Doctor Blade 刮墨刀 Philip Wong 黄水泰 Dailian International Pte. Ltd. 71, Ubi Cres, Excalibur Ctr #02-08 Singapore 408571, Tel: +65 67482662 Fax: +65 67479929 Email: email@example.com Website: www.dailian.com
DoctorBlade 刮墨刀 • Remove of excess ink from un-engraved portion area • 在无雕刻区，去除残余的油墨 • Operate durably and efficiently • 操作耐用且效率高 • Excellent quality high speed and consistency insured • 高速运作和稳定性优良品质 example例如 1. Coating of aluminum foil – lacquer & bonding 1.铝膜涂布 - 胶水和附合 2. Coating of paper stock – paper industry 2.纸料涂布 - 造纸厂
BladeAssembly(1) 刀的安置 • Minimum wear on itself & gravure cylinder • 减少印版和刮墨刀损耗 • A) Angle mounted at 55° to 65° • A) 55至65 °角度安置 • Good assembly provide better wipe of ink • 准确安置刮墨较佳 i) Adjustment action to achieve optimum result. Difference in cylinder size change nip distance and drying speed are also change. • i）调整达最佳状态。版的夹缝和干燥速度随不同的尺寸的印版改变
BladeAssembly(2) 刀的安置 • B) Distance from Nip B)夹缝距离 i) correct distance maintain balance between press speed and drying speed i)准确的距离平衡印刷和干燥速度
BladeAssembly(3)刀的安置 • C)Edge • 刮墨刀角边 i) Straight edge, that “seat” against the engraved cylinder to wipe cleanly with a minimum of pressure and wear i) 印版套上垂直刮墨刀角边只需较小的压力和损耗就能刮墨干净
BladeAssembly(4)刀的安置 • D) Mounting • D)安置 i) Straight and ripple-free, allowing for repeated, quick and precise mounting and removal i)垂直和无波浪可重复，快速和精确的安装和御下 ii) Simple gauge is helpful to insure parallel settings. Blade extensions - back-up blades must be parallel ii) 标准量度保证平行设置，延置-支撑刮刀需平行
BladeAssembly(5)刀的安置 • E)Oscillation Move back and forth a short distance across cylinder. i) Movement minimizes local wear. ii) Removes debris that collect under the blade iii) Oscillation prevents wearing to the contour of the images. iv) Oscillation approximately in ½ inches in each way with one stroke/ revolution
BladeAssembly(6)刀的安置 • F) Force i) Apply force is controllable and measurable. ii) Allow consistency of press room practice. iii) Pressure as low as practical – minimizing wear
BladeAssembly(7)刀的安置 • G) Deflection i) Press and holder design enables to attain the required parallelism and stiffness. ii) Directly related to pressure, doctor blade thickness and back-up blade thickness. iii) The wear on a gravure printing cylinder is caused mostly by doctor blade wiping action.
BladeAssembly(8)刀的安置 • G) Deflection iii) The wear on a gravure printing cylinder is caused mostly by doctor blade wiping action. iv)when the press is in motion, doctor blade is deflected.
BladeAssembly(9)刀的安置 • H) Lamella i) 50µm mainly for films, foils, publication printing ii) 75µm mainly for general packaging, paper board, décor printing iii) 100µm mainly for Flexo, ANILOX, coatings iv) 125µm mainly for Flexo, ANILOX in conjunction with ceramic rolls
Doctor Blade Wear (1) 刮墨刀的损耗 >Wear - deterioration of surface through use, is affected by a variety of conditions. 1) Amount of loading 2) Reacts differently with each application. A) Adhesive i) Caused by the shearing action of micro-contacts formed between the two surface roughness that carry the load between the blade and cylinder. ii) occurs because of failure of the ink film, which should separate the two surfaces.
Doctor Blade Wear (2)刮墨刀的损耗 B) Abrasive (cutting wear) i) Occurs whenever hard particles are present between the blade and print cylinder as they rub against one another. ii) Gravure inks areformulated to be as non-abrasive but some pigments - inorganic ones, are inherently more abrasive than others.
Doctor Blade Wear (3)刮墨刀的损耗 i) Potentially abrasive particles include: 1) Ink pigment 2) Insoluble vehicle particles 3) Dried ink 4) Rust from solvent lines 6) Paper dust 7) Particles of clay coating 8) Doctor blade particle 9) Chromium chips from the print cylinder.
Doctor Blade Wear (4)刮墨刀的损耗 ii) In-line filtering on press - to reduce the abrasive hazards iii) Abrasive contaminants is tested with an abrasiveness tester iv) Abrasiveness test equipment and procedures are available from GGA and other sources v) Excessive dumping of solvent into the ink fountain can cause local precipitation or pigment flocculation -wiping problems
Doctor Blade Wear (5) • C) Fatigue i) Cracking of the doctor blade owing to cyclic pressure being applied during use ii) caused by a rough or damaged spot on the end radius of a print cylinder iii) With the high grade steel now used for doctor blades - this is seldom a problem.
Doctor Blade Wear (6)刮墨刀的损耗 • D) Corrosion Chemical damage to the doctor blade, or damage through friction with a print cylinder damaged by oxidation or other chemical reactions. i) Occurs if corrosive material gets into the ink, creating blisters or pitting in the chrome surface. ii) Corroded by rust formation of water base inks 1) PH is too acidic 2) Too alkaline 3) After an overnight shutdown. iii) Prevention - Use of stainless steel blades
Doctor Blade Materials (1)刮墨刀的原料 A) Steel Blade. Material in strip steel used in gravure printing 1) Special steel 2) Cold rolled 3) Hardened 4) Tempered
Doctor Blade Materials (2)刮墨刀的原料 Conditionsofthestripsteel. 1) High quality 2) Clean 3) Inclusion-free
Doctor Blade Materials (3)刮墨刀的原料 Resistant applications 1) Stainless steel 2) Hardened 3) Tampered • Remark: It is as durable as carbon steel.
Doctor Blade Materials (4)刮墨刀的原料 Analysis of stainless steel (corrosion resistant)
Doctor Blade Materials (5)刮墨刀的原料 B) Plastic Blade used in gravure • Material 1) Polypropylene 2) Teflon 3) Nylon **Remark: Width maximum : 60mm Applicable : Coating roll & corrosive ink Life-span : Shorter than steel
Doctor Blade Materials (6)刮墨刀的原料 * Specifications 1) Flatness & Straightness – maxi 3.5mm (3M), maxi 1.2mm (2M) 2) Thickness from 0.10mm to 0.300mm 3) Tolerance +/- 0.10mm 4) Tensile strength: 1,860 n/mm2 5) Hardness from 500 to 600 Vickers
Doctor Blade Holder Configuration (1)刮墨刀托架配置 A) Various holders 1) Straight blade holder - back-up blade use as support
Doctor Blade Holder Configuration (2)刮墨刀托架配置 2) Curved blade holder – reduce “ripple” effect * Holder constructed with extension aluminum or Extrusion aluminum
Doctor Blade Holder Configuration (3)刮墨刀托架配置 3) Jaws blade holder – lock up blade with use of bolt
Doctor Blade Holder Configuration (4)刮墨刀托架配置 B) Various Angles i) Wiping Angles 1) Minimize cylinder wear 2) Give cleanest printing results 3) Allow high speed run
Doctor Blade Holder Configuration (5)刮墨刀托架配置 ii) Contact Angles – Normally 60 °
Doctor Blade Holder Configuration (6)刮墨刀托架配置 iii) Pre-wiping Non-contact Blade 1) Used to reduce ink load to doctor blade 2) Inking rollers are in this purposes 3) Primarily in publication printing – decrease hydraulic pressure created by high speed 4) Reduce dot skip 5) ESA ( Electrostatic Assist) to prevent dot skip
Doctor Blade Holder Configuration (7)刮墨刀托架配置 iv) Control of Blade Pressure 1) Manual Control – mechanical gear leverage by hand cranks 2) Pneumatic Control – pressure air is applied 3) Hydraulic Control – Hydraulic oil is used 4) Spring Load – Spring is used
Doctor Blade Holder Configuration (8)刮墨刀托架配置 V) Control of Blade Angle 1) Instruments on setting angle & pressure force applied 2) Presses without instruments to obtain optimum results on: a) Performance b) Analysis c) Calibration d) Modification of blade system
Blade Setting Procedure (1)刮墨刀设置程序 • Procedure to follows: • 1) Control doctor blade set
Blade Setting Procedure (2)刮墨刀设置程序 2) Contact angle
Blade Setting Procedure (3)刮墨刀设置程序 • 3) Blade to Nip distance
Cylinder Consideration (1)印版的考虑 i) Uniform Diameter Cylinder with erratic geometry size will cause 1) Doctor blade wear 2) Cylinder wear
Cylinder Consideration (2)印版的考虑 ii) Polishing and Cleaning Engravings A) Polishing 1) Un-engraved areas are machine polished or honed with water lubricated stone to f4 or (SAE standard) 2) Chromium plating in gravure cylinders has microscopic “crack” needs surface polishing 3) Non-polish cause damage to doctor in few revolution B) Cleaning Prior to chromium – as engraved debris may stay.
Cylinder Consideration (3)印版的考虑 iii) Ceramic Coating on Cylinder Highly durability on plasma-sprayed ceramic coated with engraved needs carefully polished
Cylinder Consideration (4)印版的考虑 iv) “Running in” cylinders on Press • Cylinders in a “run in” position for several minutes on a press, accepting some waste until streaking and scratching disappeared. Sandpaper polishing required.
Cylinder Consideration (4)印版的考虑 v) Rounding Cylinder Ends (Radius) • Minimize doctor blade wear • Minimize excessive bending • Fatiguing doctor blade • Doctor blade breaks on rough cylinders ends
Blade Edge Configurations (1)刀角边配置 i) Pre- Finished blade 1) Hand- finished blades are beveled at 45 ° 2) Sharpened wiping edges de-burred and slightly rounded
Blade Edge Configurations (2)刀角边配置 ii) Machine Finished 1) Honed and lapped doctor blade – between 11 and 35° with rounded tip 2) Edge is grinded to form a “lamella” 3) All pre- machine blade type worn unevenly by various portions of the cylinder. 4) Pre- machine configuration are not perfectly straight, owing to the nature of strip steel production. 5) Pre- honed doctor blades are packaged in dispenser boxes – provide safety and prevent damage.
Lubricants (1) 润滑 • Advantages of lubricants • Gravure inks possess lubricant to minimize doctor blade and cylinder wears i) Type of lubricants 1) Plasticizing oils 2) Fatty acids 3) Pigment - wetting
Lubricants (2)润滑 ii) Ink Hazing 1) Dark and strong colours will show a slight haze or scum more readily than light colours or tints. Changing the blade angle can sometimes improve wiping efficiency. 2) Cylinder needed polish when hazing that doctor blade adjustment cannot be corrected
Lubricants (3)润滑 iii) Drying Speed Effect 1) Too fast drying contributes to doctor blade and cylinder wear 2) Ink drying speed can be cured by adding slower- evaporating solvent
Lubricants (4)润滑 iv) Abrasion Problems 1) Opaque white ink which contains titanium oxide are more abrasion.
Preparing Blades for Use (1)预备使用墨刀 I) Preparation • Doctor blade are mounted : clamped, back-up blade
Preparing Blades for Use (2)预备使用墨刀 ii) Hand Finishing 1) Checking the blade with a fingernail allows the operator to feel any nicks in the blade.
Blade for Flexographic柔印的刮刀 • Single doctor blade system • Two piece of doctor blade to be mount on chamber-blade system
Make Ready and Trouble Shooting (1) 被用于排除故障 i) Checking Procedures 1) Mount blade correctly 2) Check defective materials 3) Correct angle 4) Doctor blade adjustment required
Make Ready and Trouble Shooting (2)被用于排除故障 ii) Blade Parallelism 1) Apply to new blade 2) Blade must parallel to holder and back-up blade 3) Holder must parallel to print cylinder 4) Check holder periodically for straightness and waviness.