A daunting array of options faced one of the world's leading aerospace operators recently when it confronted a tough plastics joining job. So it turned to TWI for a helping hand in assessing the field.
It needed to make a large plastics jig, not necessarily capable of withstanding heavy loading, but specifically capable of handling pressures up to 1.5 bar, and able to withstand being dropped.
The choice of joining techniques was wide. Seventeen known processes presented themselves, from those using an external heat source like hot plate welding, to those where heat is self generated like spin welding, and finally to those using electromagnetism like induction welding.
Two objectives were specified; first to perform a survey of suitable methods for joining two particular polymers. This was to include financial and ease of application comparisons. Second TWI was asked to recommend the most suitable joining process for uniting the polymers.
Hot plate welding, hot bar welding, impulse welding, hot gas welding, extrusion welding and flash free welding all came under the TWI spotlight in the category 'external heat source supplied'.
Under category two, 'heat generated by mechanical movement' vibration welding, spin welding, orbital welding, ultrasonic welding and friction stir welding drew the scrutiny of TWI's plastics specialists.
Lastly they turned their collective process skills to those methods using electromagnetism namely, resistive implant welding, induction welding, high frequency welding, laser welding, infrared welding and microwave welding.
The 17 processes, along with appraisals of their suitability, were presented to the client in tabular form with the recommendation to use hot gas welding. Second and third less attractive options were also suggested Polyphenylsulphone, the material in question, is rarely welded and requires a high gas temperature and specific filler rod of the same composition.
As a direct result of TWI's recommendations the client has now requested further work related to establishing both the tensile performance of the joints and the most appropriate welding procedure. TWI has also offered to supply operator training.
For information about TWI's capabilities please contact us.