Application of thermal spraying

Engineers engaged in printing machinery know that the precision requirements of printing machinery are quite high! Only in this way can print quality prints be guaranteed. As our company was repairing the rollers of the “Northern” offset press, a senior engineer in Hefei, Anhui Province said: “The precision requirements of printing machinery are second only to aerospace!” This sentence is for our company. A very deep warning!
Brush plating can really play its unique repairing function without disassembling and repairing the printing roller, but it does not mean that this application is a "perfect" technology! For the drums with serious corrosion damage, if not removed, due to the limited conditions, it will be difficult for the brush plating technology to achieve high accuracy! However, removal of the thermal spray after the restoration of the upper grinder can achieve a very good accuracy!
According to the experience of repairing many rollers, in order to achieve a high accuracy, the following problems are generally solved:
First, concentric issues. Due to the repair of the old parts, the bearing position of the drum sometimes occurs relative to the center hole due to wear, disassembly and assembly of the bearing, etc., and the grinding process of the grinding machine is based on the center of the two center holes as the center of processing. There is relative hopping of the two bearing positions. According to this kind of situation, we adopt the method of grinding the bearing position and the rolling body at the same time after painting and grinding, so that the two bearing positions and roll-over are “one knife live”, so as to achieve “three concentricity”!
Second, the taper (that is, shoot) problem. Due to the printing requirements, the drum requires a high degree of taper. Roller taper appears in the print: the bulk ink is heavy, overprint deviation and other issues! This requires that when the grinding machine processing, the shoot to adjust to be as small as possible. In addition, no elliptical (ie, flat) phenomenon can occur!
Third, emphasis on issues. Offset cylinders, blanket cylinders, and plate cylinders of offset presses are generally not a complete cylinder because of the requirements of their use. Some gaps are about one-third of the time, so that when the rotary machine is directly machined on the grinder, there will be "large deviation in dynamic balance" (commonly known as "overweight")! Direct processing drum will appear, horizontal ripples, tummy, oval and other issues affect the accuracy. Therefore, according to the above situation, we use different weights for the drums to reach a certain dynamic balance, and then on the grinding machine processing!
The above is just a brief introduction of several important issues for the repair of printing cylinders. Of course, there are problems such as the smoothness of the drum, the strength of the sprayed layer, and the anti-corrosion property of the material. All of them must be solved in the application!
In short, the "heat-spraying of the upper grinding machine to repair the printing roller" is an important supplement to "brush plating does not remove the repair roller"! The two make up for each other to solve the problem of wear, corrosion, damage and other problems of various printing machine cylinders (in the application, according to the specific circumstances, the application of that kind of technology is chosen as appropriate). No matter what kind of technology "repaired far less expensive than the new drum!"
Repair is also productivity! Our company's technology is willing to reduce the cost for the enterprises in the printing industry in our country, resulting in greater economic benefits!