In the intricate world of custom label printing, precision, and repeatability is not just a goal but a necessity, absolutely vital for success. The keystone to achieving this is through tests and measuring devices. Let’s look deeper into these devices that measure important properties and values during the printing process. These tools and tests are not just add-ons but are crucial in ensuring quality and consistency in both color and print.

Print Condition

The goal is to document everything possible for every job – we call this a print condition. This print condition needs to be repeatable today and tomorrow – allowing for the right result every time the same job is printed.  This is critical when considering a re-run of the same label that needs to exactly match the existing product on a store shelf.

All these measurements and tests are about getting more than just the color right, we need the print, barcode, dieline, and much more to be right as well. All of this is carried out from the very start of a job to the very finish – not just during print.

Start Documenting Process

Consider environmental factors like plant temperature and humidity.  These will change seasonally but must be known and recorded.  Document time of day job was printed, usually associated with a particular shift – days or nights.  And record names of anyone who worked on any aspect of a given job from prepress through to shipping.

Prepress Measurements

There are many variables that need to be known and recorded before any job leaves the prepress department such as:

• Plate material used
• Plate caliper and relief
• RIP settings including curves, dot shape, line screen, screen angles, resolution, and micron dot size
• plate distortion used in flexo printing
• minimum flexo dot and screening information for flexo
• trapping requirements including keep aways or hold backs

Usually, a requirement for any print job is to produce a color-accurate Epson proof that gets signed off by a client.  This is in addition to a high-resolution PDF file for content that shows all the separations or colors being used in the file.

How a job is being printed – Flexo, Offset or Digital may require different software or RIPs with settings that produce the final print result.  Also, the strategy of printing, for example, 4 Colour (YMCK) or 4/C plus PMS Spots or 7/C ECG (extended color gamut – YMCK, Orange, Green, and Violet) will dictate what is required for any particular job.

One of the jobs of the prepress department is to add any marks or IDs to a stepped file that will allow further QC and measurements to take place while the job is running on press.  Techkon Spectro Vision system is an example of an inline QC that takes place on press.

Prepress will deliver either a file for printing to a digital press or a set of plates for printing on a traditional flexo or offset press.  With newer technology, like a digital hybrid press, a job can print both flexo and digital in a single pass through the press. This means some colors will print with a traditional flexo plate and other colors for the same file will print digitally.

The Print Condition needs to record all of these values used within the prepress department for the production of any job.  This may include hard copy printed laser proofs and color-accurate Epson proof in addition to the measurement numbers.

Commonly used equipment in a prepress department includes:

• Epson proofer
• BetaFlex Pro plate analyser
• Color Viewing booth to accurately judge color at the set industry standard lighting condition
• Xrite Exact or Techkon SpectroDens

Ink Room Measurements

A previous blog, on Delta E, talked about the formulation of spot color inks using an ink draw down device as seen below.

The recipe of how a spot ink was created must be recorded exactly in order to get the color result the same as the next time the color or job is printed.

Every ink delivered from the ink room to the press must have a record of:

• viscosity of the ink that is measured with a Zahn cup since it is crucial in maintaining color consistency and quality
• ink pH level is regularly checked with a pH reading device

Both these values will change as inks are sitting press-side during a print run of a few hours or a few days due to environmental conditions.  These values must be adjusted as required to stay within the set tolerances.

Spectrophotometers are indispensable. They are used not just in the ink room but throughout the entire printing process for color matching and quality control. They ensure that colors align with specifications and maintain color consistency, reduce waste by minimizing reprints, and provide comprehensive color analysis to uphold high-quality standards in label printing.

Delta E and other color values (Lab and LCH) are recorded with a Techkon SpectroDen or Xrite Exact – both spectrophotometer devices recording in a measurement condition of M0, M1, M2, or M3.  In the printing industry, M0 and M1 are the most commonly used measurement conditions.

In accordance with the ISO 13655 standard, the “M” series of measuring mode settings were defined in order to standardize illumination conditions where optical brightening agents are utilized in substrates. The following is designed as a quick reference chart of the 4 different measuring mode settings within the “M” series.

M0 “Color measuring mode A” spectral luminance factor without polarization filter under a light source that simulates standard illuminant A (gas lamps or LEDs, 2856 ± 100 K, from 420 to at least 700 nm)

M1 “Color measuring mode D50” spectral luminance factor without polarization filter under a light source that simulates standard illuminant D50 with correct UV component < 400 nm (theoretically F8 fluorescent lamp, in practice only LEDs incl. UV LEDs, 5003 ± 100 K, under 380 to at least 700 nm)

M2 “Color measuring mode UV Cut” spectral luminance factor without polarization filter under a light source that simulates any standard illuminant without UV component (gas lamps with UV cut-off filter < 400 nm or LEDs without UV LED, from 420 to at least 700 nm)

M3 “Measurement with polarization filter” spectral absorption degree (with RGB filters) or spectral luminance factor (with spectral scanning head) with polarization filter pair (in radiated and in reflected light, crossing each other) under a light source that simulates any standard illuminant (gas lamp or LEDs, from 420 to at least 700 nm).

All measurements in a production environment should be consistent and hence use only one of the above-mentioned conditions.

Press Room Measurements

Before printing on any polymer substrate, one should take a dyne pen measurement. Dyne Test Pens are a cost-effective, quick, and easy method to measure surface wetting or surface energy ensuring optimal ink adhesion. To use simply draw the Dyne Test pen across the material surface, the liquid will either form a continuous film on the surface or draw back into droplets. If the Dyne test fluid remains as a film for 3 seconds or more then the material will have a minimum surface energy.  This result can be used to determine the suitability of a material for printing, coating, or laminating and the cleanliness of the surface prior to bonding and sealing.

For any job running on a flexographic press, the substrate and lamination specifications, weight and lot number must be recorded.

To mount plates accurately, micro dots or such markings are used to help align the plates with the help of a camera at the mount workstation. We also need to know the plate type and thickness. Plates are mounted to cylinders with a double-sided sticky back tape. Tessa is an example of a type of mounting tape and comes in a range of thicknesses, adhesive strength, and foam hardness – Tesa Red is one example of a medium soft tape.

Plates are mounted on a print cylinder of a certain size measured in gear teeth that are in 1/8-inch increments. A job will require a plate that is distorted (less than 100%) in one direction only so that when wrapped around the cylinder it covers the repeat length, for example, 8.5 inches. An 8.5-inch cylinder is 68 gear teeth – the next increment of 0.125 inch or 8.625 inch would be 69 gear teeth.

Other print variables to record include:

• press # that the job was printed on
• doctor blade manufacturer, material, and blade edge
• ink and coating vendor for each print job
• cylinder repeat,
• metering system
• die size and configuration
• run direction the job needs to print on press is critical to know since the final direction or wind direction of the machine applied finished roll is specified by the client.

All print stations or decks used to print a job must record:

• unit or station # on press,
  • the color printing in each unit
• color density
  • ink viscosity
  • ink pH
  • dryer temperature
  • Anilox #
  • Anilox count
  • Anilox volume
• Anilox angle

One needs to record every possible variable attributing to the print condition so that the same result can be repeated next print on the same press or another flexo press or possibly another printing process, for example, digital or offset.

Print Inspection Systems

For custom label printing, print inspection systems play a vital role. Utilizing advanced technology like the Techkon SpectroVision hardware with ChromaQA software, these systems detect discrepancies and uphold print quality and color while ensuring consistency from start to finish.

Techkon makes a SpectroVision Inline system for flexo and digital printing. It consists of a camera and a spectrophotometer reading color bars, and barcodes and visually checking registration that is in conjunction with Techkon ChromaQA software which then gives live feedback on how well a job is performing and offers suggestions on how to improve the print in real-time.

These inspection systems offer the ability to check both 4/C process inks (CMYK) and PMS brand or spot colors printing on press.  Additionally, they can also measure the Dependent Aim colors on the press.  Consider the example where a file was supplied with 4/C (CYMK) and 10 PMS spot colors.  The job will print as 8 colors on press due to the limitation on a number of press units – so CMYK and 4 PMS spots.  The other 6 PMS colors that were in the file, but not printing as separate spot colors on press, will need to be converted to 4/C or 7/C ECG – extended color gamut.  These colors are known as Dependent Aims (DAIM) as one is trying or aiming to achieve a PMS color without using that specific PMS color.  These DAIMs will often have a higher Delta E than an actual PMS spot color – and still need to be recorded as part of the print condition. Essentially measuring and recording all colors no matter how the job is set up to be printed.

Keep printed label samples every time a job is run on press and compare it to the color-accurate Epson proof that the client signed.

Rewinding Measurements

Rewinding is the process of breaking down a large printed roll from the press into the final roll size and quantity required by the client.  For example, if you print 50,000 labels as 4 across on one large roll, this will need to be broken down to 50 individual rolls of 1000 labels each to meet requirements.  Rewinding also ensures the finished roll wind direction is as per the client’s request.

Any waste as tagged by the printer is removed by the rewinder.

Some clients may require label numbering being printed on each label which is done while the labels are being rewound.

During this process, the rewinding device generates accurate counts per roll and also offers another print inspection system that looks at any defects in the printed label.  Having this inspection system is critical in pharmaceutical printing which has stricter measures to follow.

QC Room Measurements & Tests

A number of tests and measurements are taken while a job is being printed to ensure the highest quality result possible.

Before a job is inked, a die-cut test is performed on the press to check the following:

• die condition
• any damage including nicks on the die that will affect the matrix lift
• the depth of the cut
• perforation and holes as required for the label.

Other tests are performed offline.  A coefficient of friction test will look at how material surfaces contact and slide against one another.  This may result in friction and wear damage throughout the manufacturing and shipping process.

A number of visual inspection tests are also conducted regarding the quality of the print.  Look for pinholing defects in the job – areas where the ink and coatings are missing.  Below is an example showing pinholes on the right side of the print image.

To ensure the durability of prints, ink rub tests are conducted, determining the resistance of the ink to scuffing and wear.

Misregistration, halo, gear marks, and feathering to name a few are other print defects that one needs to ensure are not occurring.

Many label jobs are run as a step and repeat, for example, 3 across and 3 around or 9 labels within any given repeat on press. You want to know that all parts of the repeat are producing the same high-quality result.  Do not check a single label and just assume the rest of the repeat is matching.  What prints in the top left area of a repeat may not always appear equally in the bottom right area of the same repeat.

Barcode verifier devices are employed to grade the quality of UPCs, with an A or B grade being the benchmark for acceptable quality. These devices assess the quality of printed barcodes against industry standards, evaluating aspects such as contrast, edge definition, modulation, and decode quality.

Post Print QC

Flexo plates are washed and stored for the next print run of the same job.  As this is done, the following checks must be recorded on a plate card.  This is critical for determining plate condition and any remakes required.

• Date mounted and date stored
• Number of impressions printed for each plate including common plates
• Any plate nicks, scratches, and damage

Flexo and rotary dies must be checked and recorded for the condition in case a remake or maintenance is required before being stored in the die box.

• Date used
• Number of revolutions
• Any damage

Every Anilox is washed after each press run. Before they are stored

• a visual check with a microscope will determine the anilox condition
• bearings on the anilox also require regular replacement depending on the condition

Calibration: Ensuring Optimal Functioning

Many measurement devices require regular on-site calibration as well as yearly recertification by the manufacturer to maintain their accuracy.  It is crucial that a log be kept detailing the dates of the last and the next calibration date. Some companies provide loaner devices to be used to keep production running smoothly while your device is away for its checkup.

The Essence of Quality in Printing

The integration of advanced measuring devices, combined with stringent quality control processes, embodies the essence of excellence in label printing. The meticulous calibration of these devices, coupled with the keen monitoring of environmental and other conditions, ensures that every print project meets the expectations of accuracy and quality.

Each time a print job is run a large volume of data, numbers, and tests are recorded and this is known as printing by the numbers to achieve precision. Over time, as a job is reprinted, the file capturing of all elements about the print condition becomes quite large and necessary. Add to this the print samples measured and stored with each job.

Because at Kwality Labels, we are not just a supplier but a reliable partner to our clients, by making sure that our printing services are of the highest quality. The usage of measurement devices and tests is an extensive process and an absolute must for Kwality.

For superior-quality label printing in Toronto, reach out to Kwality Labels for an exceptional experience where precision, consistency, and unmatched quality are not merely objectives but assured guarantees.