Granco Clark unveils a new controlled vertical crush stretcher of novel design

To meet the continuously higher quality expectations of the extrusion customer, a closer look is being given to each of the components in an extrusion line. The aggressive jaws of stretchers often create additional scrap by distorting the cross section of profiles along their length. This is particularly true with large circle size, thin wall profiles. Sophisticated stretchers are available which perform a controlled vertical crush, but they incur additional price.

Granco Clark has developed a novel approach to the design of its controlled vertical crush stretcher (CVCS). The key difference between Granco Clark’s model and other stretchers on the market is the motion of the stretcher’s upper jaw.

The CVCS features a hydraulically-controlled pivoting upper jaw that can be set to any closing dimension, minimizing the distortion that can be caused by traditional jaw designs. For example, if stretching a 6" high extrusion, the operator can elect to crush to 3" from the lower jaw, eliminating much of the distortion that would be caused if crushed fully to the lower jaw.

The same principle governs the opening dimension of the CVCS. The home position of the upper jaw can be set to accommodate any extrusion height. If running extrusions that are not very tall, the upper jaw does not need to travel fully open, saving time on each stretcher cycle. When maximum gripping is required, as when stretching solid bar stock, the upper jaw can be set to fully pivot until the desired upper jaw hydraulic pressure is reached. This assures that maximum crushing force is exerted, preventing slippage.

The “up and back” motion of alternate stretcher designs can occasionally result in the extrusion “sticking” in the teeth of the jaw. Because the CVCS facilitates a virtually vertical motion, the extrusion does not get “hung up” in the teeth of the jaw — eliminating operational delays and manual intervention.

Our CVCS, with its simple pivoting jaw design, is easy to maintain. Reliability is enhanced because the clamping cylinder is not subjected to perpendicular forces. The streamlined construction utilizes readily available components, and also makes it more affordable than other controlled vertical crush designs.

For additional engineering and performance specifications, contact Granco Clark at (616) 794-2600 or via e-mail at gcinfo@grancoclark.com.