EML4501 Group 2 presents…. 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 I N A J O N E S J O H N B R Y A N M A L L A R Y S P O F F O R D S I L V I A P A R D O
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 Passio ion and accuracy Attention to detail and allowing customer to accurately print exactly what they need • Achieved accuracy at a large scale in another course • Passionate about designing a product that allows the customer to reach an outcome as Best at at close to what they desire as possible Econo nomic ic Engine Our team members excelled in the DML Minimize replacement • Willing to produce accurate, durable, and competition requiring per part and maximize targeting and knocking profit per subsystem. down objects. more economically advantageous parts for the long term
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) 2 (1 − 𝜉)(1 − cos 𝜄) ∆𝑧 = 𝑟𝑆 2 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 R 2 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 Name Symbol mbol Value lue Thermal Expansion 0.00064 1/ ℃ β Coefficient Viscosity 7 mm 2 /s 𝑤 Price $ $3/gallon Density 0.8 g/cm 3 𝜍 • Mineral Oil also received an ‘A’ rating when chemically tested against Nylon
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 𝜌ℎ 𝑐𝑓𝑚𝑚𝑝𝑥2 + ℎ 2 𝑊 𝑑𝑏𝑞 = 3𝑠 6 θ θ r syringe r syringe ∆𝑦 = 2𝑠 𝑡𝑧𝑠𝑗𝑜𝑓 𝑡𝑗𝑜 𝜄 𝑡𝑧𝑠𝑗𝑜𝑓2 ∆𝑦 𝑊 𝑏𝑒𝑒𝑓𝑒 = 𝜌𝑠 Δx
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 osed ed loop op feedba edback k contr trol ol 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 𝜌𝑒 𝑞𝑗𝑜𝑗𝑝𝑜 𝜌(0.6𝑗𝑜) Linear step = 51,428 = 51,428 = 3.66 × 10 −5 𝑗𝑜 ≈ 0.9309608𝜈𝑛 • This displacement can be modeled as a cylindrical volume in the syringe: 𝑒 2 • Volume = where h is the linear step 4 𝜌ℎ • 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 in 3 and requires 76.65 g of Nylon. Additionally, we will assume that we • will need 20% of that volume (0.657 in 3 ) 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 • $𝑂𝑧𝑚𝑝𝑜 = 0.75𝑦10 3 76.65 = $5.61 1.19𝑦10 −3 𝑙 0.657𝑗𝑜 3 16.39𝑑𝑛 3 $45 • $𝑄𝑊𝐵 = = $1.15 𝑑𝑛 3 1𝑗𝑜 3 0.5𝑙
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 𝜌𝑒 𝑞𝑗𝑜𝑗𝑝𝑜 𝜌(0.6𝑗𝑜) • Linear step ≈ 51,428 = 51,428 = 3.66 × 10 −5 𝑗𝑜 0.04 0.04 • Average gear backlash ≈ 𝑒𝑗𝑏𝑛𝑓𝑢𝑠𝑏𝑚 𝑞𝑗𝑢𝑑ℎ = 0.6 𝑗𝑜 = 2 × 10 −3 𝑗𝑜 12 𝑢𝑓𝑓𝑢ℎ ൗ • 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 Actual Desired ΔV Volume Volume error Controller Expansion or Compression Temperature Sensor
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