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Several months ago, while spending some time in our Innovation Group, one of our company’s founders (or I can say engineers) asked me to come and take a look at something. Standing in our innovation area, Chip walks me over to a workbench where I see an unassuming setup with a small pneumatic cylinder which holds a pencil-shaped device, only shorter. It’s small with what appears to be undersized wires and a hose coming out of the top. It’s hovering over one of Extol’s plastic test coupons which I’ve staked or riveted using ultrasonic and InfraStake modules hundreds, if not thousands of times. Nearby there is a start button waiting to be pushed.
When welding parts in production, you want to have reliable and consistent assemblies. You may have been churning out ‘good’ parts for years, but suddenly you are finding part inconsistencies and failures when none of your parameters have changed! What happened?
The origins of the verb “trend” mean “revolve or rotate” which has become “change or develop in a general direction”. It is appropriate that we discuss trends with respect to the auto market as the wheels revolve and the axle rotates, so do the trends change. Jabil recently commissioned a survey of the automotive and transportation industry seeking to understand trends from OEM’s and Tier 1’s in this market sector.
The moment is here, the process is set, the machine has cycled. How does it look? “GASP!” My staked part has FLASH!!! If you are not familiar with flash, I’m referring to the displaced plastic material from a staking or welding process that extrudes outwards and does not contribute to the strength of the joint. Flash may be observed as fine dust surrounding the joint, thin strands of plastic material in a disorganized clump, or even smooth rounded material adjacent to the weld joint. So why does flash occur in plastic staking and how can you optimize stake appearance?
Recently, we’ve been discussing conventional vibration welding and hybrid or ‘clean’ vibration welding. Vibration welding, a linear frictional weld method, you probably know all about. Hybrid – the introduction of an infrared preheat function prior to the conventional vibration weld process, is a relatively new method of welding plastic parts.
A quick review: The intent of the IR preheating prior to the introduction of frictional energy is fairly obvious – elevate the temperature of the weld joint. The anticipated result of this preheating is improved flash (plastic displacement from the joint) control and the potential in certain applications to reduce the necessary amplitude and/or force to achieve the ideal weld performance and assembly appearance.
Occasionally people will confuse vibration welding and ultrasonic welding because both processes use vibratory energy to weld plastic assemblies. However, both processes are very different from each other. Let’s look at the differences between the two processes and how you can use them to your advantage.