Optical 3D Surface Metrology€¦ · Optical 3D micro coordinate measurement | Form & roughness...

Optical 3D micro coordinate measurement | Form & roughness

The advantages of Optical 3D Surface Metrology

Measurement

on AM Surfaces


Agenda

» Traditional measurement methods of surface measurement

» Optical methods

» Focus Variation as a measuring principal


Preview

➢ The measurement of complex surfaces such as AM surfaces presents

problems when it comes to surface finish measurement

➢ Growing need to build the product with the finished surface

➢ The surface to be measured is generally not homogenous and can be very

rough in nature and often will have a geometric form/free shape

➢ Point and line based measurements do NOT reflect the true surface but only

a line on the surface

➢ This leads to a requirement for an area based measurement


Traditional Mechanical Contact Instruments

The basis of the technique is to record the

mechanical movement of a precision stylus as it is

scanned across the surface to be measured

Many Different Stylus

& Probe Designs

available Today

including hand held

devices, providing a

2D measurement


Stylus

Beam

Knife Edge Pivots

)

Coil

Coil

Simple Contact Measurement

Surface to be Measured


Stylus Tip

B

A

Profile produced by Stylus –

Smoothing the Surface B

A

Reproducing the Surface – Limitations / Smoothing

Reproducing The Surface

Actual surface

being measured


3D Measurements with Stylus Instruments

Y Axis Incremental Movement

X Traverse Direction

A map is built up of a number of X traces in Y (up to ~250)

Disadvantages:

Takes a long time to produce the 3D map (~30min or much longer)

Subject to drift depending on environment

Need to ensure the X start position of each trace is the same


Variances in Measurement with Profile Measurement (on an Optical Device» Rough “AM” Type

Surface

1.16µm Ra

1.36µm Ra

0.99µm Ra


Benefits of area based measurementsWHY OPTICAL 3D METROLOGY?

»

=

≠Area

Profile

In some cases profile based measurements

do not give enough information


Area Versus Profile Measurement

Extracted profile:

Same profile butcompletely different surface structure

- Profile Measurement gives only limited information

- You have to know your surface and what you are doing

- Area Measurement can help obtaining more reliable results


Summary of Tactile Measurements

➢ Tactile measurements provide information about the line, NOT the surface

➢ There can be large variations in line measurement results across the surface,

which one is the correct answer? – or do you move it until the correct answer

is found

➢ Very subjective and user affected

➢ Stylus smoothing of surface greatly affects the results


Optical Surface Measurement

Optical Techniques offer many advantages over tactile probing.

➢ They are non contact, do NOT cause surface deformation or damage

➢ They allow easy measurement of both line based (R values) and area

based (S values) measurement

➢ With line based they allow correct positioning of the profile line

➢ They allow both form and finish to be measured on the same surface

➢ The results are NOT subject to “stylus smoothing”

➢ There are 2 main types of instrument


1) Interferometry

➢ Interferometry is a family of techniques in which waves are superimposed

causing an interference pattern to extract surface information, commonly

used in science and industry for the measurement of small surface

variations

➢ These techniques are ideal for the measurement of smooth and flat

surfaces (these are typically not AM surfaces)

➢ They would not measure slopes greater than 30 degrees

➢ They are subject to environmental variations and results need to be

“interpreted” rather than “read”


White Light Interferometer

The Reference and Test beams must travel equal distances

from their point of creation in order for interference to be created from

the flat reference mirror

CCD

Test Beam

Reference Beam

Test Beam Length = Reference Beam Length (Optical

Path Difference (OPD) = 0)


WLI Slope Limitations

Sample is not flat

WLI use a flat reference so can only measure low sloping surfaces

Sample is steppedSample is tilted

Higher Magnification Lenses (required for roughness

measurement) can only measure up to 30 degrees and

have a small field of view


2) Focus Variation

➢ Focus variation is a method to calculate a sharp optical 3D datasets, from

Optics with a limited depth of field on which measurements are made

➢ This technique is ideal for the measurement of surfaces from submicron

to millimetres and allows measurement of line AND area based

measurement

➢ It is possible to measure slopes up to 870 and rough and sculptured

surfaces

➢ The technique is very robust and NOT generally affected by environmental

variations. Results can be easily obtained and “read”.

➢ The ideal solution for AM surfaces


How Focus Variation Works“Simple“ Explanation

9 m

DOFDOF

5 m

5 m 9 m5 m 9 m


Focus-Variation Coaxial Illumination

The specimen is

illuminated with modulated

light

The light is reflected by

the specimen and

projected on to a digital

sensor in the precision

optic

As the distance

between specimen and

objective is varied the

change of sharpness

is measured


Patented* illumination Focus Variation Ring Light Illumination

objective &

concentrator

*patent pending

The ring light helps to measure

High Angled Surfaces

Super low reflective surfaces


Optical Measurement Complex Structures Measurement of Very Rough Surfaces

• 3D Surface datasets can be joined together with image stitching

• Surface over lap, true colour and localised features all contribute to the stitching algorithm pulling the

data together

InfiniteFocus Optical 3D Measurement

3D Sensor Objective: Alicona 50x


Results from Area Based (Functional) Parameters


Results from Area Based (Functional) Parameters

Vmp 0.03Peak material volume of the topographic surface (ml/m²)

Vmc 0.89Core material volume of the topographic surface (ml/m²)

Vvc 1.04Core void volume of the surface (ml/m²)

Vvv 0.17Valley void volume of the surface (ml/m²)Vvc/Vmc 1.17Ratio of Vvc parameter to Vmc parameter


Alicona Measurement Instruments


Summary of Focus Variation on AM surfaces

» Provide full details of a surface – not just a line

» Provide “Texture” information on the surface

» Not subject to operator variances – so reduces operator influence of the measurement

» Robust and Repeatable


EdgeMasterX

InfiniteFocus G5

IF-SensorR25

ToolCobot

IF-ProfilerInfiniteFocusSL

EdgeMaster

PortableRL

µCMMCompactCobot

DiscCobot

AliconaMeasurement solutions


27

• IF is a Focus Variation based

measurement instrument that

combines

– An high powered optical

imaging system

– Optical surface profiler

Alicona Infinite Focus

Measurements:

– Non-destructive

– Accurate and quantitative 3-D surface characterisation

– Fast

– Capable of measuring a wide range of materials and surfaces


Measure 87 Degree SlopesMachine Tool Tip Cutting Edge Measurements

Positive Bevel Negative Bevel Edge Roundness

Chipping Basket Arch

Type 1

Type 2

Type 3

Type 4

Type 5


29Critical Dimensions

Measure:

Heights, Sizes,

Angles, Volume,

Form, etc.


Technology: Focus-Variation

Contouring Roughness

&


IF - Technical Specifications

Optical 3D-surface metrology based on a colour focus sensor

InfiniteFocus G5 InfiniteFocus SL

Vertical resolution >10nm >20nm

Lateral resolution >440nm >640nm

Scan height <22mm

<36mm (with new HX lens)

<25mm

Scan area 200mm x 200mm 50mm x 50mm


Application independent

» Tool industry » Micro precision manufacturing

» Medical technology and pharmaceutics

» Injection moulding » Automotive industry » Aerospace and aeronautics


Thank You for Listening

Optical 3D Surface Metrology€¦ · Optical 3D micro coordinate measurement | Form & roughness...

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Transcript of Optical 3D Surface Metrology€¦ · Optical 3D micro coordinate measurement | Form & roughness...