Part 2: Pinchweld Preparation

There was an interesting discussion recently that I thought I would bring up for readers to debate. The discussion is about the condition of the existing urethane bead once the glass is removed by the new wire-out tools. It seems that there is a belief that the bead is already trimmed to the proper height due to the design of the wire-out tools and that additional stripping is unnecessary. Also, there is some concern regarding the rough condition of the urethane bead when the new cord is used in the cut out. This brings to mind two questions.

Does the existing urethane bead need to be trimmed down or is the bead height adequate for bonding immediately?

What is the ideal surface for urethane bonding to itself, smooth or rough?

One of the selling points of the wire-out tool is that the existing urethane bead is cut closer to the pinchweld surface. This allows the technician to save time by not having to trim back the urethane bead for bonding. The directions given by adhesive manufacturers have been to trim back to 1-2 mm or 1/16” of the existing adhesive bead. The amount of bead left by the wire out tool depends on the design of the tool. The closer the wire is to the interior glass surface the closer the cut will be to the pinchweld. You will need to trim it back if there is more existing bead left by your particular tool. Remember that the 1-2 mm guideline is there for a reason and must be met as close as possible to the recommendation by the adhesive manufacturers.

There are basically two types of cut out material for the new wire-out tools, the wire or the cord. The wire cuts out the glass and leaves a smooth surface on the existing urethane bead. The cord usually leaves a rough surface. The smooth surface left by the wire is not a concern because we have been bonding to that type of smooth surface ever since we started to use urethane. The question that needs to be answered is what should be done with the rough surface left by the cord to promote adhesion?