* For your first model: when it's too small (how small exactly?) for the Shapeways' printers, then of course you should scale it (somewhat) up in Solidworks and save it as STL (or other format) again.
* For the other file, there are some practical ways to test the model (see also the 3D modeling tips
- check for 'strange' areas / difficult features in your model
- save a separate file without all such features and save this 'basic model' as STL
- upload this STL file to Shapeways and see whether the automatic check accepts this: if not, your basic model is already 'corrupt' (then: suppress other features also). If it is accepted: continu to build up your complete model step-by-step and save several stages as STL. And test the STL files at Shapeways.
This will cost some trial-and-error, but in the end will learn you exactly where the error arose. I think it's better than trying to remodel/correct a weak STL file in another program (MeshLab) than SolidWorks.
Good luck! Looking forward to seeing your design,
- just uploaded (without problems) my 8.3 w x 17.18 d x 5.5 h cm^3 new design at Shapeways yesterday. Hope this first original STL of mine indeed results in something good -
PS If you like to, you can also upload an image from your SolidWorks model in a message at this forum. I'm sure some members can spot any faults/difficulties in relation to the printing.