Computer Aided Quality Control

Computer Aided Quality Control

Automated Inspection • Automated inspection can be defined as the automation of one or more of the steps involved in the inspection procedure. • There are a number of alternative ways in which automated or semiautomated inspection can be implemented: 1. Automated presentation of parts by an automatic handling system with a human operator still performing the examination and decision steps. 2. Automated examination and decision by an automatic inspection machine, with manual loading (presentation) of parts into the machine. 3. Completely automated inspection system in which parts presentation, examination, and decision are all performed automatically.

Where and When to Inspect

• Inspection can be performed at any of several places in production: 1. Receiving inspection, when raw materials and parts are received from suppliers. 2. At various stages of manufacture, and 3. Before shipment to the customer.

Off-Line and On-Line Inspection • The timing of the inspection procedure in relation to the manufacturing process is an important consideration in quality control.

• Two alternative situations can be distinguished: 1. Off-line inspection. 2. On-line inspection.

Off-Line Inspection • Off-line inspection is performed away from the manufacturing process, and there is generally a time delay between processing and inspection. • Manual inspection is common.

On-Line Inspection • The alternative to off-line inspection is on-line inspection, in which the procedure is performed when the parts are made, either as  An integral step in the processing or assembly operation, or  Immediately afterward. • Two on-line inspection procedures can be distinguished:  On-line/in-process.  On-line/post-process.

On-Line/ in-process Inspection • The is achieved by performing the inspection procedure during the manufacturing operation. • As the parts are being made, the inspection procedure is measuring or gaging the parts simultaneously.

On-Line/ post-process Inspection • The measurement or gaging procedure is accomplished immediately following the production process.

Contact vs. Non-contact Inspection Techniques • Inspection techniques can be divided into two broad categories: 1. Contact Inspection. 2. Non-contact Inspection.

• In contact inspection, physical contact is made between the object and the measuring or gaging instrument. • In non-contact inspection no physical contact is made.

Contact Inspection Techniques • The principal contact technologies are:  Conventional measuring and gaging instruments, manual and automated.  Coordinate Measuring Machines (CMMs)  Stylus type surface texture measuring machines.

Coordinate Measuring Machines • A Coordinate Measuring Machine (CMM) is an electromechanical system designed to perform coordinate metrology.

Coordinate Measuring Machines

Coordinate Measuring Machines • To accomplish measurements in 3D, a basic CMM is composed of the following components:  Probe head and probe to contact the workpart suraface.  Mechanical structure that provides motion of the probe in three Cartesian axes and displacement transducers to measure the coordinate values of each axis.

CMM Mechanical Structure

(a) Cantilever

(b) Moving bridge

(c) Fixed bridge

CMM Mechanical Structure

(d) Horizontal Arm

(e) Gantry

(f) Column