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1、Blade STREAKS(blade lines)-Causes&Cures,A Training Course Prepared for Daewoo Tianjin Mill byJohn Moore Chemco International,Agenda,IntroductionMeasurement&Definition of Blade LinesMechanismCausesRemediesProcedures,Introduction,Blade streaks,grit streaks,drags,cuts,etc.are the most common&costly def
2、ect of the most widely used coating process in the world.The blade coater.We will discuss the definitions,mechanism,causes,cures and procedures to minimize the impact of blade lines in your operations.,Rule#1,“You Cannot Improve What You Do Not Measure”,Measurement&Definition of Blade Streaks,Measur
3、ement should be done by procedures outlined later under remediesDefinitions are provided in examples followingMeasurement at the coater head,paper machine reel and finishing are covered in remedies see attached Methods I,II,and III,Measurement&Definition of Blade Streaks,Drag streak(DS)-a blade line
4、 greater than 2mm in width and the depth of the coating layerGrit Scratch(GS)a blade line less than 2 mm in width and the depth of the coating layer,Measurement&Definition of Blade Lines,Fine Streak(FS)-a blade line less than 0.5mm in width and the depth less than the coating layerPositive Streak(PS
5、)a blade line less than 2 mm in width and higher coat weight than the coat layer,Definitions,DS=Drag StreakGS=Grit StreakFS=Fine StreakPS=Positive Streak,Rule#2,“EDUCATE AND DISPLAY BLADE LINE TERMINOLOGY.FOR ALL TO UNDERSTAND AND USE”,Measurement&Definition of Blade Streak-Sizes to think about,Size
6、 is critical when problem solving coating defects and especially Blade LinesThe following charts are intended to get you thinking on the scale of microns(millionths of a meter).Keep in mind that with your eye you may be able to see things as small as 500 micronsWith a microscope,you may see things a
7、s small as 50-100 microns,Mechanism,What causes a blade streak?“Any condition or material that stops the smooth flow of material passing under the blade which results in an area of higher or lower coat weight than the surrounding area.”,Rule#3,“Any Coating Can Cause Blade Lines at High Enough Solids
8、”Hint!-Measure and control the solids carefully.,CausesBase Sheet Related,felt hairsthread rope strandsragsplastic from grinding wet end boxes&foilsadhesives from splicing taperubber from various sealsplastic from pencils,hard hats,badges,labels,etc.,CausesBase Sheet Related,sand from water filtersf
9、ly ash and cinders from the boilerpitch particlesmetal flakes from refinersrust from pipespipe scalelinting from dryersfiber from paper break into coating,CausesBase Sheet Related,fiber from paper break into coatinghot melt gluescale from first coatair borne particlesbad pisser cuts(fiber bundles)pa
10、int peeling,CausesCoating Related,contaminated raw materialsinteraction of raw materials causing agglomeratesimproper dispersion of pigmentspoor screeningscreens with holes in the meshdried material in coating systempoor screening at the machine to eliminate fiber and dried coating,CausesCoating Rel
11、ated,dilution water containing sand,rust,etc.poor water holding of coatingpoor solids/rheology controlno pH control,CausesMechanism related,base sheet roughnessbase sheet absorbency coating water holding balancedcoating blade angle impropercoating head angle impropersetup not proper to have robustne
12、ss(ability to adjust up and down without going out of control),CausesMechanism related,coat weight range for equipment capableproper circulation to usage ratio for coatingpoorly designed coating for speed,machine,gradehard areas in the blade metal(dont wear as fast as the surrounding material),Remed
13、ies/Cure,Step 1 is to form a crossfunctional team comprised of operators,technical,quality purchasing and production managementall areas of mill represented from stock preparation to finishing departmentslearn potential causes from each areause pareto charts,fish bone diagrams,etcdevelop plans to me
14、asure and minimize,Remedies/Cure,Step 2 is to understand the current situation of your customer what type of blade streak are problemshow much is experienced/and effect on themwhen does this occur(obtain data to trace to exact dates,reel numbers,etc.can data be kept to provide for millcan samples be
15、 returned when a problem occurs,Remedies/Cure,Step 3-Monitor blade streak using control charts at the coater,reel,QC and finishinguse control charts provided to obtain understanding of severity and typetake normal steps to reduce when you feel they are severeanalyze defects and materials found at th
16、e blade,Remedies/Cure,Step 4-Try to correlate the customers problem to the type and frequency of blade lines on the machineunderstand what is normal.Amount&typeunderstand when you are near a problemunderstand when you must stop and do something drastic,Procedures,Form cross functional teams to probl
17、em solve,involve,educate,systemize the entire operationInstitute measurement systemsraw materialsmachine conditionscoating head(see control chart)quality control(see control chart)customer complaints,Procedures,Establish boilout and clean-up procedures for coating preparation,coater systems,dryers,m
18、achine,etc.Collect,analyze and measure rejects from stock cleaning systemCheck residue of coating materials,coatings prepared and coatings on the machine.Clean filters at the machine more often,Method IControl Chart for Coating Head,Method IIControl Chart for Finished Paper/Board,Method IIICustomer
19、Complaint/Comments,Summary,Blade streaks are a serious but controllable defect for blade coatingTeam effort is required on a continuous basis to maintain quality and yieldEducate,train and systemize the machine and coating processMeasure&correlate-cause and effectStrive to understand root causes,Rule#4,Most mills in the world successfully run blade coaters-if you work smart enough and hard enough you can too!,
