The Stall force means the maximum force that the actuator can exert. When a large load corresponding to the stall force is applied to the actuator when the actuator is pushed or pulled, the force to move and the force of the load are perfectly matched, and the state where the speed converges to 0 is called the “Stall” state, and the maximum force at this time is the stall Force.
The load amount should be set to under 1/3 of the stall force (this is the rated load), and if it is more than that, it will affect the life of the actuator due to overload condition.
The Stall Force can be controlled by the Goal Current described separately below. If the Stall state is made at more than 400 mA (the rated load current) load current, the motor will have a fatal effect on the life due to the drastically increased heat. Please be careful “the stall state” as much as possible at more than 400mA goal current condition. (For mightyZAP, the overload protection function is activated in case of overload condition to protect the motor, but frequent overload condition may adversely affect the life of the actuator.)
Stall state at goal current and overload protection
For force control lineup actuators, the actuator calculates the cumulative value of the current.
If the goal current exceeds 400mA, the overload protection function will operate within a certain time, but the motor will be damaged.
So, please be careful not to fall into the stall state when you set the goal current above 400mA. If the goal current is set to less than 400 mA, there is no fatal damage to the motor even in stall state. However, in this stall state, the overload protection function will be activated within 30 seconds and the motor power will be cut off.
Load
The load is the weight or force of an object applied to the actuator when you try to move an object using a linear actuator. To control higher external force(load), you may need to use higher rated force actuator for smooth and proper control. In order to increase the power of the actuator, the simplest way is to select a model of “High rated force model with slow speed” due to a high gear ratio, but in the case of the force control lineup, you can increase the power by raising the Goal Current higher than the default setting.
Duty Rate
The ratio of the actual motor working time while the actuator is powered. The recommended duty rate at a rated load is up to max. 50%, and the lower the duty rate, the longer the motor life.(If the load is higher than rated load, duty rate should be lower than 50%)
Rated Load
The Rated Load is the “maximum load that actuator can be efficiently and properly controlled” without significantly affecting the life of the actuator. The higher the rated load, the higher the force of the actuator thanks to the increased gear ratio, but that means that the speed will be slower. It may be the best choice if the actuator is selected after checking the actual load of the customer’s application. The recommended duty rate at a rated load is 50% or less.
Max Applicable Load
The max applicable load is the maximum load that can be applied to the actuator and it is two times the rated load. With a max applicable load condition, a larger current is required, so the goal current should be set to 1.6A. And lifespan of the actuator decreases rather than being used at a rated load and the duty rate must be less than 20%.
Current Control (Current Limit / Goal Current)
The 12Lf / 17Lf series support Current control feature which means user is able to control the maximum stall force that the motor can produce through current control. Current control can be made by two different parameters – the one is the Current Limit (non-volatile) parameter, where the adjusted value is saved, and the other is the Goal Current (volatile) parameter, which adjusted value is not saved when the power is turned off. The functionality of both parameters are the same, but if frequent current value adjustment is required during actuator operation, it is strongly recommended to use the Goal Current parameter(Volatile), which is not saved. (If the Current Limit(non-volatile) data is frequently saved, communication may be interrupted during the saving time, and there may occasionally be abnormal operation in the memory.)
The default value of Current Limit for 12Lf / 17Lf series is set to 800mA at the factory. The current consumption at the rated load is about 400mA, but the current upper limit value for stability (speed, acceleration/deceleration, etc.) at the rated load is 800. When the goal current is set to 800 or higher, the stall force is approximately 3 times the rated load, so that the rated load can be properly handled.
In case of the maximum applicable load is applied (which is 2 times the rated load), Current Limit(or Goal Current) should be set to 1.6A and the duty rate reduced to 20% or less. In other words, when controlling the load over the rated load, Current Limit(or Goal Current) should be increased and the Duty Rate should be decreased proportionally.
The Current 200mA is the minimum level of current. The smaller the current value, the smaller the stall force. Below 200mA, the power may be too weak to run the DC motor.
With the Current value decrease, force and speed will be decreased and thus, noise can be reduced too.