Even with a dedicated alignment jig, I occasionally still get ink overspray on the edges, especially noticeable on designs with dark or solid borders
Ink overspray on magnet edges — tolerance stacking pushes ink just past the surface
It comes down to tolerance stacking.
- The jig has its own manufacturing tolerance
- the ceramic magnets themselves vary slightly in size
- there's slight deviation in placing the jig on the print bed
- the printer's own mechanical positioning has a tiny bit of variance between jobs.
Add all these micro-offsets together, and sometimes ink lands just past the magnet surface.
The standard fix for this is either applying masking tape to the edge of every single magnet (which is unscalable for batch printing), or leaving a thin transparent buffer zone around the print. But creating this digital buffer manually is incredibly tedious—it requires either pre-shrinking the artwork in Photoshop or calculating decimal offsets in EufyMake Studio for every job.
To automate this, I added a Safety Margin slider to GammaCrop (a free pre-processing tool I built for printing ceramic magnets, featuring rounded corner cropping and local AI background removal). Now, it can automatically creates this buffer zone by shrinking the print area inward with a thin transparent border.
The new Safety Margin slider added to GammaCrop
Even if the accumulated alignment is slightly off, the ink stays cleanly within the magnet surface. Here's what I found after testing different values:
Light-colored edges
Overspray is basically invisible. You can leave the margin at 0.
light-colored edge design, overspray is not visible, no margin needed
Colorful / medium edges
0.2mm gives a perfect result when the jig alignment is spot-on.
0.2mm safety margin + good alignment = clean edges
But if the jig position is slightly off, overspray may come back.
Dark / solid edges
0.3mm reliably eliminates overspray.
0.3mm safety margin eliminates overspray even on dark/solid edges
Just make sure the magnet sits perpendicular against the jig edge. If it's slightly rotated, the print skews with it.
Watch your placement, magnet not perpendicular in jig causes slight print skew
Here is what the transparent margin looks like in EufyMake Studio after import. The exported PNG is still exactly 50×70mm (or 57×57mm) with the rounded corners and safety margin already baked in, just import , set X/Y offset and print.
What the safety margin looks like in EufyMake Studio (0.3mm transparent border)
The tool remembers your margin setting in the browser, so you set it once and forget it. Default is 0.2mm, adjustable up to 1.0mm.
Free, runs completely offline in your browser, tool.gammaland3d.com
Deep Dive: If you're interested in a deeper breakdown of the printing methodology and how tolerance stacking affects UV flatbeds, I wrote a full technical post on the GammaLand Dev Blog.
