Best practice feedrate?

I am wondering waht the best practice is for setting feedrate. Currently I have it as a parameter for all my ngcgui subfiles, but it can get tedious and make bookkeeping difficult as parts get more complex. I am wondering if subs should assume feedrate will be set elsewhere and inhereit it globally, by manually editing the result, or if a preamlbe can/should be made that sets feedrate? I would think is a subroutine needs to play w/ feed it can modify a local copy and leave it untouhced for the rest of the tools.

Just looking for input, what is smart and what is not. Writing subroutines is almost more fun than the actual machining right now.

I prefer to just set spindle speed and feed rates with each sub I create, you could use global variables, or a default value.
Keep in mind the same tool may use a different feed / spindle rates when machining different materials.

Rick G

somenewguy wrote: I am wondering waht the best practice is for setting feedrate.

It's a complicated subject.

I have found this web site to be fairly instructive:
zero-divide.net/?page=fswizard

It gives a pretty good feel for where the limit is cutting force or spindle power, and seems to have a database of what worked for other people.

Unlike most similar tools it doesn't assume that my spindle can do 20,000 rpm.

I just bought CNCCookbooks GWizard. It takes your machine parameters (i.e. spindle range and feed range) and your tool parameters (i.e. type of tool, diameter, # of flutes, etc) and calculates the slowest possible feed (i.e. just above where the tool starts rubbing) all the way up to an aggressive feed--you set the slider to one of four positions.

It has been very handy, and I'd recommend it. I'm not affiliated, just a happy customer.

cnccookbook is a great site and that tool does look amazingly useful. How much did the software cost you? I made my own very very simple version of it in a spread sheet, but being able to just trust someone elses hard work would make me a lot more productv.e

However my original question got misunderstood I think. I was wondering if I have a bunch of subroutines, should they all require I give them a feedrate to operate, or should they all require feedrate be set prior to calling them. I feel like the later is more practical, if you need to chain 10 or 30 subs together it is easier to set and forget, but if you lose the granularity.

somenewguy wrote: However my original question got misunderstood I think. I was wondering if I have a bunch of subroutines, should they all require I give them a feedrate to operate, or should they all require feedrate be set prior to calling them.

To an extent you could set SFM and cut per rev globally, and have the sub calculate feed based on the tool data. However that would always be wrong for very delicate or very massive tools.

I guess it depends on how similar to each other your tools are. I swap from 0.5mm engravers to a 100mm side and face cutter. Different factors pertain.