Norgren Collateral

Manifold Assemblies 11 The multiple layers of laminated manifolds need to be bonded securely to create a single integrated unit. To some extent, the method used will depend on the end use of the manifold. There are four methods commonly used to bond the layers of laminated plastic manifolds. Multilayerd bonded manifolds help simplify your most complex fluidic challenges Solvent Bonding In this method, the material is immersed in solvent to soen it and then the layers are pressed together. The solvent essentially puts the material into suspension, so when the two layers are pressed together and the solvent dissipates, what is le is a single solid piece of plastic. While this protects the integrity of the material, it is quite difficult to control the manifold's dimensional stability in this process. While the two parts to be bonded are in the suspension phase, they can slip against each other, moving the flow paths and other internal features out of alignment. Imprecise bonding can contribute to the carryover and retention of contaminants and debris. Finally, air trapped between layers reduces the visual clarity of the manifold, eliminating one of the key advantages to using plastic. Adhesive Bonding Here an adhesive interacts with the material of both layers. As it cures, it bonds the layers together. This introduces another material into the unit, which can raise compatibility issues. For example, if the adhesive has a different coefficient of thermal expansion or if it is stronger or more elastic than the plastic substrate, it can put stress on the surface. It is also difficult to control dimensional stability when adhesive bonding, as the thickness of the glue joint can vary or even leave voids. And as the parts being bonded are compressed there is a risk the adhesive will be pressed into the channels, changing their shape and size. Thermal Diffusion Bonding The science behind this method is that pressing two things together with enough pressure, heat and time will eventually cause the molecules of each to fuse into one. This results in a solid block of plastic with no weak spots. Pressure and heat over time can distort the shape of the channels, so it important that the pieces are machined precisely to compensate for this. The labor required to accomplish this and the time the piece must be under pressure combine to make this a fairly time consuming and costly process. Laser Bonding The method Norgren prefers to use when building its acrylic manifolds is laser bonding. Once the pieces of the manifold are machined and cleaned, a laser absorber is applied. A laser is passed over the part for a few seconds and the light wave interacts with the absorber to generate heat in a very focused area. This acts as a "flash weld," bonding the pieces together. The absorber discolors the plastic slightly, leaving a visible clue as to where the joint was, but the material itself is burnt out by the laser, leaving no residue in the manifold channels. Since with laser bonding the manifold is exposed to heat over a very small area for a very short time, the features machined into the plastic retain their original shape. Laser bonding results in very stable dimensional accuracy and integrity. Find out more norgren.com

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