The patent 5,597,520 (at least partially) expired in 2010
The patent at issue was partially complete and filed in 1990 and therefor expired at least in part in 2010. Other parts expire in 2013. Formlabs certainly has only the most modest of sales now (one presumes) and had none at all in 2010.
Such a suit at best can collect damages based on lost revenues etc. Hard to see much damages.
I certainly believe 3D has done the world a service working in the late 80's on 3D printing issues when much of the crew at Formlabs were still in diapers still there is little here and 3D should not waste many hundreds of thousands of dollars to chase an empty cup.
In two years their patent 5,597,520 will be completely in the public domain.
For the same reason Formlabs should avoid paying lawyers and just make a deal that provides something to 3D for the max time they have left. Understanding that the time depends on exactly what is infringing and which of the continuations it became part of the patent. Could be anything from 0 to 2 years but not more.
There is one possible nasty bug in ointment Dennis R. Smalley put himnself as principal inventor and as PATENT COUNSEL!
This could mean he is a great genius or that Formlabs was so poor he had to do the patent attorney duty or (God save Formlabs) he could be an ego maniacal Lawyer who intrudes on the engineers domain and uber pugnacious... a schmuck who must win at all cost and one who has no cost of suit to moderate the choices of 3D's governing counsel.
I certainly could find out more about Smalley and maybe even offer a work around to Formlabs but I've got to focus on the paying tasks. Hopefully this will help.