We generally like to keep flash times pretty short, so 1–4 s max. If you have a spare station, it’s useful to follow the flash with a cool-down station with air blowing across. This will do two things; first, it will cool the platen down (more on that later) and second, it will remove more moisture, for the same amount of heat input, so you can back off the tunnel heat even further.
The reason that we like to keep the platens cool is that if they carry heat on to subsequent print stations, then it ends up warming the ink and exacerbates drying-in issues, which is one of the biggest bug-bears that water-based ink users have to overcome. So, you can run the flash unit with less power and keep the whole room at a better temperature for working in.
Before we leave flashing, flash time and temp will depend on what ink type you’re using (Standard PERMASET AQUA, PERMATONE or PERMASET SUPERCOVER) and the proportion of the area being printed. For example, a large solid image printed with PERMASET SUPERCOVER will need a deeper flash than a few lines printed with Standard PERMASET AQUA Inks.
Next to curing; we can’t really make recommendations on curing with flash units as there are way too many variables. The amount of ink, ambient temperature, amount of ink to be cured, moisture content of the garment, capacity of the flash unit, distance from the garment and so the list goes on. Our recommended cure regime is 3 minutes @ 320’F in a tunnel dryer. If in doubt, run a test and record all the settings in a notebook.
Another concern with flash dryers is that there is quite a high risk of scorching the garment, particularly if they have synthetic content. Our general belief is that a heat press would be a more stable/reproducible proposition (and most likely faster). If all you have is the flash unit, then we can only suggest experimentation. It might be a pain, but we’d suggest keeping a notebook, record as many parameters as you can and staple both cured and wash/rub tested samples alongside your production notes. It will be a lot of work initially, but eventually this will become an invaluable resource for you.
If in doubt, talk to the flash unit manufacturer. They have more experience with their own products.