Vacuum Hold Down

Vacuum Hold Down is used to hold objects in a temporary position while being worked on. Usually the object is placed on a table filled with holes and air is pulled through the holes to create a vacuum keeping the item stationary.

First you need to determine the amount of vacuum (inches of Hg) necessary to hold the product stationary, then determine the number and size of the exposed holes. Normally unused holes are covered to reduce the amount of air necessary for the application. Some table designs incorporate valves that allow areas of the table to be turned off so that smaller items can be positioned in one area without the necessity of pulling air through the rest of the holes. 

The blower size (CFM) is determined by the number of holes that are exposed when the item is in place. The velocity through the open holes must create a pressure drop equal to the vacuum necessary to hold the object.

Envelope Manufacturing also uses vacuum hold down for handling and folding. Envelopes are picked up and positioned on a moving device that has a series of air holes or suction cups for vacuum hold down.