screen printing > Newbie

Newbie Belt-Dryer Questions

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OhNoPrinting:
so.. I pulled the trigger on an Workhorse Powerhouse dryer (maybe 3011?) after heat-pressing for 4 hours screen-printed bags, which i printed in 1 hour..

the heat-press works ok, i can wash the bags, the plastisol ink stays.

The workhorse dryer is something like 3m and has a heat-chamber of 1,5m, 12 IR elements (which reach around 400C each), the belt speed goes from 0 to 100.

When i put the belt speed on 20, the shirt only stays around 25 seks inside the chamber? So i really need to go slow, to reach 60sek?
Or can I compensate: like less time but more heat?

Question is, because I read everywhere, that plastisol should cure a minimum of 60sek with 160 degree C. (so it would need to reach 160C and then be 60seks inside, so it would be better 90seks dwell time?)

Now with the dryer set on 180C and around 30sek dwell time, my shirts (black shirt with thick yellow print) washes ok, but ink cracks..

So I guess undercured. I was reading with a tempgun 160C on the shirt coming out, but it was a bit inconsistent (mostly because I dont know how to hold that thing :-) and I should probably reading 170C, right?)
 
-> Can I cure the shirts again? or would the heatpress be the better choice in this case because it is half-cured already?

-> Is 60sek inside the heat really mandatory, or can I "cheat" with higher temperature, because that would be pretty slow moving belt and the ink just needs to reach 160C once? (does it? or really 160C for 60 seconds?)

-> If I have two prints (front and back) would it be best to print-cure-print-cure or print-flash-print-cure. Might it harm the print if it goes through the dryer a second time?

-> What would be a sign for overcuring?

thanks - will probably add more questions later.

and, yes, of course I switched the dryer off without letting the belt move till its cooled down and had to clean the dryer. again. live and learn..

Admiral:
We run a little under 40 seconds dwell but it's in a large gas dryer.  I would definitely double your dwell time and see how that goes.  We ran with an electric HIX dryer with 8ft heat, 36" wide belt with our first auto and when completely loading the belt it would cause issues if we didn't increase the heat or the dwell time.

Frog:

--- Quote from: OhNoPrinting on July 11, 2023, 05:19:20 AM ---
Question is, because I read everywhere, that plastisol should cure a minimum of 60sek with 160 degree C. (so it would need to reach 160C and then be 60seks inside, so it would be better 90seks dwell time?)



--- End quote ---

Suggested dwell time is given as insurance for curing the entire deposit of plastisol. My understanding is that if and when the entire layer of ink reaches cure temp, it is cured!

tonypep:
And this is exactly what a donut probe will tell you. As often stated, you cannot fix that which you cannot measure

OhNoPrinting:
I cranked it up to.. -5  8)



Now I got a good minute of baking.. comes out with 170/160 degree C and washes good. (testing second cycle now)

Yes, I would love a donut probe. Unfortunately it is practically impossible to get a used one here and new.. well.. not in my reach yet. I have these little paper strips I use for the heat-press and can see that I reach at least that temperature, but yes, measuring would be great.

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