Flexo Printing Roller Processing Control Points

Flexo Printing Roller Processing Control Points

1. Pay attention to material selection and welding methods

 

The precision of the outer surface of the center drum of the satellite flexographic printing machine is very high. Whether it is the dimensional tolerance, the line position tolerance or the surface roughness, it will directly affect the quality of the printed product. Therefore, in order to ensure certain accuracy requirements, the inner circle and outer circle of the center drum should adopt 45# steel plate.

 

At the interface, it is required to adopt advanced welding methods, ie CO2 protection welding or automatic countersunk argon arc welding. It requires the weld seam to be continuous and smooth, without defects such as pores, slag inclusions, cracks, etc., and to conduct flaw detection and treatment.

 

2. Reasonable arrangement of heat treatment process

 

The solder mask process must be reasonably arranged for the heat treatment process to eliminate the welding stress so as to prevent the center cylinder from being deformed in the process of processing and fully guarantee JCT PRINT its geometric accuracy. What is more important is to prevent the central drum from undergoing slight deformation during use so as not to affect its service life. The following points should be noted when arranging the heat treatment process.

 

(1) Annealing is performed on the inner circle and the outer circle of the center drum for welding, respectively, to eliminate the welding stress, the outer circular plate thickness is 50 mm, the conditioning and holding time is 10 hours, and the holding temperature is 510-560°C.

 

(2) The central roller core shaft is made of 45# forging blanks, and the outer circle (Φ260H8) of the sleeve is machined to the specified size after roughing → conditioning (48 hours) → semi-finishing process.

 

(3) Welds shall be flat, continuous, and free from defects when the side plates at both ends of the center roll are welded to the sleeve and the inner circle. High temperature annealing in the furnace after welding, the temperature is controlled at 550-600°C. Among them, in the process of temperature increase and temperature drop control, the temperature change per hour should be controlled at 50-220°C JCT PRINT.

 

(4) When welding the left and right spiral guide plates on the inner circle and the outer circle of the center roller, the rotation angle of the guide plate should be determined by the hydrostatic test data. Finally, the overall annealing is performed to eliminate the welding stress. After the welding is completed, the outside diameter of the diversion tank is determined by the inner diameter of the center cylinder outer ring, and the interference amount is 2 to 3 mm.

 

(5) Continuous welding with both end plates after assembly. After the welding, the entire body is normalizing and the forming process is performed. Normalizing temperature is 350°C.

 

3. Correctly determine the direction of the spiral groove angle

 

JCT PRINT Assuming that the design speed of the center drum is 100 rpm and the actual speed is 45 rpm, the diversion duct shall be determined based on several parameters such as line speed, flow pressure (1.5 bar) and flow rate (235 liters/minute). The direction of the helix angle.

 

In addition, the inlet structure and the outlet structure in the diversion tank directly determine the uniformity of the surface temperature of the center drum, and the temperature difference should be controlled within ±0.5°C.

 

The processing control point of the device is to use multiple rows of radiation guide troughs or draft tubes to spray the cooling liquid vertically to the area to be cooled or to a certain dead angle, and ensure that the spray range of the coolant covers all the regions in the cavity.

 

At present, this kind of structure is difficult to control the temperature at a blind spot outside the area of 150 mm at both ends of the center drum. Therefore, when the printing width is wider, the quality of heat is affected. In order to eliminate dead angles, two rows of diversion channels or diversion pipes can be provided near the inner cavity of the center drum, so that the coolant can directly cool the blind corners.

 

Coarse grinding, fine grinding and dynamic and static balance control points

 

(1) Before grinding the center drum, static balance treatment should be performed at both ends of Φ260H8. The counterweight can be added to the inner side of the two end plates, and the unbalance torque is required to meet the technical requirements.

 

(2) The selection of bearings is particularly important. According to the design requirements, SKF Bearing, the world's best JCT PRINT quality bearing manufacturer, or cylindrical roller bearings manufactured in Germany, is selected.

 

(3) Set the outer circle of the cup as the finishing reference part. The selection of its material requires the organization of dense, high strength, wear resistance and shock absorption, and also has certain toughness and plasticity. In this regard, HT300 or ductile iron can be used. During grinding, the temperature is 34°C and the water pressure is 1.5bar. According to the outer diameter of the cup, the surface roughness of the cup is 0.1-0.2μm, and the radial runout error does not exceed ±0.005.

 

Grinding process should timely detect the cup's dimensional tolerances and row tolerances. It can be detected by laser automatic detector or 2500 outer diameter micrometer and dial gauge.

 

(4) The use of multi-functional full-digital intelligent precision welding repair technology to repair the minor defects of the center drum. This technology has a very high welding accuracy (0.2 ~ 2.4mm), minimal welding impact, minimal thermal effects and a very high degree of bonding.

 

Plating, polishing and transportation control points

 

(1) There are two types of electroplating supporting equipment: pit furnace and barrel plating furnace. Because the weight of the center drum is nearly two tons, the barrel plating is inconvenient to rotate, and the plating unevenness is also generated in the barrel plating process. Therefore, the vertical plating of the pit furnace is used, and the chrome plating unilateral thickness is 0.20 mm.

 

(2) During grinding, the temperature of 34°C is used to grind the outer circle of the roller with the outer circle of both ends of the cup as the benchmark to meet the requirements of dimensional tolerance and shape-position tolerance to ensure that the thickness of the chromium layer is not less than 0.17mm.

 

(3) The size of the polishing equipment is φ500×3000 and φ2500×13000, which can be selected according to the size processing requirements. Polishing is the final finishing process that can increase the surface roughness of the center roll to a mirror finish.

 

(4) In order to prevent surface oxidation and rust from occurring due to moisture on the center drum, anti-rust oil should be applied to the surface of the roller body, wrapped with moisture-proof paper, foamed film, and blankets, and special transportation tooling should be made to prevent the center drum from being transported. There was a bump in it.