Spectacle frame components

Spectacle frames have developed into a major segment for metal injection moulding because this technology offers new design options. Two examples are described here.

The rotating spring hinge shown in Fig. 15 provides the articulation to the spectacle temple. An entirely new and revolutionary hinge design was created by star designer Ross Lovegrove. This original metal injection moulded design cannot be manufactured economically by other technologies.

The hinge is composed of two rotating discs at an angle of 27° that swivel the spectacle temple with a spring effect. These parts weigh-ing in at 2.6 g are made from 316L stainless steel, polished and nickel coated.

The innovative fixing element for rimless spectacle frames shown in Fig. 16 enables the interchangeability of bridge and temples of the spectacle. The idea is to allow the user to change the design of his spectacle without having to purchase new glasses. All that is needed is another pair of temples and a bridge. The frame elements can be interchanged with a simple push and pull. A new spectacle is assembled with a click. Four stainless steel pins weighing 0.15 g each are the basis of this design. They are manufactured by MIM and subsequently polished. These elements are directly fastened to the glasses. They are made from 17-4PH hardenable stainless steel and feature a M1.2 thread.

Automotive applications

The automotive sector has become a major consumer. Metal injection moulded parts of high complexity are used in ignition locks, as gearbox components, in the steering, in engines, in sensors, car seats, turbochargers, convertible bonnet driving and locking mechanisms, etc.

An example is the roller following type rocker arm shown in Fig. 17. This rocker arm for engines with a variable valve stroke is made from low alloy steel. It features a hollow configuration saving weight which is difficult to achieve by other processes. The variable valve lift enhances the engine performance and reduces fuel consumption.

Two sizes of the car door safety-catch (Fig. 18) are produced which are used in the manufacturing process of passenger cars. During the transport of the car body through the various varnishing processes the doors, which are already attached to the car body, are held in a certain position by these components. Polymer parts are not strong enough for the high loading.

The part weights are 4 and 5 g, respectively, they have external threads and a cross bore. The material is MIM-Fe2Ni0.5C sintered to a density of 7.55 g/cm³ and a hardness of 140 HV. They are produced at quantities of more than 100,000 parts per year.

The injection nozzle exhibiting a wedge shape (Fig. 19) is used in the stabilisation of cracked concrete structures. Several nozzles are driven into the concrete on both sides of the crack, then the surface of the crack is sealed with adhesive tape and epoxy resin is injected into the gap through the nozzles.

These parts weighing 5 g feature a 0.8 mm bore and a 5 mm inner thread. The material is MIM-100Cr6, vacuum sintered to a density of 7.55 g/cm³, and gas nitrocarburized with subsequent oxidation for a surface hardness of 830 HV. Production quantities are currently at more than 100,000 parts per year.

Continue to next page: Applications for metal injection moulded products, Part 3