Brush plating technology

The factory has a Heidelberg MOZ-S four-color two-color offset press. A few years ago, a paper-rolling accident occurred in the printing process. The second group of offset presses rolled between the blanket cylinder and the impression cylinder with several 250g. /m2 coated paper. After cleaning off the paper between the two rollers, the roundness of the impression cylinder was measured to be 0.08 mm and the roundness of the blanket cylinder was 0.04 mm. Due to the deformation of the drum, high-grade products are difficult to print on the offset printing press, and printing of general products or printing with the first color group can only be performed by increasing the printing pressure.
First, the choice of repair program Judgment and Measurement of the Deformation of the Imprinting Roller (1) The printing method determines the deformation of the drum. Roller compression deformation is usually two kinds of depression deformation and bending deformation. To correctly determine these two types of deformation, it is generally necessary to disassemble the equipment, remove the rollers, measure the axial straightness, radial roundness, and cylindricity of the talking cylinder, and determine the properties of the deformation based on the trace results. This method requires both the dismantling of equipment and the use of special measuring instruments. It is difficult for ordinary small and medium-sized enterprises to do this when it is time-consuming and time-consuming. How to determine the deformation property accurately and quickly without disassembling the device? The factory adopts the printing determination method. Put a new lining and a new blanket on the rubber roller. The liner is a rigid liner, the printing pressure is reduced to the lightest, and it is detached from the water roller, and a large-area full-area printing is performed with 128 g/m2 coated paper, and the printing pressure between the blanket cylinder and the impression cylinder is gradually increased to obtain the second The print samples of the full-color printing group under different printing pressures are shown in Fig. 1 (slightly).
From the proofs, it can be clearly seen that the two rollers and the tip portion can print ink under different printing pressures, and the mouth portion shows a blank. According to the structure of the impression cylinder, the full-version printing proofs under different pressures were compared. After analysis, the two ends of the drum and the trailing point were not deformed, and the jaws were concavely deformed. According to this, it can be determined that the impression cylinder is a concave deformation, and the deformation portion is a part of the impression cylinder.
(2) Measure the deformation of the impression cylinder. Remove the steel skin wrapped on the surface of the impression cylinder (The second color group of this machine is coated with steel skin for on-line pressing of steel wire and sleeve number).
1 Using a dial gauge to measure the rollers at both ends of the impression cylinder, the dial gauge has no runout, and the rollers at both ends of the drum are not deformed. Based on this, it can be further confirmed that the impression cylinder did not undergo bending deformation.
2 Use a watercolor pen to draw squares on the surface of the impression cylinder at intervals of 50mm in both the axial and radial directions. Fix the dial holder on the fuselage and measure the datum point of the roller without deformation. Click to move the machine. The deformation of the surface of the dial roller was measured point by point and recorded on the coordinate paper. The measurement results are shown in Table 1.
From the measurement results, it can be seen that the impression cylinder is a concave deformation, and the deformation part is a part of the fistula, and the maximum deformation amount is 0.08 mm.
2. The choice of repair program (1) electroplating or spray repair program. This is a conventional method of repairing the deformation of the drum. It must disassemble the machine, take out the drum, grind the drum on a grinder and plate or spray a metal layer on the drum surface, then grind it to the required size and precision, and then install the commissioning machine. This scheme has a high degree of precision in the repair of the drum and the process is relatively mature. However, due to the disassembly of the equipment, the drum was machined and the commissioning equipment was installed. Therefore, first of all, companies are required to have strong equipment repair technology and high level of equipment adjustment, and equipped with appropriate disassembly tools and debugging methods. These conditions are generally not available for SMEs. Secondly, this kind of scheme has a long time to repair, and it also has a large repair cost. As far as companies are concerned, offset presses are the main production equipment. Too long repair time and excessive repair costs are unbearable to the enterprise.
(2) brush plating repair program. Brush plating is a new surface treatment technology and repair process. Its basic principle is to place a specially formulated electrolyte brush plating solution between the insoluble anode and cathode (that is, the part surface) to generate a polarization reaction under certain voltage and current density conditions, so that the metal or non-metal cation is at the cathode Electrodeposition occurs on the surface to form a plating layer. Brush plating technology has many features:
1 Plating on site without dismantling equipment.
2 The shape of the plated surface is not limited, the workpiece is not deformed, and partial plating can be performed.
3 plating thickness can be controlled to achieve precision plating.
4 The coating has small brittleness and high bonding strength, and the plating hardness is greater than that of slot plating.
5 process is flexible, easy to operate, repair time is short, repair costs are low.
Because the impression cylinder is concave deformation, according to the characteristics of electric excitation plating technology, the brush plating process can be used to repair the cylinder. The reasons are:
First, the use of brush plating technology can eliminate the disassembly of the offset press and repair the drum on site, which saves a lot of time spent on disassembling the machine and debugging the machine, and eliminates the tools and equipment necessary for disassembling the machine and debugging the machine. The required technology.
Secondly, the impression cylinder is concavely deformed, and the brush plating technique has the characteristics of partial plating and precision plating, so that a layer of metal can be plated precisely at the depression of the roller to achieve the purpose of repairing the depression deformation.
Third, the hardness and bonding strength of the brush plating coating can meet the requirements of the printing roller.
Therefore, using the brush plating technology without disassembling equipment, it is feasible to repair the sunken parts of the drum in the field, and it is a preferred solution to repair the short sunken deformation time and low cost.
Second, brush plating repair process 1. Plating solution selection: nickel brush plating solution.
2. The maximum printing area of ​​the MOZ-S four-color two-color offset printing press is 480mm x 650mm, and the surface area of ​​the embossing cylinder is 312,000mm2. Due to the large plating area, the amount of deformation of the plated surface is inconsistent. Therefore, the block brush plating method is adopted. The surface of the drum is divided into several pieces according to the amount of depressions, and the respective thickness of the depression is plated to the required thickness. For the overlap between the block and the block, it is smoothed with whetstone until it meets the requirements.
3. During the brush plating process, the radial runout of the roller is repeatedly measured using a dial gauge. The measured point is more in the axial direction of the roller. The measurement reference is the undeformed part of the roller drag.
4. Brush plating operation steps are shown in Table 2.
5. Roller repair accuracy: After repairing, use the dial gauge to measure the surface runout of the roller less than 0.02mm.
6. After the repair, the surface of the drum is coated with a thin layer of butter, covered with new steel skin, and the printing is started. Under the normal printing pressure, the desired effect is achieved.
Brush plating technology was used to repair the depression of the impression cylinder. The entire repair process took only 4 days and the repair cost was about 6,000 yuan. In fact, there is also a deformation of the blanket cylinder of the second color group of the machine. In consideration of the small deformation of the blanket cylinder and the surface of the blanket cylinder, the blanket cylinder is not repaired.

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