7th week Ebubekir Çantı 030070154 part_II

1) Injection Blow Molding(new)(manufacturing)(better)

Injection blow molding combines injection molding with blow molding, thus

resulting in injection blow molding. The injection phase uses either a vertical

plastifier or a horizontal plastifier to take the thermoplastic resin from the

plastifier’s hopper and convey it into the heated barrel containing a screw

for mixing and melting the thermoplastic material into a homogeneous melt,

ready to be injected into a heated manifold. The heated manifold maintains

the homogeneous melt and distributes it to the injection cavities of the

parison injection molds. The parison  injection molds contain the parison

shape and are closed onto a metal core rod, which is centered in the parison

injection mold. The metal core rods are mounted onto the rotating horizontal

rotating table by retainers and a face bar. Once the homogeneous melted

thermoplastic material is injected into the injection parison mold, the injected

material is cooled so that the outside  skin of the injected parison will not

fracture on the opening of the injection parison mold. 

The injection parison mold is split evenly into halves and one half is

mounted to a stationary die plate and one is mounted to a movable die plate.

The bottom half of the injection parison mold is mounted stationary in

relation to the injection parison mold die plate. The heated manifold is also

mounted stationary in relation to the injection parison die plate. The injection

parison die stationary plate is mounted to the flat horizontal table by use of

die clamps and bolts, and the blow mold die set is similarly mounted at the

blow mold station. The top half or upper half of the injection parison mold

is mounted to the upper injection parison die set via holding screws and key

ways, and the upper half of the injection parison die plate is bolted to the

movable clamp, which travels upward for opening and downward for

clamping. This system is employed at the injection station and at the blow

mold station. On some of the injection blow molding machines, there is a

separate injection clamp and a separate blow molding clamp station. Other

machines employ only one horizontal moving platen, not separate clamps

for the injection station and the blow mold station. In this situation both the

upper one half of the parison injection mold which is mounted to the upper

die plate and the upper one half of the blow mold which is mounted to the

upper die plate are both mounted to this one movable platen.

 Practical guide to injection blow molding, Samuel L. Belcher, page: 6

Injection blow molding(old)

Injection blow molding is the result of the marriage of two plastic processing systems. The basis for injection blow molding is injection molding , which is the most common of all systems used to mold solid plastic articles. The molded perform from which the container is blown is formed by injecting molten resin into the preform mold. The resin is plasticated by the reciprocating screw of the injection molder.In injection blow molding , the melt is channeled through a small opening called sprue bushing. The melt is then forced under high pressure through a gate and into a mold cavity that is machined to have the shape of desired parison. However in the case of injection blow molding , this parison is called a preform.

(Plastics processing technology ; Edward A. Muccio ;pg :124 ; 1994)

3)Frequency(new)(system dynamics)


The frequency f is the number of complete oscillations that take place in
one second (the reciprocal of the period):

The unit for frequency is hertz (Hz). The angular velocity o is:

and is also known as the angular frequency, circular frequency, or radian
frequency. The projection of P on the vertical diameter is the point Q, which
moves up and down with simple harmonic motion:

Mechanical Engineer's Handbook, Dan B. Marghitu, page:341

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there is no old description
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4)Free vibration(new)(machine dynamic)(better)

Free vibration is encountered when a body is disturbed from its equilibrium position and a corresponding vibration occurs. However, there is no long- term external force acting on the system after the initial disturbance. When describing the motion of a vibrating body that can be modeled as a simple spring- mass-damper system, for example, free vibration results when some initial conditions are applied , such as an initial displacement or velocity, to obtain the solution to its homogeneous second-order differential equation of motion (Kreyszig 1983 ).

Free vibration is observed as an exponentially decaying, periodic response to the

initial conditions as shown in Fig. 1.1 . This periodic motion occurs at the system’s

(damped) natural frequency. We will discuss these concepts in more detail in

Sect. 2.4. A good example of free vibration is the motion and resulting sound of a

guitar string after it is plucked. The pitch of the sound (the natural frequency of

vibration) depend s on the string ’s length and diameter ; a shorter string produces a higher natural frequency for a selected diameter, while a larger diameter string produces a lower natural frequency for a given length. The pitch also depends on the tension in the string; tighter strings produce higher frequencies.

Mecha nical Vibrations Modeling and Measurement, Tony L. Schmitz-K. Scott Smith, page: 3

Free vibrations:(old)

This type of motion is characterized by an oscillation that occurs with a linear spring and mass system without any external force or excitation. The system is initially streched beyond a static equilibrium position and then released. Typical free-vibration problems provide the value of the initial displacement (deformation), denoted by x0, and require solutions for the amplitude, velocity, period, and/or natural frequency at a given time or position.

(Olia M., Casparian A. S., How to prepare for the fundamentals of engineering, FE/EIT exam, 1999, p. 91)

Semi-active actuators:

The power at the output port of the actuator can be expressed as a function of the conjugate variables as:

PTrans =F. v

for translational output mechanical energy, and:

PRot = T . w

for rotational mechanical energy.

Semiactive actuators are those whose output mechanical power is not positive: PTrans <0 or Prot <0. This means that the energy level in the plant is reduced. Semiactive actuators dissipate the energy of the plant they are coupled to.

Semiactive actuators can actively modulate power dissipation, but the effort they supply (whether a force or a torque) can only oppose the flow in the plant (whether a velocity or an angular rate)

(Pons J. L., Emerging actuator technologies: a micromechatronic approach, Ed. 1st, p. 33, 34)

5) Forced Vibration(new)(machine dynamic)(better)

In this case, a continuing periodic excitation is applied to the system. After some initial transients (i.e., the homogeneous solution to the differential equation), the system reaches steady state behavior (i.e., the particular solution). At steady state, the system response resembles the forcing function and the vibrating frequency matches the forcing frequency .A special situation arises when the forcing frequency is equal to the system’s natural frequency. This results in the largest vibration magnitude (for the selected force magnitude) and is referred to as resonance. Unlike free vibration, where the response of the system to the initial conditions is typically plotted as a function of time, forced vibration is most often described as a function of the forcing frequency. See Fig. 1.2 , where the peak corresponds to resonance.

Rotating unbalance represents a common type of forced vibration. Consider a

wheel/tire assembly on an automobile, for example. If the mass of the wheel/t ire is not distributed evenly around the circumference, then a once-per-revolution forcing function is produced by the unbalance d mass. This periodic forcing function (whose frequency depend s on the rotating speed of the wheel/tire) can serve to excite one of the car frame or drive train natural frequencies and can lead to significant vibration magnitude. For this reason, it is common practice to balance wheel/t ire assemblies before installing them on a vehicle. We will discuss rotating unbalance more in Sect . 3.5.

Mecha nical Vibrations Modeling and Measurement, Tony L. Schmitz-K. Scott Smith, page: 4

Forced vibrations:(old)

Vibrations are usually classified as free or forced. In the case of forced vibration, the body is subjected to external force functions that make it vibrate with the frequency of the exciting force. An alternating external force system may arise as a consequence of many natural phenomena such as waves, sound, blast, earthquake, and heavy vehicular traffic on highway pavements and bridges, as well as from any mechanically produced causes. In each case the wave motion of the disturbance will vibrate a structure at the frequency of the oscillating force. A condition of resonance will occur if the frequency of the applied force system coincides with one of the natural free frequencies of the body. At the resonant condition the amplitude of vibration will approach infinity with time. In practical situations, however, the amplitude of vibration may exceed allowable values in a short period of time, with the subsequent loss of structural integrity.

(Fertis D. G., Mechanical and structural vibrations, 1995, p. 9,10)