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Multi-color offset printing machine affects the accuracy of overprinting
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For multi-color offset printing machine overlay accuracy is critical, because it directly affects the quality of printed materials, once mis-registration can cause prints picture is not clear, writing a series of quality problems ghosting. There are many factors affecting the accuracy of overprinting. The following examples analyze the influence of the roller row on the overprinting accuracy of multi-color offset printing presses for reference by the insiders.
1. The accuracy and gap of the roller teeth pad are not good
The upper surface of the row of dental pads on the roller row is the reference surface during the transfer of the printed product. When the device is operated for a period of time, the dental pad will wear to different degrees, so that the upper surface of the row of dental pads cannot be Keeping on the same plane causes the wavy deformation of the paper crevice, which causes the difference between the length of the front edge of the paper and the actual embossing length, which causes the fan to expand in a fan shape, resulting in inaccurate overprinting.
In addition, the gap between the pads on the roller row is also a key factor affecting the accuracy of overprinting. If the gap between the dental pads is too large, the front edge of the paper will also be wavy, which will cause the paper to be cornered, resulting in inaccurate overprinting.
2. "Dead teeth" appear on the roller row
Some teeth on the roller row are inflexible or inactive, causing the socket spring to fail, and there will be a "dead tooth" phenomenon. Once the "dead tooth" appears, the roller row will not generate enough tension, thus affecting the overprint. Precision. This is because the fangs on the roller row are in normal working condition, and the spring behind the socket will generate the crepe force. If there is a "dead tooth", the fang will be in the open state, and the crepe will not be generated when the paper is smashed. The force and the paper pull force, so that the paper can not be accurately transferred between the rows of the rollers, thereby directly affecting the overprint precision of the printed product.
3. The installation position of the roller row is not allowed
Once the roller row is not in the correct position, any adjustment method will not achieve the desired result. For example, if the position of the dental row on the impression cylinder is not accurate, it will result in the inability of the individual units of the whole machine to be registered; if the position of the tooth row on the paper transfer roller is not accurate, the transfer roller will be handed over to the other rollers. At the time of the gap between the two sides of the roller pad, the paper is undulated when it is handed over, thereby affecting the overprinting accuracy.
4. Improper handover of the roller row
When the paper is transferred from one row of teeth to another, the ideal intersection point is the tangent point between the rollers. To ensure the stability of the paper transfer, the intersection angle or the intersection distance between the two roller rows should be the roller. The cut point between the centers is centered. If the junction is not accurate, the paper will be deformed at the mouth of the mouth, which will result in inaccurate overprinting of the printed product. In severe cases, tearing may occur.
In addition, if there is no handover time or the handover time is too short or too long between the rows of the rollers, the accurate and unreasonable conveyance of the paper cannot be ensured, resulting in inaccurate printing of the printed products.
5. Poor quality of the parts on the roller row
The quality of the parts on the drum row is also an important factor affecting the overprinting accuracy of the multi-color offset press. If the quality of the parts is too poor, it is prone to breakage or deformation during the operation of the equipment, causing a series of quality problems, resulting in inaccurate overprinting.