IES58755B2 - Automatic drill bit quality and position control - Google Patents

Abstract

This invention relates to the monitoring of drill bits between drill strokes in automatic drill machines, typically of a high capacity multiple spindle type used for drilling printed circuit boards. It provides a solution that allows inspection of all bits in such drill machines between each drill stroke, without reduction of machine performance in normal production drilling. This invention applies video cameras suitably mounted with optical fibers or other light deflecting accessories, adapted to provide instant means values of light intensities to a computer system to determine drill bit geometry.

Description

The present invention relates to the control of drill bit breakage, quality and setting in automatic drill machines in particular for the manufacture of printed circuit boards.

Background, some existing systems.

To detect if drills in automatic drilling machines (CNCsystems) are broken a variety of methods, some patented, are in use, primarily for the drilling of printed circuit boards. 1/ Microvawe detection of chips (spanor) in extraction system indicating that the drill bit is in working order. 2/ Light or laser beam and photodiode(s) to detect geometry and/or position of drill bit. 3/ Ultrasonic analysis of sound generated during drilling is used to indicate normal drilling or broken bit(s).

Other systems, with varying degree of accuraccy are availible.

Description and claims The use of dedicated videocameras with automatic drilling machines to capture images that are transferred and analyzed by an image processing software on a standard computer, with standard video capturing equipment with outputs to halt or redirect machine actions and/or provide alarm and information to operator at typical faults described hereinafter. The use of the word ”standard above and below refers to the minimum required equipment, without limiting the application to be incorporated with specially made equipment.

Minimum one camera, with suitable optical fibre is to be attached to each drill spindle (often 4 or more spindles per machine). The standard video signals are fed int a multiplexor ( an electronically controlled switch/selector)., which is fed to a standard video capturing board. With standard/specially made/adapted software spot images from each of the cameras can be selected and inspected for primarily the occurrence of broken drill bits, the main purpose of the system, but also for other parameters as: Size and correct setting of drill bit, wear and quality of drill bits, run out of drill bit, faulty stoppage, rotation speed speed and efficiency of dust removal to indicate proper vacuum.

There is nothing in any of the parts that go into the system described above that is subject for this patent application. The application of computerized video image capturing and processing for online drill bit inspection is however the subject of this application for patent.

Videocameras have possibly been used for inspection of tools in other specialised drilling or milling systems before this, possibly also incorporating the transfer of images to a computer and automatic processing of images.

In this application several cameras are however dedicated for the continous online supervision of a high volume production drilling machine, checking drill quality and position typically up to 120 times per minute, with immediate stoppage or corrective action at the discovery of any presettable. fault condition.

It is at the same time replacing inferior existing, some possibly patented, methods that claim to manage the detection of broken drill bits.

Limiting a patent for above invention for printed circuit boards drilling machines is not the objective of this application, although it is a satisfactory solution for the immediate purpose of the application, if such limitation has to be applied.

Details of construction for the application of existing video equipment to existing drilling machines is of no significance, as it is the application of the former to the latter that forms the trust of the application. One embodiment of the application consists of cameras suitably mounted on the machine near each drill spindle, each connected with optical fibres that are fixed in a suitable position from which images from drill bit and its environment suitable for above mentioned inspections can be carried out. The invention is not limited to the embodiment hereinbefore described.

Dated this 5th day of-rMayy-1993 By the applicant: Sleaveen Road, Macroom, Co. Cork weed ftT Details of type of pictures and methods of extracting information from images of rotating drill bits transmitted by videocamera to computer via video capturing circuit board and of guality management of drill bits enabled through the system.

The picture environment is arranged so that the drill bit contrasts against its background. A preferred embodiment hereinafter described, although not excluding other contrasting methods that inhibit disturbing light reflection from drill bit, is to have the imaged part of the drill bit in no or little direct illumination against a bright or illuminated background.

For computer image analysis of a rotating drill bit, a video camera with a typical response time in its light sensitive picture plane being slower than employed rotation speeds of the drill bit is employed. Such arrangement provides instant steady light intensity readings from each point of a captured image dependent on the geometry, condition and situation of the drill bit.

In the following computer image analysis actual light intensity distribution is compared with expected, and parameters as setting, size, critical wear and breakage, oscillation (runout) and slow rotation speed is made available for evaluation through the invention. Suitable subset of these parameters can be evaluated between each drill stroke if processing time is insufficient at very high drill speeds, where less critical parameters then can be checked at lower frequency.

Another embodiment of the invention has the multiplexing arrangement in the form that one camera is used for several optical fibres that are fitted into its lens system, necessitating the capturing of only one image consisting of a several individual images of drill bits.

Present drill wear management uses expected drill life times varying with type and thickness of material and inspection of bits in conjunction with regrinding. The present invention provides the means to measure and replace bits on the basis of actual wear, hereby taking in consideration actual variance of material, drill bits and other circumstances, enabling use of drill bits up to any required wear point, and also quick accurate evaluation of wear due to drill types, material characteristics, drill feed rate, drill rotation speed, cooling and extract::?. efficiency.

The additional detection of smear build up during drillingmolten/burnt material, usually epoxy in drilling printed circuit boards, is incorporated in an embodiment employing a colour camera.

The additional detection of critical drill bit temperatures is incorporated in an embodiment employing a camera sensitive for light in a suitable infra red spectrum. In this embodiment a background at a different temperature provides contrast. Image analyzing software in this embodiment have to be modified to allow for the added dimension of temperature distribution, which results in some lost geometrical accuracy but early information about critical bit and drill spindle temperatures.

Claims (5)

1. / The application of computerized video image analysis to an automatic high speed production drill machine for wear and situation control of rotating drill bits between drill strokes without slowing down good production and interrupt/change machine action at preprogrammable fault conditions.

2. / The use of a contrasting background and video camera with suitable time response slower than lowest rotation speed in order to capture a video image providing mean light intensities as a result of the rotation to be used in 1/ above.

3. / The use of a color video camera to detect also discoloured material on rotating drill bits in addition to above.

4. / The use of an infra red video camera to detect temperature and geometry of a rotating drill bits as in 1/ - 2/ above.

5. / The use of the information gathered through 1/- 4/ for a drill wear and drilling quality/production optimizing control system based on the continous data therethrough collected during actual drilling.