I am in the midst of a huge printing project for scale models of 3 types of heat exchangers. These files are very detailed and have extremely tight space. They require support material to successfully print them and the only way to do this is with soluble support material.
The plastic I am using is called HIPS. Believe it or not, you use what is essentially super concentrated orange oil (Limonene) to dissolve the plastic and leave the ABS printed part.