A Study of Oscillation

A Study of Oscillation

David Roisum
Finishing Technologies, Inc

There are many reasons to consider oscillation. Most fall under the overall desire to smear out streakiness in web caliper (basis weight, gage, thickness etc) so that it doesn’t build up on some downstream process; most particularly winders. Bagginess and corrugations are just a few of the many ‘winding’ defects that may be helped by oscillation. However, many defects are too wide to be economically remedied by oscillation. This is because most oscillating systems will require an additional trim loss. This forces an economic tradeoff between defect waste (and/or customer complaint) by not going far enough and trim waste by going too far. Exceptions are blown film because it oscillates the entire width (circumference of the bubble). Yet here we run into another limitation of oscillation that blown film suffers more than most. That it may not be oscillated nearly fast enough to avoid caliper buildup damage. This paper reviews the motivations in detail as well as the common machinery of oscillation. The paper also reviews the literature on the subject, that is in a word, nearly nonexistent. Next, a simple model is presented that can help guide the process designer in selection of oscillation stroke, speed and shape. Finally, the model results are compared to the nearly nonexistent application guidelines.