Ultrasonic Riveting Structure
standard rosette profile stake
The standard profile stake (Figure 1) is most commonly used for studs having a diameter between 1/8 and 5/32 inch (3.2 to 4 mm). The top of the molded stud is flat, and melt is initiated by the small, extended point in the horn cavity. The head produced is twice the diameter of the stud and satisfies the requirements of the majority of staking applications. It is ideal for staking non-abrasive (unfilled) thermoplastics, both rigid and non-rigid. Standardized threaded horn tips for tapped horns are available for studs with diameters of 1/32 to 3/16 inch (0.8 to 4.8 mm). The standard profile should not be used for studs more than 5/32 inch (4 mm) in diameter. Low profile or hollow staking should be used. For studs less than 1Æ inch, the dome stake (described below) should be used.
low profile stake
Low profile staking (Figure 2) is very similar to standard profile staking. It dif- fers in the height of the finished staked head. This reduction of head height (low profile) is advanta- geous in applications where space is limited, and it improves cycle times; however, it produces a lower strength stake.
The dome stake (Figure 3) is recommended for studs with a diameter of 1/8 inch (3.2 mm) or less, or where multiple studs are being staked. It is especially useful for very small diameters, or when the material is glass- or mineral-filled.
The knurled stake (Figure 4), available in both male and female patterns, is designed for simplicity and rapid rate of assembly, and is used when appearance and strength are not critical. There is no dimensioned horn cavity, and multiple stakes may be made without concern for precise alignment or stud diameter. A hand-held welding tool may be utilized.
For applications requiring a flush surface and having sufficient thickness in the contained piece to allow for a recess, the flush stake (Figure 5) is ideal. The tapered stud design used for dome staking is recommended, and a flat-faced horn or tip is utilized. Flush staking may be used for all thermoplastics.
The hollow stake (Figure 6) is generally used when studs are equal to or greater than 3/16 inch (4.8 mm) in diameter. Hollow studs offer advantages in molding, because they prevent surface sinks and internal voids. Staking a hollow stud produces a large, strong head without having to melt and displace a large volume of material.