Sealing & condensation redesign
Three leakage and condensation problems
Water appearing outside a SLUSHi vessel did not always have the same cause. The work separated residual slush at the spout, leakage at the rear seal interface, and condensation on the vessel exterior.
Spout
Slush retained after dispensing could melt and resemble a leak. Removing contact area also reduced engagement with the rubber seal.
Rear seal
Poor engagement between the seal and unit caused leakage in first-article inspection units.
Condensation
The cold vessel exterior collected moisture that dripped down the side, near internal and user-interface electronics.
My work: geometry development, prototype evaluation, and design changes supporting the tooling path. The constraints included existing assembly access, rubber-seal engagement, and injection-molding requirements.
Seal geometry & engagement
For the spout, reducing the surface in contact with residual slush helped drainage. Removing all of the lower material, however, sacrificed seal engagement. The selected geometry balanced the two functions rather than maximizing either in isolation.
Reduce liquid retention while preserving enough geometry to engage the rubber seal.
At the rear of the vessel, the prototype had to fit around partially accessible mounting features and clear the evaporator barrel. Contoured holes and flexibility made it possible to evaluate the change within the existing assembly.
Prototype testing
The rear-interface FDM prototype reduced leakage by over 90% in the documented prototype test. That result supported a production tooling change. It is a prototype-test result, not a stated fleet-wide failure-rate reduction.
For side condensation, I surface-modeled a gutter that routed water toward a front tab and away from the electronics. The design included 2° draft for injection molding. A clear SLA prototype made the water path visible during evaluation.
Results & tooling changes
The work produced a compromise spout geometry, a rear-interface tooling change, and a validated path for redirecting condensation. Each addressed a different physical mechanism.
How to interpret the result
The supplied project record reports the prototype improvement and tooling actions. It does not include sample counts, leakage measurement units, or long-duration reliability results; those are not implied by the percentages shown here.
Ownership under production deadline
Cooling issue before mass production
Some SLUSHi units struggled to reach recipe temperature targets, including orange juice. The recorded behavior included power spikes, early kickdowns, and warmer end temperatures.
With two weeks remaining before mass production, a solution also had to fit the release schedule. I owned two workstreams: a short-term airflow baffle and a longer-term PWM fan / PCBA update.
Release constraint
Develop a part with a manufacturing lead time compatible with the approaching production date.
System constraint
Evaluate airflow alongside the unit’s power and temperature behavior, then coordinate the electrical changes required for fan control.
Airflow experiments
I started with low-fidelity cardboard baffles, then compared opening patterns and measured airflow. The iterations changed hole size, count, and pattern to characterize how the baffle affected CFM.
That experiment provided a practical reference for the next design step: the fan work used an external power supply and tachometer, with similar baffle airflow observed at 6 V.
Pursue a manufacturable airflow restriction for the immediate release, while developing a controllable fan solution for the longer term.
Baffle & PWM fan validation
01 — Baffle for the approaching production release
Cardboard experiments progressed to 3D-printed and laser-cut prototypes. Mounting features included screw holes and press-fit spherical features. Comparative traces showed reduced power spikes and a colder final condition with the baffle.
02 — PWM fan and PCBA update
The longer-term path required an updated fan and board connections. A reworked PCBA with jumper connections supported evaluation of the PWM arrangement. The recorded comparison again showed reduced power spikes and a colder end temperature.
Drawings & engineering changes
Baffle
Released engineering drawings to the China team for die-cut manufacturing.
Fan / PCBA
Initiated an engineering change order for the new PCBA; the résumé also documents the fan update and coordination with electrical engineering.
The outcome combined prototype data with manufacturing timing. It demonstrates both mechanical iteration and integration with electrical hardware.
Evidence and scope
The plots show comparative performance for the documented tests. The project record does not establish a fleet-wide improvement, test repeatability, or a complete causal thermal model, so the project does not claim those results.
Reducing product noise
A smaller unit, a louder product
The FS601 and FS605 used near-identical systems, but the smaller FS601 was noticeably louder. The shortened divider increased the motor-housing volume, suggesting that the enclosure was amplifying the motor noise.
Separate the source from the transmission path
NVH simulations supported the housing-amplification theory. The work then targeted two contributors: gearbox excitation and contact between the gearbox and vibrating housing walls.
The design changes replaced spur gears with helical gears and removed locating knobs that coupled the gearbox to the housing.
Check noise and durability
Removing the knobs reduced noise by approximately 1.5 dB. Motor-stall testing showed no visible deformation or fracture of the screw posts. The gearbox change reduced noise by approximately 3 dB, with no performance difference reported after 1,000 hours of lifetime testing.
~4 dB quieter overall
The combined changes reduced noise by approximately 4 dB in the documented tests. The combined result was measured separately; the individual decibel reductions are not additive.
Preventing dasher stalls
Hard ice drove the system to its limit
High-protein Fairlife chocolate milk was an upper-edge recipe: hard ice accumulated, power rose past the system threshold, and the compressor shut off as the unit stalled.
Give the dasher an edge to scrape
Adding 0.4 mm microribs helped the dasher scrape ice and resolved stalling in most units. Running the ribs along the rails kept the geometry compatible with injection-mold tooling.
Some units still stalled. The next hypothesis was that more uniform ice formation gave the ribs less opportunity to catch and scrape the ice.
Test the remaining thermal cause
Comparative modifications investigated ice formation, including tape and a dasher sanded by approximately 0.2 mm to account for tape thickness. Evaporator modifications then tested the thermal-interface hypothesis and informed a manufacturing change to thermal-paste application.
Combine mechanical and thermal changes
With the microribs and evaporator thermal modification together, the documented tests reported no stalls and colder final temperatures. The project connects a molded-part change with a manufacturing-process change.