3d scanning book

8/18/2019 3D Scanning Book

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A Multi-Dimensional Look At 3D Scanning: When, Why, And How To Use It

2014 Q-PLUS Labs. All rights reserved.


2/192014 Q-PLUS Labs. All rights reserved.


A MULTI-DIMENSIONAL LOOK AT 3D SCANNING:

WHEN, WHY, AND HOW TO USE IT

INTRODUCTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. 3

WHAT IS 3D SCANNING?!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 3

CONTACT SCANNERS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

4

Coordinate Measuring Machines!!!!!!!!!!!!!!!!!!!!!!!!! 4

Articulating Arms !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 4

Form and Contour Tracers !!!!!!!!!!!!!!!!!!!!!!...!!!!! 5

NON-CONTACT SCANNERS!!!!!!!!!!!!!!!!!!...!!!!!!!!! 5

3D Laser Triangulation!!!!!!!!!!!!!!!!!...!!!!!!!...!!!! 5

White Light Scanners!!!!!!!!!!!!!!!!!!!...!!!!!!!!!!. 6

Conoscopic Holography !!!!!!!!!!!!!!!!!!...!!!!!!!!...! 6

Time-of-Flight and LiDAR!!!!!!!!!!!!!!!!!...!!!!!!.!!!! 6

Photogrammetry!!!!!!!!!!!!!!!!!!!...!!!!!!!!...!!!! 7

CT Scanning and MRI !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 7

FOR VERY SMALL OBJECTS!!!!!!!!!!!!!!!!!!!!!!!!!!!

. 8Laser-Scanning Confocal Microscopes !!!!!!!!!!!!!!!!!!!!!! 8

White Light Interferometry!!!!!!!!!!!!!!!!!!!!!!!!!!!! 8

Axial Chromatism !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 9

WHEN SHOULD YOU USE 3D SCANNING? !!!!!!!!!!!!!!!!!!!!!! 9

REVERSE ENGINEERING!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 10

FIRST ARTICLE INSPECTION !!!!!!!!!!!!!!!!!!!!!!!!!!! 10

QUALITY CONTROL INSPECTION (PROCESS CONTROL) !!!!!!!!!!!!!! 11

ANALYSIS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!..!.!! 11

DOCUMENTATION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 12

WHY SHOULD YOU USE 3D SCANNING? !!!!!!!!!!!!!!!!!!!!!!! 12

Speed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.. 13

Coverage!!!!!!!!!!!!!!!!!!!!

.!!!!!!!!!!!!!!!

13 Accuracy !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. 13

Cost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. 13

SHOULD YOU PURCHASE EQUIPMENT OR OUTSOURCE?!!!!!!!!!!!!!! 13

HOW OFTEN DO YOU NEED TO SCAN?!!!!!!!!!!!!!!!!!!!!!... 14

HOW QUICKLY DO YOU NEED RESULTS? !!!!!!!!!!!!!!!!!!!!.. 14

WHAT IS YOUR BUDGET? !!!!!!!!!!!!!!!!!!!!!!!!!!!! 14

HOW MANY TYPES OF OBJECTS DO YOU NEED TO SCAN?!!!!!!!!!!!! 14

DO YOU HAVE IN-HOUSE EXPERTISE? !!!!!!!!!!!!!!!!!!!.!!. 15

CAN YOU MEET THE NECESSARY ACCURACY REQUIREMENTS?!!!!!!!!!. 15

HOW DO YOU DETERMINE WHICH 3D SCANNER TO USE? !!!!!!!!!!!!!... 15

Surface characteristics!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

16Object size!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 16

Object shape!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 16

Accuracy !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 16

Speed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. 16

Cost!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 17

COMMON 3D SCANNING MYTHS DISPELLED !!!!!!!!!!!!!!!!!!!! 17

MYTH: NOT ENOUGH ACCURACY !!!!!!!!!!!!!!!!!!!!!!!!. 17

MYTH: THE TECHNOLOGY IS UNPROVEN !!!!!!!!!!!!!!!!!!!!.. 18

CONCLUSION!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 18


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Introduction

3D scanning is a growing

sub-field of measurement

that includes many types of

scanning devices for a

broad range of

applications. Although it is

relatively new on the

scene, 3D scanning is

widely accepted as an

effective, accurate, andfast way to collect and analyze measurement data. In fact, the level of detail that 3D

scanning can capture makes it the method of choice for many applications.

This guide will cover the basics behind the technology using a traditional information-

gathering technique:

• What – A description of the technology and the types of 3D scanning available

•

When – The most common applications for 3D scanning• Why – Advantages of using 3D scanning over other methods

• Who – Factors to help you decide whether to outsource or purchase

equipment

• How – Tips for deciding which 3D scanning technology to use

We will also dispel some common myths related to 3D scanning so you can embrace

this technology with confidence.

What Is 3D Scanning?

In general terms, 3D scanning involves the collection of dimensional coordinate data

about the shape and size of an object. After the data is collected, it is processed using

point cloud software that can be used in a number of ways. With reverse engineering,

a digital 3D model can be generated from the data and used for a range of

applications. With dimensional inspection, the data can be compared to an existing


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Portable Optical CMM

Some applications call for a portable solution, for example, taking

measurements on a shop floor or in the field. In these cases a portable CMM

can be used to gather measurement data for areas that are difficult to reach.

The hand-held device transmits data wirelessly and allows the operator to moveboth the part and the scanner during the measuring process.

Form and Contour Tracers

Form and contour tracers are purpose-specific devices that use extremely

accurate continuous contact sensors and styli to obtain small-part geometry.

These devices are especially useful for scanning objects that include threaded,

cylindrical, or round features.

Non-Contact Scanners

The main reason to utilize non-contact

scanners is immense amounts of data

that can be collected quickly. Also, in

many cases, using a contact sensor is

not appropriate because the act of

touching the object during measurementwill alter its geometry, thus creating an

inaccurate 3D model. Objects that are

fragile, flexible, or otherwise sensitive are

more suitable for the following types of

3D scanning technologies:

3D Laser Triangulation

With this type of 3D scanning system, a laser is projected onto the surface of anobject and a camera captures the reflection. The laser can be in the form of a

single point, a line, or an entire field of view. When the reflection is captured,

each point is triangulated, measured, and recorded, resulting in a 3D rendering

of the shape and surface measurements of the object. Laser scanning tends to

work better with more reflective surfaces than structured light scanners.




White Light Scanners

White light scanners, also referred to as structured light scanners, use halogen

or LED lights to project a pattern of pixels onto an object. The distortion of the

pixels created by the object’s surface and the resulting light pattern can be

measured and used to reconstruct a 3D image. Such scanners also may useother colors of the light spectrum such as blue or red light though the effect or

improvement in results is small.

Conoscopic Holography

Another type of 3D laser scanning technology is conoscopic holography. A

single laser is projected onto the object, and the reflection is returned along the

same path. The reflected beam goes through a conoscopic crystal and is

projected onto a charge-coupled device (CCD). The diffraction pattern is thenanalyzed to determine the precise distance to the surface. The most common

applications for this type of device are measuring small features as well as

interior surface geometry where triangulation would not be possible. It is highly

precise and commonly found on multi-sensor vision systems. This technology

works fairly well despite surfaces that are highly reflective or absorbent.

Time-of-Flight and LiDAR

This type of laser scanning uses a time-of-flightlaser rangefinder based on LiDAR technology to

measure the distance between the laser and the

object’s surface. The laser rangefinder sends a

pulse of light to the object and measures the

amount of time it takes for the reflection to return

in order to calculate the distance of each point

on the surface.

Point measurements are taken by aiming the

device at the object and using a series of mirrors

to redirect the light from the laser to different

areas on the object. Although the process may

seem cumbersome, typical time-of-flight 3D


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laser scanners can collect between 10,000 and 100,000 points per second,

which is much faster though less accurate than contact sensors.

Photogrammetry

Perhaps the oldest type of non-contact 3D scanning method, photogrammetryhas been in use since the development of photography. In simple terms,

measurements between two points on an image can be used to determine the

distance between two points on an object. Several factors play a role in the

accuracy of this type of system, including knowledge of the scale of the image,

the focal length of the lens, orientation of the camera, and lens distortions.

Photogrammetry can be used to measure discrete points using retro reflective

markers which can be highly accurate given the measurement envelope. More

recently, photogrammetry coupled with special image processing software canbe used to obtain complete and dense point clouds. These point clouds are

typically less accurate than other forms of scanning, however only a camera and

software is required making it one of the lowest cost methods of 3D scanning.

Photogrammetry is also often used in combination with other types of 3D

scanning technologies that produce point cloud results, primarily to increase the

measurement range by creating a reference frame of discrete points on which to

match multiple 3D scans.

Lastly, one particularly interesting feature of photogrammetry is that the

measurement envelope is virtually limitless.

CT Scanning and MRI

Magnetic resonance imaging (MRI)

and computed tomography (CT)

scanning are generally known for their

medical applications, but they can

also be used for 3D scanning in

metrology. CT scans use x-rays to

detect and display both the internal

and external geometry of an object.




MRI scans use nuclear magnetic resonance to do the same.

The two types of scanning devices have different capabilities with respect to the

density of objects. MRI scans are generally better for objects that are made from

softer materials, whereas CT scans are more suitable for objects that are morerigid and made of harder materials. Objects that are made from materials that

contain no water are not suitable for MRI scanning. However, when either MRI

or CT scanning is possible, MRI often produces more detailed results that can

be refined by adjusting the radio frequency and magnetic fields while

scanning. One main advantage of these types of scanning systems is the ability

to collect data about the internal geometry of the part without destroying or

damaging it.

For Very Small Objects

In addition to the form and contour tracers that use contact sensors, small objects can

also be scanned with non-contact methods.

Laser-Scanning Confocal Microscopes

A confocal microscope uses a process called optical sectioning to collect images

from various depths. These images can be reconstructed with a computer tocreate a 3D model of complex small objects. Unlike other laser systems, a

confocal microscope only sees one depth level at a time, which allows it to

generate a highly controlled depth of focus for very small objects with tight

tolerances.

White Light Interferometry

This non-contact measurement system allows you to obtain surface

measurements at the micrometer level. The technology behind white lightinterferometry uses wave superposition to measure distances based on data

collected about reflected wave interactions.

Interferometers can also be combined with microscopes to measure very small

objects. Because they rely on the detection of waves and not optical images,

interferometers are also useful for measuring objects with reflective surfaces.


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This technology is limited in terms of the angle of surface that can be measured

but for what it can detect, it is virtually unbeatable in accuracy.

Axial Chromatism

Like interferometry, axial chromatism

also uses white light to collect

measurement data. However,

whereas interferometry uses the

superposition of waves after they are

reflected off the object, axial

chromatism measures the wavelength

as it hits the surface of the object.

This method produces more reliableresults when measuring surface

roughness or step-height depth, due

to the minimum mathematical

calculation required.

The tolerances of large objects may allow the use of a thin whitening spray to

facilitate scanning but the geometry of very small objects could be potentially

buried by it. Fortunately, all of these methods work well with various types ofsurfaces from reflective to absorbent.

When Should You Use 3D Scanning?

3D scanning can be used for a broad range of applications, but it offers the most

benefit for the measurement of objects with non-prismatic geometry. Other methods

typically require data extrapolation or exclusion, but 3D scanning allows you to capturesignificantly more data points over the entire surface of the object.




Reverse Engineering

Reverse engineering is the process of

evaluating an object to better understand

how it functions or to have the ability to

replicate it. The challenge in reverse

engineering a physical object lies not

only in determining how it was made with

little or no knowledge of the original

production process but in accurately

determining what its geometry is.

Examples of reverse engineering applications include:

• Artifacts for replication with a 3D printer

• Car floor contouring for production of molded mats

• Teeth for artificial replacements

• Replacement parts for manufacturing processes

• Replacement parts for aircraft

Regardless of the application, the first step in reverse engineering is creating an

accurate 3D CAD model of the original object and/or an engineering drawing. 3D

scanning is one of the fastest, most accurate methods for creating 3D digital models,

especially for objects with irregular geometry.

First Article Inspection

The manufacturing industry relies onfirst article inspection to measure

parts, verify engineering

specifications, and refine

manufacturing processes. 3D

scanners can be used to create a full

point cloud dataset of the first article


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produced on a manufacturing line for comparison to the engineering digital model

and/or drawings. Process modifications can be made based on the deviations

between the first article and the drawings.

Often, time is of the essence when a manufacturer develops a new product, which iswhy 3D scanning can be so useful for this type of application. The results are

accurate, and with advance preparation, turnaround time can be fast relative to other

technologies. Post- processing of 3D scan data can be programmed in advance of

production so once the full dataset is obtained the part can move on to the next

operation and the scanner can move on to the next part with measurement results

computed in as little as a few seconds.

Quality Control Inspection (Process Control)

Parts on a production line must be periodically inspected to ensure that they continue

to meet specifications, and to confirm that the manufacturing process is operating as

expected. 3D scanning can be used for off-site testing in a specially equipped

metrology lab; it can also be integrated directly into a manufacturing line to speed up

the quality control process.

Analysis

3D scanning is just a method for collecting information about an object. What can be

done with that information is at the user’s discretion. Uses for the data captured with a

3D scanner include:

• Comparing the profile of objects by color mapping

• In depth “blue-printing” of geometry

• Compensatory process control

• Analyzing the aerodynamics of an object• Evaluating the potential causes of an automobile collision

With point cloud data and a 3D model, you can use a range of techniques and

software programs to analyze an object’s shape and various other dimensional

characteristics.




Documentation

3D scanning can capture and document the

state of an object for future reference.

Perhaps you want to create a 3D model of

a series of prototype parts so you will have

a record of each version used in an

experiment. Perhaps a tooling die had to

undergo numerous manual modifications to

correctly produce a part and the specific

changes need to be collected for use in

making the next die. An archaeologist

might want to capture every contour of an

artifact for historical documentation.

Regardless of the application, 3D scanning

gives you the ability to capture the shape of

an object in a digital format that can be

used indefinitely, no matter what happens tothe original object.

Why Should You Use 3D Scanning?

3D non-contact scanners are faster, and therefore potentially more cost-effective than

other metrology techniques such as a CMM. Advances in both scanning technology

and point cloud data processing are bringing 3D scanning to the forefront ofmetrology.

Some of the advantages of using 3D scanning over other types of technologies

include:


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Speed

Automated 3D scanners can measure thousands of points per second, which is

much faster than manual measurement devices.

Coverage3D scanners are able to collect and measure millions of data points on the

surface of an object, often in a matter of minutes—an achievement that was

neither practical nor possible before the technology was developed.

Accuracy

Strides in 3D scanning technology have continually improved the accuracy,

making it an increasingly formidable measure measurement method. The level

of detail you can capture has improved significantly as the ability to gather moredata points has increased.

Cost

3D scanning is a cost-effective measurement solution compared with alternative

technologies, especially when you factor in its relative speed and ease of data

acquisition.

Of course, 3D scanning is not appropriate for every measurement application. If youneed to measure only one dimension or if the object has extensive interior surfaces or

if the tolerances are very tight, a different approach might make more sense.

Should You Purchase Equipment or Outsource?

If you determine that 3D scanning is the right choice for your application, you must

decide whether to purchase equipment for in-house use or outsource scanningservices to a qualified provider. Several factors play a role in this decision,

including:




How often do you need to scan?

If you perform regular real-time in-process

quality control checks, on-site equipment is

imperative. However, if you need first articleinspections of complex parts or periodic in-

process measurements, working with an

outside measurement lab can save you time

and money. You won’t have to worry about

maintaining equipment or hiring qualified

staff, and you have more control over the costs.

How quickly do you need results?

Instant measurement results likely necessitate having your own equipment, especially

if you have the resources to support it. However, a qualified lab can also produce fast

results, especially if you work closely together from the beginning of the project.

Measurement programs can often be generated in advance of the arrival of the

part.

What is your budget?Before purchasing a new system, be sure to factor in the lifetime costs of equipment,

training, and maintenance. If you expect to regularly use the equipment for a long

period of time, purchasing may be the most cost-effective solution. However, if you are

uncertain about whether you will need 3D scanning capability in the long term, starting

with outsourcing is prudent. Another factor to consider is evolving technology. One of

the benefits of working with good outsourcers is that they stay on the cutting edge,

purchase the latest equipment, and learn the newest techniques.

How many types of objects do you need to scan?

If you know that you will only ever need to measure one type of object that is the same

size and has the same types of surface characteristics, you can purchase a device


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with confidence. However, if you are not sure how your measurement needs will

change over time, outsourcing is perhaps a better solution.

Do you have in-house expertise?

Most 3D scanning equipment requires a

level of training that your staff may not

possess. Of course, you can hire

qualified operators or train your existing

staff, but this requires an investment that

can also take some time. Outsourcing to

a metrology lab will allow you to dedicate

your personnel resources where they arebest suited, thus leaving the scanning

requirements to the experts.

Can you meet the necessary accuracy requirements?

Depending on your industry and application, NIST traceability and other regulatory

requirements may be necessary. If this is the case, you must ensure that both your

equipment and processes are in compliance. If you are not confident that these

requirements can be met in-house, outsourcing to an expert is wise.

How Do You Determine Which 3D Scanner to Use?

Different objects require different types of 3D scanners, and several factors play a role

in determining which type of system to use. Whether you decide to purchase your own

equipment or outsource, you will need to determine which type of scanning method

makes the most sense for your application.

Using a 3D scanner to create a model for replication of a children’s toy is completely

different from using the same technology in the aerospace industry. The details of

your specific project will inform which type of technology is most appropriate.




Consider the following factors when making your decision:

Surface characteristics

Is the object shiny, smooth, rough, dark, pitted,

or soft? Each type of 3D scanning technologybrings its own strengths and weaknesses to

different types of surface characteristics.

Understanding which type of system will work

best with your object is the first step to

selecting a 3D scanning method.

Object size

3D scanning can be used to measure objects from the nano level to entirebuildings, and everything in between. Naturally, no single piece of equipment

can cover this entire range.

Object shape

Although 3D scanning is generally recommended for objects with non-prismatic

geometry, there are still factors within that classification that play a role in

determining which type of scanning technology to use. For example, an object

with deep boreholes may require a touch probe in combination with lasertriangulation.

Accuracy

Reverse engineering a precision part or scanning an object for medical use

requires a higher degree of accuracy than replicating a souvenir. Factors such

as NIST traceability and the end application can help you determine which type

of 3D scanning equipment to select.

Speed

Some 3D scanning equipment produces faster results than others. In general,

speed is related to accuracy, so if you do need a high degree of accuracy, the

job will likely take longer. However, if you are using 3D scanning for first article


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inspection and need quick results, you may be able to select a solution that

meets your requirements for both speed and accuracy.

Cost

Every business operates with a budget. Accuracy and speed generally comewith a higher price tag, so carefully consider your needs before making an

investment.

If you do not have expertise in 3D scanning, work with a qualified professional to help

you select the right equipment for your application. Producing useless results that

don’t meet your accuracy requirements is a waste of time and money, and breaking

the bank for a level of accuracy and detail that you don’t need won’t make sense,

either.

Common 3D Scanning Myths Dispelled

Because 3D scanning is still a relatively new technology in the field of metrology, there

are some common myths and misconceptions about it. Understanding the truth behind

these myths is important for ensuring the success of your project.

Myth: Not Enough Accuracy

The reality is that metrology-class devices do exist. If NIST traceability is important to

you, 3D scanning is still very much a possibility, provided you work with the

appropriate equipment and a provider that can go over the various system accuracy

statements, and provide validation as well as gage repeatability and reproducibility

tests.

The basis of 3D scanning technology is the collection of data points. The more data

points the equipment is able to collect, the higher the resolution you will be able to

achieve. Accuracy also depends on many other factors such as camera quality and

correct calibration. Although not all 3D scanning tools will produce results with the

level of accuracy you need, chances are there is a solution that meets your

requirements.




Myth: The Technology Is Unproven

The truth is that a good provider can use multiple techniques to prove out accuracy

and demonstrate that the 3D scanning results are correct. Just because there is not

yet a formal American or International Standard for determining the accuracy of a 3Dscanner does not mean the accuracy of a scanner cannot be determined. In some

cases, 3D scanning may be just one component of the overall measurement

approach.

3D scanning technology has been proven to be a valid measurement tool, but

working with trained professionals and properly calibrated equipment is essential to

ensure accurate results. Remember, there is no one-size-fits all solution for 3D

scanning. Selecting the right equipment for your application is critical for success.

Conclusion

3D scanning is an increasingly proven

technology that is here to stay. New

technological strides are achieved on an

ongoing basis, making it even moreaccessible and reliable. Whether your

project entails reverse engineering, first

article inspection, object replication, or

documentation, there likely is a 3D

scanning solution that will meet your

needs.

When determining what 3D scanning approach to take, base your decision primarilyon these three straightforward factors:

• Accuracy

• Speed

• Cost


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Understanding the specific requirements of your application and the limitations of

your equipment is the first step to ensuring success.

Whether you decide to purchase your own equipment or outsource 3D scanning

services, Q-PLUS has the latest available technology and the skills to help yousuccessfully navigate your project. We are an authorized reseller for dozens of

manufacturers, and because we use the same equipment every day in our own labs,

we are uniquely qualified to help you select the appropriate solution. Should you

decide to outsource services, we’ll work with you from the beginning to ensure that

we thoroughly understand your needs and can help you achieve your goals in the

most cost-effective manner.

Contact Q-PLUS Labs today for a consultation and a free quote. We work in a broadrange of industries including aerospace, medical, archaeological, precision

manufacturing, and more.
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