Printing on Cylindrical Items the Myths and Truths: Image Distortion and Pad Choices
In the world of Pad Printing there are continual possibilities. However with all of the potential, there happen to be certain particulars that we must learn and develop from. The opening rule of thumb when printing on cylindrical items is: it is best suited for an image that covers only ¼ the circumference of the cylinder. Often times the cylinder is hollow, i.e. water bottles, if these cylinders are collapsible under the pressure of the pad it is possible that internal support, e.g.: pressurizing the cylinder or internal mechanical support, may be necessary to minimize collapsing the cylinder and therefore contributing to distorting the image.
The second rule of thumb is going to be: the bigger the machine the better. The pad needs to be compressed to a point where the outer portions of the image are on the downside of the curve of the cylinder. This, coupled with a pad that has sufficient meat and print area to transfer the image, are more suited to a machine capable of higher compression force.
Beware of Distortion.
- The image, when transferred, will tend to stretch as you compress the pad to reach the outer portions. This is to say, you can have a 5.25″ image etched in the plate but you will end up with a 6″ image when measured on the circumference of the cylinder.
- Images tend to either smile or frown. This is more evident when there is “straight” copy at the top or bottom of an image being transferred.
Now when printing on cylindrical items there is a myth that a flatter pad will provide an easier vehicle, due to decreased need for compression, to transfer an image. However a flatter pad, as with most pad printing applications, will nearly always introduce other issues, i.e.: pin holing, to the process and cause distortion. If the image is screened, you are going to find decreased opacity of the image at the outer portions due to stretching. This stretching caused the screen pattern to be more apparent and opens up the “holes” in the screen… decreasing opacity.
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