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SPRING 2013

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Distributor's Link Magazine Spring Issue 2013 / VOL 36 / NO.2

138 THE DISTRIBUTOR’S

138 THE DISTRIBUTOR’S LINK HEAT VERSUS ULTRASONIC INSTALLATION continued from page 64 General Descriptions Ultrasonic Installation - An ultrasonic insertion machine converts electrical power into a mechanical vibratory output. The downward force is typically provided by a pneumatic cylinder while ultrasonic horn delivers mechanical energy to the metalplastic interface. Ultrasonic horns (manufactured from various metals including titanium alloys, stainless steel and aluminum alloys) directly contact the metal Insert. As the horn vibrates, the mechanical energy is transferred to the plastic surrounding the Insert creating heat – and ultimately the melting – necessary for insertion. Heat Installation - Heat insertion of Inserts is accomplished by transfer of heat from the heated tip through the Insert to the plastic, or by preheating the Inserts and then pressing them in. In both cases, a controlled force is applied to the Insert to ensure that the plastic is sufficiently melted before the Insert is installed. Since heat installation requires heating the entire Insert and not just the metalplastic interface, the Insert material should have excellent thermal conductivity (brass and aluminum are common choices). This enables the Insert to efficiently transfer heat to the plastic. (It also enables the Insert to cool down quickly after installation). Once the plastic reaches its melting temperature, it begins to fill the retention features of the Insert and then solidifies while inducing minimal stress. Primary Features, Benefits, and Limitations of Ultrasonic and Heat Insertion Due to faster insertion and shorter cooling time, ultrasonic insertion typically has a shorter cycle time than heat insertion when installing a single Insert that has not been preheated. However, heat equipment that preheats the Insert will have comparable installation time as compared to ultrasonic equipment. In addition, when installing multiple Inserts simultaneously, heat insertion will offer faster throughput. ADVANTAGES OF ULTRASONIC INSTALLATION • Short cycle time for small Inserts. Ultrasonic installation is generally fast for smaller Inserts (under 1/4” OD), and slows as the Insert size increases. • Can be repurposed. Ultrasonic machines are often re-utilized, or converted from an initial plastic-to-plastic welding process to Insert installation. • Interchangeability. Horn sizes and shapes can be easily changed to accommodate different Insert sizes. DISADVANTAGES OF ULTRASONIC INSTALLATION • Insufficient melt. – Poor fixturing/clamping of components often times results in cold pressing the Insert. This happens because of damping, which refers to the dissipation of mechanical energy. The damping effect results in poor installation because the mechanical energy is not being localized around the Insert. – When Inserts are driven too quickly, the plastic does not have time to fully melt. This is a common problem with ultrasonic insertion that often causes high stress and poor retention within the plastic that can lead to part failure. Failure can happen during installation, but the worst case scenario is when failure happens in the field. – The vibratory forces applied via the horn are difficult to control and sometimes parts are forced into the hole before melting has occurred at all. Damage to the Insert or the plastic host can be severe. While sophisticated control systems can help solve this problem, they can nearly double the cost of an already expensive ultrasonic insertion machine. – Slight size variations of the Insert and/or hole can be enough to cause insufficient melt – even when the speed of the insertion is slowed down. • Metal particulates and flakes. Metal particulates and flakes may appear when the ultrasonic horn vibrates against the Insert and chips off the Insert material. please turn to page 144

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