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Detailed Design Review & Component SelectionP15551 High Temperature Pellet Based 3D Printer Head
Alyssa Palmieri, James Allen, Kylan Ames, Ray AliNovember 13, 2014
High Temperature Pellet Based 3D Printer Head
Most current 3D printers use plastic filament as feedstock. The goal of our project is to create a 3D printer head that uses ordinary plastic injection molding pellets as feed stock. It should be able to withstand temperatures up to 380°C, which is 100°C higher than max operating temperatures of current printers, and should also be able to print for 10 hours continuously.
Engineering RequirementsTop 8 Engineering Requirements (Importance of 7+)
System FunctionsPRIMARY
Storing: HopperHeating: Cartridge HeaterCooling: Cooling FanDriving: Auger Screw
Stepper Motor
Feedback: Thermal Feedback
Pressure Feedback
ALTERNATIVE
Storing: HopperHeating: Cartridge HeaterCooling: Cooling FanDriving: Metering Gear Pump
Stepper Motor
Feedback: Thermal Feedback
Pressure Feedback
Justification for Alternative+ History of screw solution difficulties+ Simplicity of Gear Pump+ Innovative Design+ Similar size/weight to current printers+ Contingency plan for solution failure
- Unknown solution feasibility- Difficult to design/fabricate?
Subject Matter ExpertsName Expert in Feedback
Dr. Steven Day/Dr. Michael Schertzer Fluids ● A pump is feasible
● Calculations for non-newtonian and newtonian fluids are similar
Dr. Michael Schrlau Heat Transfer ● Decouple functions - heat then drive
Harbec Inc. Injection Molding ● Time while molten increases plastic degradation● Stock auger screw is cost-effective solution
Professor Bonzo Machining Capabilities
● Machining of a variable flight depth screw is possible ● Test stock auger screw for POC before fabricating one
Rachel Screw driving plastic pellets ● Found out what didn’t work with screw driving
Subject Matter Experts Cont.Name Expert in Feedback
ITT Goulds Pumps Centrifugal pumps
● Positive displacement pump (Gear Pump) is a strong option● PD pumps handle high viscosity well● Limit thermal conduction paths between components
Liberty Pumps Pumps
● Gears meshing might add unwanted shear energy to molten plastic ● Elastomer seal within the pump may not be able to withstand high temp.● “Mag-drive” pump could eliminate need for a seal● Progressive cavity pumps are used for very viscous fluids and have “fairly
accurate flow rates”● Wet end of heated pump should be metallic
Component: Hopper
Functions● Hold plastic pellets
Comments/Concerns● Unsure of cost associated with fabrication● Concerned with added weight to the print
head
Component: Heater Cartridge Functions
● Provide necessary heat to the system to melt thermoplastics
Comments/Concerns● Maximum operating temperatures of 540°C to 760°C depending on sheath
material● To achieve a temperature of 350°C, the heater will need to be roughly 300 Watts
Costs and Information● Omega ¼” diameter heating cartridge, 2” length, 250 Watts. PN: CIR-1024/120V,
cost $66.00● Omega ⅜” diameter heating cartridge, 2” length, 300 Watts. PN: CIR-
20204/120V, cost $50.00
Component: Heater Cartridge (cont.)
Component: Auger Screw FunctionsTransport bulk material through barrell to nozzle. Produces shear heat in screw.
Comments/Concerns● Initial proof of concept with the filabot works with ULTEM pellets● Produced non-uniform cross section of filament with air bubbles● Cylindricity of auger
Costs● $27.02
Auger Screw Proof of ConceptLearn how to use the Filabot Wee
Testing Process:1. Locate Filabot2. Ask Brinkman Lab employees for help with testing
for the first time3. Plug in the Filabot4. Turn up the temperature to 240°C5. Once temperature is at 240°C, add pellets & start
running the screw6. Test for about 2 minutes to watch the process7. After testing look at how hot the Filabot can get
Auger Screw Proof of ConceptLearn how to use the Filabot Wee
What we’re looking for:● Observe how the Filabot works to transport the pellets throughout the
system● Also see if the Filabot can get up to 350 degrees C to test our
ULTEM pellets.
Results:The extruder worked and printed filament strands.
Auger Screw Proof of ConceptTake off insulation and see what is heating
Testing Process: 1. Cut zip ties off the insulation and take off insulation2. Look to see what is heating the aluminum to heat the plastic pellets3. Look to see how big the aluminum cylinder is compared to the screw driving the pellets
Auger Screw Proof of ConceptTake off insulation and see what is heating
What we’re looking for:● What was heating the pellets● How big the aluminum cylinder is
compared to screw driving the pellets
Results:We found that there is a small heating cartridge melting the pellets held by a set screw. The aluminum block is also much larger than we thought.
Auger Screw Proof of ConceptTest Filabot with ULTEM 1000 Plastic Pellets
Testing Process: 1. Turn on the Filabot
2. Get temperature up to 240°C to purge out any of the old material
3. Once at temperature, turn on the screw to purge
4. Once material is purged, turn the temperature up to 350°C
5. Once at temp, add ULTEM pellets and turn on driving motor
6. Run for 2 minutes and observe
Auger Screw Proof of Concept
Test Filabot with ULTEM 1000 Plastic Pellets
What we’re looking for:● If Filabot can extrude ULTEM 1000 pellets
Results:The Filabot worked with the ULTEM pellets.
● Some residual material was still in Filabot and coated the ULTEM filament initially● Then turned down temperature to 320°C to see if the pellets would still melt and noticed that
the strand of plastic coming out of the Filabot was chunky and inconsistent● 350°C found to be ideal temperature (Sufficient melting, without burning)● Screw moved material too fast through the nozzle for it to melt consistently● Moisture in pellets cause air bubbles when being printed. Need to dry first.
Auger Screw Proof of ConceptTest Filabot with ULTEM 1000 Plastic Pellets VerticalTesting Process1. Turn on the Filabot
2. Get temperature to 350°C
3. Add plastic ULTEM pellets
4. Cover hopper to prevent pellets from falling out while vertical
5. Run screw
6. Tip the Filabot vertical when the material starts to come out of the nozzle
7. Run for 2 minutes
8. Stop and let Filabot sit for 10 minutes to allow pellets more time to warm up
9. Run the screw for 2 minutes
Auger Screw Proof of ConceptTest Filabot with ULTEM 1000 Plastic Pellets VerticalWhat we’re looking for:
● If Filabot can be tipped vertical (like a 3D printer) and still properly function
Results:The Filabot works with it being turned vertical.
● Noticed air bubbles ○ Pellets having moisture in them○ Material moved too quickly through the system, didn’t melt enough
● Possibly require additional heating prior to driving● The speed of the screw needs to be slower for our application
Auger Screw Proof of ConceptTest Filabot with ULTEM 1000 Plastic Pellets Vertical
❖ Material Starts off smooth during initial printing
❖ Material is chunky after running for about a minute
Auger Screw Proof of Concept
❖ Allowed the Filabot to sit for about 10 minutes with the pellets in the hopper to try to dry the pellets and create a more consistent flow, which it started off chunky and then became more consistent
❖ Material is very consistent after the heat took part in helping to dry the pellets
Component: Gear Pump (Alternative) Costs
● Spur gears: ~25 each● Housing: ~20● Seal/ gasket: ~5
Functions● Precisely outputs a volumetric flow rate● Heating cartridge maintains appropriate temperature
Comments/Concerns (pressure)● Gear meshing leading to unwanted shear energy, could negatively affect pump performance● Mechanical seal (elastomers) do not perform at these high temperature
Component: Stepper MotorCosts
● $10-20 (free from customer)
Functions ● Produces a torque to drive the auger screw.
Comments/Concerns● Compatible with 3D printers● Reliable● Easily adjust RPM● Can adjust torque output with speed belt/ gear ● Must be properly separated from heated components
Size ● Torque must be able to produce a 35lb linear force
Additional Misc. ComponentsInsulation
● Required to maintain safe printing environment for consumer● Also considered to lower heater wattage required● Fiberglass or mineral wool can insulate high temperatures
Arduino Microcontroller● Provided by customer● Used to control stepper motors, axis controls, temperature monitors, power supply, etc.
Nozzle● 0.4mm diameter exit, can be purchased relatively cheaply from various sources. ● Alternatively it can be machined without significant difficulty.
Aluminum Block● Our 3D printer has 1.75” diameter aluminum bar for an extrusion head, which will be used as a
starting point for the barrel outer diameter
Extrusion Screw● Extrusion screws are used to melt plastic and create filament● Typically they are multiple feet in length, we are constrained to inches● The flight width for this design is only 0.04”, so there are concerns with bending or breaking
○ Might be able to deviate from accepted designs to increase this width● Screw to barrel clearance is also small, 0.0004”. Tolerance will be difficult to hold● This design will be considered if the small scale auger screw design fails or is insufficient● Cost is likely to be high
Screw Design Calculations
Screw Design Calculations (cont.)
Test Plan: Heater CartridgeWhat ● Temperature● Wattage
How● Simulate operating conditions.
○ Temperature:■ Use thermocouples to measure temperature of heater after
steady state conditions○ Wattage:
■ Power heat cartridge until the output is at the proper level, then measure the voltage and current to calculate wattage
Test Plan: Stepper Motor/Auger Screw
What ● RPM● Mass/Volumetric Flow rate
How ● RPM
○ Visually identify the number of rotations in a given minute.● Flow rate:
○ Extrude filament for a certain amount of time onto a scale to measure the weight of material coming out.
Test Plan: Thermal Feedback❖ Thermocouples should be calibrated before use. ❖ A common way to calibrate thermocouples is to place
them in a heated bath at 30°C and measure the voltage. ❖ Voltages are measured at 5 degree increments up to
60°C, and then again at room temperature. ❖ A voltage-temperature plot can be created and
compared to known values. ❖ There should be programmable methods of cutting
power once the desired temperature is attained.
Test Plan: PrintheadWhat:● Print time● Flow consistency
How:● Print Time
○ Load printer and set run time for 10 hours, check for any failures and add additional material as necessary.
● Flow consistency○ Setup printhead and visually inspect material leaving the nozzle for air bubbles,
surface texture, color, uniformity, etc., to ensure consistent flow.○ Measure mass flow rate coming out of nozzle
Bill of Materials
Bill of Materials
Risk Assessment
Risk Assessment
Risk Assessment
Risk Assessment
Risk Assessment
Risk Assessment
Risk Assessment
Next Steps! Week 13-15➔ Focus on narrowing down components ➔ Start to order some components with long lead times➔ Focus on understanding Non-newtonian fluids
◆ see SME◆ look up more textbooks
➔ Update test plans◆ focus on low-risk subsystems
➔ Focus on calculations for the gear pump◆ see SME
➔ Continue 3D modeling and creating drawings➔ Continue adding more to BOM ➔ Visit machine shop to see if pump casing is machineable inhouse ➔ Lower scores/takeaway risks on the risk assessment➔ Test auger screw with BFB stepper motor
Questions?
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