Etching a substrate: processes – Gas phase etching of substrate – Etching inorganic substrate
Patent
1998-04-13
1999-11-30
Breneman, Bruce
Etching a substrate: processes
Gas phase etching of substrate
Etching inorganic substrate
216 67, 427577, B44C 122
Patent
active
059936800
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of removing a hard carbon film formed over the inner surface in sliding contact with a workpiece of a guide bush mounted in an automatic lathe to hold the work piece rotatably.
BACKGROUND TECHNOLOGY
Guide bushes mounted on a column of an automatic lathe to hold a rod-like workpiece rotatably at a position close to a cutting tool are classified into a rotary type and a stationary type. A rotary guide bush rotates together with a workpiece and holds the workpiece for axial sliding. A stationary guide bush remains stationary and holds a workpiece for rotation and axial sliding.
A guide bush of either type has a portion having a taper outer surface provided with slits to make the same portion elastic, a threaded portion to hold the guide bush on the column, and an inner surface for holding a workpiece. The inner surface always in sliding contact with a workpiece is liable to be worn and, particularly, the inner surface of a stationary guide bush is worn rapidly.
Therefore, we have already proposed a guide bush wherein a hard carbon film is formed over the inner surface thereof coming in sliding contact with a workpiece when the workpiece is rotated and slid so as to dramatically enhance wear resistance of the inner surface and prevent seizure from occurring between the inner surface and workpiece.
The hard carbon film is formed of a hydrogenated amorphous carbon closely resembling diamond in properties. Therefore, hydrogenated amorphous carbon is also called diamond-like carbon (DLC).
The hard carbon film (DLC film) has a high hardness (not lower than Vickers 3000 Hv), is excellent in wear resistance and corrosion resistance, and has a small coefficient of friction (about 1/8 that of a superhard alloy).
The guide bush having an inner surface to be in sliding contact with a workpiece, coated with the hard carbon film, has wear resistance more excellent than the conventional guide bush having an inner surface attached with a superhard alloy or a ceramic material.
Accordingly, an automatic lathe employing the stationary guide bush provided with the hard carbon film over the inner surface thereof as described above is able to achieve heavy machining, in which depth of cut is large and cutting speed is high, with high accuracy for an extended period of time without damaging the workpiece or causing seizure.
Further, the hard carbon film may preferably be formed on an intermediate layer formed over the inner surface of the guide bush to enhance adhesion between the inner surface and the hard carbon film.
When the intermediate layer is formed of a two-layer film consisting of a lower layer of titanium, chromium or a compound containing titanium or chromium, and an upper layer of silicon, germanium or a compound containing silicon or germanium, the lower layer secures adhesion to the inner surface (alloy tool steel as a substrate metal) of the guide bush, and the upper layer bonds firmly to the hard carbon film. Therefore, the hard carbon film adheres firmly to the inner surface of the guide bush with high adhesion.
The hard carbon film may be formed on a hard lining member of a superhard alloy, such as tungsten carbide (WC), or a sintered ceramic material, such as silicon carbide (SiC), formed on the inner surface of the guide bush. An intermediate layer interposed between such a hard lining member and the hard carbon film will further enhance the adhesion of the hard carbon film.
Even if the guide bush is provided with the hard carbon film over the inner surface thereof as described above, however, the necessity for removing the hard carbon film from the inner surface thereof will arise so as to render the guide bush reusable in case any defect in the hard carbon film is detected during a test after formation thereof, the hard carbon film is damaged after use over a long period of time, or any other trouble is found occurring thereto.
In such a case, it is conceivable to remove the hard carbon film formed over the inner surface of the guide bush by use of
REFERENCES:
patent: 5160405 (1992-11-01), Miyauchi et al.
patent: 5458733 (1995-10-01), Tessmer et al.
patent: 5679269 (1997-10-01), Cohen et al.
Koike Ryota
Miya Yukio
Sekine Toshiichi
Sugiyama Osamu
Toida Takashi
Ahmed Shamim
Breneman Bruce
Citizen Watch Co. Ltd.
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