Through hole depth measurement method and device
AssigneeLockheed Martin Corporation
InventorRussell L. Miller
Life of this patent
Estimating the term…
Abstract
A through-hole depth measurement device includes a cutting force sensor configured and mountable in a position to sense cutting force exerted by a drill bit of a drill against a workpiece or stack of workpieces. A controller is coupled to the force sensor, is coupleable to a workpiece surface position sensor, and is configured to record the through-hole depth of the workpiece or stack of workpieces in response to signals received from the workpiece surface position sensor when the drill bit reaches a drill bit exit point. The cutting force sensor is configured and positionable to sense cutting force transmitted between a drill spindle and a spindle housing.
Claims14
A device for measuring the depth of a through-hole formed through one or more workpieces, the device comprising:
- a cutting force sensor configured and mountable in a position to sense cutting force exerted by a drill bit of a drill against a workpiece or stack of workpieces;
- a workpiece near-side surface position sensor comprising a pressure foot supported for reciprocal motion along a pressure foot axis, and further comprising a pressure foot axis position sensor configured to sense the position of the pressure foot along the pressure foot axis;
- a workpiece far-side surface position sensor;
- and
- a controller coupled to the cutting force sensor, coupleable to the pressure foot axis position sensor and the far-side position sensor, and configured to record a through-hole depth of a workpiece or stack of workpieces as being the difference between a workpiece near-side surface position indicated by the pressure foot axis position sensor and a workpiece far-side surface position indicated by the far-side position sensor when the controller receives a decaying force signal from the force sensor indicative of drill bit breakout.
A method for measuring the depth of a through-hole formed through one or more workpieces, the method including the steps of:
- positioning a drill spindle with an attached drill bit into axial alignment with a desired hole location adjacent a workpiece or stack of workpieces;
- rotating and advancing the drill spindle axially causing the bit to cut into the workpiece or stack of workpieces,
- monitoring cutting force and workpiece surface position sensor readings as the drill bit is cutting through the workpiece or stack of workpieces;
- detecting a decay in cutting force indicative of drill bit breakout;
- determining workpiece near-side surface position from the position of a pressure foot along a pressure foot axis;
- and
- determining workpiece far-side position by polling pressure foot axis and workpiece far-side surface position sensor readings at instance of breakout;
- and
- calculating hole depth as being the axial distance between workpiece near-side surface position and workpiece far-side surface position.
A drilling device comprising:
- a spindle housing;
- a drill spindle carried by the spindle housing;
- a drill bit carried by the drill spindle;
- at least one workpiece near-side surface position sensor comprising a pressure foot supported for reciprocal motion along a pressure foot axis, and further comprising a pressure foot axis position sensor configured to sense the position of the pressure foot along the pressure foot axis;
- at least one workpiece far-side position sensor comprising at least one cutting force sensor disposed axially between the spindle and the spindle housing;
- and
- a controller coupled to the workpiece near-side surface position sensor and the workpiece far-side position sensor and configured to record a through-hole depth of a workpiece or stack of workpieces in response to signals received from the workpiece near-side surface position sensor and from the workpiece far-side position sensor when the drill bit reaches a drill bit exit point.
Dependencies are inferred from the claim text.