Posted to News on 27th Aug 2013, 10:57
Infra-red heating solves plastic filter housing welding problem
Two of the largest Omega infra-red emitters ever manufactured by Heraeus Noblelight have helped the International Plastic Welding Consultancy (IPCW) to provide an important client with a more efficient, productive and precise approach to the welding together of two large diameter plastic halves of a swimming pool filter housing. The emitters are fitted within a custom-built system, which was purpose-designed for a South East Asian client of IPCW.
Pipes, tubes and vats are typical of the plastic containers which are joined together by heating and softening the exposed rims of the two injection-moulded half-shells and then bringing these two halves together under pressure to effect a fusion welding. Polypropylene filter housings for swimming pools are manufactured using this method, but they present an additional challenge as, when they are installed, they are readily visible to users of the pool, so the weld joint needs to be optically perfect.
These large, thick-walled and pressure-resistant filters had formerly been assembled using a welding system with resistance heating elements in an aluminium block with a Teflon coating. The heating elements were pneumatically swivelled in and out of position. However, the polypropylene, which flows easily when melted, tended to stick on the heating element, so that quality and speed of production could no longer meet the increased production requirements. Consequently, a more efficient approach was sought.
This was provided in a custom-built welding system designed by Dr Uwe Egen of IPCW. It features two 61cm diameter Omega infra-red emitters (so-called because they are in the shape of the Greek letter omega), each emitter being fitted with a 180 degree gold reflector, so that emitted heat is precisely targeted. In operation, two Omega emitters are swivelled into position to project their radiated heat onto the rims of the half-shells. After they have sufficiently melted the plastic rims, they are swivelled away so that two halves can then be fused together.
An intelligent control system, which was fitted in the existing control cabinet, helps to maintain an intensity/time profile. Combined with the correct welding pressure, this ensures an optimum welded joint.
Dr Egen comments: "The infra-red system has replaced the contact heating elements, so that now we have much shorter cycle times. However, the main advantage of the infra-red technology for me is that the two halves can be precisely centred. Infra-red heats without contact, so there is no longer any possibility of contact surfaces sticking together and then shifting out of position."
To learn more about Omega infra-red emitters from Heraeus Noblelight, pleae go to the website at www.heraeus-noblelight.com.
