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Clinching:

Clinching is a joining procedure by forming for connecting sheet metals and profiles. At a first glance, the connecting technology in clinching looks similar to the self-piercing riveting with a similar goal. The difference is, however, that when clinching without additional or auxiliary joining elements non-detachable connections are manufactured by local cold forming. The main feature of this joining technology consists in the fact that the form-looking connection is formed out of the material of the partners to be connected.

A characterisation of the clinch joining processes is possible

1- after the joining part formation: clinching with and without cutting portion

2-after the kinematics of the tool parts: single-and multi-stage clinching

In clinching with cutting function the part to be joined comes under local effect of a comined shearing and clinching procedures and a cold upsetting procedure The sheet metal material shifted from the sheet metal plane is upset so that through widening a force form-locked connection results. Clinching and cutting limit the joining procedure.

In clinching without cutting function a force- and form-locked connection is created in a combined hobbing and clinching procedure (hobbing limits the joining area) as well as a cold upsetting procedure (the clinched material volume is upsetted). For the single- and multi-stage clinching without cutting function appropriate tool systems with and without movable die parts were conceived. While during the single-stage with moving die parts different material flow behaviour of the joining parts is achieved by the deformable lamellaes, this effect, relevant for the formation of a undercut, can be realised in single-stage clinching without moving die parts by an appropriate ring channel in the die.

(Production of Profiles for Lightweight Structures, S. Chatti, p.205)

Injection molding of Thermoplastics:

When thermoplastics are heated, they experience a change of state; they turn soft and melt, becoming flowable. When cooled down, they solidify again. This is the reason that plasticating units are operated hot and molds are operated cold when working with thermoplastics. Generally, the temperature difference is more than 100 C. The thermoplastic materials developed for injection molding generally constitute relatively low-viscosity melts result that injection times are short and low clamping forces are needed.

The injection mold should remove the heat from the material fast and steadily. Therefore, the cooling system has to be carefuuly designed. The coolant-usually water, provided the mold temperature is below 100 C - flows through channels around the cavity. For reasons of economics, such as the quality of the molded parts, which depends heavily on uniform heat flow in the mold, the cooling circuit is monitored very precisely and cooling equipment is used to ensure that the coolant is always at the same temperature.

Molded parts requiring no machining can only be produced if all joints and mold parting lines are so well scaled that is unable to penetrate and harden there. Otherwise, flash would be formed and machining become necessary. To this end, all joint gaps must remain smaller than 0.03 mm even during full injection pressure, until the melt has solidified. These requirements are particularly demanding where large molded parts and large injection molding machines are involved as the molds must be extremely rigid and the clamping units must function very precisely; the rigidity of clamp plates is particularly critical.

(How to make injection molds, Georg Menges, Walter Michaeli, Paul Mohren, 3rd Edition, p.107)

Elastic modulus:

The modulus of elasticity, or Young's modulus (E) is the slope of the stress-strain curve in the elastic region. The relationship is Hooke's Law:

E = σ/ε

The modulus is closely related to the binding energies. A steep slope in the force-distance graph at the equilibrium spacing indicates that high forces required to separate the atoms and cause the material to stretch elastically. Thus, the material has a high modulus of elasticity. Binding forces, and thus the modulus of elasticity, are typically higher for melting point materials. In metallic materials, modulus of elasticity is considered a microstructure insensitive property since the value is dominated strongly by the strength of atmoic bonds. Grain size or other microstructural features do not have a very large effect on the Young's modulus. Note that Young's modulus does not depend on such factors as orientation of a single crystal material. For ceramics, the Young's modulus depends on the level of porosity. Young's modulus of a composite depends upon the stiffness and amounts of the individual components.

Young's modulus is a measure of the stiffness of a component. A sitff component, with a high modulus of elasticity, will show much smaller changes in dimensions if the applied stress is relatively small and, therefore, causes only elastic deformation.

(The science and engineering of materials, Donald R. Askeland, Pradeep Prabhakar Phulé, 5th Edition, p. 198)

Critical to Quality (CTQ):

Critical to quality is another quality coomunication method to improve the understanding of your customer's needs and wants. Determining what the customer really needs and wants is a step above most companies' involvement in obtaining information and using it to increase their business growth.

CTQ represents the key measurable characteristics of a product or process whose performance standarts or specification limits must be met to satifsy the customer's (interna or external) wants. They combine design and manufacturing improvement efforts with customer requirements. They may include the product's attributes or specification limits plus any other factors related to the product. A CTQ is often interpreted from a customer qualitative statement to an action and a quantitative business need or specification. CTQs align improvement or design efforts with customer requirements.

CTQ products are what the customer expects of a product through its communicated needs with a supplier. The customer should list and express its needs in plain language, and it is up to the supplier to convert them to measurable terms using quality methods such as design failure mode and effects analysis

(Total Quality Process Control for Injection Molding, M. Joseph Gordon Jr., 2nd Edition, p.66)