TSB
screen printing => Screen Making => Topic started by: siestasol on April 26, 2014, 01:08:16 PM
-
Hi there,
We just buy an used MSP 3140, any suggestions for time exposure before we run a exposure test.
Aquasol HV w/diazo. 2+1 round coating. Plastisol and waterbase discharge.
Thanks in advance.
-
Doesn't that unit expose by light units instead of time?
-
HV with 3140. 2+1 coating dull edge, about 3 seconds per coat. NO Diazo!!!
We are at approx 1.5 min for 305 mesh and about a min more for the 110.
pierre
-
any suggestions for time exposure before we run a exposure test.
Autotype Exposure Calculator (https://www.google.com/search?q=autotype+exposure+calculator&oq=autotype+&aqs=chrome.1.69i57j0l5.6432j0j7&sourceid=chrome&es_sm=122&ie=UTF-8)
That unit runs in light units and depending on the age of the bulb, calibration of the light integrator and your input line voltage settings asking us what we use is about the same as asking Tonto to head into town to get the supplies for the week.
-
I think Pierre has it right and meant 30 seconds per coat to get to 1.5 minutes.
The key is your film type.
For that reason I recommend a step test using your film. My calculators are a solid 3.5 dmax, so the time I get with good black film may be too much for a more transparent ink jet or vellum.
Here is the link: http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf (http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf)
Set your integrator up in the beginning to 1 second = 1 light unit. (this helps evaluate the bulb strength, see below)
Run the step test described above to determine best exposures. Use light units for this, more accurate.
When 2-3 months have gone by, use a stopwatch and time 60 light units. If you are getting 90 seconds or more instead of 60 seconds the bulb has aged. 3140 bulbs need changing more often than a Tri Light at 6,000 watts. Always keep a spare bulb made by Nuarc/M&R. If you see discharge screens failing and the screens used to print discharge fine, swap out the bulbs. This is my most common tech call, older bulbs that have lost their UV punch.
If you are seeing that with a 1:2 coat you are losing halftones back off to 1:1 dull edge coating or 1:2 sharp edge. Coaters vary a lot in the amount of emulsion they lay down. I have one company here in Socal that coats once on the print side, thats it. Sometimes a thinner coating can achieve a stronger screen since it gets exposed completely. I prefer 1:1 or 1:2 myself, but these guys are running 20k runs!
-
I think Pierre has it right and meant 30 seconds per coat to get to 1.5 minutes.
I meant it takes 3 seconds to do each coat (the time it takes to actually pull the scoop coater from the bottom to the top of the frame). We coat rather slow and thus have a slightly higher EOM. For somebody coating faster the time would be shorter.
Alan,
what's the impact of the Diazo on the exposure times (when added to HV/HVP)?
pierre
-
Oh thanks, sorry for the misunderstanding on the 3 secs.
Adding diazo increases exposure times by 25% depending on exposure unit.
Al