Vacuum Hold Down

Vacuum Hold Down is used in processes that require the holding of large objects in a temporary position while being worked on. This is usually accomplished by placing the product on a table filled with holes and pulling air through the holes so as to create a vacuum and keep the item stationary. The engineering centers on the number of holes that are exposed when the item is in place. The velocity through these holes must create a pressure drop at least as much as the vacuum necessary to keep the item in its stationary position. 
It is necessary that others determine the amount of hold down vacuum necessary to hold down the product and to determine the number and size of the exposed holes. (Note that it is a good practice to cover as many of the exposed holes with a sheet so as to reduce the amount of air necessary to solve the application.) In many table designs the table is quadranted off by valves so that smaller items can be positioned in one of those quadrants without the necessity of pulling air through the rest of the holes. 

Envelope Manufacturing is an example of a specialized type of air table. In this application the envelope is positioned on a moving apparatus that has a series of air holes for vacuum hold down. In many cases the envelope machine has individual vacuum pumps, normally of the sliding vane variety. The need for continually maintaining these units has led to the use of a centralized vacuum pump. Since the air entrained in the system is filled with minute, but abrasive, dust particles, an inline filter must be placed in front of the vacuum pump to keep the pump from being damaged.

 System Details

Amount of Vacuum necessary

In, Hg.

Diameter of table holes 


Largest number of exposed holes for design purposes 

Total Volume of air


Amount of Vacuum Necessary

In., Hg
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