We are in the process of purchasing such a machine that marks panels with 
the use of an ink jet print head.  I have contacts at two different 
companies that have quoted on the piece of equipment.  Merix Loveland
also uses a system that marks panels with an inkjet system.  They have
had good success with it (except when they have a mechanical failure).
I had several concerns when I first began looking at these types of 
machines, the first was machine thruput we manufacture product on four
different panel sizes 18x24,12x18,14x18,18x18.  Also the lotcode location
is part specific which requires alot of data download capability(similar
to an NC file for a driller).  From discussions I have had and from 
watching the machines operate it was determined that these types of 
machines could achieve a thruput of 200 panels/hour (with some mix 
assumptions).  My second concern was ink resolution and adherence. We 
currently are creating an etched lotcode on all of our product and it
has excellent durability.  One concern you might have is the inks ability
to adhere to the surface you are marking-- Soldermask is the surface 
typically marked upon with this type of equipment and the color of the
soldermask will make a difference as to the contrast between the color
of the mark and the color of the board.  Most inkjet manufacturers 
recommend the use of a dark ink, because it adheres the best and has 
excellent durability through solder reflow.  If you wish to get some
more info call me at (5030 359-9300 ext 4508.

Josh Moody
Process Engineer
Merix Corporation
Forest Grove, Oregon