Cooperation with profiles.MicheleLanzetta (UniPisa)
Chronology
September 2018 ECM tests in Stanford
January 2019 Transverse engraving with sharpened WC tool, tip still > 3-4 mu Big deformation of contiguous grooves on plastic Even bigger on aluminum
June 2019 Blank and diamond coated blades received (Mark's visit in Pisa)
September 2019 Stanford (Arul's) blade holder has been manufactured with our CNC in Al, preliminarily simplified (without adjustment on one degree of freedom, because tests will be done on 5-axis CNC)
October 2019 Modeling and tests on soft material (plastic) with regular blades
Modeling
[Link to paper Microwedge Machining for the Manufacture of Directional Dry Adhesives] introduces the process with wax
Problem is between
- machining [papers on well known Merchant and Shaw's theories (mid 1900s) and
- indentation [some attempts in the literature, not consolidated theory available)
It is not one of the two, but a mix of the two, a new problem
Other peculiarities of the tool
- knife or blade (small cutting angle beta)
- sharp edge - small edge radius
- low wear expected, tool material is much harder than cut material (e.g. for plastic as it was for wax)
FEM are limited because of the subjectivity of identifying the cracking node in the mesh (known since the 1970s)
Some theory is necessary to identify some dominating parameters in order to optimize the trajectory and interprete results, e.g. the blade angle fi vs the groove slope
Some quick stop test would be required, how to?
Each new groove harms the previous one, so the sequence should be defined (up- or down-wards)
The blade engagement is like the activation of cutting but we stop the process during the transitory
One side of the groove is smooth no problem, but there is material accumulation on the opposite one, due to the compression inside the material
Inward and outward trajectory should be defined
- inward to achieve smooth surface, and prevent damage on previous groove
- outward to not damage the new one and maybe spoil the opposite surface to avoid self sticking