Customer Handoff & Final Project Documentation
Table of Contents
Final Design Output
The final design used a silicone ventricle with air as the driving force to push water through the system. The water passes through the check valve and into the arterial tank. The arterial tank is pressurized to model the body's blood vessels resisting the flow. Then the water passes through the turn valve. The turn valve changes the correctional area of the tubing. This causes a change in compliance of the modeled blood vessels. As the turn valve is closed the pressure in the arterial tank rises. After the turn valve, the water enters the venous tank which models pre-load in the system. The pre-load is the pressure of the blood coming from the lungs that fills the heart. Since this process is similar to pouring instead of forcing liquid into the heart, the tank is open to atmosphere. Pre-load pressure can be adjusted by changing the height of the plunger to vary the water head. Finally the water returns to the heart to begin the process again.
Controls in LabVIEW software can change the heart beat and duty cycle of the system. The heart beat sets a time for each sequence on then off of the solenoid which makes up one beat. The duty cycle controls how fast the solenoid fires to alternate between air and vacuum pressure supplied to the pump chamber.
Video Description of Overall System
Test Results Summary
Engineering Requirements vs. Accomplishments
Detailed Testing Document
See Test Information Here: FinalTest
Risk and Problem Tracking
- Ventricle Non-Uniformity
- Currently the ventricle mold creates a thicker boundary towards the top then the rest of the side walls. This is inherent to the mold design and does not affect the outputs of physiological parameters.
- Broken Ventricle Mold
- The positive part of the mold snapped when making the last ventricle. Currently there are three ventricles available to the customer (Thin, Normal, and Tick walled). Also, the file required for 3D printing has been provided. It is recommended that the customer used the construct to print a new positive mold. The Pursa 3D machine should be used at a minimum of 20% density for the crosshatching.
See Live Document Here: Problem Tracking
See Poster Here: Poster
Final Project Documentation
Manuals, Drawings, and Protocols
See Manuals Here: Manuals
See Additional Diagrams Here: Additional Diagrams
See Drawings Here: Drawings
See Build Instruction Here: Build
See Technical Paper Here: Paper
See Live Document Here: Final LabVIEW
See LabVIEW User Manual Here: Manual
Bill of Materials
See Live Document Here: Final BOM
Future RecommendationsOverall, the new design demonstrates physiological parameters modeled after the human heart and circulatory system. Optimizing smaller components of the system would increase the longevity. The current valves satisfy the system needs however, they are bulky and aesthetically displeasing. They also use a hinge which can wear out or break over time. Ball and cage valve are simple to construct using clear PVC piping. The ball can be 3D printed in the Rochester Institute of Technology construct. These valves have no connected moving parts which decreases the wear from constant use of the valves.
The solenoid currently driving the airflow was taken from a scrapped machine used to control HVAC. This solenoid is not typically used at the high frequency that the system demands. Also, since it was previously used, the remaining lifespan of the device is undeterminable. It is recommended to replace the current solenoid with one that is unused and rated for frequencies of 1 to 3 Hz. It would also be desired that the solenoid can allow higher flow to the chamber. An increased flow rate allows the system to change chamber pressure more dynamically.
The current mold for ventricle fabrication is a two-part mold. When the silicone cures, it clings to the positive insert which can cause difficulty removing the ventricle and damage to the mold. Using a spray to keep the silicone from gripping the 3D printed surface could prevent this problem. Another option is to redesign the negative part of the mold so that it is two separate sections. The process of extracting the silicone would involve separating the two parts of the negative instead of pulling the positive out.
The current LabVIEW program produces pressure and flow outputs that were desired. The code has opportunities for optimization. Parameters such as stroke volume, compliance, and total peripheral resistance could be calculated using the current outputs within the LabVIEW program. The system’s manual controls are the turn valve, pressurizing the arterial tank, and moving the plunger of the venous tank. Purchasing additional motors and sensors could allow LabVIEW to control these actions from the front diagram. This would decrease the opportunity for human error during laboratory experiments.
Action Items for Gate Review
- Customer Meeting
- Documentation of Broken Mold Problem?
- Ventricle Molding Directions
- Disassembly Directions
- Electrical Drawings
- Pressure Sensor Manual
- Labview File Documentation (file name, location?)
- Final BOM Spend vs Budget
- Quantify Results Documentation