Why Texture Changes the Draft Math

A smooth, polished wall releases at 1° to 2° on many resins, per Fictiv’s draft guidelines. A textured wall is a different part. Every grain peak is a small undercut. The plastic flows into thousands of them and grabs the steel on ejection.

Pull a textured part with smooth-wall draft and you get drag marks. The grain smears along the draw direction, usually worst at the end of the wall farthest from the ejectors. On matte faces it looks like a faint wipe. On glossier textures it can show as bright streaks.

Scuffed texture is a surface defect you cannot fix at the press. No process change grows the draft back. The fix is welding and re-texturing steel, which costs more than cutting the draft in CAD on day one. When a buyer asks why the first shots look scratched, the answer is almost always draft.

The One Rule Mold Shops Quote

The shop rule is easy to remember in CAD. The texturing guide from MoldMaking Technology puts it at one degree per side minimum for every 0.001 in of texture depth. That stacks on top of your baseline. A polished core running fine at 1° needs about 2.5° with a 0.001 in grain.

The resin matters as much as the grain. Softer materials flex off the texture with less fuss. Stiffer resins with higher shrinkage grip the core and need the upper end of the range. Your texture house publishes a default depth per pattern. Base your draft on that depth, not a guess. That rule is the starting point for any draft angle for textured surfaces, not the ceiling.

Specify a texture without a depth callout and the texture house uses its default. Your steel gets whatever that default is.

VDI 3400 Draft by Grade and Resin

VDI 3400 is the German engineering standard for EDM-cut textures. Grades run from 12 (fine) to 45 (rough). The minimum drafts below come from resin-by-resin shop guidance, drawn from finishing.com and upmold reference tables. Glass-filled grades of the same resin need more than the unfilled numbers shown.

Note the resin spread at the rough end. PC at VDI 45 needs 7° per side, two degrees more than PA at the same grain. Stiffer, higher-shrink resins hold the texture harder, so their draft climbs faster as the grain deepens.

Shops commonly add 1° of safety margin on top. Measuring your way out of a drag problem costs more than a degree of extra taper.

Mold-Tech Serials: Draft by Texture Depth

Mold-Tech is the US chemical-etch standard from Standex Engraving. Each serial carries a default etched depth in inches, and the published minimum draft follows that depth directly. The A-series values below come from Mold-Tech specifications. For how textures and polishes get applied to steel, see our mold finishing process overview.

MT-11020 shows a range because vendor tables list both 2.25° and 2.5° for that depth. Use the higher number. A quarter degree costs nothing in CAD and buys ejection margin you will be glad to have on a tall cosmetic wall.

Deeper series go past the A range. B, C, and D series grains run deeper and rougher, with published minimums from 2.5° up to about 8° depending on the pattern. When your industrial designer picks one of these, check its exact default depth with the texture house before quoting the tool.

Glass-Filled Resins and Deep Features Need More

Glass fiber makes everything about ejection harder. Filled composites shrink less, so they relax less off the steel, and the fibers leave a rougher surface against the mold. A common shop baseline for glass-filled resins is 2° to 3° on all sidewalls before texture is even added. Wall thickness drives shrinkage behavior too. Our wall thickness masterclass explains the link in full.

A tall core drags along its whole length. One practical guideline adds 1° for every inch of draw depth, on top of the texture number. A 3-inch-deep textured boss at 0.002 in grain is therefore running at 3° texture draft plus roughly 3° of depth draft.

Watch where the part decides to stay. Draft must follow the mold’s draw, or the part sticks to the wrong half. Holes and pockets should taper toward the half that carries the ejector system. Texture on a core that stays behind on the cavity side turns a draft problem into a stuck-part problem.

When the Design Cannot Take the Draft

Sometimes the industrial design leaves no room. Mating faces, snap fits, and tight packaging fight every extra tenth of a degree. You still have options, but each one trades something. Texture and draft decisions belong in the mold design phase, alongside gate, cooling, and ejection layout; see details of mold design.

A blended grain keeps most of the look with a smaller draft penalty. It works best where the full depth was chosen for feel, not function.

A second option is selective texture. Keep the deep grain on the faces the buyer sees and touches, and run the hidden or low-visibility walls smoother. This is a standard trick on housings where one show face carries the brand texture.

What you should not do is promise 0° with texture and hope the press sorts it out. It will not. Parts either stick, drag, or come out with the grain half-erased. If the design really cannot move, get the agreement on blended texture in writing before steel is cut.

Specifying the Draft Angle for Textured Surfaces on Your Drawing

Call out both items explicitly on the drawing and the purchase order. Write the texture standard and serial, the exact depth, the draft per side on each textured face, and the resin. “MT-11020, 0.0015 in depth, 2.5° per side, ABS” leaves nothing for the shop to interpret.

For the general rules, our guide to deciding draft angles covers smooth walls, core versus cavity, and resin effects.

Confirm the default depth in writing with whoever textures the steel. Specify the serial without a depth and the texture house uses its default. Your mold quote may rest on a different assumption.

Ask the mold maker to confirm the draft angle for textured surfaces on the DFM report before the first cut. That one line catches most texture-draft mistakes, because it forces the shop to state a number against the standard you quoted.

Try the Interactive Draft Angle Tool

Common Questions