BELLOW ZERO A L I C E H A F N E R M A K E N N A L E H M A N N N - - PowerPoint PPT Presentation

BELLOW ZERO

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 TAT I O N O U T L I N E

• Hedgehog concept
• Overview of design
• Detailed look at subsystems and design decisions
• 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

• Achieved accuracy at a large scale in another

course

• Passionate about designing a product that

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

Passio ion Attention to detail and allowing customer to accurately print exactly what they need Econo nomic ic Engine Minimize replacement per part and maximize profit per subsystem. Best at at Our team members excelled in the DML 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 AT 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)

∆𝑧 = 𝑟𝑆2

2(1 − 𝜉)(1 − cos 𝜄)

2𝐹𝑢

M AT 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

• Necessary displacement

(11.5 mm) below yield to 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

• Balance deformation of each bellow about their

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 mbol Value lue Thermal Expansion Coefficient β 0.00064 1/℃ Viscosity 𝑤 7 mm2/s Price $ $3/gallon Density 𝜍 0.8 g/cm3

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 𝑊

𝑑𝑏𝑞 =

𝜌ℎ 6 3𝑠

𝑐𝑓𝑚𝑚𝑝𝑥2 + ℎ2

∆𝑦 = 2𝑠

𝑡𝑧𝑠𝑗𝑜𝑕𝑓𝑡𝑗𝑜 𝜄

𝑊

𝑏𝑒𝑒𝑓𝑒 = 𝜌𝑠 𝑡𝑧𝑠𝑗𝑜𝑕𝑓2∆𝑦

rsyringe Δx θ θ 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

• The needle and casing assembly is inserted into a

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

07 degr gree ees

• Clos
• sed

ed loop

• p feedba

edback k contr trol

• l with sensor and encoder

to ensure accurate rotation

• Mounting in any orie

ienta ntation tion

• Enclosed brushless motor with permanent magnet
• 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 𝜈𝑛

Linear step =

𝜌𝑒𝑞𝑗𝑜𝑗𝑝𝑜 51,428 = 𝜌(0.6𝑗𝑜) 51,428 =3.66 × 10−5𝑗𝑜 ≈ 0.9309608𝜈𝑛

• This displacement can be modeled as a cylindrical volume in the syringe:
• Volume =

𝑒2 4 𝜌ℎ

where h is the linear step

• Mini

nimu mum m displaced splaced volu lume me = 0.0136 136 𝝂𝑴

M O D U L A R A S S E M B LY

• Four symmetrical bases
• Interlocking shape for easy assembly

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 by medical tubing a Luer lock connectors

• Syringe snaps into place and

is secured by a hinged 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

Cat ategory ry Cost OTS Parts $2,397.28 Raw Materials $25.95 Manufacturing (3D printing) $133.51 Assembly $$$? Total al $2,556.7 .74 4 + $$$?

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:

• $𝑂𝑧𝑚𝑝𝑜 =

$55 0.75𝑦103𝑕 76.65𝑕 = $5.61

• $𝑄𝑊𝐵 =

$45 0.5𝑙𝑕 1.19𝑦10−3𝑙𝑕 𝑑𝑛3

0.657𝑗𝑜3 16.39𝑑𝑛3

1𝑗𝑜3

= $1.15

C O N C L U S I O N

• Accuracy on a small scale to meet our

customer’s needs

• Thank you all for coming!
• Questions?

F O R M U L A A N D S I M U L AT 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 GT H

• Ultimately, main limitation of the design is alignment (sagging) and range of motion
• Possible solutions:
• Increasing wall thickness and pressure
• 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 ≈

𝜌𝑒𝑞𝑗𝑜𝑗𝑝𝑜 51,428 = 𝜌(0.6𝑗𝑜) 51,428 =3.66 × 10−5𝑗𝑜

• Average gear backlash ≈

0.04 𝑒𝑗𝑏𝑛𝑓𝑢𝑠𝑏𝑚 𝑞𝑗𝑢𝑑ℎ= 0.04 ൗ

12 𝑢𝑓𝑓𝑢ℎ 0.6 𝑗𝑜=2 × 10−3𝑗𝑜

• Solu

lution tion:

• Greater gear pitch→ less backlash
• 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 ∆𝑊 = 𝛾𝑊

𝑝∆𝑈

B L O C K D I A G R A M

Temperature Sensor Controller Expansion

• r Compression

error Desired Volume Actual Volume ΔV