# Thread: 40 IPM is the max?

1. ## 40 IPM is the max?

OK....here are the assumptions I am making:

1) The max # of flutes on an endmill would be 4 (perhaps this is wrong?)

2) The maximum chip load (roughing) is .005"

3) The maximum RPM for an X3 is 2000 RPM

So....the formulas are:

IPM = RPM x IPR

IPR = Chip Load x Flutes = (.005" x 4) = .02"

Therefore:

IPM = (2000rpm) x (.02") = 40 IPM

So why should my cnc mill be capable of 100ipm + ?

What is a good maximum limit for IPM on an x3?

Thanks!

2. Originally Posted by caleb105
OK....here are the assumptions I am making:

1) The max # of flutes on an endmill would be 4 (perhaps this is wrong?)

2) The maximum chip load (roughing) is .005"

3) The maximum RPM for an X3 is 2000 RPM

So....the formulas are:

IPM = RPM x IPR

IPR = Chip Load x Flutes = (.005" x 4) = .02"

Therefore:

IPM = (2000rpm) x (.02") = 40 IPM

So why should my cnc mill be capable of 100ipm + ?

What is a good maximum limit for IPM on an x3?

Thanks!

youve left out alot of data.

the size and type of cutter, along with the type of cutting and material being cut will impact the feed per tooth. for example 2 flute 1/2 emd mills can range from .001 recomended feed in HSS to .04" (not a typo) on some fancy carbide ones for aluminium cutting.

2000rpm is definitely a limiting factor though and with typical hss tooling 40ipm would be optimistic on cutters under 1/2". you can certainly force the machine faster (ive done that by accident), but the tool and workpiece wont thank you and neither will the gears in the spindle head.

3. When you are not in a cut but positioning between cuts (or moving to a tool change position, etc., i.e. cutting air) you will appreciate having fast travel rates, but on a machine with a small work envelope it becomes less of an issue. On an X3, you will likely never approach 40IPM in a cut unless you are machining butter (or aluminum with a high speed spindle). You will certainly never be taking .04" per flute. That would twist an X3 into a pretzel and you would be replacing inserts every pass. My RF45 with servos maxes out at 80IPM but it seems like an eternity when rapiding from one end of the 22" x travel to the other, but is in fact only 15 seconds or so. In a production environment, this would cost me some profit, but for a hobby machine (which mine is) it's acceptable. Other than that, it's just a bunch of chest-thumping. That said, I tuned mine way up when I got it and had to back it down to it's current reliable setting.

Joe

4. Thanks for the info guys.....

So I should plan on about 40ipm being my max cutting rate, but make it capable of 80ipm when "cutting air"?

5. Originally Posted by caleb105
Thanks for the info guys.....

So I should plan on about 40ipm being my max cutting rate, but make it capable of 80ipm when "cutting air"?
for rapids, tune the thing to be as fast as possible without stalling and still having decent acceleration.

my little kx1 goes 100ipm rapids comfortably, but will do most cutting at 5-50ipm (5k rpm spindle) depending on materials and cutters.

6. 40IPM is plenty, just don't read the forums here too often.

7. A stepper-drive machine that is capable of cutting at 40IPM *should* be more than capable of doing rapids at 100 IPM, without doing anything special simply because the torque requirement for cutting is FAR higher than for doing a rapid.

Regards,
Ray L.

8. would it be possible to see thoes kinds of cut speeds in wax?

I've thought about using machinable wax to make a couple molds, and having never even seen machinable wax before, i have no idea what kinds of speeds to plan for...

9. Originally Posted by caleb105
So why should my cnc mill be capable of 100ipm + ?

What is a good maximum limit for IPM on an x3?

Thanks!
There is no maximum limit for IPM. High IPM is a measure of the drive/motor efficiency. Good efficiency equals lower chance of missed steps. It is NOT just about cutting speed--Cutting speed will be influenced by material and force/spindle-speed required. Inefficient systems may not be able to provide sufficient force to cut at optimum rates without stalling and missing steps.

FIRST: Understand that YOU can always set the upper limit of your IPM by software control. You can easily slow down an efficient CNC. It is very difficult and often very expensive to SPEED UP an inefficient CNC.

High IPM really saves time when your spindle has to move from one place to another without cutting. Time saved always translates into money saved during production.

If you have lots of time to waste, have no intentions of ever doing any kind of production, will NEVER want anything like an automatic tool changer (or multiple fixtures) and/or are not dealing with a large area to cover like on a router--Then by all means limit your upper rapid speed. But do it in software--NOT by crippling your machine with inefficient components.

CR.

10. Originally Posted by Crevice Reamer
There is no maximum limit for IPM. High IPM is a measure of the drive/motor efficiency. Good efficiency equals lower chance of missed steps. It is NOT just about cutting speed--Cutting speed will be influenced by material and force/spindle-speed required. Inefficient systems may not be able to provide sufficient force to cut at optimum rates without stalling and missing steps.

FIRST: Understand that YOU can always set the upper limit of your IPM by software control. You can easily slow down an efficient CNC. It is very difficult and often very expensive to SPEED UP an inefficient CNC.

High IPM really saves time when your spindle has to move from one place to another without cutting. Time saved always translates into money saved during production.

If you have lots of time to waste, have no intentions of ever doing any kind of production, will NEVER want anything like an automatic tool changer (or multiple fixtures) and/or are not dealing with a large area to cover like on a router--Then by all means limit your upper rapid speed. But do it in software--NOT by crippling your machine with inefficient components.

CR.
Nice quotes from mariss CR, what do you use all of your machines speed for, ANYTHING? Anything at all? Examples please.

11. Originally Posted by chinli
Nice quotes from mariss CR, what do you use all of your machines speed for, ANYTHING? Anything at all? Examples please.
You think my words came from such a wise man as Mariss? I am HONORED sir!

CR.

12. Originally Posted by chinli
Nice quotes from mariss CR, what do you use all of your machines speed for, ANYTHING? Anything at all? Examples please.
Crevice reamer answered the question in your quote - getting the spindle from one cutting operation to the next(cuting air) justifies the rapid speed - especially when you are making more than one of something. On a part that takes ..say 10 minutes to cut when using 50 ipm rapids may only take 5-7 minutes with faster rapid speeds, depending on how often the spindle is repositioned for a different feature on the part. Any time the spindle comes off the work to start a new cut, fast rapids save time - picture peck drilling 20 holes, for instance. On a small machine with slow rapids, more time is spent moving the spindle up and down than actually "drilling", so any increase in rapid speed on the z axis will translate directly into the part production time. The same part on the same machine with the same peck drill parameters, but with faster rapid speeds can cut the time down by 50-75% easily. Now picture making 50 of these parts on both machines - the guy with faster rapid speeds is upstairs banging the wife while the "slow rapid" machine guy is hopelessly watching the z axis go up and down.

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