v a 10 · 2012. 7. 4. · 2 — microscan guide to dpmi microscan guide to dpmi — 3 1...

GU I D E L I N E S F O R

D I R E C T PA R T MA R K ID E N T I F I C AT I O N

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1 INTRODUCTION

2 SYMBOLOGY SELECTION

3 READABILITY

4 MARK PLACEMENT

5 MARKING METHODS

6 MARKING METHOD SELECTION

7 MARK QUALITY VALIDATION

8 READERS

9 VENDORS

APPENDIX10

Microscan Guide to DPMI — 32 — Microscan Guide to DPMI

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1

INTRODUCTION

Bar codes have been successfully used to identifyproducts since the 1970s when they were first intro-duced to the grocery retail business. Since then, theyhave been widely adapted by other industries. Near lyevery shipping and receiving department relies on barcoding technology to improve inventory visibility.Today’s manufacturer, however, can no longer besatisfied knowing how many raw components arecoming in the door and the amount of completedproduct leaving the facility. Manufacturers must alsoknow the status of their work-in-process inventory aswell.

While the overall concept of product tracking is notnew, the automated tracking of product down to theindividual part and component level has proven tohave even greater bottom-line impact. The most directway to ensure complete quality control of the produc-tion process is to directly mark a part with a machine-readable code and track it through its entire life cycle.This is called Direct Part Mark Identification (DPMI).

Recognizing the benefits of direct part marking, manyindustry associations have already established stan-dards for marking individual parts and components fora variety of applications. The EIA, SEMI, AIAG, DoD,and the SPEC 2000, aerospace industry have alladopted DPMI standards for applications in theirindustry.

Additional companies are using DPMI for their owninternal applications. DPMI can be used to opti-mize line performance, identify defects, increasefirst-pass yields and as a result, reduce the costsof manufacturing. Manufacturers also rely on DPMIfor identifying incoming parts for maintenance andreturns, resolving warranty issues and liabilityclaims as well as tracking high-value componentsto prevent theft.

Two dimensional symbols such as Data Matrix arethe most common symbologies used for DPMIapplications because of their small size, datacapacity, error correction, and ability to be appliedby a variety of marking methods. All a manufac-turer needs is .1 inch of square space on a compo-nent and it can be marked with a 5 or 6 digit DataMatrix symbol. As a result, Data Matrix enablesthe traceability of components such as crystaloscillators or custom ASICs that in the past couldnot accommodate any type of machine-readableform of identification.

While 2D codes have been in existence since theearly 1990s, the introduction of the smart cameradesigned specifically for reading linear and 2Dcodes has enabled the widespread adoption of thetechnology in the last few years. Smart camerashave succeeded where vision systems have failedin providing manufacturers with a robust imagingsolution capable of high performance read rates ondirectly marked symbols with the ease of use andprice point of a bar code scanner.

With more than 20years experience

solving auto IDapplications,

Microscan providesthe necessary

expertise to helpyou achieve

success in yourDPMI applications.

For moreinformation on

Microscan’scomplete product

line of imagers andsmart cameras,

please call (425)226-5700 or visit

www.microscan.com.

— These areonly someof the manysymbologiesin use today.

Code 128

PDF417

RSS

Data Matrix

QR


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2

SYMBOLOGY SELECTION

Industry StandardsThe first step in selecting a symbology is to familiarizeyourself with applicable industry standards. Industrystandards will dictate what symbology needs to beused, as well as other parameters such as density,data content, data syntax and other specifications.Each standard is different. Some provide the manu-facturer with some flexibility, others do not. Pleaserefer to The Industry Specifications Table for a list ofcurrent industry standards relating to DPMI applica-tions.

In addition to investigating industry standards,review the standard specifications established byISO for the symbology. Many application challengescan be avoided simply by starting out with a goodsolid bar code. Following the specifications willhelp you accomplish this by giving you a solidfoundation of the characteristics of the symbology.

Assessing Application NeedsFor applications not related to a specific industrystandard, it is important that you carefully evaluatethe needs of your application before you select asymbology. First determine if you will be usinglinear bar codes or 2D codes. If you are unsure,ask the following questions:

APPLICATION TIPS

• What are the goals of the application?• What type and how much data will

you need to encode?• How much real estate is available

for the symbol?• How will the symbol be applied?• Will the symbol be used for internal purposes

only, or will it be read externally as well?• Is symbol permanency a concern?

Two dimensional codes, such as Data Matrix, aremore commonly used for direct part markingapplications than linear codes. Data Matrix, forexample, offers the robust Reed Solomon methodof error correction and much higher data capacity.

If yourapplication doesnot have astandard, youmay still benefitby reviewingstandards forapplicationsresembling yourown.

INDUSTRY SPECIFICATIONS TABLEInternational Standards

ISO/IEC 16022 Bar Code Symbology Specification – Data Matrix

ISO/IEC 15415 Bar Code Print Quality Test Specification – Two-dimensional symbols

AIAG Standards

B-1 Bar Code Symbology Standard

B-4 Parts Identification and Tracking Application Standard

B-13 2D Symbology White Paper

B-14 Guidelines for use of Two-Dimensional Symbols

with the B-10 Trading Partner Labels

B-17 2D Direct Parts Marking Guideline

ATA and IAQG Standards

ATA Spec 2000, Chpt. 9 Automated Identification and Data Capture

AS9132 Data Matrix (2D) Coding Quality Requirements for Parts Marking

DoD Standards

MIL-STD-130 Identification Marking of U.S. Military Property

Electronics Industr y Association (EIA)

EIA 706 Component Marking

EIA 802 Product MarkingASA Standards

NASA Standards

NASA-STD-6002 Applying Data Matrix Identification Symbols

NASA-HDBK-6003 Application of Data Matrix Identification Symbols to Aerospace Parts

Using Direct Part Marking Methods/Techniques

Semiconductor Association (SEMI)

SEMI T7-0303 Back surface marking of double-sided wafers with a Data Matrix code

SEMI T2-0298E Marking wafers with a Data Matrix code

SEMI T8-0698E Marking of glass flat panel displays with a Data Matrix code

SEMI T9-0200E Marking of metal lead-frame strips with a Data Matrix code

SEMI T10-0701 Test method for the assessment of Data Matrix code quality


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Since Data Matrix uses only one element size toconstruct the code, it lends itself more easily to abroader range of marking methods than linear barcodes. Bar code symbologies rely on several differentelement widths to encode data, making it much moredifficult to be generated with certain marking methods.

The main advantage to using a linear bar code is theability to read it with a laser scanner. Since manydirect part marks have low contrast levels, imagersoften times provide a more robust reading solution.

ART

— The MS-Q Imager from Microscan reads a variety of traditional bar codesand 2D symbols. The MS-Q Quadrus (shown here) specializes in hard to read

codes directly marked onto parts.

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bar code if text or any other mark encroaches intothis area. This is the most frequently violatedrequirement when applying a bar code. In applica-tions where space is at a premium, some products,such as Microscan’s Quadrus EZ™ are a little moreforgiving of quiet zone requirements. As a generalrule, try to keep from violating the quiet zone whenmarking your symbol.

3

READABILITY

Readability is used to describe how well a reader candecode the symbol. The most important thing, beforea project gets too far underway, is to be sure that youare creating the best symbology possible. It doesn’tmatter if you purchase an excellent reader that canread poor quality codes if others down the supplychain using less quality readers, can’t decode it.Several different factors must be addressed to createa good quality code: contrast, quiet zone, errorcorrection, element size, and mark consistency.

ContrastStrive for the best contrast possible between the lightand dark elements of your symbol, whether it is alinear bar code or 2D symbol. Good contrast createsa strong bar code signal which makes it easier for theimager to differentiate between the light and darkelements of the symbol. This will make it easier forthe imager to read the code as well as reduce thechance of noise interference. Good contrast alsoincreases the ability to read at longer distances.

Quiet ZoneThe quiet zone is the area surrounding the symbol thatmust be kept free of text, marks or objects. Accordingto the ISO specification for Data Matrix, this spaceneeds to be a minimum of a one element widthsurrounding the entire symbol. In a bar code, thequiet zone is commonly referred to as the spacepreceding the first bar and trailing the last bar in a barcode. As a general rule, this space needs to be aminimum of 10 times the width of the narrow bar inyour bar code. The imager will not be able to read the

3

— Keep inmind that 2Dcodes cantolerate muchlower contrastlevels thanlinear 1Dsymbols.

Error CorrectionWhen selecting the error correction level, unlessyou are adhering to a standard that says otherwise,be sure to select ECC 200 if you are using DataMatrix. This incorporates the robust Reed Solomonmethod of error correction, ensuring the maximumdata security for your symbol. If your symbol isdamaged in some way – scratched, a corner torn offor ink blotches on it, the symbol may still bereadable. Since most products in the industry havestandardized on ECC 200, you will have morehardware options to choose from.

— Althoughhighly damagedthis symbol can

still be readwith imagerssuch as theQuadrus EZ

and MS-Q.

The diagramsbelow offer a

more detailedlook at specificparameters ofa Data Matrix

symbol.


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For example, to ensure you are achieving consis-tent marks with an ink jet system, evaluate thecleanliness of the environment. How clean is thesurface of the part before it is marked? Cancleanliness be controlled? Can the part be washedbefore marking? If the surface has debris, such asdirt or oil, the ink will adhere to the debris insteadof the part, resulting in an inconsistent, poorquality mark.

If you are using dot peen, the hardness of thestylus must be properly matched to the hardness ofthe part. You will also need to select the bestpossible shape of the stylus for your applicationbecause it directly affects how light is reflected tothe mark. When determining the depth of themark, consider comparing the relationship betweenthe marked and unmarked areas of the part. If themark gets too crowded to the point that the ele-ments are overlapping one anther, then it wasmarked too hard. If the elements are too spreadout, then it wasn’t marked hard enough.

Element SizeAlways make the symbol as large as possible. Eventhough 2D codes can be marked as small as 50microns (2 mil), it is not recommended unless theapplication requires it. In most applications, a largersymbol is easier to mark and read accurately, and willensure a greater depth of field. In addition to makingit easier for the reader to decode the symbol, you willmost likely have more equipment options to choosefrom. More products on the market are capable ofreading a 10 mil Data Matrix code than a 2 mil DataMatrix code.

Mark ConsistencyMark consistency is critical in creating a readablecode. Just because two codes appear identical to thenaked eye, does not mean they look the same to theimager. Axial non-uniformity measures the consistencyin spacing between the elements in both the x and ydirections. In order for the 2D symbol to be readable,it is important that the elements are consistentthroughout the symbol, forming a perfect square. Ifthe symbol is not square, the distortion could becaused by slack in the marking system or from mark-ing around a curved surface.

While some variation in mark quality can be expected,try to avoid fluctuation as much as possible. Somemarking methods are more prone to consistencyissues than others.

The symbol here is a goodexample of consistent

element spacingand good mark depth.


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4

The following guidelines can be applied to success-fully mark a curved part on a reflective substratewith a Data Matrix code:

APPLICATION TIP

• Format the Data Matrix symbol into a rectangle,as opposed to a square.

• Position the code on the part so that the widthwraps around the curve instead of the length ofthe symbol. This minimizes the degree ofsymbol distortion caused by wrapping aroundthe curve.

• Choose the smallest density size possible,taking care that the element size is not sosmall that surface noise interferes with thereader’s ability to decode the symbol.

• In cases where the substrate is highly reflec-tive, diffused exterior light can be applied to theapplication to evenly light the symbol.

TextureSurface texture can create a lot of noise andinterfere with the reader’s ability to locate anddecode the symbol. If possible, select a surfacethat is free from debris and texture. If this cannotbe avoided, look for an area where the texture isuniform in magnitude and direction. For example,brushed aluminum or stainless steel. Textures thatare random in magnitude and direction, such asrough cast iron, can be more challenging. As ageneral rule, Microscan recommends that theelement size of the matrix code be a minimum of 5times the size of the texture noise on the surfaceto avoid readability problems.

— Parts withcomplex

curves, such asthe dimples ona golf ball, are

most oftenevaluated on a

case-by casebasis to

determine thebest solution

for reading thecode.

MARK PLACEMENT

Physical LocationWhen determining where to place the symbol on yourpart, choose a location that is free from surface relief.Surface relief can make it difficult for the reader toview the code. By casting shadows over part of thesymbol, surface relief can also make it much moredifficult to light the symbol evenly.

Keep in mind that the quiet zone is also consideredpart of your symbol and must be free from surfacerelief as well. No exceptions. Quiet zone violationsare one of the most common reasons why readerscannot decode symbols. If marks, text or surfacerelief infringes on this area, the reader may not beable to locate the symbol.

Curved and Reflective SurfacesFlat surfaces are usually preferred over curved sur-faces for making symbols. If a flat surface is not anoption, look for an area with a uniform curve such as acylinder. Uniform curves are much easier to mark thancomplex curves. The degree of curvature, the amountof distortion caused by wrapping, and the reflectivity ofthe surface all affect the readability of the symbol. Asa general rule, the smaller the diameter of the partand the more reflective the surface, the more difficultthe symbol is to read.

Highly reflective surfaces such as polished stainlesssteel can also present a challenge because they aremore difficult to light evenly than a non-reflectivesurface such as plastic. Flat illumination is often themost effective way to illuminate codes marked onreflective surfaces.


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5

permanent inks do exist, ink jet is not consideredby some industry standards as a permanentmarking method. Take care to ensure that youselect the most appropriate ink for your substrate.Disadvantages include routine maintenance toprevent the jets from clogging, and the additionalcost of consumables.

Laser EtchThis marking type uses lasers to etch the symboldirectly into the surface of the part. In addition toproducing a clean, high resolution mark on a varietyof substrates ranging from metal to plastics toglass, laser-etching is also well-suited for auto-mated environments requiring high volumes. Sincethe top layer of the part’s substrate is removedduring the etching-process, sometimes the minimalresidue that results may not be suited for someclean-room applications. The type of laser (Yag,CO2, YVO4) must be matched to the applicationand will affect price considerably. While laseretching equipment has a higher entry cost thanmany marking methods, there is no additional costof consumables and maintenance is minimal.

MARKING METHODS

There are many methods to mark parts. Some of themore common ways are laser etch, dot peen, electro-chem etch, and ink jet. Selecting the best method forthe application is critical to achieving success. Sinceeach method has its own advantages and limitations,it is important to educate yourself on as many meth-ods as possible and experiment on sample partsbefore selecting the one for your application.

Electro-ChemicalThis marking process uses a low voltage electricalcurrent to pass through a stencil to the part’s surface.In order for this method to work, the part must have aconductive metal surface. This method will not workfor anodized, powder-coated or non-conductive coat-ings. Unlike other permanent marking methods,electro-chemical etching does not weaken or distortmetal parts because the molecular structure of thepart is not altered beyond the depth of the mark. Asa result, very thin-walled parts and those with finesurface finishes can be safely marked without dam-age. Since electro-chemical etching is a more in-volved process than other methods, it is not suited forhighly automated applications and is commonly usedfor small product runs.

Ink JetThis type of marking uses small, circular dots that aresprayed directly onto the surface of the part. Ink jettypically produces high contrast marks, depending onthe substrate the symbol is applied to. Although

— Twoexamples of

laser etching asymbol onto

glass.

16 — Microscan Guide to DPMI

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5

Microscan Guide to DPMI — 17

Laser etch onsilk screen

High contrast, square &round element shape

Application:- Electronics

Advantage:- Good contrast- No consumables- Permanent

Disadvantage:- Displaces surface- Process creates debris

Ink jet on plastic High or low contrast,round element shape

Application:- Bio-science- Pharmaceuticals- Packaging

Advantage:- Low cost: limited consumables (ink)- Limited damage to surface

Disadvantage:- Potentially poor resolution- Not permanent- Bleeding can affect mark quality

Marking Method Grid Marking Method Description

Advantages

& Disadvantages

Advantage:- Low-entry cost- High speed- Easy to read if contrast is good

Disadvantage:- Not considered permanent by

some industry standards- Dot registration can vary- Consumables- Mark quality dependant on

surface cleanliness- Difficult to read if contrast poor

Contrast levels vary widely, roundelement shape

Application:- Post-packaging- Warehousing- Automotive

Ink Jet on substrate

Pre-printed packaging Typically high contrast, square elementshape

Application:- Product labeling- Product packaging- Document processing

Advantage:- Economical- High speed- Good contrast- Easy to read

Disadvantage:- Less flexibility

Thermal transferlabel stock

High contrast, typically black on whitelabel stockSquare element shape

Application:- Product labeling- Packaging- WIP tracking, various industries

Advantage:- High contrast- Low-entry cost- Easy to read

Disadvantage:- Not permanent- Higher cost: consumables

Dot PeenDot Peen is a percussive marking method, usingchanges in depth to create the contrast between thelight and dark elements of the symbol. Dot peen isrecommended for applications where the symbol mustlast the entire life cycle of the part. In the aerospaceand automotive industries, this can be several years.Suitable substrates for dot peen marking must havesome hardness so material memory does not returnthe surface to its original condition.

Additional Marking MethodsMethods available include metal stamp, engraving,electrical arc pencil, embossing, cast or forged (bumpybar codes), molded, rubber stamp stencil, and decalco-mania. While not as common as the four methodspreviously discussed, these are all viable markingmethods for creating direct part marks and are usefulfor specific applications.

18 — Microscan Guide to DPMI Microscan Guide to DPMI — 19

Marking Method Grid Marking Method Description

Advantages

& Disadvantages

Chem etch on silicon Typically medium contrast, squareelement shape

Application:- Semiconductor

Advantage:- Permanent- High quality mark- No debris from process

Disadvantage:- Potentially toxic material bi-product- Potentially complex process

Dot peen on smooth,highly reflective metal

Low contrast, dependant ondifference in depth to create lightand dark elementsRound or square element shape,dependant on shape of stylus

Application:- Automotive- Aerospace- DOD

Advantage:- Permanent- No consumables

Disadvantage:- Alters surface- Low contrast mark- More difficult to read- Inconsistent depth will create smaller elements- Background noise

Dot peen ontextured metal

Low contrast, dependant on differencein depth to create light and darkelementsRound or square element shape,dependant on shape of stylus

Application:- Automotive- Aerospace- DOD


Disadvantage:- Alters surface- Low contrast mark- Very difficult to read, due to high degree of surface noise created by texture

Marking Method Description Advantages

& Disadvantages

Thermal print onfoil packaging

Typically good contrast,square element shape

Application:- Pharmaceutical Pkging

Advantage:- Economical

Disadvantage:- Reflective nature of marking

method may require additional lighting- Deformation of surface may

affect readability of code

Ink jet on glass Good contrast, round element shape

Application:- Pharmaceutical Pkging- Clinical R&D- Electronics

Advantage:- High contrast- Low entry cost- Limited damage to surface

Disadvantage:- Not permanent- Bleeding can affect mark quality

Laser etch on metal Low contrast, square element shape

Application:- Electronics- Automotive- Aerospace- DOD- Medical device

Advantage:- Permanent- No consumables- High quality mark

Disadvantage:- Process creates debris- Affects surface of substrate

Laser etch onglass epoxy

Medium contrast, square elementshape

Application:- Electronics

Advantage:- Permanent- No consumables- High quality mark

Disadvantage:- Process creates debris- Lack of contrast; difficult to read- Affects surface of substrate

Laser etch on rubber Very low contrast, square or roundelement shape

Application:- Automotive


Disadvantage:- Process creates debris- Affects surface of substrate

Chem etch on metal Typically medium contrast, squareelement shape

Application:- Electronics- Semiconductor- DOD- Aerospace- Medical device

Advantage:- Permanent- High quality mark- No debris from process

Disadvantage:- Potentially toxic material bi-product- Low-volume use only- Potentially complex process

Marking Method Grid


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6

Material CompositionBe sure to select a method that will have the leastamount of impact to the composition of your part.Experiment with different depths. Sometimes thiscan make the difference in success or failure of amethod. If your part has a thin wall, you may wantto avoid dot peen as it may permanently damageyour part. If your part is powder-coated, electro-chemical etch will not work.

PermanencyDetermine how long the symbol needs to last. Thisis often dictated by what is encoded in the symboland what it is used for. If the symbol is usedstrictly for in-house work-in-progress tracking, thanit need only survive the manufacturing process. Forthis type of application, ink jet may suffice. If it willbe read repeatedly throughout the supply chain orfor the entire life cycle of the part, than a morepermanent method such as dot peen may benecessary. Keep in mind, life cycle is defineddifferently, depending on the industry and the part.

ProductionWhat is the production environment? Is it a highlyautomated facility? Will most of the codes be readby manual presentation? Some marking methodsare better suited for high-volume production, suchas ink jet and laser etching. Electro-chemicaletching is better suited for low-volume or semi-automated environments. Consider how themarking method may affect output capabilities andpotentially affect the cost of manufacturing.

— A Datamatrix code

laser etchedonto a crystal

oscillatorcomponent for

work-in-progresstracking.

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MARKING METHOD SELECTION

Before you start evaluating marking methods, firstdetermine if an industry standard applies to yourapplication. Industry standards will often timesspecify specific marking methods to be used, inaddition to symbol specifications. For your reference,the Marking Method Reference Grid (located on p.17-19) provides examples of the more common DPMImarking methods in use today. If a specific markingmethod is not specified or recommended for yourapplication, then use the following guidelines to helpyou determine the specific needs of your application.Important factors to consider are permanency, mate-rial composition of the part, manufacturing process,cost of the part, and production volume.

— TheMarkingMethodReferenceGrid (p. 17-19)providesexamples ofthe morecommon DPMImarkingmethods in usetoday.


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Manufacturing ProcessDetermine where in the manufacturing process yourpart will be marked. How will the various steps affectthe integrity of the symbol and its readability? Forexample, a manufacture of medical devices laseretched a 2D symbol on the titanium case of a device.After the device went through the wet-blasting steriliza-tion process, the appearance and contrast levels ofthe 2D codes changed. These types of changes canbe easily accommodated by smart cameras or imagersdesigned for reading a variety of code types. However,if your part is painted after it is laser etched, the laseretched mark may not have enough depth to still bereadable.

— The MS-Q (above) and the Quadrus EZ™ imagers from Microscan worktogether in many challenging applications that require both a robust

handheld imager and a fixed-mount imager.

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If a symbol grade based on the complete specifica-tion is not necessary, the reader can perform thequality validation. Many readers have built insoftware to monitor symbol quality based onseveral aspects of a specific specification or theneeds of the application. Imagers can also performsimple quality checks by using the pass/fail settingto validate whether or not the symbol was readable.Quite often this is sufficient for codes that will onlybe used within the factory and do not need to beread outside the facility.

MARK QUALITY VALIDATION

Symbol quality validation is the practice of comparingthe quality of a direct part mark to a pre-determinedstandard. The pre-determined standard of measure-ment for the application can be an established indus-try specification, or it can be a quality thresholdestablished by the factory for internal use.

Many manufacturers perform quality validation to meetstandard requirements, but monitoring symbol qualitycan provide additional benefits as well. It can also beused to monitor how well the direct part markingequipment is performing. A smart camera mounted bythe marking equipment can signal an operator whensymbol quality begins to deteriorate. The operator canthen make the necessary adjustments before itimpacts production and parts need to be scrapped. Ifthe codes are used for automated equipment setupduring production, quality validation can reduce therisk of manufacturing errors or down time caused byunreadable codes.

VerifiersQuality validation can be performed a few differentways, depending on the needs of the application. Truesymbol verification compares the symbol to theestablished specification, producing a report on everyparameter in the specification and a symbol gradebased on the results. Verifiers must be used for thispurpose. In order to achieve consistent results, it isimportant that verification is performed in a controlledenvironment.


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Once you know the answers to your applicationneeds you will be able to focus on the features thatyou do need and spend less time comparing bellsand whistles that serve no real function in solvingyour specific application.

Hand Held ImagersHand held imagers are designed for applicationswhere the imager must be presented to the symbolby an operator. Excellent hand held applicationscan be any application that does not involve aconveyor, robot or indexer. Typically, they are usedfor low volume scanning, or reading parts that aretoo large or awkward to be presented to a fixedposition reader. For example, in the aerospaceindustry, it is not practical to try and read a DataMatrix code on an 800 pound helicopter enginewith a fixed position reader. An operator can muchmore easily read the code using a hand heldimager. Many hand held imagers offer a variety ofconfigurations, including wireless interfaces,providing the operator with additional mobility.

Since hand-held imagers are not designed forautomated applications, their decoding rates areconsiderably slower than fixed imagers, and theyare often not as robust. Since the reading environ-ment quite often cannot be controlled with exteriorlighting as easily as it can be with a fixed imager,many hand held imagers struggle to read the morechallenging, low contrast directly marked parts.Robust optics are critical in a hand held imager if itwill be used to read low contrast codes.

READERSMost direct part marks must be read with imagers,due to the low contrast marking methods employed tocreate the mark and the wide-spread use of 2Dsymbologies for these applications. Two dimensionalcodes must be read by imaging-based technology, andimagers can decode bar codes with much lowercontrast levels than laser scanners. Imagers can bedivided into 4 categories: hand-held imagers, presen-tation imagers, smart cameras and vision systems.

APPLICATION TIPS

• What is the speed of your application?

• What is the required distance between the imagerand the code you are reading? Will this vary, or isit fixed? Can it be adjusted?

• What type of code will you need to read? Is it lowcontrast, is it on a reflective or curved surface?This will help determine if special lighting may berequired.

• What is the environment like? Will you bereading codes in a freezer, or near a smelter? Willit be operating in direct sunlight? Will it need toundergo routine wash-downs?

• How will you be using the data? Will the reader besending signals to serial devices based on decoded information? Will you require data parsing?

• Ease of use. Who will be setting up the reader?Does it need to be easy to configure to minimizedowntime between product runs?

— Each type ofreader has itsadvantages Inorder to selectthe best readerfor yourapplication youmust consideryour particularneeds

Microscanoffers twohand-held

imagers, theMS-Q Basic

and the MS-QQuadrus.


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Presentation ReaderPresentation readers are hand held imagers mountedas a fixed position reader. In order to perform indynamic applications, the reader operates in a continu-ous read cycle, automatically reading the code whenthe operator places the part in front of the imager.Since the reader operates in continuous read mode,they do not necessarily make an efficient solution fordynamic applications. Continuous read mode isrecommended for diagnostics only. This mode con-tinually outputs data from the bar code. Most manu-facturers only want 1 data point for symbol decode.Continuous read also does not allow the control of theread cycle by a sensor or other device. If the readcycle cannot be controlled, then you will not be able todetermine whether a product has passed the scanner.

Fixed-position ReadersFixed-position imagers are designed for readingsymbols on parts in dynamic applications where thepart is presented to the imager in an automated orsemi-automated environment such as the productionlines found in automotive manufacturing. Instead ofan operator pointing the reader at the symbol andpulling the trigger, fixed-position imagers are triggeredby an external sensor. As the part approaches thereader, the sensor signals the reader to decode thesymbol on the part.

The two types of fixed position readers used fordynamic applications are vision systems and smartcameras.

— The Quadrus EZ imager is ideal foruse on a line where a part is in an

automated environment.

— Presentationreaders aregenerally usefulfor speeding upsome hand-presentationapplications byeliminating thestep of pullingthe trigger eachtime theoperator needsto read a code.


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Vision SystemsVision systems are a sophisticated imaging systemmade up of separate components: camera, lightsource, decoder and frame grabber. Since visionsystems were originally designed for much morecomplex tasks than simply decoding a symbol, mostrequire custom programming to accomplish a simpledecode and several hours of training to operate themonce they are installed. The best time to considerusing a vision system for a direct part marking applica-tion is when other tasks need to be performed inconjunction with reading the 2D codes such as partinspection.

Smart CamerasAnother form of fixed position readers, smart camerascombine the separate components of a vision systeminto one integrated package, resembling the traditionalbar code scanner. Since most smart cameras aredesigned to perform one task, in this case reading barcodes and 2D codes, their optics and decode algo-rithms are optimized for these specific applications,providing maximum performance for the application.New advancements in technology such as push buttonsetup enable some smart cameras to be setup on lineand reading codes in less than an hour without thehelp of a monitor or a computer. As a result, smartcameras bring a much lower total cost of ownership tothe application. Not only do they have a dramaticallylower entry cost, they are easier to install becausethey do not require the custom programming andextensive training involved with operating a visionsystem.

— Smartcameras bringa much lowertotal cost ofownership tothe applicationcompared tovision systems.

— The Quadrus EZ™ imager from Microscanis the industry leading fixed-mount 2D reader

designed for tough to read symbols including dot peenand etched codes.


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CONCLUSION

Like most bar coding applications, success beginswith the quality of the mark itself. A solid understanding of the parameters that define the best typeof symbol for an application will help eliminate mostchallenges before they occur. Before you moveforward on implementing your DPMI solution, be sureyou have taken the following steps:

— Followingthese guidelineswill help younavigate throughthe challenges ofDPMI and willensure thesuccess of yourapplication.

APPLICATION TIPS

• Established well-defined objectives for yourapplication

• Determined the specific data requirementsof your application

• Selected the most appropriate symbology

• Selected the best marking method for thesubstrate

• Identified the optimal location on the partfor the mark

• Understand the factors that determine goodreadability

• Evaluated your application requirements forthe imager

• Researched vendors providing theappropriate equipment and DPMIexperience

VENDORS

Direct part marking identification applications do notneed to be difficult. Like other bar code or 2D codeapplication, success begins with the best qualitysymbol possible. General education on the param-eters that determine a good symbol will solve mostapplication challenges before they occur. Selecting avendor who understands DPMI applications will pro-vide the necessary technical expertise to navigatethrough the remaining challenges.

To achieve success, it is important the vendor youselect be well-experienced in auto-ID applications. Dueto the nature of DPMI applications and their uniquerequirements, they typically need to be solved on anindividual basis. For this reason, it is in your bestinterest to select an auto ID vendor with a completeproduct line dedicated to solving these applications.Many auto ID vendors have been manufacturingproducts for linear and 2D symbol applications foryears. Since auto ID products are engineered specifi-cally for reading and decoding symbols, their optics,image processing platforms and decode algorithmsare all optimized specifically for reading and decodingsymbols. Machine vision companies lack experiencein bar coding applications and their products are notdesigned for reading bar codes. As a result, theirproducts require custom programming and a greatdeal of training in order to simply decode a symbol.

Criteria to consider when selecting a vendor includestrong global presence and superior customer sup-port. The vendor should offer a broad network ofoffices and representatives , capable of providing thelocal technical support you need during your installa-tion, where ever your facility is located.

— Smartcameras fromAuto IDcompanies willprovide farsuperiorperformance inDPMIapplicationsthan visionproductsdesigned forgeneral imageanalysis.


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FREE SYMBOL EVALUATIONS

Microscan is dedicated to direct part markingidentification. In addition to a suite of productsspecifically engineered to read directly markedsymbols on a variety of substrates, Microscan alsooffers a full service applications lab staffed byapplication engineers who know and understandDPMI.

During the last few years, the lab has receivedhundreds of 2D samples for DPMI applications.For each one, the engineers perform a very thoroughevaluation of symbol quality and provide recommen-dations on improving readability if needed.

Symbol testing and evaluations are a free serviceMicroscan provides to anyone interested in pursuingdirect part mark identification.

Send us a sample of your 2D code today, and getyour DPMI project off to a great start.

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— Microscan bar code scanners and imagers are sold through a globalnetwork of systems integration companies who specialize in automationand bar code solutions.

MicroscanCorporate Office1201 S.W. 7th StreetRenton, WA 98055Tel 425 226 5700,1 800 251 7711Fax 425 226 8250Email [email protected]

Microscan EuropeLemelerberg 172402 ZN Alphen aan den RijnThe NetherlandsTel 31 172 4233 60Fax 31 172 4233 66Email [email protected]

Microscan Asia PacificRepresentative Office31 Kaki Bukit Road 3#06-04/05, TechLink,Singapore 417818Tel 65 6846 1214Fax 65 6846 4641Email [email protected]

Please contactus for your

nearestMicroscanPreferredPartner


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SYMBOL QUALITY VALIDATION PARAMETERS APPENDIX

MIL-STD-130 Symbol Quality Validation Parameters

Following are the 2D symbol validation parametersrequired by the DoD, based on the ISO/IEC 16022specification.

Symbol Contrast measures the contrast between thelight and dark elements of the symbol and lets theuser know if contrast settings are less than accept-able. All the pixels that fall within the area of the testsymbol, including its required zone, will be sorted bytheir reflectance values to select the darkest 10% andthe lightest 10% of the pixels. The arithmetic mean ofthe darkest and the lightest pixels is calculated andthe difference of the two means is the Symbol Con-trast.

Print Growth is the extent to which dark or lightmarkings appropriately fill or exceed their moduleboundaries. These values are determined by countingpixels in the clock pattern of the binary digitized image,then comparing it to a nominal value and Min. andMax. values.

Axial Non-Uniformity is a measure of how much thesampling point spacing differs from one axis to an-other, namely AN=abs (XAVG – YAVG) / ((XAVG + YAVG)/2) where abs () yields the absolute value. If a symbol-ogy has more than two major axes, then AN is com-puted for those two average spacings which differ themost.

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Axial Non-Uniformity

Unused ECC is the correction capacity of Reed-Solomon decoding and tests the extent to whichregional or spot damage in the symbol has erodedthe reading safety margin that error correctionprovides.It is expressed in the equation e+2d<d-p• e is the number of erasures• t is the number of errors• d is the number of error correction code words• p is the number of code words reserved for error

detection


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Dot Center Offset

Dot OvalityDefinition of Ovality

D-d less than or equal to 20 percent of the cell size

Definition of Nominal Cell Size,and Dot Center Offset

IAQG 9132 Symbol Quality Validation Parameters

Following are the 2D symbol validation parametersrequired by the IAQG specification 9132. This specifica-tion is recommended for validating the quality of dotpeen marks.

Dot Center Offset measures the deviation from theideal dot centers. The worst case gives the quality ofthe worst dot in percentage and its position in the grid.Passing grades are 80 to 100%.

Cell Size is the percentage of the ideal cell size thatthe dot fills. Worst case indicates the quality of theworst dot in the percentage and its position in the grid.For dot peen symbols, this is referred to as Cell Size,and for Laser or Chemical this is called Cell Fill. Thecalculation used for both is similar.

Angle of Distortion is the angular deviation from a 90degree plane between row and column.

Dot Ovality identifies the extent of the oval distortionof the mark.

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If you track with bar codes, then you should know Microscan

Microscan is a leading manufacturer of fixed position bar code scanners forautomated tracking. Microscan offers a full range of products to read all linearbar codes, plus 2D symbologies and invisible ink.

MicroscanCorporate Office1201 S.W. 7th StreetRenton, WA 98055Tel 425 226 5700,1 800 251 7711Fax 425 226 8250Email [email protected]

Microscan EuropeLemelerberg 172402 ZN Alphen aan den RijnThe NetherlandsTel 31 172 4233 60Fax 31 172 4233 66Email [email protected]

Microscan Asia PacificRepresentative Office31 Kaki Bukit Road 3#06-04/05, TechLink,Singapore 417818Tel 65 6846 1214Fax 65 6846 4641Email [email protected]

See our websites for completeinformation on Microscan products,specifications, and applications.

h t t p : / / w w w. m i c r o s c a n . c o m

Corporate information,

full product line, eLearning

h t t p : / / w w w. q u a d r u s - e z . c o m

Resource for 2D symbologies

and decoding solutions

h t t p : / / w w w. s m a l l s c a n n e r s . c o m

Resource for embedding bar code

scanners into equipment

@Copyright 2004, Microscan, Rev B

v a 10 · 2012. 7. 4. · 2 — microscan guide to dpmi microscan guide to dpmi — 3 1...

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