In starch-moulded gummy production, the angle of the depositor nozzles relative to the starch bed is one of the most direct mechanical influences on final shape symmetry. The best angle from a fluid dynamics perspective is a nozzle held normal, or perpendicular, to the starch bed, meaning the nozzle centreline is at a 90° angle to the bed surface, with no tilt from vertical.
Why nozzle angle affects gummy shape symmetry
When a gummy slurry leaves the depositor nozzle, it enters a pre-formed starch cavity as a viscous, typically non-Newtonian fluid. If the nozzle is tilted relative to the bed, the stream carries a lateral momentum component. Instead of filling the cavity evenly from the centre outward, the deposit impinges off-centre and reaches one wall of the starch impression before the other.
This creates an asymmetric fill pattern that can show up as:
- Uneven dome height or a lopsided crown
- One-sided “skirting” or flashing where slurry pushes into the starch wall
- Inconsistent tailing or stringing at the nozzle cut-off point
- Air entrapment on the slower-filling side
- Thickness variation across the finished gummy
What fluid dynamics says about the best angle
At the low flow rates and small nozzle diameters used in gummy depositing, the flow is dominated by viscous and gravity forces rather than high-Reynolds-number turbulence. For a clean, symmetric deposit, the velocity profile at the nozzle exit should be as axisymmetric as possible.
A perpendicular nozzle gives the slurry a straight, downward momentum vector into the centre of the starch cavity. The fluid then spreads radially outward in a uniform pattern, so the fill front reaches all sides of the impression at roughly the same time. This produces the most repeatable dome geometry, cleanest edges, and best mirror-image symmetry left-to-right and front-to-back.
By contrast, even a small tilt, often only a few degrees, introduces a horizontal velocity component. Fluid dynamics predicts that the impingement point shifts off-centre and the radial spread becomes skewed. Because gummy slurries are shear-thinning and relatively viscous, they do not quickly self-level after an uneven deposit, so the asymmetry tends to persist into the final set gel.
Shape symmetry, piece weight, and dose uniformity
Asymmetric fill widens piece-to-piece weight spread. When slurry pushes into one wall of the impression and skims the other, the finished piece carries more mass on one side. For functional gummies, piece weight is the main surrogate for active dose, because the active is dispersed through the mass. Weight checks run during and after depositing, and pieces must stay inside a defined range to meet dosage-uniformity requirements. One contract manufacturer reports that 10-15% weight variance is typical across the industry, while tuned depositing lines run in the low single digits. A tilted nozzle works against that goal, adding an uncontrolled source of weight spread on top of the viscosity and temperature variation every depositor already manages. Pieces outside tolerance become rework or scrap, and on a functional formula they can mean the active is under- or over-delivered against label. Keeping the nozzle square to the bed removes a weight variable that is purely mechanical and therefore fully correctable.
Practical guidance
The most reliable configuration is therefore to keep the nozzle axis at 90° to the starch bed plane, with the nozzle centred directly over the deepest point of the mould cavity. In practice, this is usually described as 0° tilt from vertical. Equivalent results require controlling the entire depositing assembly so that nozzles remain perpendicular across the full width of the machine, not just at the centre. That means checking the depositing head as a unit at setup, so every nozzle sits square to the bed and directly over its cavity, and re-checking after any nozzle change.
Other variables such as nozzle height, nozzle diameter, deposit volume, slurry viscosity, and starch bed firmness also influence final symmetry, but the nozzle angle is a primary geometric variable. At KorNutra, keeping depositor nozzles precisely perpendicular to the starch bed is a core part of maintaining consistent, symmetrical gummy shapes across large production runs.