VDI 3400 GRADE GUIDE · PHYSICAL COMPARISON
VDI 15 sits one step above VDI 12 in the published comparison chart. The useful decision is whether that visible step is large enough for your part and inspection conditions.
Published grade on this site: VDI 15 · Indicative comparison value: Ra 0.56 µm
This Ra figure matches the widely published Charmilles/Agie-derived VDI 3400 comparison chart, cross-checked here against an independent EDM reference-standard supplier's published specification (see citations below), not only against this site's own material. It is an indicative comparison value, not a licensed-standard quotation, gloss measurement, texture-depth conversion, guaranteed molded appearance, or contractual tolerance. If another document (for example a downloadable PDF) shows a different rounded figure, treat this page as the controlling reference until confirmed otherwise with your supplier.
How to evaluate VDI 15
Fine-side finishes can be visually subtle; assess them under controlled, representative lighting. VDI 15 is a fine grade that teams often confuse with VDI 12 in photographs. A tactile comparison on the physical plaque, not a screen image, is what actually separates the two.
Before you specify this grade
Place VDI 12 and VDI 15 side by side; have design, tooling, and quality review the same plaque rather than separate photos.
- Mark exactly which faces receive the texture and note the direction of draw.
- Name the physical master and confirm its material and condition.
- Approve appearance on a molded sample using the production resin and color.
- Define the measurement method and acceptance limits if Ra is contractual.
Can the team consistently distinguish this finish from the adjacent finer grade?
Compare adjacent grades
Look at the reference plaques together rather than relying on a phone or monitor image. The physical plaque helps align design, tooling, purchasing, and inspection; a production-material trial remains necessary for final appearance approval.
Need the physical reference?
Review the available VDI reference plaques and confirm which scale or material version covers your target grade before ordering.