Originally Posted by SRT Mike  I am turning 6061 Aluminum, to a finished diameter of around 2.25". The part is around 3" long and it is an arc (it ends up being something of an egg shape).
Any recommendation on how to get the absolute best surface finish? Machine is very big and rigid - Okuma LC40 and has a max spindle speed of 2500RPM.
What type of insert should I use - what geometry and (if applicable) what coating on the toolbit insert to get the best finish? What about the feed and speed?
The parts are going to get anodized later so if I can get a ready-to-anodize finish it would be perfect! |
Lower your RMP to about 1200. Then Feed at .002 IPM with a .008 Tool Nose Radius. You will have to play with this to get the best finish while maintaining good production. This will give you around a 20 Micro Finish.
The Egging is being caused by Vibration in the Spindle which was more than likely hit a few times. Or the Bearings might be a little sloppy from many hours of use.
Also if this Shaft is long and you are using a Live center make sure it isn't a cheap one.
The only way I have found to take the Slop out of a Spindle is to reduce the RPM and try to maintain a productive run off of parts.
Inserts, try Sandvik. The Carbide Grade should be a C1 with a Positive Rake and a good Coating like TiALN. This coating keeps material from welding itself to the insert land at the Nose Radius. You will have to know the Size Insert for your tool holder too.
My best guess is that your machine has 1 inch tool shanks with CNMG, DNMG, or VNMG style Inserts. If so you will be looking for CNMG430.1 ANSI Designations for the .008 TNR.
Oh, it is wise to use a depth of cut that is slightly more than the Nose Radius. so be sure to leave enough for finish.
Cheers!!
