metrology is science considering measurement -...

Metrology is science considering measurement

Categories:› Scientific – deals with organization and development

of etalons and their conservation(highest level)

› Industrial – deals with function of measuring devices used in industry in manufacturing and testing processes

› Legal – deals with precision of measurement in situations where the exact measurement is necessary for justice of economic transactions, health and security

Fields of metrology:› Weight

› Electricity

› Length

› Time and frequency

› Thermometry

› Ion radiation and radioactivity

› Volume

› Acoustic measurements

› Etc.

Continuity

Is property of measured value or etalon

value that can express the relation to

reference on national or international

level. This relationship is expressed

through an uninterupted chain of

relationships between components

where the unceratainity is known.

Unit definition

International etalons

National etalons

• Home national etalons

• Foreign national etalons

Reference etalones

Company etalones

Measurement

Etalons are changing with development of

science

Length etalon - meter

1795 – bar made of brass

1799 – bar made of platinum and iridium

1960 - 1 650 763,73 times the wave length of

radiation that is equal to transition of electron

from quantum level 2p10 to level 5d5 in

Cryptonium-86

1983 – distance reached by light in time of

1/299 792 458 second.

Basic procedure for securing the continuity ofmeasurement is the calibration. Calibration isaquiring metrological characteristics ofmeasuring device. This is made by referencingthem to etalones.

Reasons for calibration:

1) To secure that the value measured by thedevice is same as to another device ormethod

2) To secure the measured value is correct

3) To secure the reliability of measuring device.

Direct

› measuring device measures directly the

wanted quantity or property

Indirect

› measuring device measures another

quantity or property from that the wanted

quantity or property can be calculated or

derived

Absolute

› I acquire directly a value of quantity or

property

Comparatory

› I acquire the difference between the etalon

and the measured value only

caliper

micrometer

block gauges

pasameter

microskope

lengthmeter

laserinterferometer

…

CMM (Coordinate measuring machine)

basic comunal device - calliper

precision:

› 0,1; 0,05; 0,02 mm (nonius, Vernier scale)

› 0,01 mm (digital)

range… 150 ÷ 3000 mm

types:

› classical(nonius)

› digital

› with indicator

with nonius (Vernier sc.)

outer dimension

inner dimension

depth

digital

presentation:

display

display + output (RS232, USB)

IP66 – waterproof cover

solar powered

indicator

The most common device:

caliper

precision:

› 0,01; 0,005 (mechanical)

› 0,005 ÷ 0,0001 (digital)

range… (0 ÷ 25) ÷ (900 ÷ 1000) mm

types:

› mechanical

› digital

measurement

outer dim.

inner dim.

depth

special types:

plate

tubes

prizmatic

…

special types:

plate

tubes

prizmatic

tolerances

thread

threetouch

holemicrometer

…

micrometer

www.somex.cz

0 30

20

0 30

20

0

0

00

2,24 2,76

2,51 2,49

indicator gauge

not absolute

measurement

must watch the

„hand“ to see if it

did not run the full

circle

scale division!!!

indicator gauge examples

accuracy (4 grades):

› 0,5 ÷ 0,05 mm (cca 5 mm)

› 8 ÷ 4 mm (cca 1 m)

range … ~ 0,1 ÷ 1000 mm

types:

› steel (~ 800 HV)

› sintered carbide

› ceramic (~ 1350 HV)

properties:

ground, polished, lapped

no surface protection

thin oil film

geometric precision

primary block accuracy

(0,02+0,05 .L [m]) mm

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dimenstions

a set of different dimensions in a box (ex. 32 pcs set)

1,005 mm (1pc)

1,01-1,09 step 0,01 mm (9pcs)

1,1-1,9 mm step 0,1 mm (9pcs)

1-9 mm step 1 mm (9pcs)

10-30 mm step 10 mm (3pcs)

50 mm (1pc)

for specific value = put together parts› Handle with care!!!

Together with a two-axis

table with micrometric

screws it is a universal

measuring device

The ocular includes the

„crosshair“

› Two perpendicular lines

› Three lines rotated 60°

› Four line rotated 45°

› Shape lines (thread profiles)

Universal Length Measuring Machine

Accuracy – 1 ÷ 0,1 mm

Measuring range – up to 6 meters

Laserinterferometer

Accuracy = up to 0,01 mm

(depending on measured

length)

(0,5+1,1.L/1000 ) mm

Range:

very variable

(up to 100 meters)

Angle gauges

Square – for right angle

Protractor

Sine bar

level

Like linear block gauges

For fast measurements in practical life

Mainly 90°

Also 45°, 60°, 120°a 135°

Rotary arm

digital

With moving arm

Rotary arm

digital

With moving arm

With occular

inclinometer

Used with block gauges

Mechanical – hydraulic

Gyroscopic -

Digital - accelerometer

threepin method

gauges

thread snap gauge

microscope

Micrometer

Problem is that the thread si too complex to bemeasured. And also that the diameters are not recognizable on the part

Nominal diameter (Major and minor diameter)

Indirect measurement – we measure the „Diameter over

pins“ and we can calculate from it the nominal diameter

For pitch measurement

Gauge is placed to the thread

Thread snap gauge

Thread plug gauge

List of tasks:

1. Profile projector measurements (-o-)

2. Cylindrical plug gauge control on microindicator (-o-)

3. Cone measurement on a laboratory microscope

4. Angle measurement with an optical bevel

5. Frontal run-out measurement (-o-)

6. Run-out measurement of a rotary part (-o-)

7. Thread measurement using a three wire method

8. Measurement using a laboratory microscope (-o-)

9. Gear measurement

10. Machine operational accuracy – PC evaluated

11. Run-out measurement of a spindle

12. Batch measurement of cylindrical parts

Task:

Measure the spacing R (distance between center points) of

clamping holes in the spring plate. Use the profile projector for

the measurement.

Measure and write down the coordinates of

tangents of measured holes!

Attention! – micrometrix thread has two revolutionsper milimeter Ring scale division is 50 scales.

Carefully read if you see the „half-milimeter line“

on the main scale + add the value from the ring.

Hole CoordinateCenter

coordinate

Diameter

value in axis

Diameter

valueSpacing

1

X1.1

X1.2

Y1.1

Y1.2

… … … …

Problem:

Decide about the applicability of the GO and NOT GO ends

(good and bad ends) of a workshop cylindrical plug gauge for

hole diameter control. Use the microindicator for measuring.

Deviation with a block gauge (40 mm) = -35

Deviation with a measured part = 12

Total deviation = 12-(-35) = 47

Scale = 0,001 mm

Dimension of deviation = 47 scales = 0,047 mm

Dimension of measured part = 40 + 0,047 = 40,047

mm

!!! Results discussion !!!

Problem:

Measure the frontal run out of a universal clamping head used for

workpieces clamping in both open and closed state.

Write down the values and express them by using a column chart.

(measured values in columns, separate columns for different places

of measurement).

Position [mm] clamp 1 2 3 4 Check no.1

Open -0,02 -0,01 0,01 -0,01 -0,02

Closed -0,04 -0,03 0,02 0,01 -0,04

-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

clamp 1 2 3 4 open

closed

-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

clamp 1 clamp 2 clamp3 clamp 4

open

closed

MAX

MIN

Runout = maximum value

ex. RUNOUT OF OPEN CLAMP = MAX-MIN

Problem:

Measure the radial and axial run-out of rotary (spindle) part

Express the results with a polar chart and mark the maximum run-

out value in this chart.

0.22

0.24

0.26

0.28

deviations for axial runout [mm]

Problem:

Measure the nominal thread diameter d2 and the

lead (pitch) of a metrical thread on given part.

Compare the measured values with nominal values in

table. Discuss the results.

Thread cross hair

movement of crosshaird2

3

2 1