We have really had a tough time getting things to stick on the build platform for the SD3.  I had it working well enough for two class demonstrations, but I was printing short items and had the z-level set really low so the extruder was really pushing the plastic down.  Since that creates widened prints (see prior post), we decided to do something more serious.  We tried using different polyimide tape on plate glass, but I don’t think that improved much.  I ended up resorting to using ABS acetone (I throw in waste ABS of a single color into a 4oz. acetone bottle – I have about 8 of those bottles with different color ABS in each.  If you look closely at the close-up photo, you should notice a cloudy pink mass around the stage.  Awhile back, I’d just use a few grams of ABS in the 4oz., but ended up having about 10-15g in each bottle so it goes on kinda thick so I spread it quickly as the platform is heating.  I end up with a coating that is 0.1-0.2mm thick but I’ve never had jobs fail to stick to that!  The unfortunate part is that they stick so well that I’ve occasionally ruined the polyimide getting off the objects.  Also, I have to use straight acetone to dissolve the remaining material from the tape in order to switch colors (that’s another reason that removable glass plates are nice – some people use tempered glass and some use marble, but I use the cheap stuff that Home Depot sells and then I sand the edges and corners so as not to get cut).