[DigitalInkArts]

I am using a Nu-Arc unit deals with light units rather than standard times. I am currently at 30 seconds which is .3 on my unit I use for spot colors but even this is slightly inconsistent. I am having a hard time trying to determine the times for spot and halftones.

With an online calculator I found it says to Guesstimate my time then multiply by 1.5 and divide by 8. What I get is 0.05625.

So what do I use, .6? In light units that is well over a minute and I know already that 45 seconds and 1 minute is over exposing. So I need to start at possibly 10 seconds which means this equation to determine my times is no help at all.

I am using a fast photo polymer which may be the difference but even still I should be able to get consistent times as all my screens are coated the same. 2 on each side. I was getting pinholes with one coat on each side.

Any help on this will help me keep my sanity. I have a halftone job approaching and I have zero confidence I can burn these screens to do the job.

I also worry about the fact that in between exposures I have a 45 second wait for the vacuum to do its thing. I have owned this unit for 3 months and just have not been able to figure it out.

 

[binkspot]

3140?
Emulsion?
Mesh counts?
Is it taking that long to draw down or is it the count down after it draws down then starts exposing?

 

[rhilferding]

Start with something like this: FREE Screen Printing Exposure Calculator

It allows for 1 exposure to accomplish a multiple of tests.

We had NuArc for years. I would say we "never" had an inconsistency in light output. In the initial calibration, 1 light unit equals 1 second. Then you can time the exposures and when you get to 1 light unit is longer than 1 second - you get an idea of how old and worn the bulb is.

Sometimes emulsion is too fast. The emulsion that works great for that 100 light bulb will not work with a 2K UV rich bulb.

I suggest you deal with one issue at a time - start with pinholes: [media]http://www.mrprint.com/images/articlesTips/screenPrepFor.pdf[/media]


Good Luck!
Robert

 

[DigitalInkArts]

Ulano QTX Hi Fi.
156 mesh
The unit I warm up for 10 minutes before I use it,Even then there is a slight 8 seconds where it is not at its full brightness. I tried adding a little time to compensate for this and it over exposed.

The pinholes are gone with the extra coat of emulsion.

I have tried that calculator before I tried the one I currently have. No luck with either on half tones. I am blowing out at 30 seconds so I guess I will start at 10 seconds and go up? It just made no sense to use the equation for figuring my times. It doesn't apply when I use the answer.


When I turn on my exposure unit and I count it out just to get an idea of real time, It is 12 seconds before each unit changes with the exception of the first change, which is 6 seconds. ( i could make a video if a visual helps )

so I do not understand how one second is one unit? New bulb too. ( it is the Mercury unit not the Halide)

Maybe I better go back to my 500 watt lamp. I got good screens from that.

 

[sben763]

Most photopolymer emulsions are prone to humidity issues. I was using CCI HPV (Ryonet hifi is same) and unless its below 35% humidity results were all over the place. Been using Saati Chem PHU and the difference is night and day. At 45% humidity having same results as 35%. I haven't tried above that yet with Saati emulsion.

The bulb needs properly calibrated at least the light integrators I have used. The emulsion should have a number of light units to expose.

 

[DigitalInkArts]

I think I got it. After coating the screens twice both sides and testing it turns out that a 1:10 is perfect. one coat on each side at 30 seconds would be great but there were too many issues.

I tried two tests on two different screens and washout was terrific on both free calculator tests. Going to keep fingers crossed on the next job.

 

[DigitalInkArts]

I ordered my dehumidifier. They didnt have the one I wanted in store. Should be a few more days. Then I will have to retest! ugh.