Trapping artwork question

[ajflex]

Hello all,
I am new here as well as flexographic printing world.
I am a graphic designer and I need to learn the pre-press requirements to send artworks for flexo printing.
couple of questions.
1- Do vector artworks need to be all subtracted from each other so there is no hidden shapes underneath?
2-how can I create the trapping on my artwork so the print company will see it and make the plates accordingly?
3-why do I need to worry about LPI and Print angle and halftone type? I read a pre press requirement from a company that says"Use a screen value of 42.5 dpi for half tone images. Use only 10%, 20% and 30% line value. and Halftone images in Mezzotints are more corrugated friendly than dots". Aren't these the adjstments that printing company does when sending the artwork for plate making machine?

Thank you in advance
also I would appreciate if you can give me any other advise for flexo printing art requirement so it will make the process easy on the print company.
Alex

[barb]

Hello ajflex!

1 - It sure would help a lot to the printer's prepress department, but in my experience - it's not a big deal.

2 - In my practice I have always warned my customers not to put trapping themselves - it's easier and safer if the printer/plate maker does it.

3 - Yes, all of this should be printers worries because they know better what they need. It's their job to warn you if something needs to be adjusted that may affect your design.

My advice is - keep it simple and ask your printer if there are any limitations you should know about before you are finished designing.

I work in a prepress department for over 3 years and one of my best and successful experiences are when the designer sends me their artwork, explains what they want to achieve and also immediately asks if everything is suitable for our printing abilities. That way I can warn them for any possible issues that may occur and the result at the end is much better.
Of course, the majority of them believes anything they do can be printed and when we do adjustments I have to explain bit by bit why something can't be done, or can be done differently - and better.

Every printer has their abilities and limitations, and as a designer I believe the only way you can be happy with the final result is when you know upfront what to expect.

Hope this helps!

Also try and google tips for designing for flexo, you'll find some stuff that are general rules. Save them and later when you have the product in front of you, inspect the print. I think that's the best way you can learn over time what can you avoid or make different way to get an even better result!

[ajflex]

Hello ajflex!

1 - It sure would help a lot to the printer's prepress department, but in my experience - it's not a big deal.

.....

Thank you very much Barb with the detail info.

[guy de cafmeyer]

There are some real basics that one would need for good flexo design , including :
.What is the colour of the substrate ? If for example it is white , you can then design without having to consider this , as
.Number of print stations available , if it is an 8 colour press , then this should also be considered when designing . It remains preferable to print company logos etc as separate colours , and not part of the cmyk , as some clients like to "fiddle" the print to achieve a certain result , thereby affecting the logo .
.Do not vignette down to zero's . preferably do vignettes down to say , 3 or 4 % .
.Trapping needs to be done by the reprohouse/printer , as trapping is different for different presses .
.As far as possible barcodes should be done in the machine direction ... direction of web travel through the press .
.Do not use a spot and screen combined , rather split into two plates/colours , as different ink metering rollers ( aniloxes) will possibly be used .
Hope this helps !