In short: Before you approve a digital proof for custom printed bags, check seven things: the artwork sits on the factory dieline, logos and text stay 10 mm inside seals and zippers, all files are vector with outlined fonts, every brand colour has a Pantone reference, white ink is marked on clear or metallic film, text is at least 5 pt and lines at least 0.2 mm, and barcodes are dark on a light background. Heyi Custom Bags sends a dieline and a digital proof with every order; production starts only after you sign it off.
The 7-point pre-press checklist
| # | Check | Pass condition | What goes wrong if skipped |
|---|---|---|---|
| 1 | Dieline | Artwork placed on the factory dieline at 100% scale | Logo lands on a gusset fold or the back panel |
| 2 | Safe area | Text and logos 10 mm from seals, zipper and edges | Heat seal crushes or hides the print |
| 3 | File format | AI, PDF or EPS; fonts outlined; images 300 dpi | Fuzzy logos, substituted fonts |
| 4 | Colours | Pantone C or U reference for each spot colour | Brand colour shifts between batches |
| 5 | White underlay | White ink layer marked on clear, frosted or metallic film | Colours look dull or see-through |
| 6 | Minimum sizes | Text at least 5 pt, lines at least 0.2 mm, reversed text at least 7 pt | Fine text fills in or breaks |
| 7 | Barcodes | Dark bars on white or light background, minimum 80% size | Scanner fails at retail checkout |
1. Design on the dieline, not a mock-up
The dieline is the flat template of your bag with seal areas, zipper line, gusset folds and bleed drawn in. Keep it on a locked layer and export with the dieline hidden; a 3D mock-up is for approval, not production.
2–3. Safe area and file format
Keep all live content at least 10 mm from the top seal, bottom seal, side seals and zipper, and 5 mm from gusset folds. Supply logos and text as vector (AI, PDF, EPS) with fonts converted to outlines; place photos as CMYK TIFF or high-quality JPEG at 300 dpi at final size. One PDF per bag size.
4–5. Colour and white ink
Gravure and flexo presses print spot inks, not screen RGB. Give a Pantone reference for every brand colour and state whether it is coated (C) or uncoated (U). On clear, frosted or metallised film, add a separate white layer under the colours you want solid; leave white off where the film should show through. Ask for a drawdown on the actual film when colour matters.
6–7. Minimum text, lines and barcodes
- Positive text: 5 pt minimum; reversed (knock-out) text: 7 pt minimum.
- Lines and rules: 0.2 mm (0.5 pt) minimum; reversed lines 0.3 mm.
- Barcodes: black or dark blue bars on white, 80% to 100% magnification, quiet zone 3 mm each side; avoid placing across a gusset.
For a step-by-step guide to preparing the files themselves, see how to prepare artwork for custom printed packaging bags. Related products: custom printed die-cut handle bags and custom printed frosted zipper bags.
FAQ
What is a dieline for a packaging bag?
A dieline is the flat, to-scale template of a bag showing its cut size, seal areas, zipper position, gussets and bleed; the factory supplies it and artwork is placed on it before proofing.
How many colours can be printed on a custom bag?
Heyi Custom Bags prints up to 10 colours by gravure with Pantone matching; most brand bags use 1 to 4 spot colours plus a white underlay on clear or metallic film.
Why does my colour look different on frosted film than on the proof?
Frosted and clear films have no white base, so inks look translucent unless a white underlay is printed beneath them; a drawdown on the real film shows the true result.
How long does proof approval take?
A digital proof is usually sent within 1 to 2 working days of receiving final files; production starts after written approval and takes 15 to 25 days.
Pre-Press Support From Heyi Custom Bags
Heyi Custom Bags runs in-house pre-press at its factories in Dongguan, China and Haiphong, Vietnam: our team checks every file against this list, fixes dielines and sends a digital proof before plates are made. Factories are ISO 9001, ISO 14001 and GRS certified; MOQ is 5,000 pcs per design for brands, retailers and wholesalers, with production in 15 to 25 days and direct shipping to the USA, UK, Canada, Australia and the EU. Send your artwork and bag specification for a quote and dieline within 24 hours.