Who do trust? Combining Recommender Systems and Social Networking for Better Advice

Disclosed is a roller forming machine for converting a flat metal strip into a louver having long, narrow fins that extend lengthwise of the strip and are all bent laterally in one direction oblique to the plane of the strip. The fins are produced by a pair of fin forming rollers which slit the strip and bend out the fins to a larger acute angle to the plane of the strip than is desired in the finished louver. The strip then tends to twist along its length due to asymmetrical residual stresses generated by fin formation. To remove the twist, the strip is passed between cylindrical straightening rollers whereby the fins are bent partway back towards coplanarity with the strip, thus generating new residual stresses which oppose the original ones due to fin forming. One straightening roller is adjustable towards and from the other so that said new residual stresses can be empirically brought into equilibrium with the original ones.