Date of Award

12-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Mocko, Gregory

Committee Member

Summers, Joshua

Committee Member

Choi, Hongseok

Abstract

Many manufacturing processes used to mass produce parts rely on expensive and time consuming tooling. These processes include sheet metal forming, injection molding, casting, and thermoforming. The time invested in design and development of tooling can be justified for high-production volumes. However, for low-volume production and customized products, the tooling investment cannot be amortized. Flexible tooling has been developed to address the needs of smaller production volumes. Reconfigurable pin tooling is an example of flexible tooling that relies on a matrix of adjustable-height pins to produce approximate surfaces. A key challenge in pin-based tooling is achieving accurate high quality surfaces due to the undulations caused by the pins in mimicking the desired shape. This research studies the effects of process parameters on surface quality. A testbed pin tool and thermoformer are fabricated to support this research. The pin tool comprises of a 10 by 10 matrix of square pins. Each pin measures 0.25 inch by 0.25 inch by 2.5 inches and is actuated manually using screws. Twenty-one exploratory and thirty-two shape specific experiments were conducted with 12 inch by 12 inch polystyrene sheets to check the feasibility of producing undulation-free surfaces. The parameters that influence the quality of the surfaces are heating time, sheet thickness, and sheet to fixture distance. Surface quality is measured by conformance with respect to the tool and the intensity of undulations. The surface-reproducibility and the measurement-repeatability errors were determined to be ±0.0045 mm and ±0.00027 mm respectively. The surface quality can be improved by reducing intensity of undulations by controlling the process parameters. The quality of thermoformed surfaces using the pin tool is a function of heating time and the intended shape.

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