Polyurethane Cuff Dipping Machine Design Review

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Polyurethane Cuff Dipping Machine Design Review

• Todd Clark
• Noah Hopson
• Jason Johnson
• Chris Knowlton
• Kris Koster
• Mike Schierbeek

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Overview

• Design a fixture/machine that can
• Manufacture polyurethane cuffs to a predetermined
  thickness using pre-existing mandrels for the
  cuffs.
• Measure the viscosity of the polyurethane
  solution
• Reduce or eliminate bubbles that appear in the
  solution.

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Process Overview

• Polyurethane solution is created by dissolving
  polyurethane pellets in a solvent
• A stainless steel mandrel is then dipped into the
  polyurethane solution
• The solvent flashes from mandrel, leaving only
  the polyurethane
• This polyurethane is left as a thin layer over
  the mandrel

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Objectives

• Design a polyurethane cuff dipping machine
  capable of
• Producing quality cuffs
• Reduce bubbles in the dip solution
• Ensuring a fully mixed dip solution
• Using a smooth dipping profile
• Accepting multiple part programs
• Monitor process parameters
• Active viscosity control
• Ambient temperature and humidity

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Constraints

• Budget of 25,000
• Use a dipping system that will eliminate sparking
• No brushed DC motors
• Use materials that are compatible with
  Tetrahydrofuran (THF)
• Clean room compatible

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Specifications

• Dipping
• Must be able to dip two 15 in. mandrel bars
• Minimum velocity of 0.04 in/sec
• Store 1 gal. of THF solvent for viscosity
  adjustment
• Store 2 gal. of premixed polyurethane for dip
  tank level adjustment
• Fits through a standard 32 inch door
• Store multiple part programs
• Operating and maintenance access should be on one
  side

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Scope of Work

• Research
• Polyurethane dipping process
• Polyurethane solution mixing
• Design
• Size components
• Determine component placement with overall
  ergonomics in mind
• Construction
• Assemble frame
• Place components
• Wire machine
• Testing/Calibration
• Programming
• Test program
• Calibrate viscometer

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Frame

• MayTec aluminum extrusion
• Durable and sturdy machine platform
• All components contained within the frame

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Linear Actuator

• Stepper motor driven
• Easily controlled
• Accurate positioning
• Ball screw linear system
• Smooth motion profile
• Accurate positioning
• Long operating life
• Speed range of 0.04 in/sec to 0.8 in/sec

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Mandrel Bar Rotator

• Two pneumatic rotary actuators
• 40 in lbs of torque at 80 psi (each)
• Smooth rotation
• Adjustable speed
• Based on air flow

• Rotation along the long axis of the mandrel bar
• Uniform velocity for all mandrels
• Eliminates solution creep due to excessive
  movement

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Dip Tank

• Stainless steel construction
• Accepts (2) ten mandrel bars
• Level is monitored by a capacitive proximity
  sensor
• Incorporates
• Viscometer
• Solution/Solvent fittings
• Drain
• Magnetic Stir Bars

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Viscometer

• Cambridge Viscosity viscometer
• Inline process model
• Adapted for in tank operation
• 2.5-50 Cps sampling range
• Continuous viscosity sampling
• 4-20 mA analog output for viscosity adjustment

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Dip Tank Lid

• Seal eliminates unwanted solvent evaporation
• Eliminates solution contamination
• Dual pneumatic cylinders operate lid system
• Guides move lid off and behind tank for dipping

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Mixing System

• Based on proven laboratory stir plate technology
• Three stir bar magnetic couplers
• Belt driven system
• AC induction motor controlled by VFD

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Reservoir System

• Tanks are stainless steel pressure vessels
• Fluid level is monitored by capacitive proximity
  sensor
• Solution and solvent transferred to the dip tank
  via stainless steel braided PTFE hose
• Flow controlled by needle valve and PLC
  controlled solenoid
• Tanks are attached to a drawer to make changing
  easier

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Guard System

• Dipping door is operated by two pneumatic air
  cylinders
• Controlled by palm buttons via PLC
• Safety bumper switch prevents operator from being
  pinched

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HMI Controller

• Allows user to change process parameters
• Allows manual operation of system components

• Displays process parameters to the operator
• Displays machine status

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Overall System

• Compact Size
• 30 wide x 40 deep x 68 tall
• Meets required specifications
• Safe and ergonomic design
• Maintenance oriented
• Fully adjustable dipping process

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Budget

• Project budget of 25,000
• Estimated completion cost of 23,500

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Schedule

• Begin Ordering Parts April 30th
• Begin Construction May 5th
• Begin Programming May 12th
• Finish Construction June 10th
• Finish Programming June 23rd
• Testing and De-bugging through July 7th

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Questions???