I'm posting a second answer because this method is completely different from my first answer.
Another way to make 3D printable text is with ImageMesh:
hello = Rasterize[Graphics[{Text[Style["Hello", Bold, 60]]}], "Image"]; text = ColorNegate[ImagePad[ImageCrop[hello], 6, White]]; stack = Image3D @ Join[ ConstantArray[helloConstantArray[text, 20], ConstantArray[ColorConvert[ConstantImage[1, ImageDimensions[hello]]ImageDimensions[text]], "RGB"], 5] ]; ImageMesh[stack, Method -> "DualMarchingCubes"] 