Export to dwg creates multiple versions of blocks

I am trying to export a dgn file to dwg and for some reason every instance of identical cells get exported as separate blocks in the dwg file (i.e. 10 instances of cell 327W get exported as 327W_1, 327W_2, etc.). The cells are normal cells in the dgn file (not shared). In the export tool I have it selected to create single block for duplicated cells but for some reason it always turns out the same. Any ideas or tips would be appreciated.

Update: When I open the dwg file MS the cells are now showing as shared cells all with individual definitions. No clue why the dwg version of this file is showing as shared cells but maybe that's a clue for someone with more experience than me.

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  • No clue why the dwg version of this file is showing as shared cells but maybe that's a clue for someone with more experience than me

    MicroStation has several types of cell, including normal and shared cells.  AutoCAD blocks are equivalent to MicroStation shared cells.  When you export a DGN file as DWG, normal cells are converted to blocks.  See this help article.

     
    Regards, Jon Summers
    LA Solutions

  • Thanks Jon, that makes sense. Any idea why MicroStation takes multiple instances of a normal cell, call it CellA, and creates individual Autocad blocks ,or shared cells, on export (CellA_1, CellA_2, etc.)? Is this simply a limitation of the export command? I've tested importing the dgn directly to Autocad and the results are the same so maybe it's the only way Autocad can interpret normal cells.

  • Mike,

    Thanks for providing the file. I am seeing the name differences as well in the translated DWG file. I will continue to investigate this. I do see that the files original format was V7 so this might have something to do with the issue.

    Regards,

    Regie


       

  • That is the old limitation of Microstation export it has hardcoded algorithm how it compares cells and if Microstation "thinks" they are not equal then they are renamed as AutoCAD blocks(shared cells) can't have different geometry or attributes as they are instances and not full elements.

    Even setting do not create duplicates causes such behavior and no option to actually force no duplication and just use same cell for all equally named cells even if it means some data loss. In other cases MS silently drops unsupported elements without asking but for some reason for cells it goes extra steps to corrupt resulted files.
    Regarding v7 files I have also noticed that in v10 CONNECT version data cleanup doesn't find some cells as duplicates so this could be related to same issue that it "thinks" they are different. Try to copy two cells which are renamed afterwards in DWG and copy them in new file one over another and try to run duplicate cleanup if it is not working then it means it wrongly compares as different even if geometry is the same.

  • I think MicroStation is seeing a slight variation in the cell and this why it is creating a new block. I blocked out all the other cell elements except for two cells and found the only difference was the rotation angle of the circle that was part of the cell. I made a copy of the cell and there was no duplicate block created as the rotation angle is the same but in the cell where there was slight rotation difference (2 degrees) a new block was created. 

    Cell Sample_V8.dwg

    I am confirming with development to see if this would be considered defect or by design which would require a change request in functionality.

    Regards,

    Regie


       

Reply
  • I think MicroStation is seeing a slight variation in the cell and this why it is creating a new block. I blocked out all the other cell elements except for two cells and found the only difference was the rotation angle of the circle that was part of the cell. I made a copy of the cell and there was no duplicate block created as the rotation angle is the same but in the cell where there was slight rotation difference (2 degrees) a new block was created. 

    Cell Sample_V8.dwg

    I am confirming with development to see if this would be considered defect or by design which would require a change request in functionality.

    Regards,

    Regie


       

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