Tóm tắt

Export PNG-24 with transparency at 300 dpi at the final print size
Convert text to curves and keep strokes ≥ 0.5 mm, negative space ≥ 0.8 mm
Run preflight in Studio or the RIP and press Fix on what it flags

Format

PNG-24 with an alpha channel. Not JPG (no transparency), not GIF (256 colours), not PNG-8 unless the design is flat.
PDF/AI are fine for vector logos — ZoroPrint rasterises them at 300 dpi with a transparent background.
PSD/TIFF: flatten what you can; hidden layers and layer effects are the usual source of surprises.

Resolution

300 dpi at the size it will be printed. A 1000 px logo is 85 mm wide at 300 dpi — fine for a chest print, blurry across a back. Below 150 dpi ZoroPrint warns you; below 100 the edges visibly stair-step.

Colour

Work in sRGB. Do not convert to CMYK in Photoshop: the RIP does the separation with the printer’s ICC profile, and a file already in CMYK gets converted twice. Pure black (#000000) prints as rich black through the profile — you do not need to build it yourself.

Thin things

Strokes and text stems at least 0.5 mm (6 px at 300 dpi). Thinner lines lose their white underbase and print grey on dark garments.
Negative space (gaps inside letters, between lines) at least 0.8 mm, or the powder bridges it.
Isolated dots and specks smaller than 1 mm: delete them. They peel and look like dirt.

Background

Turn every background layer off before exporting. A “transparent” PNG with a white layer at 1 % opacity prints as a white rectangle. Preflight in ZoroPrint flags this as “opaque background”; Fix removes it.