and brittle then less material is removed.

Materials That Can be Machined through Ultrasonic Machining

Ultrasonic machining process has very wide range of engineering materials that can be machined. And why it is so, you already know the reason behind. However, I have to give few names in front of you which are mostly machined through ultrasonic machining so that you can easily recognize it. Following are the engineering materials that are machined by this process:-

• Glass
• Engineering ceramics
• PCD (Polycrystalline Diamond)
• Quartz
• Single crystal materials
• Ferrite
• Graphite
• Glassy carbon
• Piezoceramics

There are any more if I have not mentioned here then let me know. However, apart from the engineering materials ultrasonic machining process is also capable of machining wide variety of shape and sizes like round shape, square shape, holes and cavities with varying depths etc.

From as small as 0.008 inches to a very large workpiece can easily be machined through ultrasonic machining process. Aspect ratio can be more than 25-to-1 and depends upon the shape and size of the worpiece.

Advantages of Ultrasonic Machining

• All hard and brittle materials can be machined in ultrasonic machining
• High dimensional accuracy
• High surface finish
• There is no change in the chemical & physical properties and also the grain structure remain same throughout the machining process
• Cracks and defects can easily be detected whatever is the orientation
• Higher production rate

Disadvantages of Ultrasonic Machining

• Highly qualified and skillful operator and integrity is required
• There is no certified record of the inspection as that of in radiography
• Some steels like austenitic steel may mask defects due to large grain size of the welds
• Lack in the concentration may mislead the readings which can cause damage and need to be repaired

Other Engineering Applications of Ultrasonic

• Casting and welding of metals
• Measurement of velocity of moving fluids
• Forming of plastics
• Measurement of density, viscosity and elastic constants
• Measurement of hardness and grain size determination of metals
• Flaw detection, leak detection etc
• Nondestructive residual stress determination

This was a brief information about ultrasonic machining if you want some more information comment below

Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two.
Suspension systems serve a dual purpose — contributing to the vehicle's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and a ride quality reasonably well isolated from road noise, bumps, and vibrations.

The components of the suspension consist of:

• Tires
• Wheels
• Shock absorbers
• Mcpherson struts
• Springs
• Sway bars
• Torsion bars
• A arms
• Lower control arms
• Axles
• Alignment
• Tire pressure

The various components of the suspension systems of every vehicle are designed to counteraffect the forces of gravity and inertia! Even though every car is different, every system accomplishes the same objective:-

•  Keeping tires on the road surface. Engineers call this "road holding". It's important for the tires to stay in contact at all times, because friction between the tires and the ground is what lets the car accelerate, stop and corner. The suspension keeps the weight centered to maintain the grip.
• Stable steering and handling. The suspension keeps the car or truck body from tipping or rolling in a corner.
• Passenger comfort. Keeps the cabin isolated from the bumps on the road. Suspensions absorb that up-and-down energy and disperse it without too many bobbles.

     How does the Suspension System work?

The suspension system connects your vehicle to its wheels. It is designed to counteract the forces of gravity, propulsion and inertia that are applied to your vehicle as you accelerate, slow down or stop in such a way that all four wheels remain on the ground!

The tires - which are mounted on your vehicle’s wheels (or rims) - are the most important and visible components of the system. They transfer the power of the engine to the ground when your vehicle moves and they counter that motion when it stops.

As you drive over a bumpy road, shocks are absorbed by the combined work of a shock absorber (or damper) and a coil or leaf spring mounted on each wheel. The spring is a device that stores energy in order to supply it later on. It is actually the spring that handles the abuse of the road by allowing the wheel to move up and down with respect to the frame of the vehicle. In return, the shock absorber softens the suspension moves entailed by the spring by “absorbing the shocks”. The shock absorber is a steel or aluminum hydraulic cylinder filled with oil and pressurized with nitrogen. As the suspension moves, a piston is forced to move through the oil-filled cylinder. The energy produced from the motion of the piston is dissipated as heat which in turn is absorbed by the oil.

     Types of suspension system for independent system

• MacPherson strut type
• Double wishbone type
• Semi trailing arm type

MacPherson strut type :

This system is usually use for most widely in independent suspension system for small and medium sized cars.These type are so popular so in FF(Front engine and front wheel transmission)type of car,used as the rear suspension.
Characteristic for MacPherson: The construction of the suspension is relatively simple. MacPherson type,have small number of parts,so when it component is less,then less weight.The effects is unsprung can be reduce.

The space for the suspension is small,the usable space in the engine compartment can be increased. Since the distance between suspension support point is great,there is a little disturbance of the front wheel allingment due to installation error or part manufacturing error.Therefore, except for toe-in,allingment adjustment ordinarily unnecessary.

Double wishbone type:

This is usually used for front suspension for small trucks and for front and rear suspension for passenger cars. Characteristic for double wishbone: Wheels are mounted to the body via upper and lower arm. Suspension geometry can be designed as desired according to the length of the upper and lower arm and their mounting angles.

For example if upper and lower arm are parallel and have equal length,the tread and the tire-toe ground camber of the tire will change.As a result,it is not possible to obtain adequate conering performance.In addition, in the tread will cause excessive tire wear.

To solve this a design is normally employed in which the upper arm is made shorter than the lower arm so that the tread and the tire-to-ground camber of the tire fluctuate less.

Semi trailing arm type:-

Is used for the rear suspension in a few models.With this suspension,the amount by which the toe angle and camber change(due to the up-and-down motion of the wheels) can be controlled at the design stage, in order to determined the handling characteristics of the vehicle.

Signs of troubles related to the Suspension System:

• Excessive tire wear

• Poor steering control or off-center steering wheel

• Excessive bouncing over road bumps

• Loss of control during sudden stops

• Excessive swerving while changing lanes

• Front-end nose diving during quick stops

• Vehicle sag in front or rear

Carnot Cycle

Carnot Cycle

The Carnot cycle is an ideal reversible cyclic process involving the expansion and compression of an ideal gas, which enables us to evaluate the efficiency of an engine utilizing this cycle.

Each of the four distinct processes are reversible.  Using the fact that no heat enters or leaves in adiabatic processes we can show that the work done in one cycle, W = Q₁ - Q₃ where Q₁ is the heat entering at temperature T_H  in the isothermal process A -> B and  Q₃ is the heat leaving at temperature T_C in the isothermal process C -> D.

Remember, this is the ideal heat engine (reversible) efficiency.  It sets the maximum theoretically attainable efficiency of any real engine operating between the same two temperatures.

Be careful.  The temperatures in the ideal gas law must be in Kelvin, therefore the temperatures in the efficiency equation are also in Kelvin.

How spark plug works

How spark plug works

A spark plug  is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark.

Spark plugs have an insulated center electrode which is connected by a heavily insulated wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a spark gap inside the cylinder.
Internal combustion engines can be divided into spark-ignition engines, which require spark plugs to begin combustion, and compression-ignition engines (diesel engines), which compress the air and then inject diesel fuel into the heated compressed air mixture where it autoignites. Compression-ignition engines may use glow plugs to improve cold start characteristics

 

Spark Plugs and Spark Plug Wires                                                                                                                                                                     Spark Plugs deliver electric current from the ignition system to the engine to ignite the engine’s fuel and air mixture.

Bad spark plugs can cause a car hesitates, jerks, or shakes during acceleration or driving. If the spark plugs are new but you see incomplete electric spark, check on the spark plug wires 
If both the spark plugs and spark plug wires are working properly. You may have to check on the ignition system.
For car equipped with mechanically timed ignition (usually is older car), check on the distributor, ignition coil, both battery connectors, and all wires.

 Plug Types:-

Some cars require a hot plug. This type of plug is designed with a ceramic insert that has a smaller contact area with the metal part of the plug. This reduces the heat transfer from the ceramic, making it run hotter and thus burn away more deposits. Cold plugs are designed with more contact area, so they run cooler

The carmaker will select the right temperature plug for each car. Some cars with high-performance engines naturally generate more heat, so they need colder plugs.
If the spark plug gets too hot, it could ignite the fuel before the spark fires; so it is important to stick with the right type of plug for your car.