Prototype RTV Mold Tooling: Actual Sample Schedules

If you need a prototype custom RTV mold, a “two-week sample” is usually four gates, and only one of them is pouring rubber.

Prototype RTV lead time is a queue problem wearing a mix-cup costume. Platinum cure is hours to a day. The rest is drawing freeze, master print or CNC, inhibition control, jacket, and someone with a scale who is not also running production.

If you need a date, schedule the gates. If you buy a single calendar number, you bought a hope. Steel LSR sample calendars are a different quote.

Gate 1: The drawing has to stop moving

Nothing else is real until CAD, dump material, and the inspection list stop changing.

This gate includes:

• Parting line and pour intent
• Flash at the split, cosmetic faces, as-cast vs trimmed
• Platinum vs tin, Shore 10A–20A typical
• Shrink assumption: platinum ~0.1–0.3%, not LSR 2–3%
• Whether this sample must be the production chemistry of the *dump*

Duration is almost entirely on the buyer. A shop that starts printing while you still have two lip versions is not fast. It is generating scrap masters.

Don't pay for expedite on Gate 1. There is nothing to expedite except your own decisions.

Common mix-up: paying expedite while two lips are open

Expedite applies to named later gates, not to drawing changes. A shop that pours during that argument generates scrap rubber.

ISO 3302-1 on the sample packet is a drawing class if the article is rubber. Adding it at ship date adds a week you will blame on the shop.

Gate 2: Make the master

Pick the prototype mode, because the calendar is different.

Printed master. Days, not weeks, if the printer is in-house. Platinum still needs wash, UV post-cure, barrier coat. A print sitting on a bench is not a master.

CNC aluminum or machined resin. Often the next week after freeze if cutter paths are simple. Cores, textures, and high polish add calendar because they add *people*.

RTV tool off an existing master. Fastest when you already have a solid pattern. The mold rubber’s cure is hours to a day. The master is the long pole.

Steel “prototype” (SPI Class 105 intent). This is not a prototype RTV schedule. It is a production *part* tool with a short life rating. Treat it as weeks of design and build, even if someone labeled it proto.

Freight of the master sits in this gate. So does alloy on the shelf.

Gate 3: Tryout, which is not a ceremony

First pours exist to find flash at the split, shorts, inhibition (platinum on dirty prints), and whether the jacket is sane.

A honest prototype tryout loop:

1. Mix 1:1 or 10:1, vacuum degas until the foam collapses, assemble jacket, first casts.
2. Measure a short list: fill-weight, flash, Shore, sag (0.5–1.5 mm edge is a missing jacket).
3. One tool tweak if the issue is vent or key, not a dump redesign.
4. A small sample lot, not a production release.

This gate dies when the vacuum bench is booked, when the platinum kit is not the agreed grade, or when the buyer wants “a few more” after changing a rib. Shops that quote “tooling 10 days, samples included” have either bundled a thin tryout or they will invoice the second loop.

Don't compare an RTV clock to an LSR aluminum tryout as if they produced the same object.

Gate 4: The packet that lets you use the mold

Samples without data are props.

Minimum packet for a prototype RTV lot:

• As-cast vs post-cured state of the *dump*, named
• RTV batch / grade identity
• Fill-weight or dimensional check against the drawing, even if it is five balloons
• Visual standard: flash, inhibition stick, transparency of the skin

If you need a full first-article packet, say so at Gate 1.

What to ask when you're buying

• Four dated gates: freeze (buyer), master complete, first pours, packet?
• Which process — platinum/tin RTV, not steel proto?
• Expedite applies only to named gates?
• Inhibition control on printed masters?
• Recast path if the first skin tears in tryout?

Worked example: 12-cavity bear, printed master

A 12-cavity 18 mm bear, food-contact, first dumps needed for a show. Gate 1 freeze in 3 days (buyer). Printed master + post-cure + barrier, then platinum 10A–20A skin, mix 1:1, vacuum degas, jacket, first casts in a short week after freeze. Packet: fill-weight every pocket. “24-hour silicone samples” would have been RTV off a *ready* master, not a new print. A parallel 2–4 week aluminum LSR sample is a different object.

When this article is the wrong quote

If the question you need answered is LSR flash at heat, don't buy an RTV calendar. Quote a parts OEM. A physical sample already in hand can skip Gate 2. Geometry can override quantity: a three-part core still adds people, not hours of mix.

Related reading: custom RTV molds, CNC vs printed masters, FAI, gummy trays.

A schedule you can put on a whiteboard

Ranges, not promises. Local queues move them.

| Path | After CAD freeze, typical shape | | --- | --- | | RTV tool off an existing master | Days to a short week for first casts | | RTV tool off a new printed master | Add master print + post-cure + inhibition control | | New CNC master + RTV skin, open-and-shut | On the order of 1–3 weeks including tryout | | Two-part with cores or heavy texture | Add design and fit time; think extra weeks, not extra hours | | Class 105 steel labeled “proto” | Production-part calendar — wrong object |

Where buyers add weeks without noticing: shipping a sticky master into platinum; asking for production dump color on pour one when the color is special-order; requiring full PPAP-like paperwork without listing forms at RFQ; splitting DFM across three emails so freeze never happens; paying for “expedite” that only jumps Gate 2 while Gate 3’s bench is still booked.

Write the PO like this: “Samples due as four dated gates: freeze (buyer), master complete, first pours, FAI/sample packet. State platinum or tin RTV. Expedite applies only to named gates, not to drawing changes.”

Send the STEP and dump material. We will date the gates and say which process you actually asked for.

We would not recommend a single date with no gate list

We would not recommend steel lead time when you asked for a glove. We would not recommend an RTV calendar when the question is LSR flash at heat. We would not pour platinum on an undercured print to “save a day.” Raising Shore A first is the wrong fix for a late jacket.

RUUIPON Mold Structure Decision: schedule the split on the freeze, not during tryout. Flat back? open-back is faster. Deep undercuts that will not peel? two-part — add calendar. Soft 10A–20A or wet dump? mother mold in Gate 2, not as a surprise in Gate 3.

flowchart TD
  A[Need a date?] --> B[Gate 1 freeze - buyer]
  B --> C[Gate 2 master + box]
  C --> D[Gate 3 pour + jacket tryout]
  D --> E[Gate 4 packet]
  A --> F{Asked for steel proto?}
  F -->|yes| G[Wrong object: part-tool calendar]
  C --> H{Platinum on SLA?}
  H -->|undercured| I[Add wash + UV + barrier]

Typical shop values

Caption these as typical shop values, not a named lot.

| Item | Typical shop value | | --- | --- | | Mix | Platinum 1:1 or 10:1; vacuum degas | | Cavity Shore | 10A–20A skin with jacket | | Platinum shrink | About 0.1–0.3% | | RTV cure | Hours to a day — not the calendar | | Loaded-tray edge sag | About 0.5–1.5 mm if jacket slipped Gate 2 | | Off existing master | Days to a short week for first casts |

FAQ

Why is a "two-week sample" usually four gates? Only one gate is pouring rubber. The others are drawing freeze, master make, tryout, and a packet that lets you use the mold. Mix minutes are hours. Calendar dies in queues and waiting.

Should I pay expedite while two lip versions are still open? No. Gate 1 is the buyer's freeze of CAD, dump, flash, and inspection. A shop that pours during that argument generates scrap rubber. Expedite applies to named later gates, not to drawing changes.

Is SPI Class 105 steel a prototype RTV schedule? It is a production *part* tool with a short life rating. Treat it as weeks of design and build even if someone labeled it proto. Printed masters and RTV off a ready pattern live on a different clock.

Why are "24-hour silicone samples" almost never a new RTV tool? They are almost always RTV off a ready master, or a reprint of a dump. New printed or CNC masters with inhibition control and tryout are people time, not mix time.

What buyer moves add weeks without looking like delay? Shipping a sticky master into platinum. Production dump color on pour one waiting on a special-order paste. Full PPAP-like forms added at ship date. DFM split across emails so freeze never happens. Expedite that only jumps Gate 2 while the vacuum bench is still booked.