how to make the gripper grasp the object toughly

[Yangziqi1920]

Hello everyone
Now I am doing pybullet with dobot robot, I made my own urdf file through solidworks, but when I want to make my gripper grasp the object tough, but it doesn't work rightly, my griper cannot grasp the object.
I saw many examples such as panda kuka robots, their gripper can rightly grasp the object. I want to know why?
Thanks for your answers!

pybullet.setJointMotorControl2(RobotUID,
FINGER_JOINT_NUM,
pybullet.POSITION_CONTROL,
targetPosition=0,
force=self.fingerTipForce)
this is my method.

[Steven89Liu]

Could you provide a simple test that i can reproduce your issue? thanks.