Working With Custom Inks

If you’re a NOVA user, you may be planning on printing an ink that Voltera doesn’t provide. This guide will help prepare you for working with new materials, so you know what to look for and how to ensure you get the best results possible.

Will this print?

If you’re trying to figure out whether or not a material will print with NOVA, the most important thing to remember is that NOVA works best for screen printable materials. Whether or not you have a datasheet, here are a few useful rules of thumb or reference points.

Look for “screen-printable” inks

When you’re buying a printing ink or material, they’ll almost always be categorized by their printing technology. Screen printable inks are paste-like (high viscosity), while inkjet, gravure, flexo, or other inks are generally water-like (low viscosity). If the datasheet says it’s screen printable, you’re on the right track! If it doesn’t say, ask what printing method the material is intended for.

Estimating printability

Let’s say a datasheet only lists a viscosity number, you just have a material in a jar. What then?

Compare with a reference table

While it might be counterintuitive, you are actually probably a good gauge for viscosity just by handling the material.

First, have a look at a reference table, like this one from Thinky Mixer (who also have a very helpful viscosity guide):

Reference table for viscosity

Most screen-printable inks will fall somewhere in the bracketed range (between 1 - 1000 Pa.s, or 1000-1,000,000 mPa.s), but that’s still not really all that helpful.

Instead, start by tilting the jar. If the material doesn’t flow on its own, try moving the material with a stir stick. Watch and feel how it moves around, and then have a look at the chart and compare relative to other familiar materials, in terms of texture.

Does it flow like yogurt, honey, toothpaste or mustard? If so, you’re probably in the clear!

Does it flow like water, oil, or very loose adhesive? This is probably going to be a challenge.

Does it not flow at all, like rubber? This will absolutely not work. You can’t really break a smart dispenser by trying, but I wouldn’t recommend it.

Using viscosity numbers

We recommend taking viscosity numbers with a large grain of salt, for a number of reasons.

1. Viscosity values are not fixed. They can hugely vary depending on the method used for measurement (rheometer? viscometer?), the shape of the measurement device (cone, plate, spindle…), the measurement parameters (shear rate, holding time, even the measurement program and how you loaded your sample), and even the temperature in the room (which is why we heat the smart dispenser).

2. Viscosity units can be misleading. 1 cP (centipoise) is the typical viscosity of water. 1 kcP (kiloscentipoise) equals 1000 cP, and is often used for higher-viscosity (screen printable) materials. 1 kcP is also equivalent to 1 Pa.s (Pascal-second), which is the SI unit for viscosity.

3. Viscosity is only one of many parameters that determine flow properties of an ink. Among elasticity, yield stress, adhesion, thixotropy, and others, viscosity only tells part of the story.

If you must rely on a viscosity number, we’d recommend only using it as a rough reference:

• Is the viscosity reported in cP, not kcP or Pa.s? These are typically low-viscosity, water-like materials, usually intended for screen printing. Unless it’s in the high hundreds to low 1000s of cP range, chances are this will not print like a screen printable ink. It doesn’t mean you can’t use it, but set your expectations accordingly.

• Is the viscosity reported in kcP or Pa.s, not cP? These are usually in the right range of screen-printable inks, until you get to the 1000s of kcP (millions of cP) - though, even then, it could just be reported incorrectly.

• Is it between 1-1000 kcP / Pa.S? Different sources will give different numbers - so again treat this as a rule of thumb - but this is a reasonable range to expect screen printable inks to be reported in.

The Calibrate Procedure is your Best Friend

When starting out with a new material, using a different nozzle type, or even changing the smart dispenser preheat temperature, it’s always a good idea to lock in some settings with NOVA’s calibrate procedure.

Even if you eventually need to do some manual print setting adjustments, this process will usually give you some insight into how your print is going, and if you have to change out your nozzle type. Take your time, and you’ll be sure to find some good quality settings in short order.

Calibration