Cavity Count vs Piece Weight on RTV Trays | RUUIPON

Cavity count on a custom RTV tray is a layout bet against piece weight, not a nozzle-map exercise. Extra pockets mean thinner webs, more rubber, a larger jacket, and a loaded sheet that can sag about 0.5–1.5 mm at the edge. When that happens, outer-row gummies often run 3–6% heavy versus the center. You do not fix that by asking us for Baker Perkins pitch, depositor spacing, or a “how many cavities per shift” formula. Those questions are a steel/depositor job on wydsilicone.com — their article on cavity count versus shift output is a different intent. Here we decide how many pockets a platinum skin and a rigid jacket can hold without the grams drifting.

RUUIPON pours the tray in Bao’an: master, box, A/B, vacuum, jacket. Prototype 3–7 business days after CAD lock. MOQ 20 pieces per design.

Does not apply when you already have a depositor drawing with nozzle coordinates, when you need a mogul starch tray, or when the object is an LSR *part*. Send those packs to WYD. It also does not apply to a one-cavity resin figurine — that is structure, not sheet layout.

What actually moves grams on a flexible sheet

Piece weight on an RTV tray is cavity volume plus how the sheet sits while you fill it. A 24-up that looks even in CAD will dump light in the middle and heavy on the rim if the jacket is weak. Flood-and-scrape hides some of that until you weigh. A hand pipette hides less.

Layout knobs we actually turn:

• Border. A skinny frame curls. Leave rubber and jacket at the edge so the sheet stays flat on the bench or the table.
• Web between pockets. Too thin and pockets talk to each other; too thick and you wasted count for no stiffness.
• Cavity depth vs sheet size. Deep pockets on a large sheet are a sag machine. Cut count or thicken the jacket — do not raise Shore as the first move.
• Family layouts. Two geometries on one sheet only if Shore, shrink, and dump cycle can be the same. A shallow logo tile next to a deep mascot is not a save.

ISO 3302-1 M2 on the tray drawing does not make sixteen pockets weigh the same. It is a rubber class.

The photo that would prove a layout call is a loaded tray on a flat plate with a straightedge at the edge (sag visible), then a weigh sheet of every pocket on one dump, center versus outer row. A hero photo of one pretty bear is not that evidence.

Typical shop values

Caption: typical shop values, not a named PO.

Common mix-up: sending a depositor pitch and calling it an RTV RFQ

Pitch between nozzles, registration holes for a Baker Perkins-class line, and “how many cavities per mold” as a shift-output number belong on a steel or aluminum depositing tool. We will not pretend an RTV jacket is that tool. If your copacker sent a pitch drawing, forward it to WYD and keep this site for the flexible tray you flex by hand or on a simple table. The purchasing mix-up is comparing a 24-cavity RTV sheet price to an 80-cavity steel depositor plate because both say “cavities.”

Worked example (anonymized)

A pectin brand wanted 24 bears on a 300 × 200 mm sheet, 4.0 g target, about 2,000 dumps a month. First layout packed the border. Loaded sag showed on the outer row; those pieces came in heavy in the 3–6% band. We cut to 18, thickened the jacket, and kept the same pocket. Grams tightened. They still bought MOQ 20 of the 18-up, not 20 of a 24-up that would have shipped the lightest center as the lot. CAD map was USD $50 because they had a sketch and a gram target, not a cavity STEP.

We would not recommend

We would not recommend maxing cavity count on an unsupported 10A sheet to “get the unit cost down.” You will pay it back in grams.

We would not recommend raising Shore A to stiffen a floppy multi-cavity sheet before you add a jacket or cut count.

We would not recommend freezing 24 pockets while the logo and the gram target are still moving. Extra cavities are extra recast area.

What to ask when you are buying

• What is the target gram, and will you weigh every pocket on the witness dump — not one hero cavity?
• What is the sheet size limit on my bench or table?
• Is a rigid jacket in the price, and what sag do you expect loaded?
• Are we talking RTV layout, or do I actually need a depositor plate (WYD)?
• If the CAD is still open, can we prototype 8-up before multiplying?

Related: custom gummy molds, sample before production, spare molds and rotation, contact.

RFQ copy-pack — RTV tray layout

Paste into [email protected]:

Object: RTV tray layout (not depositor pitch / not WYD 023) Pour: pectin / gelatin / chocolate / other + peak °C Target grams per pocket Sheet size limit (mm) and how we fill (hand / flood-scrape / table) Cavity count I want vs count you recommend for flatness Jacket: required Food-contact path: 177.2600 / LFGB / craft-only Prototype 3–7 business days after CAD lock MOQ 20 per design after weigh-sheet sign-off If this is a nozzle map, route to wydsilicone.com

Send grams, sheet size, and the pour. We return a cavity map that holds weight — not a max-count render. Phone +86 135 3006 2969. Bao’an since 2018.

How we would weigh a layout (method, not a lot result)

We would dump the real pour on the prototype tray, let it set the way you will in production, then weigh every pocket on one sheet. Chart center versus outer row. A straightedge on the loaded jacket shows sag before you argue about recipe. Fill this grid — empty until you run it.

If the outer row sits in that 3–6% heavy band, cut count or thicken the jacket before you freeze 24-up production. Do not “average” the sheet and call the target hit.

FAQ

If I double cavities, do I double output? Only if fill, peel, and jacket flatness stay even. A 24-up with four heavy outer pockets is a 20-up with a scrap column.

Can you match my copacker’s depositor pitch on this RTV tray? Not as a pitch drawing. That is a WYD steel/depositor RFQ. We can match a *sheet size* you already run on a table.

Why are the edge pieces heavier? Loaded sag. Outer row sits deeper, so it holds more. Jacket and border first; Shore later.

Should I family-mold two SKUs on one tray? Only if Shore, shrink, and dump cycle match. Otherwise you will chase two gram targets on one pour.

Does tooling payment let me cut a second 24-up at another shop? A tooling charge is not unrestricted ownership of master, jacket, or CAD. Write archive and recast terms on the PO.