Cost Factors When Buying a Custom RTV Silicone Mold

If you're comparing custom RTV silicone mold quotes, cost splits into master, RTV volume, splits/keys, jacket, first dumps, recast terms, inspection, and freight. A piece price without that split isn't a quote. Two shops can look far apart because one bid a tin glove off a dirty print and the other bid a CNC master, keyed platinum skin, fiberglass jacket, and a recast. Both might be honest. They're not comparable.

This is a buyer memo, not a price list — no fake dollars. Name the factors so you can see which ones you actually turned on. If the other PDF is full of cold-runners and cavitation steel, that's a molded-*part* quotation, not this mold.

Master, rubber, splits, jacket

Tooling cost follows:

• Master: CNC aluminum vs SLA (finish, barrier coat, texture house) vs a physical sample
• Cavity count and whether family trays share a jacket
• One-piece glove vs keyed split vs inner core / mandrel
• Platinum vs tin, Shore, certified food lots (FDA 21 CFR 177.2600, LFGB)
• Jacket: plaster, resin, fiberglass, printed shell
• Vacuum degas, detail coat, mold box / flask
• Finish (SPI A-range hours on the master) and chemical or laser grain

A dearer platinum + jacket can be the cheaper program if it kills recasts and dump waste. A cheaper tin glove can be the cheaper program if the SKU dies at 80 casts. The factor is annual dumps plus flash spec at the split, not a belief that "silicone mold" is always an investment.

Scrap is a cost factor: bubbles, inhibition, torn keys, setup pours. Color changes of the *dump* are scrap events. Bunch SKUs that share a grade.

Labor, dumps, and documents

Pour-table hour is visible. Scalpel time at the split isn't, until it is. Design keys for the flash spec you wrote. Punching, packing so jackets don't warp, and incoming photos can exceed the mold line on consumer goods. A technician-hero process that won't survive SOP is a cost factor.

FAI packs, retains, and lab tests are lines. A "full cert pack" with unnamed tests is unbounded. Name extraction, durometer, ASTM D412 / D624, or skip them. Export packing, air samples versus sea bulk, duty, and HS description belong in landed cost. The factory mold price isn't landed cost.

Common mix-up: two lonely prices as the same job

A lot of RFQs compare the bottom line of a tin prototype to production platinum. In the shop that usually means you're haggling a production skin down to prototype construction. Build a comparison table even a crude one:

• Process family (platinum RTV / tin RTV — not LSR/HCR/extrusion mixed in)
• Master type, cavity count, jacket type
• Recast yes/no, who owns master and jacket
• Grade family and dump-color count
• Flash spec and measurement state
• First-dump pack contents and who pays the correction pour
• Certificates named
• Incoterms and sample freight

If a cell is blank, that quote is incomplete. The lowest number in a blank table isn't a savings. It's a future ECO.

China cluster quotes often look light on the master because polishers and jacket shops are dense. They still need the same table. A trading-company margin can be worth it if the desk owns process. It isn't worth it if it hides the pour table.

Currency, payment milestones, and inventory are quieter factors. Paying 100% before first dump shifts all risk to you. Staging at freeze, master buyoff, first-dump pack, and SOP shares it. Holding ocean inventory to protect a launch is a real carrying cost.

What to ask when you're buying

• Can they fill every cell in that table, or is the number a hope?
• Platinum vs tin, recast included, master custody?
• Annual dumps so cavitation and jacket type actually match?
• Food test as grade letter vs article extraction — which did I turn on?
• Payment milestones vs 100% before the pour?

Haggling production platinum down to a tin glove isn't cost control.

When this cost memo is the wrong comparison

LSR/HCR part tools amortize steel and cold-runners; don't force them onto this table. A local walk-in recast for a single art master can beat a China landed model. Geometry can override quantity: a three-piece mandrel chocolate can cost more than a 12-cavity shallow gummy tray at the same dump count.

Related: low-volume casting, high-volume dumping, China sourcing.

Worked example

A 12-cavity gummy, 18 mm, food-contact platinum, CNC master, fiberglass jacket, mid four-figure dumps/month in season. Quote A was a tin glove, no jacket, no recast. Quote B was platinum, keyed split, jacket, one recast in the price. Piece price on A looked friendlier until season-two size drift and a new master showed up. They bought B and flew the first-dump pack. An LSR *part* line on a third PDF was ignored as the wrong object.

Quote comparison table to copy

Fill every row or treat the quote as incomplete: chemistry, master type, cavities, jacket, recast, ownership, dump band, flash spec, pack contents, certs, Incoterms. Then send the STEP, dump material, and which rows you actually want turned on. We'll price that hardware list — not a lonely number with blank cells.

We would not recommend comparing a tin glove to production platinum as one number

We would not recommend haggling a keyed platinum skin plus jacket down to prototype construction, or paying 100% before first dump because the unit price looked friendly. We would not mix LSR/HCR/extrusion into the same comparison table. We would not treat a blank cell as a savings. Raising Shore A first is not a cost-control lever.

RUUIPON Mold Structure Decision: glove vs jacket is two options on the same chemistry and flash spec. 1–4 cavities for a dying SKU; 12–24 plus spare skins when depositing is real. Three-piece mandrel chocolate can cost more than a 12-cavity shallow gummy at the same dump count.

flowchart TD
  A[Quote] --> B{Same hardware list?}
  B -->|tin glove vs Pt + jacket| C[Not comparable]
  B -->|cells filled| D[Master + rubber + split + jacket + pack + recast + freight]
  D --> E{Annual dumps real?}
  E -->|tens-hundreds| F[Fewer cavities; jacket optional only if shallow]
  E -->|depositing volume| G[Cavitation + spare skins + nests]

Typical shop values

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

| Item | Typical shop value | | --- | --- | | Cavity Shore | 10A–20A platinum RTV, jacket behind it at volume | | Mix | Platinum 1:1 or 10:1 by grade; vacuum degas until the foam collapses | | Platinum shrink after full cure | About 0.1–0.3%; tin is cheaper on the drum and keeps moving | | RTV skin wall | Often 8–15 mm — rubber volume is a real line | | Loaded-tray edge sag without a jacket | About 0.5–1.5 mm — dump waste is a cost factor | | Outer-row gummy vs center if the tray sags | Edge often 3–6% heavy | | Cavity-count bands | 1–4 low volume; 12–24 depositing |

FAQ

Why is the jacket so visible on the tool quote? Because it's real hardware: rigidity, registration, and whether a 10A–20A skin holds size. At volume it returns money in dump yield. At a few dozen art casts it may never return. Ask for glove vs jacket as two options on the same chemistry and flash spec.

Does a cheaper Shore A equivalent save money? Sometimes on drums, often on risk. Equivalents can move tear, shrink, and food-contact status. A cheap gum that forces a recast or a failed extraction isn't cheap. Freeze a window, and price a delta first dump if you allow a second source.

Where do food-contact tests sit in cost? Either as a material-grade letter (cheaper, weaker claim) or as article testing (dearer, stronger). They aren't a free PDF. Budget the lab and extra first-dump pieces. Putting "FDA" on a PO without a method is how you get a letter that won't survive a retailer audit.

Should I compare dump cost at 1,000 and at 50,000 on the same mold? Yes, if both quantities are real. Cavitation and recast decisions flip with quantity. A quote that only gives one quantity is hiding the amortization story. Also compare setup per lot; low volume lives there.

Is IP protection a cost factor? Yes: extra PO legal work, no-photography clauses, sometimes keeping the master at home. It's cheaper than a copied SKU if the geometry is the product. It's optional theater if the cavity is a generic ice cube. Choose on purpose.