The document describes a project to develop a system to mechanically control the speed and direction of the middle spray arm of a dishwasher. The goals are better cleaning, more efficient spray systems, and reduced cycle time. The proposed system would use an AC motor, injection molded spray arm and wheel, and a chain drive. Testing showed controlled rotation is more efficient than hydraulic rotation, reducing flow rate at the same pressure by 19%. Challenges include fitting the system with adjustable upper baskets. The total material cost is $144.79 and production cost is estimated at $20-30.

1. Controlled Rotation Spray System for the Middle Arm of a
Dishwasher
Derek Baker • Tyler Curtis • Thomas Michalik • Kyle
The rotation of a spray arm is controlled by
the pressure and flow of water spraying out
of the nozzles of the spray arm. The goal of
the project is to develop a system to
mechanically control the speed and direction
of the middle spray arm of a dishwasher.
Project Description
•Better cleaning in the dishwasher
•More efficient spray systems
•Reduced cycle time
•Enabling new spray system features
Benefits
Total Material Cost:
$144.79
Fabrication Hours:
15 Hours
Approximate unit production cost: $20-$30
Economic Analysis
•Implement a variable speed AC motor
with forward and reverse capabilities
•Utilize injection molding for the spray
arm and the wheel to make one piece
•Remanufacture the side of the tub wall
to have a flat surface at the through-
hole to support chain drive
•Redesign the upper basket to provide
space for the drive gear to operate
Final Recommendation
Testing and Validation
1. Hydraulic Rotation,
lower spray arm only
2. Controlled Rotation,
lower spray arm only
3. Hydraulic Rotation,
Alternating wash
4. Controlled Rotation,
Alternating wash
Controlled Rotation vs. Hydraulic RotationSpiralgraph with Drive Nozzles : Rotating vs Non-Rotating
0.00E+00
1.00E+04
2.00E+04
3.00E+04
4.00E+04
5.00E+04
6.00E+04
7.00E+04
0.00E+00 1.00E+01 2.00E+01 3.00E+01 4.00E+01 5.00E+01 6.00E+01
Flow (L/min)
Pressure(Pa)
Drive Nozzles
No Drive Nozzles
42 L/min
34 L/min
Pressure = 35000 Pa
19% drop in flow rate at same wash arm pressure by shutting down
2 drive nozzles on main arm. It is more efficient to drive the wash
arm by an electric motor than hydraulically.
1
2
3
4
Finite Element Analysis of
Drive Gear
Finite Element Analysis of
Spray Arm
Finite Element Analysis of
Spray Arm
•Transfer power to the upper spray arm
•Make the system work with adjustable upper
baskets, which move up and down
•Have a negligible impact on capacity
Challenges
Motor $48.37
Chain $37.75
Sprocket $18.44
Clutch $34.37
Bushings $5.86
Drive Gear Supplied
Spray Arm Supplied
Professional Advisors: Kristopher
Delgado
Jordan Fountain
Faculty Advisor: Indrek Wichman