This week, I focused on the prototyping of my end effector's progress on its way to being a Tangential Oscillating Cutter. Following Neil and Nadya's suggestions of following "Sprial Development", I worked on getting a prototype to cut (straight lines) by oscillating first (with a DC motor) and next week I can focus on the tangential cutting (rotating the blade).
Laser Cut Cam Shaft
In order to understand cam designs and stroke geometries, this quick prototype let me play with different lengths.
After doing some math on the board with the help of Jack from the D-Lab Shop I was able to remember all the geometry relationships of cams. My prototype was at a stroke length of 4 inches and needed just a stroke length of about the thickness of foamcore, so about 0.2".
Hinge as Eccentric Cam
Thanks to Gwyn's help, I made a hinge with a bent nail to function as an eccentric shaft. The thickness of the nail and the thickness of the L-brackets I used to bend them gave me the Cam throw I was looking for.
Shaft Collar Coupling
I made my own coupling for the two shafts: the motor shaft and the eccentric nail to drive the hinge.
First I went for the design that used an olfa blade.
In an effort to mount onto the fabinabox and cut as soon as possible, I paused development on this blade holder and used Nadya's idea to start from an exacto knife. I made a cut and slit into the knife (it's just an extruded rod of aluminum in there, in case you were wondering!) and used a set screw.
Eventually, after some testing, the set screw let loose and didn't hold on. I went back to the shop and just made a through hole in the xacto knife and the leaf spring to run a bolt and nut through it.
I made some extensions and modifications to Ilan's multifab design for a vinyl cutter. Since the motor mount would need to flex to hold the motor in place, I used a delrin sheet that I borrowed from Nadya.
Finally, assembled altogether.
Movement with Button Control
First I got it to use a button as an on-off switch.
Oscillating Movement by itself, connected to power supply
Running on Arduino