Co-ordinate Measuring Machine

Question 1

Co-ordinate Measuring -Definition of spatial points

Answer 1

• Selection of probing strategy
• Selection of measuring means
• Determination of a measuring run

Question 2

-Probing of spatial points

Answer 2

• Alignment of workpiece
• Conducting the measuring process
• Recording of spatial points

Question 3

-Linking of spatial points

Answer 3

• Evaluation of measured data

- Linking of form elements for further results

Question 4

What is CMM

Answer 4

• CMM is an electromechanical system designed to perform co-ordinate metrology
• CMM uses a probe that can be positioned in three dimensions relative to the surfaces of a workpiece
• x,y and z co-ordinates of the probe can be accurately and precisely recorded to obtain dimensional data about the part geometry

Question 5

Types of Co-ordinate systems

Answer 5

Machine co-ordinate system
-with the co-ordinates of x-y-z referring to the machine’s motions

Part co-ordinate system
-where the 3 axes relate to the datums or features of the workpiece

Each point on the workpiece is unique to the machines co-ordinate system

CMM combines the measured points to form a feature than can now be related to all other features

Question 6

Alignment of CMM

Answer 6

-CMM measures the workpiece’s datums establishes the part co-ordinate system and the CMM software mathematically relates it to the machine co-ordinate system
Translation- moving the starting part of the measurement from its present position to another place on the workpiece
Rotation- moving of the features’ datums which are not at right angles to one another onto a common axis

Question 7

CMM- Measurement of features

Answer 7

-work pieces are made up of simple geometric elements
features are planes, edges, cones. created by machining or forming

-Measured features
CMM measures the features directly by touching the surfaces that make up the feature with the probe

-Constructed features
Features cannot be measured directly and must be constructed mathematically from measured features before their value can be determined

Question 8

CMM- Mechanical structure

-worktable

Answer 8

• Usually made from granite because of its inherent stability and durability properties
• heavy and with elastomeric isolation pads excellent to prevent effects caused by environmental vibration
• prone to thermal bending due to low thermal conductivity and large mass