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The testing system consists of a fixture containing a heat sink, an air-tight shell, and swappable periphery seal adapters. The heat sink contains two heating cartridges controlled by an RTD and an Arduino. The P&ID control loop can be set to maintain temperature from ambient temperature up to 175 C. The seal adapters allow for multiple types of seals to be tested.
The entire fixture is moved vertically by a stepper motor, which rotates a threaded rod. The stepper motor actuates the fixture to predetermined positions, and incorporates a hard stop at the bottom position. This hard stop is fixed to a pedestal, which contains springs. These springs provide compliance in case of motor overdrive due to skipped steps in the motor. Emergency stop switches are also included at to top of the linear rod for reference position and homing, and a switch at the bottom and to prevent damage to components in the case of overdriving.
Vacuum and blow-off are delivered to the fixture through a single flexible silicon tube connected to a solenoid valve that switches between separate vacuum and blow-off pumps. A pressure transmitter in the main airline allows for an Arduino to record whether the chip has been picked up and whether blow off has been achieved.
Figure 1: Overview of testing system CAD
Figure 2: Cutaway view of testing system
Figure 3: P&ID of Testing System
Figure 4: Final Bellows Profile
Figure 5: Final Bellows Dimensions (inches)
Figure 6: Final Bellows Overview
Figure 7: Bellows FEA Test; Max Von Mises Stress: 4.886e+07 Pa
The final bellows design consists of a 40 x 40 x 8 mm rounded square, made from Servometer’s Flex Nickel. The internal geometry has baffles that are 1.27 and 0.889 mm in diameter and a depth of 3.175 mm best seen in Figure 4. SolidWorks static FEA with shell element meshing was used to find the stresses on the bellows and to iteratively improve the design. The bellows were deformed by a 2.5mm fixed displacement, more than 1.5 times the amount that the bellows would experience in normal operation. Displacement shown is 1:1. As can be seen in Figure 7, the static factor of safety is greater than 15. This indicates that the bellows are nowhere near plastic deformation, and are able to be subjected to many cycles without failure.
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