A couple of problems were discovered this week. 

Firstly, the pipette setup needed to be adjusted for height, as it exceeded the required setup dimensions. Our base was about 1 cm taller than the maximum permissible height. However, reducing the height on the base side was not feasible because the magnetic stirrer base was already at its lowest possible setting. Any further shortening would interfere with the stirrer’s operation. Additionally, while the pipetting action was functioning as intended, the tip-removal process remains problematic due to stability issues. Thus, necessary components were reprinted to enhance stability for further testing on Monday.

Firstly, several modifications were made to the pipette system design. 

Initially, we considered an alternative to keep the system within height limits by shortening the beaker side—specifically, indenting it to make the overall setup shorter without impacting the magnetic stirrer’s height. However, even with this adjustment, we still needed to account for the magnetic stirrer’s fixed base height and could not proceed with this. Thus, we decided to increase the pipette’s default height instead, allowing the setup to remain within operational constraints. For this, additional adjustments were required, including recalibrating the height of the bracket and pressing the pipette buttons to ensure proper alignment. 

Corresponding changes were made to the magnetic stirring system as well. The panel holding the beakers were altered to ensure a more consistent height between the beaker and the stirrer base. This adjustment improved the consistency of the magnetic stirring compared to previous setups. However, the magnetic stirring was still a tad inconsistent occasionally, due to slight manufacturing differences in the beakers. 

Then, the tip-remover component was reworked a little bit through recalculating the coordinates of the pipette tips, as it initially wasn’t aligning correctly. 

Additionally, a change was made to the angle of the motor controlling the bracket pressing down the eject button for pipette tip removal to increase force application, compensating for an observed weakness in motor strength.

However, we quickly realised that while our stepper motor slider generated insufficient torque. This was an issue, as to press the suck and eject buttons of our pipette, a certain amount of force would be required to overcome the button’s resistance. Thus, as our current motors and stepper motor slider were unable to generate enough downward force to consistently engage the button, they were unable to facilitate proper sucking of liquid and ejection of the pipette tip.  

Despite our best efforts, our stepper motor slider was simply unable to work. Often times, professional grade stepper motor sliders are geared, where they combine a motor with a gear system, which modifies the output torque and speed. The gears work by combining different-sized gear wheels together to change the rotational speed and force. Thus, when a motor is geared down, the output speed is reduced, but the torque is increased. This function was not present in our stepper motor slider, which probably contributed to the problem of insufficient torque being generated. 

Thankfully, we were able to obtain a spare stepper motor slider from another group. From there, we used our existing pressing bracket design, and screwed on pressing brackets to the motor. This seemed to do the trick, where both our sucking and ejecting mechanisms worked!

With these changes, we will continue testing next week.