US: What's a good powerful spindle I can buy, but plug into 110V domestic outlet

[1832vin]

Hi,

I'm a hobbyist who currently has access to large machines and want to embark on a journey on creating my own CNC mill that can cut stainless, even after I loose access to the workshop I'm using right now.

I envision this to be at least a year-long project, mostly because I have no idea about the electronics, but right now, I'm looking at air-cooled spindles, and was looking for a good spindle that I can still plug into a 110V domestic outlet (i know it's a weak sauce, to be honest...) and hopefully still clear mild steel with a EN10

any ideas? or is this a pipe dream?

also, I'm looking at clear path servos for the motion control for the 5 axis, is that a good idea?

thanks

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[joeavaerage]

Hi,
cutting stainless and steel requires a slow speed spindle, say 3000 rpm for a 1/2 inch endmill, but high torque, probably better than 10Nm.

Most spindles sold to hobbyists are high speed low torque asynchronous motors driven by a VFD, typically 24000 rpm, way too fast for use in steel.
They work well but are not well suited to stainless/steel.

Having only 110V is going to make your search even tougher.

May I suggest that you look at some of the commercially available drill-mills, of which this RongFu45 is typical:

https://rongfu.com/mill-drill-machin...-machine-rf45/

They are rigid enough (just) to do OK in steel and stainless. Anything less rigid will just not work, it will flex and vibrate like hell.

I'm looking at clear path servos for the motion control

Clearpath are good quality and made to be easy to use for first time servo buyers but they are expensive for their power output. Research Delta (Taiwanese brand made in China) or DMM (Canadian
brand made in China). Both are good quality with vastly better encoders, good support, documentation and most importantly free set-up and tuning software, at fair prices. Do not be taken in
by Clearpaths repeated marketing strategy of claiming maximum or peak power/torque outputs.......look instead at the continuous or rated power. This is the far more useful
and realistic spec.

Craig

[1832vin]

yes! that one thing that was kinda bugging me, but never actually rose to surface!
i mostly mill steel with 4500rpm, and these spindles were telling me to go at a minimum 9000rpm. my poor piece is going to work harden so quick!

thankyou for the rongfu45, but I'm actually more excited about milling a CNC than having one, so i'd really rather buy just a spindle. Are there any good packages that takes care of all the electronics? or maybe just a good spindle.

+ i also wanna mill glass, so need to go real slow on those.... are there any spindle specific recommendations?

but on the servo side, thanks for recommending me delta and DMM! is there a good bang for buck recommendation for the spindles? I'm gonna make worm screws and ball screws for all of the joints, so i don't think it will need too big of a holding power.

(and maybe a good site to buy them?)

(but i also wanna make a 5 axis machine, cuz the rotating bed looks super interesting to make!!)


thanks!!

[joeavaerage]

Hi,

i mostly mill steel with 4500rpm, and these spindles were telling me to go at a minimum 9000rpm. my poor piece is going to work harden so quick!

Its very poor practice to run one of these (24000rpm) spindles at 1/2 or less of it rated speed. That really places a distinct limit on what you can do in steel.
Its not so much that the material workhardens but the tool overheats, a carbide tool that glows red hot is done for.

thankyou for the rongfu45, but I'm actually more excited about milling a CNC than having one

I was not necessarily suggesting that you get one, just that they are an example of the rigidity required to do the job you want. If you want to make your own machine, exactly as I did,
then you need to design and build it to be AT LEAST AS RIGID as the RongFu or you will be very disappointed.

+ i also wanna mill glass, so need to go real slow on those.... are there any spindle specific recommendations?

You need a spindle motor of high torque but low speed. I would suggest you use a servo as a spindle motor.

I have two spindles, a high speed (24000rpm) low torque spindle for making small parts in brass, aluminum, plastics etc and small diameter tools for making circuit boards.
When I want to do stainless or steel I swap over to a 1.8kW Allen Bradley AC servo motor driven spindle, homemade. AC servos are very torque dense and very speed controllable.
Its true you pay a premium for that low speed torque and control but its highly worthwhile.

This is a reasonably priced spindle assembly:

https://www.fasttobuy.com/bt30-taper...ol_p36468.html

And you power it with something like this:

https://www.fasttobuy.com/delta-2kw-...nc_p33936.html

Note the servo drive is nominally a 220VAC input, but you could run it on 110VAC, but just slower. I think you are going to struggle to find any powerful motors that have the torque and speed
control you want IF you remained tied to the idea of 110VAC. To be honest 3phase 380VAC-440VAC is where you should be aiming.

Craig

[joeavaerage]

Hi,
rather than using an AC servo motor for a spindle, as nice as they are, they are not cheap and all of them are 200VAC or more input. You might
well find a DC motor. There are, or used to be, many DC motors of 90VDC, 100VDC and similar. If I'm not mistaken some of the DC motors that were used
in treadmills were of that type. They could no doubt be had cheap enough on Ebay for example.

https://www.ebay.com/itm/35317935551...Bk9SR9SXioWcYQ

This one is 130VDC, which you could get from your 110VAC supply no trouble, its go plenty of boogie to, 2.6Hp.
Much cheaper than an AC servo, but of course you'd still have to come up with a power supply and DC controller, but far from impossible.

Craig

[1832vin]

i see the 380VAC, but how do i get that? like do i have a transformer that plugs into 2 sockets instead of one? or is there like a step up transformer in the power supplies that i can do that? or am i just screwed in this country?

while i have access to a workshop, i wanna put this in my flat, and i rent, so i have no idea if in the future, when i move, this machine is the most expensive door stop or not.

but i just realised how stupidly powerful i need to be milling steel at EN10. more like a EN6 for clearing mild steel. but thanks for all of your suggestions! That is interesting! using a servo motor as my spindle instead....

[1832vin]

oh, i just saw your second comment, I also thought of that, if I'm working on low speeds, i might as well just get a traditional motor, hopefully brushless, and drive it at low speeds, like the ones on a Bridgeport.... but is there a specific type of motor i should look out for?

[joeavaerage]

Hi,
with a domestic 110V connection you are limited to about 20A per circuit, unless you have a high current circuit fitted. A 20A 110V circuit will
be OK up to about 1.5kW, say nearly 2hp. With a 20A 230V circuit you could get away with (just!) 2.2kW or just a little over 3hp.
It comes down to what shaft power you want for your machine.

Here in New Zealand a domestic single phase circuit is 10A at 240V. If you take the trouble to fit a high(er) current circuit, like say what you would do with a domestic oven,
then you'd get 32A at 240V. That would allow a 3.5kW drive or about 4.5hp. More shaft power than that requires an extremely high current single phase supply and drive, a rarity, OR fit genuine
three phase (440V) AC supplies.

That is interesting! using a servo motor as my spindle instead....

AC servos have a lot of torque for their size, and good short term overload properties which make them good for use as a spindle motor, albeit at some expense. In addition
because a servo is position feedback capable, I exploit it to do rigid tapping which otherwise would not be possible with my CNC software and hardware combination.

Craig

[mactec54]

i see the 380VAC, but how do i get that? like do i have a transformer that plugs into 2 sockets instead of one? or is there like a step up transformer in the power supplies that i can do that? or am i just screwed in this country?

while i have access to a workshop, i wanna put this in my flat, and i rent, so i have no idea if in the future, when i move, this machine is the most expensive door stop or not.

but i just realised how stupidly powerful i need to be milling steel at EN10. more like a EN6 for clearing mild steel. but thanks for all of your suggestions! That is interesting! using a servo motor as my spindle instead....

First get an understanding of your electrical supply if you live in NA, you have 120v / 240v Single Phase Supply, you do not have 110v if you live in NA

And no, you can't get or use anything that is 380v (which would be 3Phase) with 120v Single Phase Supply, you can't do very much at all.

Why don't you just buy a Bridgeport type machine and convert it to CNC, you would also want to have a 240v 30A minimum Single-Phase Power Supply to run it

[peteeng]

Hi Vin - These things end up being serious chunks of metal. You say you want to put it in your flat? What working envelope are you aiming at? Peter

[Teknic_Servo]

Hi 1832vin, I’m an applications engineer at Teknic. We have a number of people using ClearPath integrated servo motors on CNC machines, including 5th axes. Selecting motion control vendors can sometimes be based on personal opinion/experience but the pertinent facts should not be lost when delivering the message. I noticed a couple of statements that could potentially be interpreted as misleading that I want to clarify:

DMM has ‘Vastly better encoders’

Some people on the forum repeatedly state that DMM and others have “vastly better encoders” because these encoders have quite a bit more resolution than ClearPath motors. But they miss the fact that there is a lot more to encoder quality than just resolution.

A good analogy is megapixels in digital cameras. Inexperienced photographers may believe that the quality of a camera is dictated by the number of pixels on its sensor. Camera manufacturers take advantage of this ignorance by touting extraordinarily high pixel counts. But the number of pixels is only one factor of many, many others that determine the quality of a photograph. The camera on the Samsung Galaxy S22 Ultra has 108 megapixels. It’s a great camera—for a phone—but the photo quality is downright poor compared to a Canon 1DX Mark III high-end professional camera that has less than one-fifth of the pixels (20.1 megapixels). There’s a reason that sports photographers are not using their cell phones to take photos for Sports Illustrated despite the fact that the phones have many more pixels.

Some people on the forum incorrectly quote the ClearPath resolution as 800 counts per revolution because some DC ClearPath models come standard with a steps per rev input resolution of 800 steps/rev. If your controller has a limited step output rate, then you want a relatively low input resolution so that you can operate the motor up to full speed. In these models, it’s true that you can only position to 800 locations per revolution, but the encoder resolution in DC ClearPath models is still 12,800 counts per rev in order to provide excellent accuracy and repeatability.

DMM motors use magnetic encoders; the native resolution of magnetic encoders is generally quite low. According to the DMM website, the DMM encoder uses a 2-pole magnet. As the motor shaft turns, hall-effect sensors pick up the changing magnetic field from the encoder disk and convert it into an analog signal. One revolution generates one sinewave. The actual encoder counts are all generated by interpolation. In other words, there is a processor and circuitry in the encoder that “estimates” the motor position based on the amplitude of the analog sinewave. This interpolation has to be accomplished in the face of errors such as run-out, noise, DC offset, short- and long-term drift, sensor hysteresis, non-linearities, temperature effects, etc. These errors can be somewhat compensated for, but as stated on DMM’s website, the accuracy of the encoder is only 0.1 degree (i.e., 1 part in 3,600). This means that because of the extreme interpolation, the accuracy is nowhere near the resolution figure (the accuracy is 18x worse than the resolution).The accuracy of the DC ClearPath servos is 3.56 times greater and the accuracy of the AC ClearPath servos is 17.78 times greater than the DMM encoders.

On top of this, in order to remove enough noise from the analog signal to be able to do even a moderate amount of interpolation, the signal needs to be filtered. This adds a delay to the encoder data of 2-10 milliseconds typically. This introduces a dynamic error that reduces the servo performance. Even worse, because the encoder is a serial encoder, the servo gets position updates at a fixed clock rate (every 100 microseconds, per the DMM website). This means that at 3,000 RPM, you would have a positional change of 327 counts before the servo is even updated.

One final point, even if the higher resolution of the other encoders was not illusory, would it even be helpful in a typical application? With a 5 turn per inch leadscrew (for example), an encoder with 12,800 counts per rev gives you a linear resolution of 1/5/12,800 inches (0.00002 inches per count). It’s a rare application that needs higher resolution than that, and you better have a phenomenal set of mechanics in order to not have the resolution get swamped out by other errors.

“Continuous power is far more useful and realistic”

There are some applications where continuous torque is more helpful than peak torque. Some examples include pumps, fans, and CNC spindles. Neither rating (as a single number) is helpful. What you need, in almost all applications, is a torque/speed curve at the expected bus voltage that shows both peak and continuous (RMS) torque. This is why Teknic provides multiple torque/speed curves for each motor model at various voltage levels on the website. And power, as a spec, is generally not very useful unless you have a lot of flexibility in how you can gear your mechanics.

Properly sizing a motor requires an understanding of both the peak and average torque (and speed) required. While the continuous torque may be more relevant while cutting an individual part, the additional peak torque may be critical to achieving higher accelerations and ultimately throughput.

A common example that illustrates the need for both peak and continuous torque numbers is CNC wood cutting. The material can vary significantly and unexpectedly, such as when cutting through a knot in the wood. The motor may need a much higher amount of torque for a brief period of time in order to prevent any cutting errors. The servo control loop and encoder also have to be able to respond quickly enough to detect and respond to the error.

The ClearPath motor setup program (MSP) is free and includes not only a sophisticated auto-tuner but also includes an onboard digital oscilloscope. This o-scope is used to collect valuable diagnostics based on FFT analysis, including continuous and peak torque numbers. We also provide tutorial videos on how to use these diagnostic tools to increase the performance of your machine.

We acknowledge that there are products from different manufacturers in virtually every market that may provide certain advantages. (Heck, we don't all drive the same car for that very reason). That said, Teknic (and I) want to ensure that accurate information is available so that informed decisions can be made.

If you have any additional questions or comments, feel free to contact a Teknic engineer at support@teknic.com or give us a call at 585-784-7454.

Aaron B. – Teknic Servo Systems Engineer

[amanda23]

Building a 5-axis CNC mill for stainless steel on 110V is difficult. A stronger 220V outlet or alternative power source is needed for a powerful spindle. I suggest starting with a 3-axis mill on 110V to learn the ropes and plan for a future upgrade. wordle unlimited