"He who marches out of step hears another drum." ~ Ken Kesey
The Heatwave is a gas dryer with convection air, not sure what to do if you have an electric dryer, I know if there isn't airflow you are kinda skating up a hill. With a gas dryer, I haven't seen a shirt, even poly "burn". Now shrinkage, there are some shirts that it's almost impossible to avoid that, like tri blends, freakin hate them especially when people want water based inks. For that, Green Galaxy makes some awesome inks that you can add their "warp drive" to, and cure them very fast at below 300 degrees. 340 "shouldn't cause a lot of shrinkage" if you temp test and see that your print is hovering at that 330-350 mark, if it rises up then you will probably see some shrinkage. We just ran a big batch of bellas and canvas, it was really humid today so we had the heat up in the dryer to 360, same speed, everything was nice. Dryer day I would have brought the heat down to 340. Really the battle is the time in the dryer. I only have 8 feet of heat in the Heatwave so it's not, "ideal" for w/b printing, you really want 12' for more, but I know that's not always an easy run to the store and buy a bigger dryer, so we just slooooowwwwwwwwwwwwww down, which sucks, but it's better than 500 fashion fit shirts with multi location printing coming back because the ink is washing out. That new Sprint 3000 is built with the WB printer in mind. When we were up at the plant for the tour we were shown how the design lends itself to forcing more of the hot air down and through the shirts to get the ideal cure of waterbased/discharge, and HSA inks, nice machine for sure, but until any of can get into one of those, slowing things down is the cure I guess.
You're absolutely right screenprintguy, it takes a way bigger/badder dryer than you might think to do this efficiently. When we were lining up dryer everyone, myself included thought the Sprint High Output was going to be overkill but I am very, very glad that is what we ended up with. Even at 16' of chamber and all that airflow and btu it still just keeps up with two presses running wb/dc/hsa. I'd second Alan's 20' chamber suggestion, sounds just about right from our experience. If that length won't fit I'd look at 72" belt v 60" then. I didn't know there was a change in circulation with the Sprint 3000, that's interesting and also good to hear. What did they modify? My guess is the air knives where re-designed?