Collision detection speed highly depends on many factors.
1.The number of pairs of checks defined in the collision map. Having a collision map with less checks will be faster.
2.The robot step used for collision checking. The collision step can be modified in the Tools➔Options➔Motion menu. Linear movements use the step in millimeters and joint movements use the step in degrees. A larger step will provide faster collision checking but the result may be less accurate.
3.Computer power: more computer power (faster CPU) and more processing threads will allow you to have faster collision checking.
4.The complexity of the 3D files. Geometries with higher level of detail, such as rounded areas, usually require more computation power. Simplifying these geometries and reducing the number of triangles will help you speed up collision checking.