Vacuum Cups

Vacuum cups are sometimes called suction cups. This is not entirely accurate as the cups cannot create suction on their own. A vacuum cup requires a vacuum source to grip a workpiece. Most vacuum cups are round because that is a strong shape that resist collapse under vacuum pressure and load force is efficiently distributed through the cup walls to the fitting. A circular shape also provides the greatest area for the space it occupies. Industrial vacuum cups usually employ a metal fitting for mounting the vacuum cup and for connecting a vacuum source to allow the inner volume to be evacuated.
 
As a vacuum suction cups manufacturer, EDCO USA manufactures a wide range of vacuum cups which helps us recommend the best cup for your application without bias.
Vacuum cups are made of rubber and included a flared lip to form a flexible seal against a workpiece allowing the cup to be evacuated with a vacuum pump. Several cups can be connected to a central pump or a small vacuum pump could be used for each cup. When the vacuum cup is evacuated, an attraction force is developed that holds the cup to the surface of the workpiece. For a vertical cup axis, this attraction force is the lifting capacity. If the load is perpendicular to the cup axis (shear load), the attraction force must be multiplied by the appropriate coefficient of friction to determine an allowable shear load. In either case, an additional factor-of-safety must be applied for prudent design. When rapid movement occurs in automation systems, a designer must consider the combined magnitude of both lifting and shear loads when selecting components.

Use Smaller Vacuum Cups to Lift Porous Materials

Depending on the contours of the workpiece, the allowable vacuum cup diameter may be limited. Multiple vacuum cups may be required to increase the total area and achieve a desired load capacity plus a generous factor-of-safety. We do not recommend increasing the required vacuum level to make a system work. Instead, increase the number or size of suction cups to increase the total effective area making it large enough for proper system design. Vacuum cups are relatively inexpensive making additional vacuum cups a cheap insurance against potential system failure.

Vacuum Suction Cup Calculation of The Holding and Gripping Forces

The vacuum force equation F = P x A (force = Pressure times Area) is difficult to apply to rubber vacuum cups because the cups are approximately sized according to the outer lip diameter. This can be misleading as it is much larger than the actual effective diameter that the vacuum pressure acts upon. A rubber vacuum cup also changes shape under load. Because of this, the effective area varies somewhat depending on the vacuum level inside the suction cup. It is more expedient to use the rated force at a specific vacuum pressure from the vacuum cup specification tables.
 
The force equation can be useful for vacuum “clamps” where a cavity with a seal formed around the perimeter is used to hold flat workpieces such as wood or stone. The area with the seal can be calculate with some degree of accuracy. Equation units must be consistent with each other. Vacuum pressure must be converted to the appropriate unit of measurement.
 
Three points define a plane. For good stability, use three or more vacuum cups spaced apart as far as possible. Start with the largest cup size that can be reliably placed on the workpiece then increase the number of vacuum cups until a suitable factor of safety is achieved. For handling boxes and other containers, apply the suction cups in corners and near the outer vertical walls. Remember, the box contents sit on the box bottom so the weight load is transferred to the box top via the side walls.