TECHLONE January 1998
TECHLONE January 1998
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What are stress cracks?
Stress cracks are breaks from the edges of laminated glass, such as a windshield, that
happen without an impact point or noticeable damaged area. While this phenomenon can
occur with seemingly no apparent cause, there are however, two major factors that have a
role in creating stress cracks. The stress crack can be caused by a manufacturing defect
within the glass or it can be attributed to the installation methods.
How do glass defects cause stress cracks?
Stress cracks can occur if the two plies of glass used to make the laminated part are not
completely homogenous with each other. Stress cracks can be a condition of tension or
compression that exist within the glass. Stress can also be caused by incomplete
annealing or temperature difference between the plies. Manufacturing processes include
multiple quality check points for every individual part during production to identify and
eliminate defective parts. Even so, it can be difficult to predict a stress crack due to
manufacturing conditions.
How do installation methods cause stress cracks?
Installation related cracks usually result from a short cut out method, where all of the old
urethane bed is not removed prior to installation. If the shape and form of the new glass is
not identical to the old urethane bed, the glass could have spots of interference on the
adhesive that lead to breaking. Installation related stress could also be formed by using
adhesives that are too rigid and don’t offer the compression and flexibility required of the
adhesive system. Usually, installation related stress cracks would develop over time after
the adhesive has been allowed to fully cure.
Why can’t I get the LOF OE Chevy / GMC truck slider anymore?
LOF stopped producing the Chevy I GMC truck slider, part number DB8317, for OE two
years ago. There are over 20 individual components required in one slider assembly with
multiple suppliers for all the individual components. When the LOF manufacturing plant
exhausted their supply of components late last year, it was discovered that the components had to be reordered in lots of 20,000. That volume of components would
have represented more than a 5 year supply of parts. Unfortunately, the decision was
made to stop making this popular slider. However, the plant is trying to negotiate smaller
order quantities of components. If they are successful, we could see this part again in our
offering.