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!

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.

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

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"?

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.

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

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.

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...

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.

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.

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.

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. :)

i was asking to see examples of what HE does with his superfast machine.
seems to just be a poser with lots of links to what other people do.

i was asking to see examples of what HE does with his superfast machine.
seems to just be a poser with lots of links to what other people do.

If his information helps someone, who the hell cares?? Aren't we all here to share information, regardless of where it comes from?

Good information is good information - who cares if the source is actively using the info or not? A boxing coach would probably get his butt kicked by the boxer he trains - does that make him a bad coach?

i was asking to see examples of what HE does with his superfast machine.
seems to just be a poser with lots of links to what other people do.

He didn't say anything about his superfast machine. He didn't say anything about super fast at all. His points about rapids are well taken and good information. The speed at which your machine can traverse without cutting IS a factor in many jobs. To argue that it's not is simply foolish. The 200IPM rapid machine I work on runs the same program slower than the 600IPM machine. If you are trying to produce something for sale, or even for yourself, it makes a difference.
Maybe you might spend more time posting useful info and helping folks instead of trying to point out the flaws in others.

Wow.....someone with 8 posts calling someone with 1,200+ posts a "Poser"?

:nono:

"Poser - Someone who likes to talk big, and look good, but doesn't do much."
1200 posts worth of copy and paste.
but thats alright, a link ferret is also useful.
someone who's a shill and talks people into buying a product should at least use that product though.

rapids speed does play a part in how quickly your job gets done, but the cutting speed is more important to me. I mean, i can do rapids at over 100 IPM, and thats handy, but what i really need is to increase my cutting speeds, cause thats where i spend most of my time. I guess the ratio of rapids to cutting speed varys depending on the job, but i would think it would have more to do with how you program it.

if what i have read is true, (and i'm not doubting it, i just havent tried it myself yet, so i cant testify) if you can just swap the motor pullys and double the spindle speed, then that would help to serve you in increasing the cutting speed. This may or may not be a good idea depending on what, and with what you are cutting. if your doing alum, and using larger endmills, then i dont know that increasting the spindle speed is a great idea, but if your using much smaller endmills, then a speed increase seems to make sence to my mind.

The bottom line is that you have to balance what you need and what you want with what you can afford, and what your skills limit you to.

In my situation, i need a reliable machine, i want a fast reliable machine, but my pocket sais i can have reliable, but just not as fast as i would like, and my skills say i have more machine than i know what to do with. But i can learn and help balance the equasion.

if what i have read is true, (and i'm not doubting it, i just havent tried it myself yet, so i cant testify) if you can just swap the motor pullys and double the spindle speed, then that would help to serve you in increasing the cutting speed.
While it may certainly be possible to simply swap pulleys like this, keep in mind that you don't get "something for nothing". Taking the same motor and the same torque curve, and simply trying to use it at higher RPM may not work out the way you like. If you've got all kinds of RPM and the spindle stalls during the cut, you are no better off than had you just left the motor where it was happy to operate and let it take longer.
The other thing to keep in mind is that although increasing the RPM will increase your feed speeds to a point, there will be other limiting factors. If your machine can't stay rigid though the cut, higher feeds are useless. These machines are complex inter-related systems. It's important to keep in mind which ones will limit you as you change the others.

escott, your right, but in mycase, where i spend 90% of my time running 1/8" and smaller endmills, i dont think im in any danger of rigidity issues.

I am aware that my increasing the rpm in this manner will reduce the available torque at the EM, but do you really think its gonna be an issue on a 1/32" endmill, or even a 1/8"?
I dont.

and on thoes rare occasions when i do use an EM larger than that, i still have low range in the gearbox to go to when i need more torque. Yes i know that it'll be less, but still, doubtfull i'll go there.

its just like a transformer. you can up the voltage, but have less available amperage, and vice versa.

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


3) The maximum RPM for an X3 is 2000 RPM




Always challenge your assumptions. 2000 rpm max is very poor performance in Aluminum, plastic, or wood. It may be OK in soft steel with large cutters, but with small cutters it is way too slow.

Mount a 30,000 rpm spindle on the side of your spindle casting and see how your calculations come out. Even a 10,000 rpm spindle will multiply your max ipm by 5 times.

Fred Smith - IMService
http://www.imsrv.com

its just like a transformer. you can up the voltage, but have less available amperage, and vice versa.
My point is that it isn't always a linear relationship. Technically neither is a transformer, but a motors curve generally looks a little funkier.
Small EM are crappy for a variety of reasons, and machine rigidity will play a role in how fast you can ultimately go regardless of spindle speed. Don't forget that you are still moving something around, and that thing has weight and therefore inertia. If the mechanics overshoot a couple tenths on a half inch endmill nothing happens. That same overcut on a tiny one can kill it.
Again, these things are a total system, and you can't look at parts of it like they are in a vacuum. It's not to say that making your spindle faster isn't a good idea, just try to keep the big picture in mind ;)

absolutely agree. the one thing that i will say is that if you have enough lash in your movement system that you can overshoot by a couple tenths of an inch, perhaps spindle speed shouldnt be the first concern.

absolutely agree. the one thing that i will say is that if you have enough lash in your movement system that you can overshoot by a couple tenths of an inch, perhaps spindle speed shouldnt be the first concern.

Probably the meaning in escott76's 'tenths' is tenth of a thousand, in other words 0.0001".

In machinist 'lingo' tenths are .0001" and 1/10 of an inch is a hundred thou.:)

escott, your right, but in mycase, where i spend 90% of my time running 1/8" and smaller endmills, i dont think im in any danger of rigidity issues.

I am aware that my increasing the rpm in this manner will reduce the available torque at the EM, but do you really think its gonna be an issue on a 1/32" endmill, or even a 1/8"?
I dont.

and on thoes rare occasions when i do use an EM larger than that, i still have low range in the gearbox to go to when i need more torque. Yes i know that it'll be less, but still, doubtfull i'll go there.

its just like a transformer. you can up the voltage, but have less available amperage, and vice versa.

"i dont think im in any danger of rigidity issues." - Don't be so sure.... One of the things that can kill tiny endmills is vibration, which is related to rigidity. Small vibrations that can be absorbed by a large endmill can quickly fatigue and break a small one. At 1/32", even a few tenths can do it. Spindle runout is another critical factor, for the same reason.

Regards,
Ray L.