The short answer is that there is no single “optimal” pressure that applies to every starch mold, starch condition, or cavity design. At KorNutra, we treat cavity printing as a process window rather than a fixed number. The goal is to apply enough pressure to transfer the mold pattern cleanly while keeping the starch bed uniform and easy to release.
How pressure affects cavity quality
Starch is a granular, compressible material, not a rigid die. On a mogul line, the print board presses into a leveled tray of conditioned starch, and the starch compacts and takes the shape of the cavity. That compaction gives the cavity its structural integrity, so it can hold deposited syrup without deforming. Pressure influences two competing outcomes:
- Edge definition: Too little pressure leaves rounded or shallow edges, incomplete cavity depth, and inconsistent piece weights.
- Uniformity: Too much pressure forces starch to pack unevenly, especially at the cavity walls, floor, and around fine details.
Higher pressure can sharpen edges, but only within a narrow range. Beyond that range, the starch begins to compress unevenly. You may see dense zones, hard spots, surface sheen, edge crumbling, or poor release because the compacted starch grips the mold board.
The balance point
The practical optimum is the lowest pressure that consistently produces clean, fully formed cavities with smooth release. If you need to increase pressure to get sharper edges, increase it in small increments and stop as soon as edge quality stabilizes. Additional pressure after that point usually creates more problems than it solves.
Factors that change the optimal pressure
- Starch moisture, oil, and conditioning: Molding starch is conditioned to a target moisture and oil content, and drier or poorly conditioned starch compacts differently. Most gummy and jelly lines hold it at 5.5 to 7.0 percent moisture; below 5.5 percent it becomes too dry to hold a clean impression.
- Particle size distribution: Finer starch may compact more easily and require less pressure.
- Cavity geometry: Deep cavities, sharp corners, and intricate details may need slightly more pressure, but they are also more prone to uneven compaction.
- Tray fill and leveling: Inconsistent tray fill will make any pressure setting look wrong because the starch bed varies from one tray to the next.
- Board condition and temperature: Worn or warm boards change how starch releases and how pressure transfers.
Cavity definition and dose accuracy
Every cavity you print is a fixed-volume deposit site. If cavity depth drifts tray to tray because pressure drifts, the deposited volume drifts with it, and so does piece weight. That variation passes straight through to active potency per piece and to label-claim compliance. Industry sources put typical deposit weight variance in a gummy facility at 10 to 15 percent before a line is tuned, so cavity quality is a dosing problem first and a cosmetic one second. A tight piece-weight distribution at the lowest usable pressure protects the label claim and your overage costs at the same time.
What we recommend at KorNutra
Start on the low end of your equipment’s pressure range and run a short validation matrix. Evaluate each setting for cavity depth, edge sharpness, release cleanliness, and piece-weight consistency. Weigh enough pieces at each setting to see the spread rather than a single average. The best setting is usually the lowest pressure that meets all of those criteria. If you see shiny or streaked cavities, visible density lines, or torn edges, you have likely exceeded the useful pressure window.