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Max workable file size for importing mesh into OS

Hi all I'm rebuilding a large vintage aero engine and will be getting some parts scanned to import into OS then regenerate as onshape models. The largest is a 1m long, 0.12m diameter hollow trunk with four outlets, (2 at each end). It has compound curves at the outlets and it quite an elegant piece. Another is a large dinner plate sized casing that holds 4 bearing bushes. Commercial scanners can give me lots of point cloud points at 0.1mm dimensional accuracy but I'd like some guidance please about the practical maximum mesh file size to not overwhelm OS? With thanks Paul   

Best Answer

  • GWS50GWS50 Member Posts: 204 PRO
    Accepted Answer
    I do a lot of mesh work, in fact lately almost every job has some scan data involved.

    It doesn't really matter what the real world size is rather the number of faces. I use Meshlab to decimate the scan data down to about 100th faces and export as an OBJ. This will give a smaller file size than STL, and don't include the material file (.mtl) as it won't be useful to the CAD world.
    I have used files with up to around 500th faces but it can slow things up rather, sometimes the extra detail can be useful but not always.

    The best way to deal with the file once imported is to 'manoeuvre' it into the orientation that you want in the part studio and then derive it into another part studio where you want to do the design work. That way you have a reference file if you want to take the Mesh into other studios.

    It is quite rare for a mesh to be all nicely lined up with the XYZ axis, unless it has come from a digital sculpting program, and transform with mate connectors or rotate about a sketch can be useful for this,

    To get the the mesh into an assembly you will need to decimate down to below 10th faces (which is rather blocky I'm afraid) and then convert to a STEP file using FreeCAD or the new version of InStep, which you will have to pay for. (STEP files can be quite large in size)

    Often the mesh data needs repairing and I have found Meshmixer to be a good (free) software for this.

    If you run into specific problems I will try and help.

    There is a FANTASTIC featurescript called Boolean Plus by @MBartlett21 which will let you boolean a mesh.

    Good Luck

Answers

  • Paul_J_PremakumarPaul_J_Premakumar Member, Onshape Employees Posts: 180
    Hi @paul_noonan783,

     There isn't a simple answer to this question, because there are a few other things to consider example, amount of memory the imported data consumes, how many triangles the import will create etc..

    Question : What format are you planning to import this into Onshape?

    Take the following with as guidelines rather than absolute rules

    1. The larger the file ( especially in the GB range), the longer Onshape will take to process and the higher the chance of translation issues.
    2. The finer the mesh, the more data the browser needs to render - you may run into interactive performance issues

    For #1 you may need to try this by trial and error. For #2 you can checkout our compatibility page to determine the limit of your machine https://cad.onshape.com/check


  • GWS50GWS50 Member Posts: 204 PRO
    Accepted Answer
    I do a lot of mesh work, in fact lately almost every job has some scan data involved.

    It doesn't really matter what the real world size is rather the number of faces. I use Meshlab to decimate the scan data down to about 100th faces and export as an OBJ. This will give a smaller file size than STL, and don't include the material file (.mtl) as it won't be useful to the CAD world.
    I have used files with up to around 500th faces but it can slow things up rather, sometimes the extra detail can be useful but not always.

    The best way to deal with the file once imported is to 'manoeuvre' it into the orientation that you want in the part studio and then derive it into another part studio where you want to do the design work. That way you have a reference file if you want to take the Mesh into other studios.

    It is quite rare for a mesh to be all nicely lined up with the XYZ axis, unless it has come from a digital sculpting program, and transform with mate connectors or rotate about a sketch can be useful for this,

    To get the the mesh into an assembly you will need to decimate down to below 10th faces (which is rather blocky I'm afraid) and then convert to a STEP file using FreeCAD or the new version of InStep, which you will have to pay for. (STEP files can be quite large in size)

    Often the mesh data needs repairing and I have found Meshmixer to be a good (free) software for this.

    If you run into specific problems I will try and help.

    There is a FANTASTIC featurescript called Boolean Plus by @MBartlett21 which will let you boolean a mesh.

    Good Luck
  • paul_noonan783paul_noonan783 Member Posts: 8
    Thanks Paul and GWS50. It will be OBJ or STL. I think I'll stick to about 100,000 faces as suggested above. Thanks for the tip about Boolean Plus and offer of ongoing help. Cheers, Paul. The engine is of this type if you're interested.      https://en.wikipedia.org/wiki/Rolls-Royce_Kestrel


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