Before reading this post It might be worth reading a blog entry that I made back in January 2011 http://rapman-education.posterous.com/safe-support-material-removal-that-really-wor
In that post I revealed that PLA support material can be removed from an ABS printed object using hot water (or for a quicker but riskier result you can use caustic soda NaOH). The hot water method requires the object is kept in hot water for 36 to 48 hours…. But this is a little difficult to do. Help is at hand though as 3D Systems Bits from Bytes now supplies ultrasonic tanks that will contain the liquid and keep it hot.
These might seem a little pricy but certainly In schools where safety is so important it’s a worthwhile investment if you regularly print with PLA support material.
3D Systems Bits from Bytes have just released a video on YouTube that shows you how it’s done.