FDM PLA Masters for Platinum RTV Molding | RUUIPON

An FDM PLA print can be an RTV master if you treat it as a texture machine: nozzle width kills fine serifs, layer lines copy into chocolate or resin unless you sand, fill, and seal, and scale drift on a desktop printer stacks on top of platinum shrink of about 0.1–0.3%. This is not the SLA oligomer-inhibition protocol and not the general "3D printed master" overview. PLA is usually quieter chemically than a raw photopolymer once it is clean and sealed, but it is noisier geometrically. If you wanted invisible type, send an SLA that is washed and sealed, or pay the USD $50 CAD when we should stop fighting your FDM and remodel a pour-ready master.

RUUIPON pours around sealed prints in Bao'an, Xinhe Blvd, Shajing, since 2018. Prototype is 3–7 business days after CAD lock — lock includes "this FDM is sealed and the millimetres are the millimetres." Production is MOQ 20 pieces per design. Mix 1:1 or 10:1. Steel/LSR *parts*: wydsilicone.com. SLA chemistry path: SLA wash/UV/seal. Overview: 3D-printed masters.

Does not apply when the print is SLA/DLP, when the FDM part is the mold box only, when you wanted the print *to be* the production mold, or when the filament is a mystery blend with a "wood fill" that sheds fibers into platinum. We would not pour a food logo against unsealed 0.3 mm layers and call the ridges "artisanal" unless you signed that look.

Nozzle width is the serif limit

A 0.4 mm nozzle cannot hold a 0.2 mm hairline. The rubber will copy the droop, not the CAD. If the wordmark is the SKU, either thicken the type in CAD ($50 when that scope applies) or change process. Layer height of 0.2 mm on a chocolate bar face is a visible stair under raking light. Sanding flattens stairs and rounds the type you cared about — pick which loss you can ship.

PLA vs PETG vs ABS as masters: PLA is stiff and easy to sand, and it can creep in a hot car on the way to Bao'an. PETG is tougher, stringier, and can stay greasy. ABS wants ventilation to print and a solvent-smoothed face that you must fully flash off before platinum. Name the filament. We would not guess a sealer from a photo of a beige brick.

Scale: print a 100 mm bar on the same plate and measure it. A 98 mm print plus platinum 0.1–0.3% is a silent stack. ISO 3302-1 M2 on the dump drawing does not make the FDM "precision."

The photo that would prove an FDM master: raking light across the face, caliper on a 100 mm witness bar, sealer sheen, underside showing infill not open to the cavity. A rainbow vase print is not a master.

flowchart TD
  A[FDM STL] --> B{Serifs wider than nozzle?}
  B -->|no| C[$50 CAD: thicken type or change process]
  B -->|yes| D[Print, measure 100 mm witness]
  D --> E[Sand / fill stairs you did not sign]
  E --> F[Seal, then 20 g platinum slug]
  F --> G{Slug snap-cured on the print?}
  G -->|no| H[More seal or remodel]
  G -->|yes| I[CAD lock, 3–7 business days pour]
  C --> I

Seal is fill, not UV

FDM seal is about closing porosity and hiding stairs, not about cooking oligomer. Shellac, a compatible high-build primer, or a filled fairing — fully cured, no wet solvent against platinum. A greasy "release" spray as the only seal is how you inhibit or how you copy orange-peel. Food wells need a barrier you can defend; we would not pour couverture against raw PLA layers even if a slug cured, because the texture is still the product.

Hollow prints with 10% infill can collapse or leak platinum into the lattice. Print solid, or close the back. Trapped air in infill boils out under vacuum as pits.

Structure Decision still applies to the printed *shape*: flat back → open-back tray. Undercuts that will not peel → split. Printing a one-piece undercut mascot in PLA does not force a one-piece glove.

Failure: stairs in chocolate, or a collapsed hollow

Symptom: every bar shows printer terraces; or the master crushed in the flask.

Cause: unsigned layer height; thin walls vs pour head.

Confirm: raking light on the master next to the first dump.

Fix: fill and seal, or remodel at $50 when that CAD scope applies. Recast. Do not "just pour a second tray" from the same raw brick.

True platinum tack against FDM is less common than against raw SLA, but dirty prints, sulfur-tinted "metal" filaments, and leftover PETG grease still happen. Slug first.

Typical shop values

Caption: typical shop values, not a named PO.

FDM habits we would not recommend

We would not recommend raw 0.28 mm layers as a chocolate texture unless you signed a photo.

We would not recommend 10% infill as a pour-ready master.

We would not recommend shipping PLA in a hot van without a scale check on arrival.

We would not recommend using FDM because "SLA inhibits" — seal the right process.

We would not recommend a new print every reorder; keep the sealed master.

Worked example: 0.2 mm type on a 0.4 mm nozzle

Logo ice cube, 40 mm, 0.2 mm engraved type in CAD, buyer-printed PLA at 0.2 mm layers. Type melted into stairs. We took the $50 CAD, thickened the engraving to a millimetre band the nozzle and the rubber could hold, printed *our* sealed master (or CNC if the face needed it), poured platinum 1:1. Prototype 3–7 business days after CAD lock. Production MOQ 20 of that design. The desktop brick stayed a mockup.

Mix-up: FDM is "good enough because it's 3D printed"

Process family is the spec. FDM is texture and scale drift. SLA is oligomer and fine type. SLS is powder porosity. Related: custom logo molds, CAD from sample.

What to ask when you're buying an FDM path

• Nozzle width and layer height, and a photo in raking light?
• Filament name — PLA, PETG, ABS, filled?
• Solid print vs infill, and a 100 mm witness bar measurement?
• Food face (seal + signed texture) or craft?
• After lock, 3–7 business days, then MOQ 20 / design?

RFQ copy-pack — FDM PLA master

Paste into [email protected]:

Object: RTV mold from an FDM master, not an LSR/HCR part Filament, nozzle, layer height 100 mm witness measurement Dump: food or craft Seal already done? Yes/no File: STL + photos in raking light + millimetre scale CAD: pour-ready OR USD $50 3D if we must remodel Prototype 3–7 business days after CAD lock, then MOQ 20 per design Who keeps the sealed master

Send raking-light photos and the witness bar, not "I 3D printed it." We will not guess stairs into chocolate — not a blank quote request. Phone +86 135 3006 2969. Xinhe Blvd, Shajing, Bao'an. Shop since 2018.

FAQ

Can I use a PLA 3D print as a silicone mold master? Yes, after you treat it as texture: sand/fill/seal, measure scale, slug-test. The print is the pattern. The rubber is the tool.

Will layer lines show in the cast? Yes, if you did not fill them. Sign that look or pay for a finished master.

Is FDM safer than SLA for platinum? Usually quieter chemically once clean; noisier on detail and scale. Different failure. Do not skip the slug.

Do you always charge $50 if I already printed PLA? No. $50 is when we still have to model. A sealed, in-scale print with locked mm can skip that scope.

Can I reprint PLA for every reorder? Size will drift. We would rather recast from the sealed master. Tooling charge ≠ unrestricted ownership — say who keeps it. Clock is 3–7 business days after lock; MOQ 20 per design.