P18352: Sandia Passive Vacuum Detection Team B
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

During this phase the team is planning on proving that the system is sealed correctly and that the diaphragm can deflect to the amount desired. To do so, the vacuum chamber will be employed, dropping the pressure down to the activation point. If there are any issues with sealing the system or the diaphragm deflection they will be addressed in this phase. This is a critical step towards setting up the magnet system for the increased popping motion that will be generated.

The team verified the operation of key subsystems on the vacuum safety switch. The chamber within the switch can seal and maintain pressure when subject to vacuum, and the diaphragm can throw the toggle switch.

Test Results Summary

Pressure Safety Switch Prototype

The pressure chamber prototype was fabricated and assembled by Team VAST in the KGCOE Machine Shop. The team utilized the Prototrak Mill and Lathe to turn the aluminum stock into the chamber prototype seen below:

Full Assembly of Chamber for Vacuum Safety Switch

Full Assembly of Chamber for Vacuum Safety Switch

Kapton Diaphragm Jig

A jig was created to ensure the same size diaphragms are cut from the Kapton sheet. This jig will also ensure that the steel disc is adhered to the center of the diaphragm.
Drawing of Diaphragm Cut-Out and Disc Locating Jig

Drawing of Diaphragm Cut-Out and Disc Locating Jig

Diaphragm installed on pressure chamber body

Diaphragm installed on pressure chamber body

Pressure Safety Switch Testing

The switch prototype was run ten times in Dr. Gomes' bell jar to check the basic functions of the system.

The first tests of the switch prototype were performed to ensure that the switch was sealing. The team determined that the switch did not have a perfect seal when the diaphragm was not swelling. Once the lower magnet adjuster bolt on the bottom surface of the switch was sealed with superglue, the diaphragm began to swell as anticipated. The system was also left in the chamber for 30 minutes at vacuum, and remained sealed through this test. Although the switch prototype has been sealed successfully, supergluing over the lower magnet adjuster is only a temporary fix, as this bolt will need to turn in order to dial in the system. The team will discuss design changes that may need to occur to create a perfect seal and still allow for adjustment.

Verification of Diaphragm Displacement in Vacuum Chamber

Verification of Diaphragm Displacement in Vacuum Chamber

The next set of tests ensured that the diaphragm deflection was sufficient to trigger the switch. The lever arm and switch were installed on the switch prototype. The system was then placed in the vacuum chamber and evacuated. The diaphragm can throw the switch, but this activation occurs far too early in the cycle. The group will proceed to install the magnets and begin to calibrate the system to delay the activation of the switch.

Pressure chamber testing in bell jar

Pressure chamber testing in bell jar

The toggle switch was also tested to confirm that the contact resistance was less than the 2 ohm maximum specified by the customer. The contact resistance was less than 0.6 ohms, well within this specification.

Risk and Problem Tracking

Risk Management

Risk Management

Problem Tracking

Problem Tracking

Full Documentation:

Risk Management

Problem Tracking

Functional Demo Materials

Subsystem Review Presentation

Switch Activation Video

Plans for next phase

The team needs to determine the best way to seal the chamber while maintaining adjustability of the bottom magnet.

The team will start working on the magnet system and hopes to achieve a fulling working and reliable system by the next review.

Each team member is committed to testing and working on the system almost every week day. We have made great strides over this phase by verifying the operation of crucial subsystems, but have a great deal of work left to make the switch fully operational.


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