It is a known fact that applying a specific amount of heat to plastic resin using a heated tool will change the characteristics and shape of it, but did you also know that fine tuning the temperature and dwell time it takes to heat that resin can lead to stronger and more cosmetically appealing welded parts?
There are several myths regarding thermal heat staking and tricks to establishing quicker, stronger, and more cosmetically appealing thermal heat welded parts. Here are a few examples:
Myth 1: Post cooling a thermal tip is required on all resins to reduce or eliminate stringing and over welding of a stake or swage.
The Truth: Post cooling only needs to be introduced in a heat welding process when resins, such as Acrylic, are used that require quick cooling.
The Trick: Fine-tune the temperature below the actual resin processing temperature by making very slight changes of 10°F at a time. Each time a temperature change is made, wait 15 to 20 minutes for the changes to take effect in the heated tip. The dwell or (weld time) will need to be adjusted as well to prevent the resin from stringing or burning.
The use of a dual pressure thermal heat staking machine can also eliminate the need for post cool. This feature allows the post to be heated at a lower temperature with a small amount of pressure for a programmed time. After a small amount of time, a greater amount of pressure is applied during the dwell time, collapsing the resin with minimal amount of heat and no post cooling.
Myth 2: Large percentage glass filled or chrome plated studs lack strength and cosmetic appeal after heat staking.
The Truth: Even resins with fillers and coatings can look esthetically pleasing.
The Trick: Use a Pre-Heat to slowly heat up a stud that is to be staked. The resin starts to melt where the glass or chrome plating will not. After the Pre-Heat times out, an appropriate amount of dwell or (weld time) will fully collapse the stud with the correct amount of force applied. This will melt the remaining resin while the glass or chrome plating act as a shell to hold the resin together without melting.
Sr. Project Engineer
Dukane Corp. IAS