You refined a small part of the blank and the calculation became much slower. Why would a local change affect the whole run?
For an explicit calculation, time advances in many small cycles. Those steps must satisfy the method’s stability requirements. The size of deformable elements is one of the things that enters the calculation.
Think about the time for a wave to cross an element
The 2022 User Guide explains the local element time step using the time taken by an elastic wave to travel through the element. It depends on size and material properties such as density and stiffness.
A smaller characteristic length can reduce that local time scale. The solver obtains a global time step from the element limits, so a small region can affect progress for the model as a whole.
The guide specifies deformable elements in this global time-step calculation. That is different from saying every tiny rigid tool element directly sets the same limit. Tool mesh quality still matters for contact, for other reasons.
Find the small deformable elements
Display Characteristic length in relevant computed states. Look at whether the fine region came from initial meshing, adaptive refinement or distortion during forming.
If the region is required to resolve a bend, deleting detail simply to increase the time step may remove the behaviour you wanted to calculate.
If it is an unintended sliver or badly distorted area, investigate why it exists. Mesh checks and local refinement help you trace the setup choices.
Is mass scaling a free speed increase?
No—changing effective mass changes part of the numerical model. It can increase the stable time step, but the effect on the result must be assessed for the study.
Keep the baseline and compare the relevant response after a controlled change. Don’t describe a faster run as equivalent solely because the final picture looks similar from a distance.
And implicit calculations?
Implicit methods use load increments and equilibrium iterations with convergence controls. You cannot diagnose them simply by applying the explicit time-step explanation to every slow stage.
First identify the solver method and where the time is being spent. Then use the runtime post to organise a useful comparison of mesh, output and numerical settings.
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