In brief
Solvent screen inks can be stackable after seconds in an efficient tunnel dryer, or need minutes on a rack, or hours of post-tempering for IMD forming and moulding. Read the drying figures on the ink data sheet, then size the dryer for the dwell, temperature and sheet separation it requires.
What controls drying time
Coates lists the factors that drying time depends on: thickness of the printed ink layer and the number of overprinted layers; rack drying or tunnel dryer; temperature, air supply and air speed; the substrate printed; and any thinners or retarders added. Retarders in particular can make drying much longer.
Fast inks: a short hot-air tunnel
For its CX-AM automotive ink on polycarbonate and similar plastics, Coates gives about 20–30 seconds at 80 °C in an efficient tunnel dryer (for example two hot-air sections and one cold-air section), against roughly 5–20 minutes in a drying rack at 20 °C. For inks like this, a short tunnel after each printer is usually enough.
Slow or demanding inks: long dwell, separated sheets
Some processes need much more. For its Mara Mold MPC ink for IMD film, Marabu recommends a tunnel with two hot-air zones at 60–75 °C plus a cooling zone, then post-tempering for 4 hours at 80 °C to limit residual solvent. With hardener added, prints are not stackable after the tunnel and should go to a drying rack. When sheets must stay separated for a long time, a rack or a louver oven is the practical choice.
How a louver oven fits
A louver (rack) tunnel oven carries each sheet on its own louver through filtered hot air, so sheets get a long dwell without touching, and one oven can collect the output of several sheet screen printers. Size it from the dwell the ink needs and the total prints per hour.
Sizing checklist
- Required temperature and time from the ink data sheet, including post-tempering
- Prints per hour from all printers feeding the dryer
- Sheets in the dryer at once = prints per hour × dwell in hours; compare with the louver count
- Whether sheets may touch or stack before they are dry
- Dust sensitivity and filtration
Then confirm with a run: check stacking (blocking), adhesion and, for IMD, forming results on sheets dried on the proposed line.
Frequently asked questions
How fast can solvent screen ink dry in a tunnel?
Coates gives about 20–30 seconds at 80 °C in an efficient tunnel for its CX-AM ink. Other inks differ; use your ink’s data sheet.
Why would a printed sheet need hours of drying?
Inks for IMD forming and moulding may need post-tempering to limit residual solvent; Marabu recommends 4 hours at 80 °C for Mara Mold MPC.
Related LICHAO equipment
References and fact sources
Original technical guidance by LICHAO. Figures quoted from suppliers apply to the named products; verify process fit with your own samples.
Mr. Yang can plan a trial from your material, drawing and acceptance requirements.
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