A problem about imprint/merge which lead to export warning

I’m having trouble with complex mesh preprocessing.
First about the imprint/merge. After I use this function, the model changes as below, I don’t know why this is coming from and if this is feasible/readable.
before imprint
after imprint
The next problem comes from the process of export .e from the grid file. The tetmesh method is used here. I don’t know if it is caused by the previous problem.

Hi @krystal,

Welcome to the forum. What is the geometric size of the model? If you are working with very small objects, it is helpful to scale them into a range where numerical accuracy is at least 4 or 5 orders of magnitude greater than 1e-6. You can do this by the command

body all scale 10000

You can shift this scale on export or scale everything prior to export. The inverse problem can exist if the numerical range is too large.

The second problem would appear to be that blocks are not set correctly. A block corresponds to a group of elements that typically have the same material property and the same element type.

You must create a block and then assign an element type. From command line you might do something like

block 1 volume 1
block 1 element type hex27

From the traditional GUI panel, you can set the element type as shown in the following image.