Gehring Technologies GmbH recently introduced a surface finishing process for internal combustion engines that reportedly reduces carbon dioxide emissions through form honing.
Rather than target a cylindrical bore shape, the form honing process produces a bore shape "based on the distortions of the geometry under operating conditions of the engine," according to the company. "Through the means of form honing, the reverse shape will be produced so that in running conditions, a cylindrical shape exists. The thermal expansion due to the higher taper in the top dead center leads to a cylinder bore which has to be honed to a smaller size at the top and a larger size at the bottom.
"Thus, the piston shirt has less contact with the bore. This results in significantly less friction."
Gehring's form honing process works with newly developed process hardware, including:
- special honing tools with shorter abrasives
- dynamic stroke control
- dynamic electromechanical expansion system
- spring-mounted finish honing tool
"The conical shape is generated by feedback controlled stroke displacement with higher stock removal in the lower bore section due to increased contact time of the abrasives," accorindg to Gehring, which introuced the new process in September at EMO in Hanover. "The dynamic electro-mechanical feeding changes the radial expansion position of the honing stones during the stroke movement according to the form and improves herewith the previous conical shape."