Wood milling forces/power 1

[flapman]

Usually, in machining calculations, the cutting force made by materials are calculated this way:

F = K . S

Were K is the machining strength of the material to be cut (N/mm2) and S is section for the removed chip.

K is tabulated usually for steel and metals in a lot of books, however I need to know this K for general wood.

Can someone help me?

 

[Viktor]

Dear flapman
I will help you out. Would you please explain me what is that “the machining strength of the material to be cut” – Is it a new mechanical characteristic of material?
Regards
Viktor

http://viktorastakhov.tripod.com

 

[flapman]

Thanks, Viktor. Yes, that's the definition. Usually it is used K= k.R (where R is the standard tensile strength and k an adimensional constant for the material). We have also S= w.t (where w is the width and t is the thickness of the removed chip).

 

[Viktor]

Flapman, dear fried
Do you really understand what your answer implies? In lay language it means that the cutting force for a given chip cross-sectional area (width of cut times uncut chip thickness) depends only on the tensile strength of the work material. Whatever you do in terms of altering the cutting regime (speed and feed), tool material, tool geometry including rake angle, use coolant, etc. – all this does not affect the cutting force. Please explain me the issue – I would love to gain some knowledge on the matter.

Thank you
Viktor

 

[flapman]

Well, the equation should be valid for its purpose, and the only application can be to have a relation force-chip dimensions, so you are totally right, I need to be more specific.
My particular application is a wood milling machine with 4 mm thickness of blade and around 104 mm diameter, this machine is only for plunging in the wood up to 22 mm (no lateral movement). I have 2 targets:

1. To design the most appropiate cutting blade (nber of teeth, angles of cutter) for wood. These must come from usual recommendations in woodworking and I found some info about it in

http://www.woodweb.com

(only cutting angle, not the other angles affected).
2. To calculate the motor requirements for the application and optimum machining conditions. Here is where I need the formulae. I know that motors 620 W and 11000 rpm should be ok but need to justify. I have some clues from Hutte Engineer Manual (based on sawing bibliografy) but the aproximation is too rought, so I would like a more complete formulae.

I would appreciate your help in both lines
Thanks for your interest.
Eduard

 

[flapman]

I have had a look in your web page and is very useful!. For example, just to specify more clearly the meaning of my first question, take last page of your link at "Machining parameters" (Mitsubishi carbide), I tried to find the kc (cutting resistance) for wood, only metals appear there.

kind regards
Eduard