pitney bowes mailing systems group in stamford connecticut uses maya's tmg thermal analysis software to help develop next generation ink jet printing technology for high speed mail processing equipment.
feed, seal, weigh, frank, stack, feed, seal.
on an average day mailrooms in the us handle almost 100 million cards and letters. that's 36 billion pieces of mail a year that have to be collected, weighed and stamped before being sent down main-street usa.
at the eye of that paper hurricane is some seriously hard working automation. the volumes handled by a modern mailroom call for processing machines that can weigh and stamp up to four pieces of mail a second.
pitney bowes has been meeting challenges like that for over three-quarters of a century. their logo has become a familiar site in mailrooms large and small, ever since arthur pitney invented the postage meter.
the paragon mixed mail processor is part of a new generation of products and solutions
that will transform mailing operations forever. it will feed, seal, weigh, frank and stack
mixed mail in one operation and at high speed.
developing a next generation printer
as mail demands have grown, so have the design challenges faced by pitney bowes engineers. among them is the challenge of printing franking and advertising directly onto the wide variety of paper media that mail-processing machines are faced with.
exploring printing techniques that would enable them to change the printed text on the fly, engineers at pitney bowes realized they needed a more flexible print method than the "rubber stamp" techniques that are the current standard. they decided it was time to build a whole new printer.
the wide variety of packaging materials, and the speed at which they have to be handled, called for ink jet technology. a specially formulated "hot-melt" solid ink was investigated for its fast drying, and its ability to adhere to almost any surface. printing with this new ink presents a whole new set of challenges. the ink must be heated to 125°c before it can be used. but heating it to this temperature also ages it, so the number of times it is re-heated must be kept to a minimum.
the printer is designed to run constantly under heavy-usage conditions, so a reservoir of hot liquid ink must be available to the print head. this ink will likely be heated only once before eventually being passed through the print nozzles. however, the design also needs to anticipate medium to light usage. in these cases, ink held in the print-head's reservoir is likely to be heated and cooled many times before being passed through the print nozzles.
air is blown over the thermal valve to cool and congeal the ink. switching on the cold air blower
stops the ink flow within 30 seconds. when the front ink tub is low, the rear tub
is heated and the ink starts to flow again.
realizing that congealed ink would quickly gum up a mechanical valve, they struck on the idea of using the ink itself as the valving material. by heating the rear tub, the ink in the valve will also melt and fresh ink can flow to the front tub. cooling the valve will then solidify the ink, halting the flow in the valve until another refill is needed.
of course, the tricky part was turning that idea into a working unit. much of the difficulty involves the number of variables, including the physical dimensions of the valve, the geometry of its cooling fins, the thermal properties of valve material and ink, the cooling fan size, and air flow within the printer enclosure.
normally pitney bowes would have tackled this problem by building a number of prototypes, then testing and refining them until they arrived at an optimized system. this process would have taken at least six months.
it’s easy to set up several model parameters and vary the geometry, material properties
and thermal boundary conditions using tmg. the element mesh and thermal boundary conditions
are updated automatically after making modifications. the engineers at pitney bowes
were able to investigate 35 different designs in just a few weeks.
thermal virtual prototyping
kjell heitmann, principal engineer at pitney bowes, was called in to help find a quicker solution. "the testing lab had already drawn up a matrix of 10 different valve sizes and fin arrangements"he recalls. "they were planning to spend several months running tests to determine the optimum valve."
a long time proponent of simulation, the engineers set to work modeling the part using the i-deas master series modeling package coupled with maya's tmg thermal analysis software. "it was remarkably easy to set up the model in tmg. the engineer who performed the work had never used tmg before, but he was turning out models by the end of the second week."
despite being easy to model, the number of design variables and the transient nature of the problem made the thermal system very complex. "we had to be able to vary the rate of flow and temperature of the air, the size of the fins, and the tube material and thickness,"explains heitmann. "we even had to model the ink cooling and phase change effects."
four weeks later, armed with the results from 35 different valve designs, they were ready to take a final design to the lab - just in time to save the testers a lot of trouble. "they had just started testing," he explains. "they'd installed a valve that we knew wouldn't work. the new thermal virtual prototype valve we modeled using tmg worked the first time."
tmg was used to solve the transient thermal behavior of the valve. the hot liquid ink flowing
through the valve tube is cooled and solidified to shut the valve off. the valve tube diameter,
wall thickness and the size and spacing of the fins were critical to cooling
the ink quickly enough to close the valve.
pitney bowes' new approach to product development
the engineers at pitney bowes can effectively optimize the design of new products using maya's simulation tools. "now that we don't have to go out and build physical prototypes for every design, we can model a large number of designs in a very short amount of time. with tools like maya's esc and tmg, it has become so easy to set up an analysis and get meaningful results, i don't even do many back of the envelope calculations any more."
impressive as the results of heitmann's work were, their impact has been much more significant than originally anticipated. it has helped change the way pitney bowes does research and development. "analysis has really shortened the design cycle," says heitmann, "and that reduces the cost of development." pitney bowes has become much less reliant on testing physical prototypes and has effectively deployed maya's simulation tools up front in the design process.
maya heat transfer technologies ltd.
4999 st. catherine st. west, suite 400
montreal, quebec, h3z 1t3
visit maya at www.mayahtt.com
©1998, maya heat transfer technologies ltd.
i-deas and i-deas master series are trademarks of structural dynamics research corporation.
images courtesy of pitney bowes.