Work Rollers—New straighteners processing AHSS mate-


rials require a greater number of smaller diameter work rollers with closer spacing between the rollers to effectively stretch and compress the material. These smaller diameter straight- ener rollers provide a smaller radius around which to bend the material. This is because AHSS needs to be bent more severely in order to exceed its higher yield point. Force Delivery—Closer work roller center spacing leaves less room for the work roller force delivery mechanism. Conventional “off- the-shelf” screw jack designs cannot provide adequate force in this reduced space. COE’s experience led to the development of custom screw jack modules, which can be designed to fi t the available space and deliver the higher forces required to effectively yield AHSS. The straightener must also be designed so the upper rolls have adequate travel between the lower fi xed rolls in order to properly yield AHSS. This distance can be as much as 50–60% greater than what is required for conven- tional straighteners. System Rigidity—Greater forces require more support.


So across the machine width, the straightener work rollers must be supported better to prevent excessive defl ection that can lead to edge wave in the material and failure of the straightener geartrain. The backup structural bridges that support the straightener work rollers must be more rigid. Robust Components, Size and Durability—Although the


work rollers are smaller, there is a tendency for many of the support mechanisms to be larger. For example, wider gear face widths are required as well as outboard support of jour- nals and idler shafts in order to produce higher gear power ratings. Larger journal diameters with bigger radii and larger bearing capacity are needed to withstand the greater roll force and higher power required to straighten high strength material using the closer roller center spacing. More Horsepower—Processing of AHSS typically requires


greater motor power and torque capability to effectively process the material through the straightener. Calculating the


correct power is based on numerous factors, including: t Material thickness, width, and yield strength t Maximum coil weight the straightener is required to pull off


t Required processing speed of the coil feed line t Response/acceleration time of the straightener


Each application has unique considerations of the above variables and can result in an almost infi nite number of outcomes based on the combinations of these variables. To


COE’s HD straightener design modifi cations overcome the diffi culties that stampers face in trying to achieve the required material fl atness when processing AHSS.


properly design a straightener for any particular application requires tools that can analyze these requirements.


The Right Tools for the Job From its research, COE developed its HD Series of Heavy-Duty Straighteners specifi cally meant to tackle the processing of AHSS. These straighteners incorporate all of the necessary design and structural features demanded by these new materials. They are also capable of processing a wider range of materials—both thick and thin—than conven- tional straighteners. The success of the HD Series has now led the COE’s Research & Development team to expand the application of the technology into new product offerings. Having solution alternatives that are designed to address the challenges of today’s AHSS steels at up to 1000+ MPa removes the anguish of specifying equipment for both engineering and operations personnel alike. From an engineering viewpoint, the properly designed equipment will be capable of effectively straightening and feeding these advanced materials. From an operations viewpoint, rates of production and production effi - ciency will be improved. And, more importantly, these enhanced capabilities will allow companies to confi dently procure and process more automotive work using these advanced steels.


63 — Motorized Vehicle Manufacturing 2016


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