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Ask Dave

Dave's Diary

This feature acts as a forum and notice board to customers and others who ask for information and guidance on the best film and print process for their products.

By publishing these questions and answers Dave adds to the knowledge of his readers whilst also providing useful tips of new and existing applications.

Questions & Answers


Flexo and gravure printing proofs

How close is a GMG proof to the final print?        Lucy, Product Development   17.9.18

This is a really good question Lucy, and a critical one.

The GMG proof is made taking into account the individual press’s idiosyncrasies and is the closest representation of what that press can achieve with the artwork supplied.

The photos and images made from the process set (CMYK) should be pretty accurate and the Pantones specified for spot colours will also be matched to the Pantone matching system (with a delta E tolerance).

LAB values give a specific point in the visual colour space.

Using a spectrophotometer we can measure this LAB value and accurately match colour irrespective of substrate tolerance is within 2 delta E (industry standard).


Barcodes explained

What do the numbers in a barcode mean?           Ellie, Food Technologist   29.8.18

GS1 is the organisation who develop and monitor Global Standards for barcodes.

The first digit of the barcode is usually 5 in the UK which means that the manufacturer has joined the UK GS1 Standard.

The next 6 digits are unique to that manufacturer and the next 5 are that manufacturer’s number for that particular SKU.

The last (13th) digit is the check digit. An algorithm verifies the first 12 digits, generates the 13th digit and checks it all scans properly. This is generated/checked at repro using a computer program. Historically we had a formula we had to apply using a calculator to generate the check digit. It was a right pain! If you like working with numbers you can type check digit calculator into Google and you can see the formula. Enjoy!

The barcodes are also checked on press to make sure they scan.

The numbers are the human readable form of the dark and light ‘stripes’ of the barcode.


Which is better, Flexo or Gravure?         Karl, Designer   17.8.18

Now this isn’t something that you can give a straight answer to.

Each printing method has its own Strengths, Gravure has always been designed for high quality, high volume work while Flexo has developed lower volume production efficiencies while being able to produce high quality print.

These days the decision to print gravure or flexo is made on the preference of the individual, cost of the origination or limitations of the process (continuous colour, ink density, registration, specialized coating etc).


What does LTS mean?        Craig, NPD    10.7.18

LTS is an abbreviation for “Low Temperature Seal” and refers to material that has been developed to increase machine speed and/or work on temperature sensitive products to replace cold seal.

There are many BOPP materials which have a wide sealing window to help give machine speed flexibility without having to adjust the jaw temperatures.

Having seal initiation at 75 degrees C all the way up to 145 degrees gives a 70 degree sealing window which is a big advantage for the any production line.


Is BOPP recyclable?         Craig, NPD      10.7.18


BOPP is recyclable.

Although not commonly collected and sorted from general waste, it is recycled at the manufacturing/extrusion facilities.


What does L.P.I mean?         Trevor, Developer      29.6.18

L.P.I refers to lines per inch.

Lines per inch refers to the number of dots on a printing plate (Flexo). The higher the number the more detail the printed image will be.


Which materials are suitable for running on a VFFS that produces a lap seal?         Dave, 11.6.18

A rough rule of thumb is if the surfaces are made from the same polymer then you shouldn’t have a problem.

So BOPP/BOPP would be the most common, BOPP/CPP is also a laminate structure commonly used on lap seal applications, particularly where seal contamination can be an issue.


What does Yield mean and why is it relevant?        Alan, Buyer      4.6.18

The yield of a material refers to the number of square metres in 1 kilo.

For example the Yield of 25 micron BOPP is 44m2/kg.

 Therefor there are 44, 1 metre by 1 metre squares of film to give 1 kilo in weight.

Compared to 25 microns of PET where there are 30m2/kilo.

So for the same weight you get 14 more M2 of material in BOPP than in PET (based on 25micron)

BOPP: 1m by 1m x 44= 1kg

PET: 1m by 1m x 30= 1kg



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