Bellow ZeroB E L LO W Z E R O A L I C E H A F N E R
J O H N B R Y A N
M A K E N N A L E H M A N N
M A L L A R Y S P O F F O R D
N I N A J O N E S
S I L V I A P A R D O
EML4501 Group 2 presents….
P R E S E N T A T I O N O U T L I N E
• Hedgehog concept
• Cost analysis
• Questions
H E D G E H O G C O N C E P T
• Our team naturally values and excels at detail
and accuracy
course
allows the customer to reach an outcome as
close to what they desire as possible
• Willing to produce accurate, durable, and
more economically advantageous parts for the
long term
exactly what they need
Best at
competition requiring targeting and knocking
down objects.
P R O D U C T O V E R V I E W
• 3D printer for biological materials
• Mounts directly onto microscope within a 100- millimeter cube
• Movement of the print head is controlled by the expansion or contraction of three fluid-filled nylon bellows
• Motors, gears, controller, and power supply mounted to the wall
• Each motor accurately moves in increments of 0.007 degrees with 10,000 steps per rotation
• Minimizes vibration of the microscope, print head, and well plate
B E L L O W S A N D M O V E M E N T
M A T E R I A L A N D G E O M E T R Y S E L E C T I O N • Deformation in spherical thin-walled pressure vessels (Roark’s Formulas For Stress and
Strain)
2
M A T E R I A L S E L E C T I O N • Constant geometric properties and pressure while varying material
G E O M E T R Y S E L E C T I O N • R constrained by
customer needs, leaving
R2 and t
account for system
stresses
S Y S T E M A N A LY S I S
A L I G N M E N T W I T H V E R T I C A L A X I S
C O U N T E R W E I G H T A D D I T I O N
• Introduction of counterweights that can be used to
tune the system
respective central axes
P R E S S U R I Z E D S Y S T E M
H Y D R A U L I C S
• Mineral Oil was selected as the hydraulic fluid due to the properties listed below
• Mineral Oil also received an ‘A’ rating when chemically tested against Nylon
Name Symbol Value
Thermal Expansion Coefficient
β 0.00064 1/
H Y D R A U L I C S
• The hydraulic system allows for a minimum displacement of 0.652 micrometers
• Each bellow was calculated as a spherical cap with variables height and volume
• At the minimum motor increment, the minimum linear distance was calculated and
converted into a volume using the inner diameter of the syringe
=
6 3
2 + 2
θθ rsyringe
P R I N T H E A D A S S E M B LY
• A nylon, cubic shaped casing is fitted to the print
head needle
vertical cubic slot in the cylindrical mount
• Once at the bottom of the shaft, the needle
assembly is rotated 45° from the slot to lock it into
place
• The needle is released and free to move in the z-
direction only when the casing is set at the same
angle as the vertical slot
P O S I T I O N - C O N T R O L D C M O T O R W I T H D R I V E R , C T R L L E R , S E N S O R A N D E N C O D E R
• Increments of 0.007 degrees
to ensure accurate rotation
• Mounting in any orientation
• Compatible with Smoothieboard 5x
P R I N T F L U I D D I S P L A C E M E N T • A single step of the motor causes the piston to move 0.93
Linear step =
51,428 =3.66 × 10−5 ≈ 0.9309608
• This displacement can be modeled as a cylindrical volume in the syringe:
• Volume = 2
• Minimum displaced volume = 0.0136
M O D U L A R A S S E M B LY
• Four symmetrical bases
and mounting
• Each section weighs approx. 1kg
E A S I L Y R E P L A C E A B L E S Y R I N G E A N D T U B I N G
• Luer Lock connections
• Syringe and print
head/bellows are connected
connectors
mechanism and retention tab
P R O T O T Y P I N G • 3D printing nylon bellows system as one unit would be a new challenge for students to
explore
• Bellows as an accurate displacement mechanism for 3D printing has not been tried or
commercialized
• System can be easily tailored to different customer needs based on syringe sizes, motor
choices, needle gauges, gear sizes, etc.
• Potential for nanoscale accuracy depending on design choices
C O S T
Total $2,556.74 + $$$?
C O S T 3 D P R I N T I N G • The bellows, mounting and delivery systems will be 3D printed as a unit to reduce assembly costs. The material
selected for the structure will be Nylon.
• Since the bellows are hollow and parts of the design contain undercuts steeper than 45°, supporting material is
necessary. PVA is a water-soluble polymer that presents excellent film formation, it is compatible with nylon
structures due to its bonding power and has a melting point of 200° C which is lower than that of Nylon. PVA can
be melted out of the hollow spaces in the bellows once fabrication is complete.
• The whole structure has a volume of 3.284 in3 and requires 76.65 g of Nylon. Additionally, we will assume that we
will need 20% of that volume (0.657 in3) in PVA support material as this is the standard percentage of infill material
for 3D printing.
• According to the 3D printer manufacturer Xometry, the quote of 3D printing the bellow-mount-delivery system as
a whole structure using Nylon is $140.27. The raw material calculation are as follows:
• $ = $55
C O N C L U S I O N
• Accuracy on a small scale to meet our
customer’s needs
• Questions?
F O R M U L A A N D S I M U L A T I O N T R E N D
P R O B L E M : C O U N T E R W E I G H T S • System is more rigid fully pressurized
• Issue arise when volume in each bellow are at different levels (ex. One bellow is at
maximum displacement and other bellows are at minimum displacement)
• Potential solution: varying counterweight system
• The system can indeed be balanced using counterweights – variable system
P R O B L E M : R I G I D I T Y A N D S T R E N G T H • Ultimately, main limitation of the design is alignment (sagging) and range of motion
• Possible solutions:
• Guiding/track system
P R O B L E M : G E A R B A C K L A S H • 51,428 steps per motor revolution
• Linear step ≈
• Dual-pinion system
P R O B L E M : M I S A L I G N M E N T O F P R I N T H E A D N E E D L E
• Solution: Ball Catch Latch
• Steel ball with a spring underneath is imbedded in the
cylindrical mount
• A small indent is in the bottom surface of the cubic mold
• When the mold and print head needles is rotated 45º,
the ball “catches” into the small indent in the model and
thereby holds it in place
• Can be uncaught by applying small force to rotate back
into original position
H Y D R A U L I C S S E N S O R
- A temperature sensor will continuously determine the temperature of the oil and modify the volume of the bellows accordingly
- Beta is the expansion coefficient shown in previous slide
- Solving for ΔV would determine how much volume the control system would need to change
=
B L O C K D I A G R A M
Temperature Sensor