File Conversion Solution from STL (3D) to CSV (series of layered bitmap)

Hello,  I have acces to a Voxeljet sand/binder 2.5D printer. The interface only reads bitonal bitmap images, one at a time. For more complex forms, it can read a CSV (excel-type table) of ordered layers of PBM (bitmaps). On Rhino one can export as STL for a number of printing solutions. However, to my knowledge, it cannot export more than one image file and unfortunately only as jpg (not as PBM or bmp). I've automated contours at successive heights of thickness, but I don't know how to export as a series of bitmap PBM into a CSV file. Does anyone know a single program solution? It would be great to script this through Grasshopper. Any ideas would be appreciated. Thanks in advance for your thoughts.