Page 1 of 2

.8kw spindle better than D611?

Posted: Thu Mar 31, 2016 2:49 pm
by jointhebeagle
I'd really like some user input here.

I have an S3 with the Dewalt 611. As we all know, aluminum is kind of the upper bounds of the 611, so I'm looking to upgrade to an aircooled spindle.

Those that have done it, or are in the know......... is a 220v .8kw spindle significantly better than the 611. Or do I need to go to the 1.5kw. If I need the 1.5kw, can the S3 handle the extra weight?

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 2:55 pm
by superfrog
I have not tried the Dewalt, but the 0.8kW air cooled spindle I got is very nice with nearly no vibration and negligible run-out after break in.

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 3:53 pm
by jointhebeagle
superfrog wrote:I have not tried the Dewalt, but the 0.8kW air cooled spindle I got is very nice with nearly no vibration and negligible run-out after break in.
Can you link which you bought? How does it handle aluminum?

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 5:20 pm
by superfrog
I think the cheap chinese 24k RPM spindles are pretty much all coming from same factory. The one I have is 65mm diameter and air cooled. I would keep away from the 80mm diameter ones because of weight. There is a fairly rare 65mm 1.5kW if you think you need it (Even on the more rigid SO3, I doubt you could get anywhere close to using this much power).

I got mine from Amazon for £135 but the seller has stopped selling them. Ebay has tons of identical spindle + VFD sets for about the same price ( search for "spindle 0.8kW VFD" ) and check that it is an air cooled one and that it is 65mm diameter.

Only buy if you are happy with electrical work as you will have to wire and encase the VFD and sort out the spindle cable.

I have not tried on aluminium as yet but as it has more than the required power for a small endmill, does not vibrate, has no play, and the internet is full of people cutting aluminium with these spindles, I am pretty sure it would be fine.

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 5:58 pm
by superfrog
For reference, a cut that is out of the SO3 realm of possibility, data according to FSWizard:

A 6mm 3flute carbide cutter in 6061 Al slotting at 2mm depth gives the following:

SFM=366, IPT=0.03423, RPM=19414, FEED=1993.56
DOC=2, WOC=6 = 100% = 180deg
MRR: 23.9 cm^3/min
HP: 0.4
Torque: 0.2 Nm
Breaking Torque: 1.41 Nm
Cutting Force: 58.91 N
Tool Deflection: 0.0134 mm
Max Tool Deflection: 0.0931 mm
Effective Dia: 6.0000 mm
Chip Thickness: 0.0342 mm

0.4HP is 300W. I would take the 800W advertised figure with a pinch of salt but it still feels like the power is amply sufficient. (and there is no way you are getting 60N of force out of the steppers for X/Y at 2000mm/min)

For a still past what people do with ShapeOko, a 2 flute carbide 1/8" endmill, slotting at 2mm depth in 7075 Al

SFM=239, IPT=0.01135, RPM=24000, FEED=544.91
DOC=2, WOC=3.175 = 100% = 180deg
MRR: 3.5 cm^3/min
HP: 0.1
Torque: 0.0 Nm
Breaking Torque: 0.21 Nm
Cutting Force: 17.88 N
Tool Deflection: 0.0083 mm
Max Tool Deflection: 0.0960 mm
Effective Dia: 3.1750 mm
Chip Thickness: 0.0114 mm

requires, as you can see for yourself, nearly no power, and is already putting quite a load on steppers.

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 6:28 pm
by jointhebeagle
superfrog wrote:a bunch of stuff
Hey, frog, thanks, but all of that is way over my head. What does it boil down to?

Sorry. <_<

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 6:52 pm
by superfrog
In short, that the 800w spindle is already overkill for most thing you can conceivably do with a SO class machine.

That being said, it is not a bad option and will do Al as fine as the machine can, or if you prefer that you will reach other limits on the machine well before you reach the limit of the 800W spindle (mostly flex but also ability to pull the tool through).

The only better thing would be a faster lighter spindle. They exist but they cost a lot more money and could prove a bit underpowered at lower RPM.

All that is more from theoretical knowledge than from practical experimentation though, please wait for other opinions.

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 7:15 pm
by jointhebeagle
superfrog wrote:In short, that the 800w spindle is already overkill for most thing you can conceivably do with a SO class machine.

That being said, it is not a bad option and will do Al as fine as the machine can, or if you prefer that you will reach other limits on the machine well before you reach the limit of the 800W spindle (mostly flex but also ability to pull the tool through).

The only better thing would be a faster lighter spindle. They exist but they cost a lot more money and could prove a bit underpowered at lower RPM.

All that is more from theoretical knowledge than from practical experimentation though, please wait for other opinions.
Thanks. I just got off the phone with Apollo at Carbide 3D.

He suggested the Kress 800w spindle as a more turn-key solution. Better product development (presumably) with better product support.

Instead of 0 to 24000 rpm like the Chinese spindles, it's advertised as 10000 to 29000 rpm. I wonder if it will cut aluminum well at 10000 rpm...

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 7:31 pm
by superfrog
If that's any consolation, I would not run the Chinese one much below 10kRPM either !
Kress are nice and you are much less likely to kill yourself while connecting the VFD.

Re: .8kw spindle better than D611?

Posted: Thu Mar 31, 2016 7:36 pm
by Jimf
All of the vfd spindles have a minimum recommended rpm. Mine is set at 8000rpm. They will spin slower but there is not much torque at lower rpm. The air cooled versions need to run atleast a few thousand rpm to keep the fan working to cool it down.

A vfd powered spindle is better over other types. The lower bearings are usually larger and can handle the side cutting forces better than a Kress or smaller routers/DC type spindle motors.

I have a larger cnc with a 2.2kw water cooled spindle. It is much nicer than the Porter cable router I used before. It keeps constant rpm under load and crazy amount of power. No problems doing full depth 3/4" pass in plywood/mdf at high speed.