How To Use; Usage - SMC Networks MWB 32-UT Series Operation Manual

3. How to Use

3-1. Usage

① For intermediate stop, take stopping accuracy and overrun into consideration.
As this is a mechanical lock, there will be a slight time difference for the stop signal and delay of the cylinder.
The cylinder stroke during the delay is called overrun. The range between maximum and minimum overrun
is referred to as overrun. The relation is shown below.
a. It is necessary to place the limit switch taking account the amount of overrun to achieve the desired
stop position.
b. The length of the limit switch needs to be overrun + α for detection (switch detector length).
c. The operating range of standard SMC auto switches is between 8 and 14mm (varies depending on switch
type and cylinder bore size.)
switches which posses self-holding function of the output signal to the outside of the cylinder in order to
adjust the overrun .
② In order to reduce overrun and improve the stop accuracy, reduce the time between the
generation of the stop signal and stopping by locking as short as possible.
a. Use an electric circuit for control and solenoid valve with high response.
b. Keep the lock release solenoid valve and lock release port as close as possible.
c. If b is difficult, install a rapid exhaust valve between the lock release solenoid valve and lock release port.
③Piston speed is the most significant factor in stopping accuracy.
Examples when used in combination with an air cylinder.
a. Piston speed has to be stable before the stop position. If the piston speed varies due to the change of
load or interference the stop position will vary.
b. During cushioning or acceleration of the operation start, the variation of stop position is high (as the
change in speed is high).
Limit switches
Fig. 5 Overrun of intermediate stop
For an overrun exceeding this value, install proximity switches or limit
- 15 -
Stop signal position
Overrun
Stop position