Are you looking for ways to improve your UV printing ink adhesion?
Well, we've got great news! Whether you're trying to get better print results on metal, glass, or wood, or you're just troubleshooting ways to fix prints that won't stick to your substrates, this post has your solution.
Today, we're diving deep into some of the best tips around to keep your UV prints sticking like they're supposed to.
Why Ink Adhesion Matters in UV Printing
The importance of UV ink adhesion can't be understated. When a print fails due to poor adhesion, it's not only frustrating, it also forces you to reprint or abandon the design altogether.
But prints that won't stay put aren't just annoying. They actually cost you ink, time, and money.
Print quality is also important, especially if you own a business. In that instance, UV prints that flake or peel can force you to lose sales and/or affect your reputation.
Don't worry, though; the secret to getting durable UV prints can be distilled down to just a few simple strategies.
Top Strategies for Improving UV Ink Adhesion
Select the Right Substrate
All substrates are not created equal. Some simply hold ink better due to their surface energy. This energy is referred to as "wetting" and can be checked by sprinkling a few drops of water onto the substrate. If these drops bead, then the surface is potentially problematic.
If not, then your surface will likely hold ink well. To eliminate any confusion, you can also purchase Dyne test pens to evaluate a surface's wetting properties.
image: dyne testing
Discussing the science behind wetting is a bit out of the scope of this post; however, you should be aware that the better the wetting, the better ink will adhere.
Here's a quick reference for how common substrates tend to behave, and where to go deeper on each one:
Proper Surface Preparation and Cleaning
Cleaning and prep are important parts of any additive manufacturing process. When it comes to UV printing specifically, dirt, dust, and oils can act as a barrier between ink and object.
So, to get the best results with your UV printer, you'll need to understand how to clean and prep your substrate's surface. In some cases, this prep can be as simple as wiping away dust with a lint-free cloth.
In other cases, you'll want to incorporate a little isopropyl alcohol to remove any embedded grime.
Isopropyl concentrations of 70% or greater are perfect for this task, as they will also remove moisture from the substrate surface. Just make sure you test the surface beforehand because alcohol can damage certain substrates.
For porous materials, you'll want to make sure they're entirely dry before printing onto them.
Additionally, some materials-3D-printed filament, for example-may even benefit from a little light sanding.
Using Adhesion Promoters and Primers
Adhesion promoters and UV ink primers add another layer to your print that can help keep UV ink from flaking or peeling prematurely.
If you see constant flaking or peeling, many industry professionals recommend an adhesion promoter. You'll often spray or roll these promoters onto an object before starting the printing process, and they'll cure when the UV lamp of your printer turns on.
Flame Treatment
Image: Rapidflame
A quick pass with a handheld butane torch held 4 to 6 inches above the surface raises surface energy by oxidizing the top molecular layer.
That oxidation creates polar sites that ink bonds to readily. It's fast, cheap, and surprisingly effective.
- Best for: glass and bare metal.
- How to do it: sweep the flame steadily across the print area for 2 to 3 seconds, don't linger in one spot.
- How long it lasts: the effect fades over hours to a day or two, so print soon after treating.
- Safety: only in a well ventilated area, keep solvents far away, and never use it on solvent sensitive plastics like acrylic, which can craze or crack.
Corona and Plasma Treatment
Corona and plasma treaters use electrical discharge to bombard the surface with ions, raising surface energy without the heat of a flame. The result is more consistent and safer, and it works on materials flame can't touch.
- Best for: polypropylene, polyethylene, and HDPE, which almost nothing sticks to otherwise.
- How to do it: sweep the handheld treater across the surface; the effect is instant.
- Tradeoff: these devices cost a few hundred dollars entry level, so they make more sense if you're doing production volumes.
- How long it lasts: like flame, the effect is temporary, so print the same session.
Ink Formulation Matters Too
This isn't about flexible versus rigid ink (that distinction is about preventing cracking, not adhesion), it's about the chemistry of the ink itself.
Different UV ink formulations use different resin systems, monomers, photoinitiators, and pigment loads, all of which affect how the cured film bonds to a given substrate.
Troubleshooting and Testing UV Ink Adhesion
One way to test your substrate's ink adhesion is by performing a cross-hatch and tape adhesion test.
This consists of printing on your substrate, placing a small piece of tape over the ink, and then using a specialized tool to scrape the surface of the print beneath the tape. The tape is then removed and assessed.
However, instead of purchasing expensive tools or learning a new testing procedure, you can perform a small test print on a substrate scrap to see if the ink adheres properly.
It's a quick and dirty way of evaluating adhesion that will only cost you a tiny bit of time and ink.
Fine Tune Your Print Settings
Many UV printers will allow you to fine-tune your print settings for optimal adhesion via their onboard software.
The eufyMake Studio software, for example, lets you choose from several substrate and quality options so that you can dial in your projects easily.
You can adjust ink thickness, add texture, and even preview your print before it's sent to the printer.
We recommend you experiment with these settings in eufyMake Studio until you find the ones that fit your project the best.
For more ideas on getting the most out of your printer, our UV printing tips collection covers everything from file quality to ink savings.
The Fix for Common UV Printing Adhesion Issues
Solving UV ink adhesion issues is not always a walk in the park. We hope the tips here can help you fix those kinds of issues a bit more easily. Likewise, with proper preparation, tuning, testing, and troubleshooting, you can be confident your UV prints will come out great every time.
FAQs
How Long Does UV Printing Take?
Though most prints can be completed in a few hours or less, UV printing times will ultimately be dictated by the printer, the project, and the desired quality of the print. Higher-quality prints usually need more time than experimental drafts, as do larger, more textured prints. UV printing requires patience, so it's best to start a print and go do something else while it's being completed.
Why Does UV Ink Not Stick?
Several factors influence UV ink's ability to stick. Surface cleanliness and surface prep are the two most prominent, however. Others include using the wrong type of ink (flexible vs. rigid), under-curing, and an improperly tuned printer. With the guide above, troubleshooting UV ink adhesion issues doesn't have to be difficult or frustrating.
