Search Results

In a drive to reduce overall vehicle weight, automotive manufacturers continue to look to aluminum alloys as a solution to provide complex lightweight structures. Precipitation hardened 6000 series aluminum alloys offer a mature commercially viable solution which may be produced using several different forming methods including the extrusion process. In some cases, aluminum products may be produced at a temper suitable for forming and later precipitation hardened to a temper with mechanical properties that meet structural requirements. Direct extrusion press capabilities continue to expand. In an effort to improve productivity, the runout lengths for presses have increased in an effort to reduce dead cycle time inherent to billet heating and loading. Long runouts, however, result in larger differences in pressure applied during extrusion. This pressure variation, confounded with differences in quenching and stretching, causes variation in the extruded product.

6061-O temper extruded rod may be used as feed stock in forming processes for automotive pressure vessel applications. Key parameters for forming are the strength and hardness of the material. The purpose of this paper was to reduce variation in hardness to achieve a process capability index of 1.33 or greater. Among the process steps affecting hardness, annealing is the most critical. Initially, the process showed unacceptable hardness variation. Initial anneal recipes called for a 4-hour soak at 775°F (413°C). Initial process capability for hardness was a Cpk of 1.12, with tensile strength readings very close to the upper specification limit. Initial temperature uniformity surveys of the anneal oven showed a large variation in temperature distribution, with some areas of the oven staying below 650°F (343°C). Initial improvement efforts focused on soak time.

As many underhood products have shifted from metal to plastic designs over the last decade, often parts break during assembly due rough handling conditions and less than ideal manufacturing practices. In particular assemblies often crack during screw torquing at the mounting tabs. The goal of this study is to determine how different mounting tab designs compare in strength. Designs with an external rib on the perimeter of the mounting tab behave differently than designs without a complete or lacking an external rib on the perimeter of the mounting tab. A positive correlation was found between knit line cross-sectional area and mounting tab strength for designs with an external rib on the perimeter of the mounting tab. A positive correlation was found between tab thickness and mounting tab strength for designs lacking an external rib. Material type was found to impact mounting tab strength.

Often electrical components are encapsulated in a plastic material after assembly. The goal of this study is to determine what variables are most important in reducing potting variation and identify the key machine parameters which can be used to make adjustments to the potting process. To maximize the efficiency of testing, an L18 orthogonal array was used to structure an experiment. Hose temperature, orifice size, and pressure were found to be the most significant control factors studied in this experiment. Shifting from the initial settings for these factors to the recommended settings should increase the S/N of the potting process by 14.53db. Motor speed was found to be the most significant variable for adjusting the mean of the process. The noise factors induced in this study were found to be a significant source of variation. Filters can shift the mean potting material applied by 25% over their planned usage life. Moreover, new filters induce more variation than old filters.

Plastic underhood components often crack when fastened to mating components. The goal of this study is to determine what variables are most important with relation to this problem. To maximize the efficiency of testing, an L18 orthogonal array was used to structure the experiment. Experiments were conducted using a computer-controlled electric driven screwdriver and a manual torque wrench. Control factors were adjusted by using hardware as specified for each trial. The torque value at failure was recorded for all samples. The “larger the better” S/N equation was utilized for data analysis in this study. Optimizing the design and process was found to increase the S/N by 6.9dB when verified experimentally. Fastener washer thickness, joint fit-up, and screw setting speed contribute to the gain by 46%, 28%, and 27%, respectfully.

When commercializing squeeze casting and semi-solid metalworking processes, component producers looked to conventional die casting to identify potential defects and control component quality. Several defects were expected including cold shuts, cold flows, flash, drags, warping, and gas entrapment, just to name a few. Efforts were taken to avoid these defects. New defect types, however, have surfaced unique to these high integrity die casting processes. Contaminant veins and phase separation are presented. Although, squeeze casting and semi-solid metalworking have proven to be successful, component producers have been reluctant to report defects for fear of giving these emerging processes a bad reputation. Nonetheless, these defects must be understood to avoid future problems.