Erik Kostson
Ansys Employee

In general most 3D elements should use the consistent matrix by default - with the LUMPM one can generate a lumped mass matrix, but there are some limitations and complications so look this up in the help manual - thus LUMPM should be used with care.
Search in our help manual (e.g., lumped and consistent and mass - and LUMPM command) and you will find hopefully some info about this.
Hope it helps.

All the best