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A device used for the digital imaging of offset printing plates. External drum platesetters are designed to have the plate mounted on the outside of the drum. As the drum rotates on its axis, a laser beam head moves parallel to the drum and burns the image on the plate. The external drum system does not require any mirrors to deflect the imaging lasers. The imaging head is placed closer to the plate surface. This is beneficial for imaging thermal plates, which require high-energy output for proper results. In order to change the resolution when using external drum systems, the distance between the laser beams must be changed. Unlike internal drum systems, the diameter of the beams cannot be changed.
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