| 摘要 |
The applications discloses a solution to the problem of sag in the extrusion of plastics pipes. It does so by employing a mandrel of non-circular cross-section. A computer simulation shows that the use of a non-circular mandrel can more precisely compensate sag than a simple mandrel offset as previously employed, thereby giving a finished pipe with more uniform wall thickness. Often it will be advisable to employ an offset together with the non-circular mandrel, to achieve an optimum result. The term non-circular is intended to refer to a profile which is continuously curved, with no edges; ie a deformed circular profile. A suitable shape is a egg profile. The mandrel may consist of interconnected portions 20, 22, 24 and 28 with only the final section 28 being non-circular. The sections may be interchangeable to vary the non-circular profile. |
