Written by Priyank Kishor
Global Product Manager for Pulsestaking for Branson at Emerson
Plastic swaging and staking technology is a widely used, low-cost method for connecting or “capturing” components made of many materials to plastic-based parts. Typical staking and swaging processes include heat staking, thermal insertion, or the embedding of fasteners in plastic parts, and the bonding of fabrics, panels, or membranes to plastic parts.
For years, two staking technologies have been predominant — thermal staking and ultrasonic staking. But now there’s a third, highly versatile process option called “pulse” staking.
Developed by HTE Engineering Services Ltd. (Dunboyne, Ireland), which was recently acquired by Emerson, PulseStaking technology not only accomplishes all of the same staking and swaging tasks as existing heated-tip and ultrasonic technology but also allows for more diverse and complex product designs, is gentle to electronics and circuitry, and bonds a much wider range of plastics than ever before.
Although his technology has been used in Europe for about a decade, little is known about it in other areas of the world.
The PulseStaking process employs innovative tips that combine an electrical heating element with a compressed-air cooling system, as shown in Figure 1. This design enables the process to apply instant “pulses” of heating or cooling to precisely manage the temperature of the plastic as each stake or swage is formed — a unique advantage compared to conventional tooling that operates at a fixed temperature.
The PulseStaking cycle
PulseStaking technology completes swages or stakes using a programmable cycle that applies multiple user-selectable pulses of heat or compressed-air cooling, with each pulse followed by a brief pause to promote even temperature conduction in the surrounding plastic to prevent overheating, burning, or stress.
A typical cycle is shown in Figure 2. The first heat pulse/pause (dwelling) is used to insert the tip and form the plastic, while the second pulse/pause (welding) welds other materials. These are followed by an initial cooling of the near-finished shape. The third heat pulse/pause allows for tip removal without sticking, after which the finished shape is re-cooled.
The unique characteristics of PulseStaking technology enable it to perform all of the same types of stakes or swages as previous technology, often with a higher degree of aesthetic consistency and quality. However, the greatest strength of the technology is its ability to process parts and applications that were difficult or impossible with previous technologies, including:
- Complex 3D part designs with varied surface contours and multiple, closely aligned post or flap features
- Parts made with any of a growing number of advanced, blended, glass-reinforced or chromed/metallicized plastics
- Parts that must capture fragile or heat-sensitive components (weaves, filter elements, fabrics, ceramics, metals)
- Parts that must capture and hold delicate, heat- or vibration-sensitive electronic components such as printed circuit boards, soldered components or sensors
PulseStaking technology offers advantages for working with complex, contoured, and closely aligned part features because of the unique tip design.
Unlike traditional tips, which radiate heat at all times, pulse tips are independently and instantaneously heated and cooled and localized in their heating effect. Therefore, pulsing tips can be positioned much more closely and in more complex configurations than traditional heated tips.
Also, because pulsing tips heat up only during their short operating cycle, there’s no risk of unintended radiant heating, even if tooling or tips pass very close to non-target surfaces.
The ability to vary tip and plastic temperatures within a staking or swaging cycle enables the PulseStaker platform to deliver superior particle-free and cosmetic results for a wide range of materials, including materials with levels of glass fill exceeding 30%.
For example, glass fibers tend to stick to traditional thermal tips and pull away from a finished stake when the tip is removed. However, a pulsing tip can first melt/form/cool a finished stake, then pulse a different, lower temperature to release the tip without sticking.
Compared to other forming technologies, PulseStaking technology can also join a wider variety of different materials to plastic components or housings, including metal shims; plastic keys or buttons; filters, fibrous cloth or insulating materials; printed circuit boards, electronics or sensors; and fragile glass or ceramic elements.
Beyond the realm of current applications, the flexibility and versatility of PulseStaking technology open up a variety of new part design and production options.
First, heating tips are available in many standard and custom shapes (e.g., domed, rectangular, lozenge) and can be operated singly or, if production and cycle times require, densely grouped into larger tools capable of performing many forming operations simultaneously on a single part.
Secondly, the localized heating characteristics of each tip enable swaging or staking operations on angled or geometrically complex part surfaces and access to deep cavities or other difficult-to-reach areas.