Part 1: Solution Strategies
Strategy 1: "L" Shaped Desk
The first strategy I explored was a desk on the ground, with a rail and a cantilever tabletop as shown in the image.
Lead Screw Estimation:
Bearing Length Estimation:
The predicted error from the error apportionment for bearings under geometric sources of error were used to determine the length of the bearing/slider for the vertical axis .
The dimensions from the result were used to prototype a precision linear axis. (See Week 3: Hardware)
Structure Stiffness Estimation:
With the initial dimensions, the stiffness of the desk was significantly lower than the desired stiffness. The resonant frequency of the desk was close to that of human organs, which would be a very un-favourable design. Modifications were made to the design to include truss shapes to reduce deflections and increase natural frequency.
Bearing Stiffness Estimation:
Following my first order analyses, I am confident that this design will achieve the required functional requirements.
Part 2: Precision Linear Motion Axis with Actuator
Objective: Design actuator location on linear motion axis
Ideally, for smooth travel, it is best to have the applied force along the centre of friction. Given the thickness of my current slider, I do not think it will be possible for me to have the actuator (lead screw), pass through the middle of the slider.
However,as the thickness of the slider for my desk will be double the current thickness, it might be possible to actuate the slider along its centre of friction.
Part 3: Peer Review
I received valuable feedback on my analysis of strategy 1, which led me to make changes to my spreadsheet.