Tip grabber

Of all the parts of the STM, the tip grabber was probably the most difficult to design and went through the most iterations. The idea is that the grabber will be loaded into the microscope like a sample holder, at which point its pincers will open to release a tip into the microscope, or close to remove one. The pincers need to open as wide as possible, but there’s very little space for the mechanism … this is our best solution so far.

A single compression spring is held down by a retaining ring (both from McMaster-Carr) to provide the force that closes the pincers. The pincers are opened by advancing a 0-80 screw that is threaded through the back knob. This screw is turned by the same linear-rotary feedthrough used to move samples around, by picking up an adaptor holding a short Allen key.

The retaining ring is the weak point of the design; sometimes the base piece is printed with a deep enough groove to hold the ring securely, and sometimes not.

Autodesk Inventor files are here. STL files (for 3D printing) are here.

(Assembly instructions coming soon.)