HP, Torque, and SFM

[mcrae_andrew]

From our other post in the Efficient Roughing Catagory, I would like to find out how people like to process their jobs.

Each machine will have a given amount of available horsepower. As we know that HP=Torque*RPM, what is the preference for size of cutters.

I Had a job that lost big because I choose wrong and I would like to see how others do it. (Used a 5 Inch cutter where a 3" should have been). The diameter of the cutter needed to keep the rpm down (SFM) and so the machine ran out of torque to drive the cutter at a nice MRR. A 3" would have smoked along at a better DOC and maintained the same MRR or better. Lets develop the mathematical model for this and sell it to CNC Software (Can't disclose a price here on the WEB!).

Andrew

[ 10-15-2001: Message edited by: mcrae_andrew ]

[Guest CNC Apps Guy 1]

Sounds ike a good idea Andrew, but doesn't High-Feed have MRR calculations in it?

Many factors go into the M aximim Metal Removal rate for a given cutter. Geometry needs to be taken into account. Maybe shear angle could be part of the equasion?

On another note, I've noticed that some machines that specify, say, 10HP don't have adequate torque through a large enough range in the curve range. I'd think some tests would be required to get some data to work off of.

JMT for now

[Michael Reynolds]

Hi Andrew,

First of all, you have to differentiate the horsepower at the motor from the hp at the spindle. When you buy a machine, the seller usually tells you the hp at the motor, but by the time torque is transmitted thruough belts -n- stuff, you lost sometimes half of your hp. So, if you know the efficiency rating of the motor, you can figger out "what the machine is capable of". This is a link to one of the pages in my web site, & it'll get you close.

http://cadfree.corning-cc.edu/~reynolds/ma...%20formulas.xls

Hope this helps!

Mike R.