What if I do not know the hardness I need?
Defining your requirement is the most difficult phase, especially in the prototyping stage. Thus processes that offer the ability to bridge the predicted hardness have an advantage. There is nothing worse than waiting several days for parts, to conclude within a couple of minutes that a harder or softer grade is required. With both SLS and Objet additional part prices will be fairly linear (i.e. 2 parts will be double the price of one), however with PU this is not the case as the part price is only one element of the total cost. Ordering a couple of extra parts either side of the predicted hardness can be very effective and a good insurance policy!
Silicone tooling and PU parts, Polyjet and SLS with TPE210S can all offer a range of hardnesses. PU is typically available from around 35 - 90 Shore A, SLS from 40 - 70 Shore A and Objet from 27 Shore A upwards.