Machining cobalt-based dental alloys with tungsten carbide mills

Milling characteristics of dental alloys have been investigated and compared. The four differently configured tools used were made of cemented tungsten carbide. Most were uncoated but one was coated with a diamond-like carbon layer. The dental alloys studied were cobalt-chrome (Co-Cr) and cobalt-chrome-titanium (Co-Cr-Ti) alloys, fairly strong alloys. There is a requirement for a reliable test to evaluate the properties of dental tools by measuring the cutting forces during milling. A full characterization of dental mills is a difficult task, because the geometry of the mills is complex, with conical multi-cutting surfaces. In this study a more comprehensive understanding of the effects of cutting rate on cutting forces was achieved by varying the tool cutting speed and measuring the force on the workpiece as it was driven into the rotating tool at a fixed feed velocity. It was observed that the cutting forces were changed by varying cutting speeds. Side milling required lower forces than central slot milling. After milling the surfaces of the dental tools and dental alloy specimen were analyzed by scanning electron microscopy

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Effects of Increasing Feed Rate on Tool Deterioration and Cutting Force during End Milling of 718Plus Superalloy Using Cemented Tungsten Carbide Tool

Understanding how feed rate (ft) affects tool deterioration during milling of Ni-based superalloys is practically important, but this understanding is currently insufficient. In the present study using a 718Plus Ni-based alloy and cemented tungsten carbide tool inserts, milling experiments were conducted with ft = 0.10 mm/tooth under either dry or wet (with coolant) conditions. The results are compared to those based on using ft = 0.05 mm/tooth from previous studies. The milling force (F) was monitored, the cutting tool edge was examined and the flank wear (VBmax) was measured. As would be expected, an increase in ft increased F. It was found that F correlated well with VBmax for the high ft (0.1 mm/tooth) experiments, as opposed to the previously observed poor F-VBmax relationship for the lower ft (0.05 mm/tooth) value. This is explained, supported by detailed failure analysis of the cutting tool edges, by the deterioration mode to be dominantly edge chipping with a low occurrence of fracturing along the flank face when the high ft was used. This dominancy of the deterioration mode means that the tool edge and workpiece contact was consistent and thus resulted in a clear F-VBmax relationship. A clear F-VBmax relationship should then mean monitoring VBmax through monitoring F is possible

Kajian Teknis Produksi Alat Muat Dan Alat Angkut Pada Kegiatan Pengupasan Overburden Pada PT. PCN Kab. Tanah Bumbu Prov. Kalimantan Selatan

xvii, 98 Hal.; 26 C

Machining cobalt-based dental alloys with tungsten carbide mills

Milling characteristics of dental alloys have been investigated and compared. The four differently configured tools used were made of cemented tungsten carbide. Most were uncoated but one was coated with a diamond-like carbon layer. The dental alloys studied were cobalt-chrome (Co-Cr) and cobalt-chrome-titanium (Co-Cr-Ti) alloys, fairly strong alloys. There is a requirement for a reliable test to evaluate the properties of dental tools by measuring the cutting forces during milling. A full characterization of dental mills is a difficult task, because the geometry of the mills is complex, with conical multi-cutting surfaces. In this study a more comprehensive understanding of the effects of cutting rate on cutting forces was achieved by varying the tool cutting speed and measuring the force on the workpiece as it was driven into the rotating tool at a fixed feed velocity. It was observed that the cutting forces were changed by varying cutting speeds. Side milling required lower forces than central slot milling. After milling the surfaces of the dental tools and dental alloy specimen were analyzed by scanning electron microscopy

Information on individual interfaces in ternary polymer blends from positron annihilation lifetime studies

Positron Annihilation Lifetime Spectroscopy has been used to determine the free volume content in the ternary blends of SAN/EVA/PVC. The method of deriving hydrodynamic interaction parameter (α) in binary polymer blends was modified for ternary polymer blend system characterized by three distinct interfaces. Each interface characterized, is associated with an α and its assertion for the ternary blend are compared with available literature data