Best practice feedrate?

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03 Jan 2014 04:14 #42301 by somenewguy
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.

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03 Jan 2014 15:48 #42311 by Rick G
Replied by Rick G on topic Best practice feedrate?
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

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03 Jan 2014 20:09 #42319 by andypugh
Replied by andypugh on topic Best practice feedrate?

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.

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04 Jan 2014 09:51 #42338 by tenaja
Replied by tenaja on topic Best practice feedrate?
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.

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04 Jan 2014 10:29 #42340 by somenewguy
Replied by somenewguy on topic Best practice feedrate?
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.

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04 Jan 2014 10:42 #42341 by andypugh
Replied by andypugh on topic Best practice feedrate?

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.

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04 Jan 2014 10:55 #42343 by somenewguy
Replied by somenewguy on topic Best practice feedrate?
this is one of those "now that I have asked this question out loud, it sounds dumb" moments, which Iahve alot. It's why I love IRC. Sometimes evne when the channel is empty I get my answer... Anyways I will ALWAYS ask for tool settings to bepassed to the subroutine, hopefully I never have a situation where I run out of 30 variables. The (now) obvious logic being that in a file I can simply set a variable #<feedrat> and pass it to each sub individually. then I only need to change it in one place per file, or every sub can be unique and non-ambiguous. The only real issue left is I don't konw for a fact that I can pass a variable to a subroutine, however NGCGUI is happy to do it for me, so hopefully this is defined behavior. Time to go restructure all my subs slightly.

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04 Jan 2014 10:57 #42344 by somenewguy
Replied by somenewguy on topic Best practice feedrate?
oh and driving it by SFM and IPT sure would be sexy, but my machien doesn't have spindle speed control or a huge range of speeds, so my commands will be less automagical. However when I finally do upgrade and get a VFD and all the other things I dream of, that sounds like a reaasonable idea.

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04 Jan 2014 16:49 - 04 Jan 2014 20:12 #42347 by Rick G
Replied by Rick G on topic Best practice feedrate?

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.


Perhaps not by everyone.

You can of course use a global variable. Or a preamble sub to set the feed rate once and then forget it. If there are no tool changes the feed rate may stay constant at which case just set it once.
Some subs might be called from the main ngcgui sub in which case the feed rate can be passed on with the call.
However I add the spindle and feed rate fields to all subs just to confirm and to edit if I want to use a different rate perhaps for finishing or final pass.

Also if you have the same name for the parameter in all your subs after you fill it out the first time it can automatically be filled in on the remaining subs.

.....
#<feed> = #1 (= feed)
.....


Rick G
Last edit: 04 Jan 2014 20:12 by Rick G.

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06 Jan 2014 06:18 #42375 by somenewguy
Replied by somenewguy on topic Best practice feedrate?
I am going the preamble route, as it makes the most sense, and all my subs will accept a '0' input on non-sensical inputs to mean "do not alter current setting". I have very little control over my machine (manual tools, belts for speed, etc etc) so 90% of my worrying is about future proofing my code and learning how to do things "right" now while it doesn't matter.

also in 2.5.3, the sub will accept #<namedparam> as input, however it will NOT accept #<namedparam> inside of NGCGUI. It also wont let me type the letter 'd', it just adds 0.0000 and lets me fill it out like insert, which is a cool feature but I had no idea it existsted and its not in the list of keybindings. what is it and can I turn it off?

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