  We study kink scattering processes in the (1+1)-dimensional $\varphi^6$ model
in the framework of the collective coordinate approximation. We find critical
values of the initial velocities of the colliding kinks. These critical
velocities distinguish different regimes of collisions. The exact equation of
motion for the $\varphi^6$ model is also solved numerically with the same
initial conditions. We discuss advantages and disadvantages of the collective
coordinate approximation, and also outline its applicability limits. Resonance
phenomena and the so-called escape windows are also observed in the kink
collisions.
