Bell Spigot Processing Issues

• Large diameter double wall bell forming requires the outer wall NOT to be vacuum formed into the cuff blocks until the inner wall & cuff air can assist in lifting the plastic into the cuff blocks – the indirect negative effect is that our vacuum pumps become highly inefficient during an approximate 10 minute timeframe – vacuum pump overheating and oil expulsion are the unfortunate side effects
• Thinning inner wall of the last corrugation prior to bell formation – this indirect negative effect is related to the purposeful ‘thinning’ of the bell’s wall – the thinning of the bell’s wall is required to ‘hover’ the plastic above the 2^nd stage outer caliper
• Rippled bell surface located where the gasket seats on the inner surface of the bell after one has assembled a bell and spigot – this is caused by purposefully ‘thinning’ the plastic in this area for process purposes thereby allowing the exterior bell stiffening ridges to create the rippling effect appearing on the inner surface of the bell – process related
• Bell thickening as one approaches the flared end of the bell – the thickening of the bell’s wall at the flared end is not intentional but is instead caused by the need to slow the cuff formation process down while initiating cuff air – this thickens both the inner wall and outer wall
• Bell flaring inwardly instead of outwardly – probably due to bell thickening – can cause gasket rolling issues when assembling pipes