Draft Angle on Flexible Silicone RTV Molds | RUUIPON

Buyers skip draft on custom silicone molds because the cavity peels. That is true for a lot of open-back gloves: a 10A–20A skin will stretch off a mild wall that would lock in polycarbonate or steel. It is not true for everything we pour. You still want a draft conversation on deep logos, inner cores, jacketed straight walls that cannot stretch because the mother mold is holding them, and texture that is a reverse hook. Typical talk on walls that must still read is about 1–3°. Zero draft plus a rigid jacket is a scuff or a tear, not a flex trick.

RUUIPON marks draft at DFM, before A/B. Bao'an since 2018. Prototype 3–7 business days after CAD lock. Production MOQ 20 pieces per design. Simple 3D is USD $50 when that CAD scope applies.

Does not apply when the tool is a steel HCR or LSR cavity (flash land, shut-off, heated cavity). Draft on those tools is a parts conversation on wydsilicone.com. It also does not apply when the part already needs a split — draft on a doomed one-piece will not save a closed loop. Run structure first (DFM before tooling).

When peel substitutes for draft — and when it does not

Peel can substitute. Open-back, soft skin, mild wall, you can roll the cavity off the dump (or the dump out of the cavity) in one direction. Chocolate bars, simple gummies, shallow resin cabochons. We still like a little draft on logo wells so the dump does not tear in the serifs.

Peel cannot substitute. (1) A jacket or mother mold that makes the wall behave like a rigid tool while the dump is in it. (2) An inner core or plug you must pull along an axis. (3) Deep recessed letters with reverse taper. (4) Texture that is a mushroom or a hook. (5) A through-hole that traps rubber.

If peel is unsafe even with draft, we split, plug, or core. Draft is not a second demold direction.

flowchart TD
  A[Wall or logo in the CAD] --> B{Open-back soft peel, no jacket lock?}
  B -->|Yes| C[Peel may substitute; still talk 1-3 on logos]
  B -->|No| D{Can we add 1-3 deg and keep the listing?}
  D -->|Yes| E[Put draft on the master]
  D -->|No, listing dies| F{Split / plug / core instead?}
  F -->|Yes| G[Structure change — KEEP/FLATTEN]
  F -->|No| H[We would not pour zero-draft jacketed walls]
  C --> I[CAD lock]
  E --> I
  G --> I
  I --> J[3-7 day prototype]

Typical shop values

Caption these as typical shop values.

We would not recommend

We would not recommend zero-draft jacketed walls because "silicone is flexible." The jacket is why it is not flexible in the pull.

We would not recommend adding 5–10° of draft on a logo so aggressively that the listing becomes a pyramid. If the brand mark dies at 3°, we shallow the depth or split; we do not bury the letter.

We would not recommend using more Shore to fake draft. Harder rubber peels less.

We would not recommend treating ISO 3302-1 M2 as a draft spec. M2 is a drawing class for rubber articles.

Worked example (anonymized)

A 40 mm resin coaster, 8 mm vertical rim, printed jacket, UV dump. RFQ: "no draft, silicone will flex." First proto (buyer insisted) scuffed the rim on demold and tore a 0.2 mm outer ring. Recast: 2° on the rim, same 15A skin, same jacket. CAD change was simple 3D at USD $50. Lock, then 3–7 business days. Rim released. The 8 mm wall was never going to peel while the jacket held it. MOQ 20 per design on the drafted tool. Tooling charge was not unrestricted CAD ownership; the PO kept the file with us for recast.

The photo that would prove it: scuffed rim still in the jacketed cavity vs the 2° recast. A hand stretching a glove mold of a *different* geometry does not prove draft on this coaster.

Common mix-up: draft is only for injection plastic

Engineers who live in steel skip draft on RTV because the YouTube glove mold had none. Glove molds that peel in free air are one family. Jacketed trays, cores, and logo wells are another. Ask which family you bought. Related: logo depth, undercuts.

What to ask when you're buying

• Is this wall peelable in free air, or is a jacket locking it during the dump?
• What draft keeps the listing readable (1–3° talk)?
• Logos: shallower vs more draft vs split — which KEEP?
• Inner core: pull axis and draft on the core?
• Will CAD lock wait until draft marks are on the screenshot?

Related: DFM review, custom logo molds, contact.

RFQ copy-pack — draft vs peel

Copy to [email protected]:

• STEP/STL in mm, or photos with a millimetre ruler
• Dump and whether a jacket / mother mold is expected
• Walls that must stay vertical for the listing (call them out)
• Logo file and acceptable depth / draft
• Preference: add 1–3° / shallow the feature / split
• Simple 3D: USD $50 when that CAD scope applies
• Quantity: prototype after CAD lock, then MOQ 20 per design

Matched next step: send the file with the walls you refuse to draft so we can mark the alternative, not "no draft, silicone flexes." Phone +86 135 3006 2969. Licheng Technology Industry Park, Xinhe Blvd, Shajing, Baoan.

Draft on the master, not in the rubber

You cut draft on the master (or you build it in CAD before the print). Pouring a thicker RTV skin does not taper a well. A 10A glove over a zero-draft core still locks on the core axis; the extra rubber just gives you more to tear. If the master is already CNC'd with vertical walls, draft is a CAD reopen — budget the $50 simple 3D line when that scope applies, or a larger remodel if the whole rim moves.

Texture is draft in disguise. A sandblast that undercuts is a million tiny hooks. A light bead blast that still has a pull direction can stay. Tell us whether the listing needs that texture on a jacketed wall. We would rather shallow a texture than ship a mold you destroy on demold 3.

Cores and plugs get their own draft, often toward the pull. A straight steel pin in a platinum glove is a different object (and often a WYD-style *part* insert). On this site a printed or machined core in the RTV stack still wants a taper you can pull by hand.

If two quotes disagree on draft, they probably disagree on jacket. An open glove and a jacketed tray are not the same draft spec. Put jacket yes/no on both PIs before you compare the angle.

FAQ

Do all RTV molds need draft like plastic injection? No. Many open-back gloves peel with little or no draft. Jacketed walls, cores, and deep logos still need the 1–3° conversation — or a split.

Will more Shore let me skip draft? Usually the opposite. Softer skins peel more. Harder skins need more draft or a structure change.

Can you add draft only on the logo wells and leave the outer wall vertical? Often yes, if the outer wall peels in free air. If a jacket locks the outer wall, that wall wants draft too.

Does platinum shrink (0.1–0.3%) act like draft? No. Shrink is a master-compensation band. It does not taper a well.

If I approve draft after the first proto, is that a new MOQ? It is a new CAD lock and a new 3–7 day pour. Production quantities stay MOQ 20 per design on the approved tool. The $50 line applies if we still have to edit the model.