brushless outrunner spindle

[cletero]

So, I've been thinking in this idea for a while, but haven't found many up to date, down to earth discussions on the subject, so though I'd ask here. Hope this is the correct forum category .

I have a CNC router with a Ridgid 2401 router as a spindle, but think it's about time to go another way. So I had a friend machine me a spindle with ER16 capacity, with metal housing and proper bearings, and to power it I was thinking of using one of those outrunner motors some people have used. Sadly, the posts and videos I have found are far outdated and there recommended parts no longer exist, so I was thinking of using this:

EMAX GT Series 1100KV Outrunner Brushless Motors Type For Rc Plane (GT2815/07) | eBay

50A Brushless ESC Mystery Cloud 50 APM BEC RC Speed Controller for RC Airplane | eBay

Multi Servo tester 3CH ECS speed controler tester Power (F008) | eBay

and this:

AC 110V-220V TO DC 5V 12V 24V Switch Power Supply Driver Adapter LED Strip Light | eBay

I planned connecting them to 12V, 40A (max), the motor is 1100 kv which should give me 1100kv*12V=13200rpm and motor is rated at 36A max, so 12V*36A=432W max. Based on Gwizard data, I would rarely use over 200W anyway (MDF, nylon and very light Aluminum cutting under 1mm DOC).

I would use belt drive and have 25T and 15T gears so I could have a 15/25 combination for low speeds (7920rpm max) or 25/15 combo for high speeds (22000rpm max). This depending on whether I'll be cutting plastics, metal or MDF which cuts better at high rpms. Of course, the rpms are adjustable anyway, but this would avoid losing power over the speed controller.

However, given my limited knowledge on motors and electricity, wanted to hear some thoughts on the subject and about compatibility between the items I selected. Also, if someone can chip in on how to maintain a constant rpm when the bit contacts the material to start cutting.

Thanks for any feedback.

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[grg12]

Hi cletero

I built something similiar: Motor: LPH 3026 ( max 45 A, 1900KV), Brushles "Heli" ESC, cheap 30A 12V power supply and DIY controller (basically "Servo Tester" with rpm readout). Power trasmission with MXL tooth belt. Power supply is underpowered - but for my application (cutting aluminum with 3mm endmill, up to 1mm DOC) it never was a problem. Spindle typically runs at 14krpm, motor 28krpm (2:1 reduction).
I had high hopes for "Heli ESC" since it has "Governor" that should provide stable rpm - sadly, i don't see any difference - is governor active or not. The moment endmill hits material rpm goes down about 10-20% (depending on DOC, WOC and - most critical - sprayer efficiency at delivering enough cooling liquid). Spindle is quite usable in 70%-100% nominal rpm range, with rpm reduced under 50% (with servo tester) torque drops and spindle is easy to stall.
Despite this - i'm quit happy with it. Biggest dissapointment - it's quite laud.

[cletero]

So I see we have a similar application with aluminum.
I have heard about the governor mode not working very well, my guess is that the load varies a lot more drastically in milling than in helicopters and such.
Good to hear about the torque drop with rpms... I'll have to consider that, as it limits the usable rpm... maybe I'll get some more gear combos.
If it's quite loud it would disappoint me too, but I guess it's comparable to my Ridgid router.

Is the DIY controller hard to do, considering I have not much experience in electronics? I have thought about getting a laser tachometer, but it would be nicer to have a more direct feedback.

Thanks a lot for your feedback!!

[grg12]

Is the DIY controller hard to do, considering I have not much experience in electronics?

I almost destroyed my ESC during construction In case you decide to make your own controller - 3 things that i learned during the process.
1. battery eliminator (BEC) in ESC has no fuse - if you short it, it's gone.
2. soldering on ESC is hard since it's PCB acts as a massive heatsink (lots of cupper in it) - normal soldering iron was not enough to remove remains of exploded transitor.
3. cheap reaflective optical sensor is able to sense rotating nut (for rpm detection) but without black/white markings signal is very noisy and readout shows confusing values...

And to noise level - it's quiter than typical router, problably in the range of good household vacuum cleaner.

[cletero]

And to noise level - it's quiter than typical router, problably in the range of good household vacuum cleaner.

Ok, so it would be fine for me, great!

I think it's better if I seek for some help if I decide to build the DIY controller .

I really appreciate your help, thank very, very much.

Have a great day,

Alfredo

[ger21]

I think you'd be much better off to just buy a cheap chinese spindle.

Also, if someone can chip in on how to maintain a constant rpm when the bit contacts the material to start cutting.

More power.

[cletero]

I think you'd be much better off to just buy a cheap chinese spindle.



More power.

Thanks, but that would take the fun out of it he he he

Plus, I'm also looking at another, more powerful outrunner motor and my spindle will have adjustable run out... if this doesn't work then I'll just use my current router to power it.

Thanks again!