Coordinate Measuring Machine (CMM): Construction and Working Principle

Coordinate Measuring Machine (CMM)

1. Definition

In this article, we will learn about the Coordinate Measuring Machine (CMM): Construction and Working Principle. Coordinate, a device that automatically measures and coordinates the three coordinate levels of a job simultaneously with the probe through touch contact called measuring machine (CMM). Fix the job on the table and move the probe head to touch the probe on the job.

2. Components of CMM

• Probe
• Mechanical structure
• Displacement Transducer
• Drive control system
• CMM software
• Computer with printer

3. Construction And Working Principles

i) Probe

The most important part of CMM is the probe. This probe touches the job only when X, Y, Z coordinate levels are measured. The probes tip is made of diamond or rubber material
Will be made to harden by. Probe tip can be a single tip or multi-tip. Commonly used touch-trigger probe.

ii) Displacement Transducer

It is an electronic device. The probe measures the distance between the points touched on the job and converts it into digital values.

iii) Mechanical structure

Various structures are used to move the probe onto the job.

a) Cantilever
b) Moving bridge
c) Fixed bridge
d) Horizontal arm
e) Gantry
f) Column

It is through this structure that the probe is given movement on the X, Y, Z-axis.

a) Cantilever Structure

In the cantilever configuration, the probe is mounted on a vertical quill and moves in a z-axis direction and a horizontal arm-mounted fixed on a table. Quill lengthwise Can also cause y-axis motion by moving.

Advantages

Convenient access to the worktable High throughput Large work parts can also be measured Small floor space is sufficient.

a) Moving bridge structure

The design of the moving bridge structure can be seen in the picture. The probe is the bridge structure Fixed and placed on the stationary table.

b) Moving Bridge Structure

The color that measures the work part is fitted. It is a more stable structure than the cantilever structure. The moving structure is the two-leg in the bed.

 

If the legs do not move at the same speed, both legs will twist and the bridge will twist. To avoid this you need to install a dual-drive system.

c) Fixed Bridge Structure

This type of bridge structure is fixed to the bed in the CMM. But the worktable moves in the x-direction and the structure moves in the X-direction.

 

This eliminates the yawing effect (leg twisting) in the bridge structure and makes measurements at high rigidity and high accuracy.

d) Horizontal Arm Structure

The horizontal arm configuration system is similar to the cantilever. But the vertical column with the horizontal arm is set to move.

 

The arm moves vertically and horizontally in the column, causing y-axis and z-axis motions. It has a large workspace area so it is used to measure automobile bodies.

e) Gantry Structure

It is set to make large objects. The quill in it is two fixed Moves and measures in the arm on the vertical rail.

f) Column Structure

It’s like a machine tool. In which the work moves and causes x-axis y-axis motions. The probe quill gets vertical column I move z-axis motion.

iv) Drive Control System

The drive control system is used to move the probe and touch the job. Probe movement is controlled in many ways. They are

a) The manual operated drive system operator moves the probe with his hand and measures the coordinate levels.

b) Motor-driven CMM with computer-assisted data processing Computer-aided operation by moving the operator probe and measuring the surface of the job.

c) Computer-assisted motor drive system is to move and measure the probe using the motor with the help of a computer.

d.) A direct computer control system is a program based probe moving and measuring system with the help of computer and CMM software.

4) Principle of Working of CMM

The workpiece is first held at the table. Then move the probe head in the X, Y, and Z direction with the help of the drive system on the mechanical structure, the sensing probe a tip is touched on the measuring positions of the job, and the dimensions Is recorded.

In the same way probe. 3 co-ordinate levels are measured starting at several points on the workpiece.

The CMM machine can measure the following dimensions:

• Center distance
• Diameter and length of the cylinder
• Intersection and angle
• Checking of Straightness, flatness, etc
• Checking of Parallelism, squareness.

Advantage of CMM

• Larger parts can be inspected in less time.
• Inspection time is short
• There will be no change in inspection in different jobs.
• Has good repeatability.
• Small batch inspection is also economical
• The error caused by the operator is minimized.

Disadvantages

• The size of the CMM machine is large so it can be fixed in one place.
• The CMM machine is too far from the machining center.
• Situation to be.