Hi, 
ive created a 3D print of a two peice mould which can be used for injecting, the 3D printed mould is made out of ABS fillament, i was wondering if its safe to inject polyurethane (xencast) ?

or is there a liquid silicone i can use?

thanks

You would need to use a release agent other wise the resin would stick to the ABS plastic. You have to be careful that you don't use a release agent with too many solvents in it - ABS can be vulnerable to solvent attack, especially by styrene. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant