Hydrophilic sealing material for live centers in machine tools

• Published in: Wear Vol. 477; p. 203838
• Main Authors: Yamaguchi, Hajime, Higuchi, Katsunori, Sakata, Koshi, Akiyama, Tetsuya, Kasamura, Keiji, Nakashima, Yuta, Nakanishi, Yoshitaka
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 18.07.2021; Elsevier Science Ltd
• Subjects: Bearings; Boundary lubrication; Cooling rate; Cutting fluids; Cutting tools; High speed machining; Hydrophilicity; Lubrication; Machine tools; Mechanical components; Oil seals; Sealing; Seals; Servomotors; Cutting tools; Boundary lubrication; Bearings; Seals
• DOI: 10.1016/j.wear.2021.203838
• ISSN: 0043-1648

A live center is an important mechanical component of a lathe. Water-based cutting fluids are used when high-speed machining or cooling properties are required. We performed an implementation experiment of the hydrophilic seal into an actual live center for preventing ingress of water-based liquids, which can protect bearings in the live center. The sealing structure was similar to that of an oil seal, where the seal lip is closely attached to the counter-face. Polyvinyl formaldehyde (PVF) with hydrophilic characteristics and a micro-level three-dimensional porous structure was selected as the seal lip material. The water-based cutting fluid was injected to the hydrophilic live center, which was rotated by servo motor. It was confirmed that the PVF seal could prevent the ingress of cutting fluids because the grease in bearings remained, and a stable frictional torque was achieved. The PVF seal color changed to that of the cutting fluid after the experiment, suggesting that the porous hydrophilic layer adsorbed the cutting fluid appropriately. On the superficial PVF layer, microscopic damage of the PVF was observed, however, the continuous porous structure was retained. It was supposed that the adsorbed cutting fluid acted as a boundary lubrication film for separating the dynamic seal surfaces. •Polyvinyl formal (PVF) was used as a machine tool live center sealing material.•The hydrophilic PVF live center seal prevented water-based cutting fluid ingress.•The proposed hydrophilic PVF lip seal protected the live center bearings.•The seal contributed to stable bearing frictional behavior.•The seal prolonged the service life of the live center.