Dual-Flow fittings limit vacuum leakage in a system where some of the suction cups may not be in sealing contact with the work piece. Since vacuum flow is limited by a small orifice, DF fittings are only recommended for non-porous parts or for slightly porous light weight parts.
There are two main ways to apply DF fittings: The first is to bring DF equipped suction cups into contact with the work and then turn on the vacuum source. Non-sealing cups will leak and cause the associated Dual-Flow valves to close to orifice flow only.
The second way is to turn on the vacuum source to close all DF valves before the suction cups contact the work and then allow the DF orifice flow to establish vacuum within the cups once contact is made.
In either case, part release is accomplished by removing the vacuum source and admitting atmospheric air to reopen the Dual-Flow valves. For a faster cycle time, use a blow-off pulse of compressed air to break the vacuum and release the part more quickly.
SIZING A VACUUM PUMP:
From the table below, determine the orifice flow at your systems maximum vacuum operating level. Multiply this by the maximum number of non-sealing cups in the system. Select a pump that will give this total flow rate at the system vacuum level plus a factor of safety.
CAUTION: If DF fittings are used with a heavy porous part, the part may be dropped suddenly due to porosity flow thru the part being greater than the available orifice flow. This can occour even if there is excess vacuum pump capacity. For this type of system, use Flow Sensor Valves. |
