Last updated: 2026-09-04 · 5 min read
Mold Texturing Approval — How Do You Select the Right Texture, Approve the Texture Sample, and Avoid the Costly Mistakes That Require Re-Texturing?
Mold texturing etches a pattern into the cavity surface — it is irreversible. Changing it requires re-machining (removing 0.1–0.5mm of steel) and re-texturing — $1,000–5,000 and 2–4 weeks delay. The approval workflow: catalog → test area → customer sign-off → full texturing → T1 comparison. Most common mistake: insufficient draft angle (1.5° per 0.025mm depth) causes texture tearing during ejection.
Key Facts
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Flash — Thin excess material that escapes between the mold parting line or around ejector pins. Cause: insufficient clamp force, worn parting line, excessive injection pressure, or contaminated mold surface. Flash thickness: 0.02–0.1mm. Requires secondary trimming to remove. The related guide covers adjacent topics.
What Are the Four Texture Types and How Do You Select the Right One?
Four types, by method and application:
| Type | Method | Depth Range | Application |
|---|---|---|---|
| SPI polish (A1–C3) | Diamond paste polishing | Ra 0.01–0.5 μm | Optical lenses, chrome-plated parts |
| VDI 3400 standard | EDM electrode erosion | Ra 0.2–6.0 μm | Automotive interiors, enclosures, electronics |
| Custom (Mold-Tech, Textron) | Chemical etching with photoresist mask | 0.01–0.5mm depth | Leather grain, wood grain, geometric patterns |
| Laser texturing | Laser ablation | 0.01–0.3mm depth | Complex 3D patterns, functional textures (grip, air release) |
Three factors drive the selection. The cosmetic requirement: how much surface detail is needed. The draft angle available: deeper textures require more draft. The resin being molded: filled resins wear textures faster. The texture supplier provides a sample plaque etched on the actual steel grade — this sample is the approval baseline.
The catalog sample is on a flat plaque. The texture will look different on a curved surface, a thick wall or a thin wall. Before approving, request a texture trial on the actual part geometry — the curvature and wall thickness change the appearance.
What Is the Approval Workflow and What Design Rules Prevent Re-Texturing?
Four steps in the approval workflow:
- Texture selection from catalog. The customer selects a texture (Mold-Tech MT-11010, VDI 3400 #24, etc.) based on a catalog sample. The catalog sample is on a flat plaque — appearance changes on curved surfaces.
- Texture trial on the mold (test area). The mold maker textures a small test area (20×20mm) on a non-critical surface. The test area is molded and the sample is presented for approval. Check: color appearance (texture changes perceived color by 5–15%), gloss level (texture reduces gloss), tactile feel (roughness, grip).
- Customer sign-off and full texturing. The customer signs the texture sample as the approval baseline. The mold is sent to the texturing shop for full etching (3–10 working days).
- Post-texture T1 comparison. T1 samples are molded and compared to the approved sample. Check: texture depth (profilometer, ±15% of target), pattern consistency (visual under standard lighting), color match (spectrophotometer). If T1 matches → accepted. If not → re-texture required ($1,000–5,000 + 2–4 weeks).
Four design rules that prevent re-texturing:
| Rule | Requirement | Consequence of Violation |
|---|---|---|
| Draft angle | 1.5° per 0.025mm texture depth | Texture tears during ejection → re-texture or reduce depth |
| Wall thickness uniformity | Variation less than 30% | Texture appears darker on thick walls, lighter on thin walls |
| Parting line land | 3–5mm untextured land around parting line | Texture prevents mold halves from sealing → flash |
| Filled resins (GF30+) | Specify 1 grade deeper than target | First 50,000 shots wear texture down; deeper start = target level at end of life |
The draft angle rule is the most common source of re-texturing. A Mold-Tech leather grain (0.1mm depth) requires 6° draft. If the part designer only allows 3° draft, the texture tears during ejection. The fix: either reduce the texture depth (changing the appearance) or increase the draft angle (changing the part dimension). Both require re-texturing.
Parting line — The line where the two mold halves (A-side and B-side) meet. Parting line location affects: gate placement, ejector pin marks, witness lines, and cosmetic appearance. A well-designed parting line minimizes visible witness marks. The related guide covers adjacent topics.
Texturing is irreversible. The approval workflow — catalog selection, test area, customer sign-off, T1 comparison — exists because re-texturing costs $1,000–5,000 and delays the program by 2–4 weeks. Approve the texture sample before the full etch, not after.
Frequently Asked Questions
How much does mold texturing cost?
The cost depends on texture type, mold size and textured area. SPI polish: $500–3,000 per mold. Standard VDI texture: $800–2,000. Custom chemical etch (Mold-Tech): $1,500–5,000. Laser texturing: $3,000–10,000. The cost is proportional to the textured area — a mold with texture on one cavity half costs roughly 50% less than a mold with texture on both halves.
The texturing is done by a specialized shop. The mold maker ships the mold to the texturing shop and receives it back 3–10 working days later.
Can you texture a polished mold — or does the surface need re-machining?
A polished mold can be textured directly — the texturing process (chemical etch or laser) removes the polished surface and creates the texture pattern. However, a textured mold cannot be polished back to a mirror finish without re-machining.
The texture must be completely removed by EDM or CNC milling before polishing. Re-machining cost: $2,000–8,000 (depending on cavity size) plus re-polishing ($500–3,000). This is why the texture approval must happen before the mold is textured — changing after approval is significantly more expensive than approving the right texture in the first place.
How do you verify that production texture matches the approved sample?
Three methods. Visual comparison under standard lighting (D65 daylight simulator): the production part is placed next to the approved sample at 30cm distance. Profilometer measurement: a contact or optical profilometer measures texture depth (Ra, Rz) — acceptable range is ±15% of target depth. Gloss measurement: a gloss meter (at 60° or 20° angle) — acceptable range is ±10% of target gloss value.
Verification is done on the first 5 shots after texturing and then every 50,000 shots to monitor texture wear during production.
Key Takeaways
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Prevention: approve before full etch.
If your part requires texturing, send the part drawing, the cosmetic requirement and the resin specification for a texture review. The review recommends the texture type, calculates the required draft angle and provides the approval workflow for your program.
Sources
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Sources: Plastics Technology · Plastics Technology Online · Society of Plastics Engineers (SPE) · ThomasNet