Door Trim Map Pocket Deep-Draw Mold: Draft, Texture Depth and Ejection Marks

Map pockets are the deepest draw on an interior door trim, and the one feature most often approved on a smooth prototype and rejected after texturing. They are also why a door trim tool costs more per kilogram than a bumper: the pocket core becomes a separate insert, and an Automobile Molds quote has to carry that insert, its cooling and its air circuit. The mould has to be designed for the grained surface from the first DFM review, because the texture is what removes the clearance the part was counting on.

1. Why Does a Textured Deep Draw Scuff During Ejection?

Because etching adds 20–80 µm of surface roughness to the wall, and roughness increases the friction coefficient between part and steel by two to three times — draft that worked on a polished cavity will scuff on a grained one.

Three numbers control the outcome:

• Etch depth. VDI 3400 grade 18 sits at 20–30 µm, grade 24 at 35–50 µm, grade 30 at 55–80 µm. Deeper grain needs proportionally more draft.

• Draft per unit depth. The working rule is 1° of draft for every 25 µm of etch. A VDI 24 wall therefore needs 2.0°, not the 1.0° that suits a polished surface.

• Draw depth to width ratio. Past about 1.5:1, the part grips the core and ejection force climbs faster than pin area can absorb.

The second failure is vacuum. A deep pocket with a 2.2 mm wall and good shut-offs acts like a suction cup: air cannot get behind the part fast enough, so the ejector pins push the wall outward and leave white stress marks before the part has moved 2 mm. That is not a draft problem and adding draft will not fix it — the pocket needs venting at the base and an air poppet or vented insert.

The third is thermal. The pocket core is a tall, narrow island of steel surrounded by hot plastic, and it runs 10–15 °C hotter than the surrounding cavity unless it has its own bubbler. A hot core shrinks the part onto itself, which raises ejection force exactly where the wall is thinnest.

Pocket geometry sets the floor for all three. Inside corner radii below 3 mm concentrate stress and block the air path, and a pocket base that is flat to the wall thickness leaves nowhere for the material to pack — 0.3 mm of base crowning solves it.

The same mechanics govern deep-draw Home Appliance Parts such as washer detergent drawers and fridge bins, where a 70 mm draw with a textured wall fails in exactly the same way.

✅ Bottom line: Set draft from etch depth at 1° per 25 µm, and vent the pocket base or the pins will damage the part.

2. How Do You Build and Texture a Deep Pocket So It Releases Cleanly?

Cut the pocket 0.05 mm undersize, etch first, then polish the draw direction and finish with an air-assisted ejection — texturing after final polishing is what turns a good tool into a scuffing one.

Build sequence matters more than any single dimension:

• Rough the pocket, leave 0.05 mm on the walls for etch growth, and radius every inside corner to 3 mm minimum.

• Etch before final polish. Acid attack removes 15–25 µm unevenly, and polishing after etching flattens the grain peaks that give the texture its depth.

• Polish along the draw direction only. A cross-hatch polish on a grained wall creates microscopic undercuts, and undercuts are what tear a textured surface.

• Vent the pocket base with a 0.02 mm vent land and a vented insert; add an air poppet if the draw exceeds 70 mm.

• Use sleeve ejection or a stripper ring on deep pockets, with pins only where they land on a hidden rib.

Ejection force is worth estimating before the tool is cut. A 90 mm deep pocket on a 2.2 mm wall typically needs 1.5–2.5 kN to release, and that load has to spread over enough area to stay below 8 MPa local pressure — the point where white marks start.

Steel choice follows volume and resin. Use 718H at 33–36 HRC for PP with a textured pocket, and move to a hardened insert at 48–52 HRC when the resin carries talc or glass, because a textured wall wears at the high spots first and the grain flattens within 150,000 shots.

Jusheng cuts pocket cores on five-axis centres with the draw direction as the reference axis, textures to the specified VDI grade before final polish, and pressure-tests the air circuit before tryout. Zhejiang Jusheng Intelligent Technology Co., Ltd. keeps pocket inserts replaceable, so a worn grain is re-etched as an insert rather than re-cut as a whole cavity. That approach carries directly into Home appliance molds for bin and drawer tools, where a deep textured pocket is the whole product.

✅ Bottom line: Etch before polish, polish along the draw, and vent the base; those three steps decide whether a grained pocket releases clean.

FAQ

Q: How much does a map pocket door trim mold cost? A: A single-cavity door trim tool with a 90 mm textured pocket runs 55,000–110,000 from a China factory, depending on whether the pocket core is a separate insert. Texturing a pocket of that size adds 2,000–4,500.

Q: Can a scuffed pocket be fixed without re-cutting the tool? A: Sometimes. Jusheng re-polishes along the draw, adds 0.5° of draft by spark-eroding the wall, and fits air assist. If the grain has flattened or the wall is already at minimum thickness, a new pocket insert is the only reliable fix.

Q: What cycle time should a deep pocket tool expect? A: 45–60 s for a 2.2 mm PP wall at 90 mm depth. Pocket cooling accounts for 60–70% of the cycle, which is why a dedicated bubbler in the pocket core pays back within a month of production.

Send Your Pocket Geometry for a Release Review

Send the STEP file, etch specification, resin grade and draw depth, and Jusheng returns a draft map, ejection plan and factory price within three working days. OEM and ODM programs include a texture sample before the cavity is etched, so the grain and the draft are agreed on a coupon rather than on a drawing. Ask for the ejection force estimate with the quote — it tells you whether the pocket needs air assist before you pay for it.

Mobile: +86 13516880625

Email: info@zjjsmould.com

Website:www.zjjsmould.com