How many watt do i really need (spindle choice)

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typomaniac
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How many watt do i really need (spindle choice)

Post by typomaniac » Mon Feb 23, 2015 5:00 pm

Hey all,

i am currently running a 1,5 kw chinese spindle (watercooled) which turned out to be to heavy for the machine. Therefore i am thinking about a downgrade but i am totally uncertain what to do. I love the quietness of this spindle compared to other solutions but i am not sure if something like the quiet cut spindle with 300 or 400 watt would be enough. I mostly do wood milling and i really cut a lot so i need more power than just a little »engraving«. I was thinking about the 800 or 1000 watt kress spindle but i am afraid of the noise everybody is talking about. What do you think? How much is needed and how much is too much ; )? (of course there is never too much power but the almost 6 kg of the china spindle really was overkill)

thanks a lot,
tm
Proud owner of eShapeOko #17 :-) (Dual-X, Grbl 0.8a)

Hans
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Re: How many watt do i really need (spindle choice)

Post by Hans » Mon Feb 23, 2015 5:51 pm

I use FSWizard to estimate how much power and force a given cut will require. About the heaviest roughing cut I would take is 5 lbs, which results in about .015" of deflection on my modified S1. Plugging numbers into FSWizard based on slotting .25" wide and .063" deep at 80 ipm, I get 4.6 lbs and... 0.1 horsepower. That's only about 75 watts actual cutting power required for the heaviest cut I take.

The spindle needs more power than that. For one thing, the listed power is peak power, which is made at about 1/2 the rated speed and you never want it to bog down so much that you hit that number. Another consideration is that you want the machine to be capable of pushing through even if you tell it to take a bigger cut than you should. So, I would set the minimum spindle power based on making 30% power at 90% spindle speed (from a standard theoretical motor curve), and based on twice the power of my heaviest cut or 150W. With that particular calculus, I get 500W as the minimum spindle size for my machine. No wonder the 500W DW660 has been so popular! And it should be no surprise that 1500W is overkill.

Based on purely theoretical values the 300W quiet-cut should be about the bare minimum to make that cut, with sharp tools and the ideal RPM, but because so many assumptions are made I would not be confident buying a 300W spindle. People who use the quiet-cut spindles will have to weigh in with their results.
Last edited by Hans on Fri Apr 10, 2015 12:10 pm, edited 1 time in total.
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Gadgetman!
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Re: How many watt do i really need (spindle choice)

Post by Gadgetman! » Mon Feb 23, 2015 6:35 pm

I generally cut Plywood at 600mm/minute with .5mm cuts with a 2mm two-flute with my 300W QCS.
With a 1/8" I could probably go up to 750mm/minute, or cut slightly deeper (0.75mm ) without really overstressing stressing my SO.
I hope to push it to even higher speeds after I rebuild, though. It's just that it's not stiff enough for more right now.

The QCS series have two big advantages...
1. It's called Quiet Cut for a reason...
2. It uses standard ER11 colletts, so it can fit ANY shank size up to 7mm.
(1/8", 3/16", 1/4", 1 - 7mm in 0.5mm increments)

It can also be regulated pretty well. I'm told that some materials doesn't like the 'full speed and d@mn the swarf' attitude.

It really comes down to how accurately you want to cut, how fast you want it cut, how easily annoyed yor neighbours are, how stiff your machine is and how much money you're willing to pay.
Weird guy...
Shapeoko 2014F: 1000mm X/Y, 300W Quiet Cut spindle, Arduino Uno/G-shield and GRBL 0.9i
15x30 drag chains, custom spindle mount, 9mm belts, 8mm endplates, 6mm motor plates.

typomaniac
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Location: Hamburg, Germany

Re: How many watt do i really need (spindle choice)

Post by typomaniac » Mon Mar 09, 2015 6:20 am

Hey,

sorry for getting back so late. Thank you very much for your opinion. I really would appreciate more feedback from owners of the dc spindles. From what i can read so far 300 w is not enough for me. I cut a lot beech wood with a 1/4 end mill and 800 mm/min with 1.5 mm cuts. Thats way more than Gadgetman does with his 300 W QCS. My 1,5 kw does that easily but as i said it is too heavy. I think the Kress 1050 would also be able to make cuts like this (at a lower weight) but it will be pretty loud. Does anyone own a 600 w qcs and can tell me something about the limits?

thanks,

tm
Proud owner of eShapeOko #17 :-) (Dual-X, Grbl 0.8a)

Auarhau
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Re: How many watt do i really need (spindle choice)

Post by Auarhau » Mon Mar 09, 2015 9:19 am

The kress could do that pretty easily. I did some test when I got mine.Copied from that thread "I was cutting 1250mm/sec at 4mm dept of cut for each pass, and it did not even sweat! At this point I stopped testing, but I'm sure It can do more before something gives.". This was with a 8mm two flute in plywood with a hard coat top layer. It's a very good and professional machine.

It is however awkward to mount on the shapeoko. I've not yet found a good way to do it.. And it is loud, comparable to a wood router I'd say. I don't mind because I run it rarely and short periods. And I always use hearing protection. I can do a little comparison with the kress, makita and dremel when I get home. I own all three but only use the kress on the cnc. They are all definitely loud compared to a spindle though!
ShapeOko 2. Nema 17 74 oz·in. GAUPS shield on Arduino Uno. DRV8825 Drivers x4 . Kress 1050 FME-1. Z Acme Screw. Threaded inserts table.

samc99us
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Re: How many watt do i really need (spindle choice)

Post by samc99us » Thu Mar 12, 2015 6:49 pm

Hmm,

The quiet cut 600W spindle might be a decent option in general (I like the 800W chinese spindle solutions but they are more expensive than the 1.5KW solutions!). However, there is no speed controller available for it at this moment. For me, that means it is of limited use, where a VFD solution would allow me to control the spindle speed directly in LinuxCNC.
Modified Shapeoko 2: 1500mm fully supported y-axis, 1000 mm 4060 x-axis, ACME Belt Drive Z-axis, Dewalt DNP611, full aluminum t-slot table, 4x NEMA23 180 oz/in stepper motors driven by a G540

typomaniac
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Location: Hamburg, Germany

Re: How many watt do i really need (spindle choice)

Post by typomaniac » Fri Mar 13, 2015 9:55 am

hmm. Still very difficult. 600 W sounds like a good idea but without control almost useless. Did anyone ever push its quiet cut 300 to the limits in order to find out what it is capable of? It would be really useful to know what the spindle can do. At the moment i would go for the kress because of the power but i do not know if i can handle the noise ...
Proud owner of eShapeOko #17 :-) (Dual-X, Grbl 0.8a)

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