What variables affect digital printing?

The digital print industry is booming, but it does not come to us problem free.  As we know, there are a vast number of variables which need to be controlled, sometimes with military precision, in order to achieve reproducibility of prints.

All digital print bureaus need to be able to replicate prints already approved - whether it be to satisfy an order placed on the back of a sample printed 2 weeks ago, or to add to an order printed 6 months ago.  Colour consistency is everything.  And unless you control the variables, this can be tricky to do.

Room temperature

Fluctuations in the ambient temperature the room your printer is in can visibly affect the results of your prints.  Tests have proven that the same design printed at 9am, 12pm and 5pm were different.  As were the temperatures in the room.  It heated up as the day progressed!

Solution

Install air conditioning!  All printer manufacturers specify the optimal temperatures the Mac®hine will operate in.  Note this and set your thermostat accordingly.  Without air conditioning, colour consistency cannot be guaranteed.  Using AVA Productivity Manager can help you to record the temperate and humidity of your room at the time prints were done, making it easy to replicate with your thermostat.

Humidity

Like temperature, fluctuation in humidity will also visually affect your prints.

Solution

Air conditioning should help this, and using AVA Productivity Manager will help you to record the temperate and humidity of your room at the time prints were done, making it easy to replicate with your thermostat.

The coating on the fabric

The recipe of the coating can change from batch to batch – much like the recipe of inks.  If the coating manufacturer does not adopt strict quality controls (possibly reflected by cheap services(?)) then you may notice colour differences within a print.  An example of this would be a solid colour within the print looking blotchy, or the colour slowing changing hue throughout the print.

Solution

Change supplier.  Or if you are the producer, adopt more strict quality controls on the recipes. 

Blocked print heads

Print heads get blocked all the time.  There are multiple reasons for this happening; room temperature and humidity, the recipe of inks (Mimaki’s yellow ink was notorious for eroding print heads until they acknowledged the problem and changed the recipe).  Heads will also block if you do not clean them regularly.

Solution

Try cleaning the heads manually.  Then perform a clean from the front panel of the printer.  Usually a standard clean, often performed is enough to resolve the issue, but occasionally the blockage needs a more vigorous solution.  Depending on the printer model, the options available to you differ.  But lets look at a Mimaki as an example.

Mimaki’s have 3 levels of cleaning.  Soft, medium and hard.  The harder the clean, the more ink is used.  You can also control which heads get cleaned, which is a great way of saving ink (as there is no point flushing ink through heads which are firing perfectly).  If the Hard clean does not resolve you problem, try using the FillUpInk option on the front panel of the printer.  This forces a considerable amount of ink through the head and often resolved stubborn blockages.  This should be used only on the problematic heads, and only when other cleaning methods do not work, due to the amount of ink used during the process.  If the FillUpInk option does not resolve the problem after a few attempts, you should contact the manufacturer for a possible replacement.

Inconsistent colour across wide format printers

On wider format printers, it is very difficult to get consistency across the print (by the manufacturers own admissions).  This can be due to the bar the head runs along not being completely parallel to the print bed.  If the bars are very long, then they may dip slightly in the middle (think of a tennis court net!).

Solution

Use a long spirit level to test this.  If you are onsite with the engineers, they should have one of these.  There is a spirit level on all iPhones.  To access this go to the Compass, and swipe left.  However, it’s often not long enough to get an accurate reading.  We, as software developers cannot resolve this issue and it has to be handed over to the manufacturers.

Ambient lighting

Use the PANTONE®® Lighting Indicator chips to test whether the lighting in the room is D65k, also referred to as Daylight.  If it is not, the light emitted may tint the printouts, causing them to look different to the screen.

Solution

Presuming the monitor and printer profiles are up to date and you are confident all other colour matching settings are OK, you should suggest D65 lighting is installed in the studio.  A sometimes cheaper solution could be to get a light box with D65 bulbs installed into it.

Different ink batches

The recipe of the ink can change from batch to batch – much like the recipe of the coating on most fabrics and papers.  If the coating manufacturer does not adopt strict quality controls (possibly reflected by cheap services(?)) then you may notice colour differences between historic prints and those done with the new batch.

Solution

Re-profiling can often help to resolve this, but sometimes we do need to create a new ink setting. In some cases you will have to match back to the existing prints. Usually, being honest with your customer about the change of inks rewards itself but more colour critical customers may demand a match between new and old inks. We can sometimes do this with an ink setting, but sometimes, if the colours originally printed were far out of gamut, getting back to the soft proofed colours may be impossible.

Different substrate batches

Although your supplier should be working within a tolerance, there can be differences between batches of substrate. These differences can range from its colour, weight and absorbency properties. 

Solution

Similar to when there is a difference between the batches on ink, re-profiling can often help to resolve this, but sometimes we do need to create a new ink setting. In some cases you will have to match back to the existing prints. Usually, being honest with your customer about the change of inks rewards itself but more colour critical customers may demand a match between new and old inks. We can sometimes do this with an ink setting, but sometimes, if the colours originally printed were far out of gamut, getting back to the soft proofed colours may be impossible.