IML Printing on Conventional Sheetfed Offset

[ponnapati123]

Dear all,
We have started IML printing on Conventional sheetfed offset. Printing Method - Conventional Offset Printing, Inks - IML inks, IML Waterbased varnish and IR and Hot air for the drying.

At the beginning itself we have faced many issues but now we can able to feed IML sheets but the problem is Ink is not drying and white patches on solid areas. We checked all the possibilities including Blankets, ink, varnish, fount solutions but we end up with not drying ink. Also the dot gain is very high.

Anyone having experience in IML Offset Printing please share your views on this

Thanks and Regards
Anil Reddy

 

[SteveSuffRIT]

Work with your ink supplier to correct issue.
In-Mould Labels (IML) print on synthetic plastic film (non-absorbent), so oil-based (oxidation) inks need time for air (oxygen) to dry.
Steve Suffoletto

 

[CKL]

We only use Toyo TSP inks on all synthetic type material no exceptions. We have tried other inks and have had some issues.

 

[SteveSuffRIT]

To rule out any factors from the fountain solution (over-emulsified, pH too low), does the ink dry if printed on plastic film without any water, like a little joe proof or a brayer roller roll-out?

 

[ponnapati123]

Can we print IML without adding alcohol. I think water plays major role in the non absorbent materials.
The challenge is also getting the right colour due to the IML film properties. The dot gain values are high and producing darker colours.

 

[SteveSuffRIT]

The dot gain (tone value increase TVI) is a simple fix with a CtP cut-back compensation curve.
Returning back to the original problem of ink not drying, do you have an Ink Film Thickness gauge to test IFT on metal oscillator roller?
You mentioned a water based "varnish". Is it really a varnish applied thru ink train rollers or a coating applied thru special coater (roll/anilox)? Does base ink underneath dry without this "varnish"?
Does "NOT" drying mean it scuffs, rubs, scratches, poor adhesion, setsoff/blocks? Can you provide more specific details about this?

 

[ponnapati123]

The dot gain (tone value increase TVI) is a simple fix with a CtP cut-back compensation curve.
Returning back to the original problem of ink not drying, do you have an Ink Film Thickness gauge to test IFT on metal oscillator roller?
You mentioned a water based "varnish". Is it really a varnish applied thru ink train rollers or a coating applied thru special coater (roll/anilox)? Does base ink underneath dry without this "varnish"?
Does "NOT" drying mean it scuffs, rubs, scratches, poor adhesion, setsoff/blocks? Can you provide more specific details about this?

Yes we are doing calibration to get correct dot gain values.
We don't have any meter to check IFT. We used varnish on anilox roller. The ink is not drying without varnish. We have tried different varnishes finally drying problem is solved but the glossiens level is quite low. We want atleast 80 gloss levels but with the current varnish we are able to get max 45. Can you please recommend any high gloss varnish for IML and IFT meter.
Thank you

 

[Lukew]

Years ago By accident we found an ink that dried on synthetics. We had 20000 sheets of stickers to run. At that time we were using A&S summitec - HD version which was duct fresh for all our jobs which was their hard dry version of summitec. Stupidity I didn’t realise the sticker was synthetic and I printed full stacks of 3000 sheets and got 9000 sheets into the job. Once I realised I switched to sun chemical oxidation inks. Interestingly the next day the standard summitec hd ink had completely dried and scratch resistant. The oxidation ink was run in small stacks and didn’t dry for over a week and had poir scratch resistance.
from then on we ran the summitec hd ink on everything from uncoated stocks through to synthetic etc..
Sun chemical rep couldn’t get his head around how on earth was this the ink drying better then full oxidation inks..