Browse Prior Art Database

Top Reference for Drilling

IP.com Disclosure Number: IPCOM000040650D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Clothier, RW: AUTHOR [+3]

Abstract

Fixed depth holes, also known as blind holes, can be precision drilled by air turbine driven drills. As shown in the drawing, a drill turbine 1 is fitted with a Hall effect eddy current sensor 2 that detects a tick mark 3 in the rim of the journal bearing 4. The sensor emits an electrical signal each time the tick mark passes by, one impulse per revolution. The period between pulses, or one revolution, can be timed very accurately with a microprocessor. As the drill 5 comes in contact with the panel, the drills's RPM rate will drop because of an increased load on the bit. This change in the frequency of the RPMs is a signal to the microprocessor that a top reference point has been established. This RPM reduction sensing concept can be used in conjunction with microprocessor controlled vertical motion.

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Top Reference for Drilling

Fixed depth holes, also known as blind holes, can be precision drilled by air turbine driven drills. As shown in the drawing, a drill turbine 1 is fitted with a Hall effect eddy current sensor 2 that detects a tick mark 3 in the rim of the journal bearing 4. The sensor emits an electrical signal each time the tick mark passes by, one impulse per revolution. The period between pulses, or one revolution, can be timed very accurately with a microprocessor. As the drill 5 comes in contact with the panel, the drills's RPM rate will drop because of an increased load on the bit. This change in the frequency of the RPMs is a signal to the microprocessor that a top reference point has been established. This RPM reduction sensing concept can be used in conjunction with microprocessor controlled vertical motion. A signal can be generated to the microprocessor to store the position of an attached lvdt or linear scale and to drill to the prescribed depth according to an established top reference. A reduced clamping force is required because the panel does not need to be flattened against a fixed mechanical reference, reducing strain on the drill machine and product. This RPM reduction sensing also provides the capability to detect broken drill bit and spindle actuation verification; the idea being that no RPM loss would occur if the bit were broken. If the RPM does not vary within a reasonable stroke of the scale, a broken drill bit could be declare...