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Automated Optical Inspection of Printhead Printwires Following a Grinding Operation

IP.com Disclosure Number: IPCOM000040417D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Barenboim, M: AUTHOR [+5]

Abstract

In an automated assembly line for wire printer printheads, one operation performed is the grinding of the ends of the printwires to a specified maximum height above the wire guide plate. Manual inpsection methods to ascertain the accuracy of the grinding operation are slow and complicated. The present embodiment provides an automated optical method to rapidly perform this inspection. Fig. 1 shows the top portion of a typical wire printer printhead 1, in which two groups of printwires 2, each consisting of nine wires in two rows, project through holes in wire guide plate 3. It is known, by the nature of the grinding operation, that the longest and shortest printwires are produced at the four corners of the array, i.e., the end wires of the two outer rows.

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Automated Optical Inspection of Printhead Printwires Following a Grinding Operation

In an automated assembly line for wire printer printheads, one operation performed is the grinding of the ends of the printwires to a specified maximum height above the wire guide plate. Manual inpsection methods to ascertain the accuracy of the grinding operation are slow and complicated. The present embodiment provides an automated optical method to rapidly perform this inspection. Fig. 1 shows the top portion of a typical wire printer printhead 1, in which two groups of printwires 2, each consisting of nine wires in two rows, project through holes in wire guide plate 3. It is known, by the nature of the grinding operation, that the longest and shortest printwires are produced at the four corners of the array, i.e., the end wires of the two outer rows. Therefore, to determine that all wires have been ground to, or below, the specified maximum height, it is necessary to inspect only the four corner wires. This is accomplished in the present embodiment by an optical system which "looks" along the tips of the two outer rows of wires, paths 4 and 5, and measures the height of what is "seen". It is apparent that this measures the longer of the two end wires in each of these two rows. Fig. 2 shows schematically one of two camera mechanisms required for this optical inspection. This mechanism, including shields to shut out most ambient light, is lowered over and around printhead 1 until a common spring-loaded finger 6 senses the surface of wire guide plate 3. The equipment is brought to rest with common reference edge 7 at a predetermined height above plate 3. Reference edge 7 spans the full width of plate 3 and extends over the two outer rows of wires. The two end wires 8 and 9 of the nearer of the outer...