Cavity Count vs Piece Weight on RTV Trays

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 / mother-mold support shell, 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 here. Here we decide how many pockets a platinum skin and a rigid support shell can hold without the grams drifting.

The tray itself still follows the locked path: photos, sketch, or CAD, then a 3D-printed pattern, often a temporary silicone flip, a resin production mother, then batch RTV. The resin production mother is the hard production tool. It is not the pattern. Free DFM. CAD revision about USD 50 when we edit a cavity map from a sketch. Prototype usually 3-7 business days after CAD lock. Production MOQ 20 pieces per design. Bao'an since 2018.

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 as an HTV product RFQ here, or ask us for a high-volume LSR tool. It also does not apply to a one-cavity resin figurine - that is structure, not sheet layout. An HTV/HCR compression mold RFQ stays on RUUIPON; do not send that mold-tool RFQ as an HTV product RFQ here, or ask us for a high-volume LSR tool.

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 support shell 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 support shell - 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

Reference values only. Confirm material-specific limits against the supplier’s technical data and agree project acceptance criteria before production.

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 support shell is that tool. If your copacker sent a pitch drawing, forward it as an HTV product RFQ here, or ask us for a high-volume LSR tool 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 x 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 / mother-mold support shell, 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. The cavity map was USD 50 because they had a sketch and a gram target, not a locked STEP. Path after CAD lock: pattern, often a flip, resin production mother, batch RTV.

Stay on this page / skip this page

Stay when you need an RTV tray layout that holds grams - cavity count versus piece weight on a flexible sheet.

Skip if you already have a nozzle map - a different RFQ - ask us. Skip if the object is a one-cavity figurine. Skip if you need finished HTV/HCR/LSR parts - that carton is a different RFQ - ask us.

We will not quote max cavity count on an unsupported 10A sheet to "get the unit cost down." We will not raise Shore A to stiffen a floppy multi-cavity sheet before you add a support shell or cut count. We will not freeze 24 pockets while the logo and the gram target are still moving.

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

What to send

• Object: RTV tray layout (not depositor pitch)
• Pour: pectin / gelatin / chocolate / other + peak C
• Target grams per pocket; sheet size limit (mm); how you fill
• Cavity count you want vs count we may cut for flatness
• Food-contact path if needed: 21 CFR 177.2600 and/or LFGB sections 30/31

Send grams, sheet size, and the pour to [email protected] or contact. We return a cavity map that holds weight - not a max-count render. WhatsApp +86 135 3006 2969.

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

We 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 support shell 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 different RFQ - ask us 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 the living mother, the support shell, or the CAD. Write archive and recast terms on the PO.