Improve adhesion

 

When using a UV printer, ink sometimes has a low adhesion to the substrate due to the instantaneous drying. So how to improve it?

 

1. Corona treatment

 

Corona treatment is an effective method to improve the adhesion of UV ink. The positive and negative poles of the corona device are connected to the ground and the inductive air nozzle respectively. High voltage and high frequency make the electric shock molecules spray out from the inductive air nozzle, carrying high-energy free electrons to accelerate to the positive electrode.

 

This can change the polarity of the non-absorbent material, and increase the surface roughness, enhance the ability to combine with the ink, and improve the adhesion.

 

The surface tension stability of corona treated materials is poor, and the corona effect will gradually weaken over time. Especially when stored in a humid environment, the corona effect weakens faster. So the substrate must be kept fresh.

 

2. Adhesion promoters

 

In many cases, cleaning the substrate with alcohol will improve the adhesion of UV ink. If the substrate has very poor adhesion to UV ink, or the product has high requirements for ink adhesion, you can use adhesion promoter.

 

After applying the primer on the non-absorbent substrate, the adhesion of UV ink can be improved. Unlike corona treatment, the chemical primer does not contain non-polar oil molecules, which can effectively eliminate the problem of unstable corona effect caused by the migration of such molecules.

 

However, primer can't handle everything. It works better on substrates such as glass, ceramics, metals, acrylic, and PET.

 

3. Ink curing

 

Generally speaking, when UV ink is not completely cured, it has poor adhesion on non-absorbent substrates. To improve the curing degree of UV ink, you can do these.

 

a. Increase the power of UV curing lamp.

b. Low down printing speed.

c. Extend curing time.

d. Check whether UV light and its accessories are working properly.

e. Reduce thickness of ink layer.

 

4. Other methods

 

a. Heating

 

It is recommended to heat the substrate before UV curing. After heating with near infrared or far infrared light for 15-90 seconds, the adhesion of UV ink to the substrate can be improved.

 

b. Protective varnish

 

If the UV ink still has problems adhering to the substrate, you can apply a layer of protective varnish on the printed surface.

 

c. Cut substrate

 

Cut the substrate to the required size before printing. The blade of the shearing tool must be sharp. Rotary cutter will be better than ordinary straight-edged scissors.

 

Reduce waste

 

1. Avoid frequent startup for UV printer

 

When UV printer is started, it will automatically perform a full-scale inspection. In addition to cleaning the nozzle, the ink delivery system will also automatically refill the ink, which will waste some of ink.

 

2. Manual ink absorption and automatic ink absorption

 

Some UV printers have the function of automatically moisturizing with flash lights. They only flash at inherent frequency. It is difficult to adjust according to specific environmental conditions such as ambient temperature and humidity. But in fact, this flash spraying is often unnecessary. It will waste ink.

 

3. Use up all ink before replacing ink cartridge

 

When ink is about to run out, the printer will prompt you to replace ink cartridge. In fact, there is still a small amount of residual ink in UV printer at this time. We can clean it several times through the control panel or the software that comes with the machine, and continue to use it.