Shrink fixture

Cooling fixture (shrink fixture) n. A structure of wood or metal shaped to receive and restrain a part after its removal from a mold, so as to prevent distortion of the part while it is cooling. 

Shrinkage and porosity data for one of the compositions tested, are presented in Fig. 6. The substrate is porous for coatings. Extruded ware from this composition shrinks by 0.5% between 600 and 1000°C, a value smaU enough that it may be accounted for via other engineering solutions (e.g., usage of compressible materials as fixture supports ). Thus, ware fired at 600°C may be used up to an operating temperature of 1000°G. 

Residual stress (frozen-in stress) n. Stress remaining in a part that has been chilled quickly during or after molding, extrusion, or forming. It remains because there was too little time for the stress to relax while the material was soft. Over time, high residual stress can cause parts to warp and shrink. It can be relieved and rendered harmless by annealing residually stressed parts while restraining them in fixtures. 

Fig. 16.1 Schematic illustration of an airtight hexagonal cell and electrodes designed for electrochemical measurements in ILs. (a) Vacuum fittings, (b) PEA body, (c) Fixture (stainless steel), (d) O-ring, (e) Cover glass, (f) Cu rod, (g) Heat shrink tube, (h) Pt disc, (i) Glass tube, (j) Ag wire, (k) Inner IL containing Ag(I), (1) Vycol (porous) glass, and (m) Pt wire...

Preferably, aluminum castings are used with drilled or milled cooling channels. Care must be taken to clear the flash area to ensure that the fixture can close properly. The cavity dimensions must have reduced shrink allowances that is, the cavity of the fixture must be smaller than the blow cavity. 

So that large inserts, especially those with closely toleranced centres, may be quickly cooled to allow the moulding material to shrink to its final dimensions, it is sometimes necessary to cool the fixture with water. This may be by means of sophisticated cooling holes drilled or cut into the fixture but an alternative is to clamp the hot moulding into its fixture and then immerse the complete assembly into a large container of water. Both of these methods using water are considered rather messy and damp but are usually effective as long as the water is not allowed to heat to any appreciable temperature. 

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