10:1 ratio long tools 2

[kyleb77]

We are having a bit of trouble kellering deep pocket walls with tools that have 10:1 ratio length to diameter. Does anyone know what tool holders are more rigid. Deflection is happening even at slow feedrates. Spindle will go 24000 rpm max. We tried a .500 endmill .120 radius 10:1 ratio reduced tapered shank and even at 20 ipm we had alot of deflection. Any help we be greatly appreciated

 

[jck26]

It's all about tooling forces and damping vibration. If your not using cabide you are missing a material that is 3x as stiff as steel. This will greatly reduce deflection. I'm not familar with "Kellering" so I'll keep my comments general. The deflection equation is against you since deflection is a cube of the length of overhang. You need to review the design of the tooling to minimize the tooling force that act normal to the spindle axis.

As for tool holders, if you are running at 24K rpm I'm guessing you're using HSK style holders. Additionally the tool must be balanced so that the rotational vibration does not combine with the vibration induced by the cutting process.

Also the speed, feed and DoC (depth of cut) must be examinied. This is critical in controling your problem. Talk with tool suppliers since the cutting geometry of the tool will greatly define the tool forces that drive vibration from a very large L/D ratio tool.

 

[Pressed]

Just some light reading.

[URL unfurl="true"]http://www.millstar.com/product_info/product_info_nonflash.htm[/URL]

[URL unfurl="true"]http://airy.pec.ncsu.edu/PEC/research/projects/small_mill/aspe1999_abstract.pdf[/URL]

[URL unfurl="true"]http://airy.pec.ncsu.edu/PEC/research/projects/force_feedback_tool/index.html[/URL]

[URL unfurl="true"]http://www.moldmakingtechnology.com/articles/030401.html[/URL]

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[PeaceLoveTreehugging]

There are tools available that have a shank form Densamet (High density Anti-Vibration material) greatly reducing vibrations on big overhangs. However these are also very brittle (and expensive) and great care needs to be taken limiting side forces.
Combining this with a shrink-fit toolholder for a stiff assembly that has good balance and run-out and you might get there (or at least near your 10:1 ratio needed).

 

[EnglishMuffin]

Talk to Kennametal.

http://www.mmsonline.com/articles/1196scan1.html

They have made special purpose long rotating tools with built-in vibration dampers. They are touchy to set up. Same concept has been used for a long time on non-rotating boring bars.

 

[toolingguy]

that .120 radius on the edge of your tool prevents decent penetration of the cutter into the material.
-try smaller radii and increase feedrates.
-what shape is your spindle in?
-locating tapers ok?
-try a 3 flute cutter.
-buy a 5 axis mill

 

[kagan]

http://www.schunk.de

They have a toolholder system which name is Tribos. Once a time I searched the min tool holder diameter for the same shank in a group consist of shrink, tribos, weldon, hydrolic types. The result was tribos.

The deflection equation is against you since deflection is a cube of the length of overhang.

Jck26 is definitely right. Prepare your tool with min length. If you have an extention, cut its length that you don't need. But please consider the min shank length requirement when you decide to cut it. Also reducing the cutting speed can be a solution for the long tools. Max DOC must be 0.3xDiameter but you can reduce it according to your conditions.

 

[tomwalz]

Try a cermet or a ceramic for sharper edges, and higher lubricity.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com