CAM, which stands for Computer aided manufacture, is used extensively within companies as a stand-alone system from CAD Computer Aided Design.

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09/05/07

Inspection And Quality Control In CAM Systems

 

Date Submitted-: 24th June 2002.

Contents

CONTENTS        

INTRODUCTION        

TOOLING VERIFICATION        

Fig. 1. – An Example of Qualified Tooling        

Fig. 2. – Examples of block tooling.        

DATUM AND LOCATION CHECKS        

Fig. 3. – An example of a Grid plate        

IN PROCESS MEASUREMENT        

POST PROCESS INSPECTION        

QUALITATIVE DATA AND ATTRIBUTES        

Statistical Analysis        

DATA CAPTURE        

Methods of Data Capture        

Examples of Data Capture        

Annular Rings        

Fig. 4. – Example of how annular rings work        

Considering the rings from left to right        

Microchip        

Barcode        

Fig. 5. – Matrix comparing sensor methods        

DATA TRANSMISSION FEATURES        

APPENDIX A        

Acknowledgements        

Introduction

        CAM, which stands for COMPUTER AIDED MANUFACTURE, is used extensively within companies as a stand-alone system from CAD (Computer Aided Design). However, there is a distinct relationship between the two systems where data is exchanged between each system in a CAD/CAM set-up. Cam systems cover activities that translate the design of a component into instructions that define how the component will be produced. Also, CAM can be extended into providing feedback on the manufacturing process through the use of inspection and quality control tools that are controlled by computer. CAM is, therefore, any manufacturing process that is controlled by computer. CAM can be extended to cover more complicated computer controlled techniques such as FMS (Flexible Manufacturing Systems) and CIMS (Computer Integrated Manufacturing Systems). The whole subject of CAM, especially FMS, can be broken down into separate areas that can be investigated independently. These include :-

  • Tooling verification
  • Datum and location checks
  • In process measurement
  • Post process inspection
  • Qualitative data and attributes
  • Statistical analysis

Each of these areas will be investigated in this assignment.

Tooling Verification

        When considering an automated system ensuring the correct tool with the correct tool offset is used to perform a particular operation within the manufacturing process is essential. In large production companies it is sometimes possible to find large cells of similar CNC (Computer Numerical Control) machines whose tooling is supplied automatically via a magazine, which is loaded by operators in the tool setting room/department. These tools are then delivered to the machines for use in the machining process. Information needs to travel with each individual tool identifying what the tool is and what location it needs to be in on the CNC’s tool turret. It may also be necessary for the tool offset to travel with the tool as well. If no tool offset is to linked with a tool whilst in the magazine then the offset will have to be:-

  • Pre-set at the tool setting room so that all the tools of that type are offset the same distance,
  • Determined at the CNC machine through the use of onboard sensors,
  • Through the use of qualified or block tooling.

Tooling identification can be achieved by several methods which include-:

  • The use of annular rings mounted on the tool holder,
  • Microchips attached to (or inserted) in the tool holder,
  • Bar code tags that are attached to the tool holder.

Each of these methods are discussed later under tactile and non-tactile sensing.

        Qualified tooling is a special type of tooling where known dimensions are given when the tool is supplied between a datum face and the tool tip. These dimensions are guaranteed to be the same no matter which tool (of the same type) is used. See Fig.1.

Fig. 1. – An Example of Qualified Tooling

This pre-set data means that the tool offsets will be the same no matter which tool of the same type is used and so long as the tool is set-up in the tool holder exactly the same.

        Block tooling is termed for the fact that the tool comes in blocks. The tool has a shank (in grey in Fig. 2.) that can take many types of tip holding blocks (in blue in Fig. 2.). The block is slotted over the locking tang (in magenta in Fig. 2.) and then the locking tang is tightened. Similar to the qualified tooling the dimension from the tip to the three datum faces is identical between blocks with the same tool type. Once again tool offsets will not be affected by changing tools to another of a similar type.

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Fig. 2. – Examples of block tooling.

Datum And Location Checks

        Workholding devices are designed to hold a workpiece, restricting movement in all six degrees of freedom. It is not desired that the device damages the workpiece and it must achieve these two aspects with speed and simplicity. In an automated system it would be necessary for the clamping procedure to occur without human intervention. This can be achieved through the use of hydraulics or pneumatics, which can be controlled electronically. It is also necessary that the workholding device provide repeatability for recurrent products of the same type. ...

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