Given the fragility of gray iron, how is possible to improve the surface finish, if during cutting chip seems to be torn from the cutting surface?
I assumed that you used carbide insert, to answer you.
You should try the coroguide 2.0 on the sandvik coromant web site. It will suggest you some cutting conditions for your gray iron turning operation for the one you have to no the cristallographic state (as cast, stabilized, for instance). This will allow to compare the given values with the one you use.
I suggest Sandvik as I know and use it with my engineering students in machining.
It is a freeware.
Considering turning application of grey cast iron, I would say the most common application is Brake disk and brake drum machining. As an application engineer I have tested Ceramic tools (Sialon grade) as well as CBN tools on the mentioned application to improve the surface quality of the components, since they can operate in higher cutting speeds than carbide tools. considering the cost per components as well, I may say Cermaic tools are more economical solutions for the application.
Thank you Mehdi. What happens with the surface roughness when you change cutting parameters, when you modify the type of cutting edge and so on?.
Total roughness Rt (=5*Ra for steel) can be controlled by feed rate f (mm/tr) f=(8*Rt*re)^0.5 (Rt, in mm) and edge radius re in mm of the insert. For finishing operation, kappar angle choice will present chips to run on the finished surface. Cutting speed is usually increased in finish according to roughing. Minimal chip thickness and feed rate are also important parameters to insure a stable cutting process, the surface finish and reduce tool wear. To go further, material cmc code and heat treatment , is required to choose insert geometry (NB : different of form).
At the moment I don't have quantitative results of the test to present you. but in the application of turning of a brake disc using CBN tools by decreasing the feed rate and increasing the cutting speed around 1000 m/min(at least 2 times more than carbide tools) the surface finish and cycle time have been improved.
Some further informations suggested by Sandvik with their inserts.
I hope it could be useful.
In my opinion, good cutting conditions of special materials are often a treasure. Precise Information is kept secured by the product manufacturer.
Tests are essential to obtain the finish you're looking for.
Bests regards
http://www2.coromant.sandvik.com/coromant/pdf/Metalworking_Products_061/tech_a_8.pdf
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