Technology need
Summary of the technological need
A waterproof, tough, resistant, durable, easy to process and cheap material for use as a housing material for electronics inside washing machine drums.
Background
A company specialized in household-equipment is looking for a material that can carry out all specifications of a washing ball.
Currently the washing ball occurs some technical problems:
A. Effects on waterproofness
B. Effects on breakage
C. Effects on Electronics
Due to the washing speed, warm temperatures, chemicals cracks appear on the surface of the ball whereby water and chemicals can enter the electronic design in no time.
This company is looking for strong material for this artefact that can function in this hash environment and doesn’t break.
The improvements of the washing ball will be measured on the following effects:
(1) Effects on waterproofness
• Deformation of sphere
🡪 Due to forces:
When high forces work onto the sphere, they might deform it. This can lead to a breach in the sealing, letting in water.
🡪 Due to temperature
Also high temperatures can have an impact. Materials will shrink and expand due to the high temperature differences.
🡪 Due to chemicals:
Seals can deteriorate when in contact with the wrong chemicals.
(2) Effects on breakage
• Cracks in sphere
🡪 Due to forces:
The high stresses in the sphere due to the high forces can lead to cracks in the sphere
🡪 Due to temperature:
Crimpage and expansion of different plastics and components on the inside, stresses and cracks might appear when not well
designed.
🡪 Due to chemicals:
Chemicals can weaken plastics
(3) Effects on Electronics
• Battery
TBD
Pogo pin contacts for charging are metal in plastic. Due to high temperature changes and difference in materials, stresses can appear around the contacts, making them break loose or crack.
• Motor
temp: motor force is lowered by high ambient temperature of 60°C
TBD
• PCB
Flexing of the sphere due to high forces or high temperature changes can create issues with thru-hole and SMD components.
Microfractures can appear in SMD component solder.
Larger thru-hole components can break loose.
Components will need to be selected to industrial standards (70°C).
Usual temperature rating for most non-industrial components is 45°C.
Application domains
Specifications
Environmental conditions for the ball:
(1) Washing machine speed - Fast Rotation
• +/- 0,45m diameter drum
• Max 1600 RPM angular velocity max
• Weight of sphere +/- 300g
🡪 That means a tangential velocity of 37,7m/s
Resulting in:
🡪 A centrifugal force of 1895N
🡪 A centrifugal acceleration of 6,317 m/s² ~ 644,15G
🡪An effective mass of 193,5kg
🡪Ball sticks to the edge of the drum; no bumping around.
(2) Washing machine speed - Slow rotation
• Impact on ball the most during slow rotations.
• Ball does not stick to the edge of the drum and continuously
falls back to the bottom.
• Worst case: Ball hits one of the protruding features edge-on.
🡪Ball continuously falls from a height of +/-0,45m (minus the
diameter of the ball)
🡪At slowest speed of 400RPM; the ball could fall up to 400 times a
minute.
🡪Of course this is a worst case situation with a practically empty
machine
(3) Temperature
• 60°C max allowed operational temperature.
• Questions:
🡪May the ball be used with programs above 60°C; up to 90°C.
🡪If so, the ball should not form a safety risk.
🡪Should the ball still be functional after it is misused?
(4) Chemicals
Washing products consist of a range of different chemicals.
Since we know exactly which product will be used, materials can be
checked for resistance against all ingredients in its composition.