| 摘要 |
<p>Thermoforming tools comprise a punch which is drilled to discharge a pressurised gas between the face of the punch and the thermoplastic sheet during deformation of the sheet so as to reduce contact between the punch and the sheet draw angle around the edges of the face of the punch. Arrangement is used for forming hollow mouldings from materials having a high elongation to break (e.g. 700%), esp preprinted blanks where controlled deformation of the blank is essential to obtain the required print pattern on the formed moulding. The sheet material is subject to lower drag forces and cooling rates during deformation than if in contact with a metal punch surface. Gas exhaust keeps the cavity purged of dust or fumes.</p> |
