FASTENING

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GUIDELINES:

Thermoforming allows for molded in inserts or bosses. Many different types of fasteners are available to be added to the part after molding and trimming. Avoid the bonding of blocks, this adds cost to the part.

OVERVIEW:

Fastening is one of the most difficult issues to resolve in the design of thermoformed parts. This is because it is not possible to mold in a boss or insert without it being visible on both sides of the part.

SPECIFICS:

Molded in inserts allow for one of the most cost effective ways of installing fasteners because the molding process does all the work. The only added cost is for the insert; the part will take just as long to form whether there is an insert in it or not. The sheet is the "adhesive" that secures the fastener. There is no need for glue or sonic welding of the insert.

Using bonded PVC blocks with a brass insert can also be done, but there is a cost tradeoff. The cost of the PVC, the labor to bond it in place, the cost of the adhesive, the labor to machine the block to the correct height and add a hole for the fastener or insert, all are significant. Add to this the greater probability of a lower yield rate due to the number of additional operations. The simplicity of a molded in insert has real advantages.

There are a number of fasteners that work well with thermoformed parts. A qualified thermoformer should be willing to assist you in working out the fastening requirements of your parts.