CONTROLLED AUTOMATION, INC.

BEAMLINE

PUNCH CYCLE

The punch cylinders are extended and retracted by hydraulic oil. The hydraulic valves that control the punch extend/retract direction are usually double solenoid (1 for extend and 1 for retract) and operate at 115VAC 60Hz. There are two limit switches for each punch cylinder. The limit switches are +15VDC inputs and are wired using the normally open contacts. One is made (turned on) when the punch cylinder is fully retracted (RETRACT LIMIT SWITCH), the other is made when the punch cylinder is fully extended (EXTEND LIMIT SWITCH).

When the machine initializes at the beginning of a run, all of the punch cylinders are retracted to the fully retract position (retract limit switch on). During a punch cycle, the punch extend valve and the pressure valve(s) are turned on by the computer. As the punch is extending, the computer is waiting for the extend limit switch to make. When the extend limit switch is made, the computer turns off the extend valve and the pressure valve(s). After a short delay, to let the hydraulic line pressure drop, the punch retract valve and the same pressure valve(s) are turned on. The computer now waits for the retract limit switch to make. When the retract limit switch is made, the retract valve and the pressure valve(s) are turned off, and the punch cycle is complete.

Some machines will have a punch extend limit switch and a pressure switch on the hydraulic power unit that will be used instead of a punch retract limit switch. This pressure switch is set to 1500-2000psi and is also wired normally open. The punch extend portion of the cycle is the same as above. But when the punch is retracting, the computer is waiting for the pressure switch to make instead of the punch retract limit switch. When the punch cylinder fully retracts, the piston is bottomed out, and the hydraulic pressure will start to rise. When the pressure rises to the setting of the pressure switch, the pressure switch will make, and the computer will turn off the punch retract valve and the pressure valve(s).

With another configuration, there will only be a pressure switch. This pressure switch will be used for the extend and retract limit. The cylinder must fully extend and build pressure and then fully retract and build pressure for the punch cycle.

One last configuration, the extend/retract hydraulic valve will be a single solenoid style instead of a double solenoid. When the valve is on, the punch cylinder is extending. When it is off, the punch cylinder is retracting.

COMMON PROBLEMS

Limit switches bad or not adjusted correctly.

Hydraulic valves bad or not operating correctly.

Hydraulic pressure not set correctly.

Pressure switches bad or not set correctly.