Mechanistic modelling of 5-axis milling using an adaptive depth buffer
Mechanistic modelling of surface machining with a toroidal end mill is presented in this work for 5-axis machining. A graphical representation of tool movements (using tooth swept sectors or the swept surface of the tool) is rendered using a widely available rendering engine, whereby the in-process chip geometry and tool edge contact length are determined by an adaptive and local depth buffer. Owing to the chip geometry being highly dependent on the feedrate, a detailed derivation of the relative tool-workpiece velocity is presented based on the kinematics of a tilt-rotary table configuration. The mechanistic modelling is verified with experimental results and found to agree to within 7% of the peak-to-peak forces.
The OpenGL Reference Manual
A fluid power driven roof nailing machine which receives a roofing nail and a sealing disc and, keeping them axially aligned, drives the nail through the disc into a surface to be nailed. The machine includes an arm swingably driven by a fluid motor, a sealing disc holder fixedly carried by the free end of the arm, and a nail driver positioned at the free end of the arm and mounted for sliding movement relative to the disc holder. A method of attaching roofing using such a machine is also disclosed.
Studies on root enamel (2). Enamel pearls. A review of their morphology, localization, nomenclature, occurrence, classification, histogenesis and incidence.
Enamel pearls are one of a number of different enamel structures that can be found on the roots of deciduous and permanent teeth. They have a distinct predilection for the furcation areas of molar teeth, particularly the maxillary third and second molars. They can consist primarily of enamel, but in most instances, a core of dentin is contained within them. On rare occasions, even pulpal tissues can be found. Enamel pearls usually occur singularly, but up to 4 enamel pearls have been observed on the same tooth. Depending on the study, enamel pearls on permanent molar teeth have an incidence rate of between 1.1%-9.7% with distinct differences among racial and national groups. The incidence of enamel pearls increases greatly in histological studies, suggesting that they are often obscured by a covering of cementum.