60k RPM spindle from China, any experiences? - Page 1
Forum section: electronics / general

author: jeremy
author_rank: Super Contributor
timestamp: January 24, 2018, 07:58:48 am
content: Hi all,These 60k RPM spindles have caught my attention on ebay:https://www.ebay.com.au/itm/60000rpm-Spindle-Motor-300W-ER8-Water-Cooled-D48mm-Milling-Engraving-CNC/201593950859?hash=item2eefef928b:g:HYUAAOSw8gVX44LMAdvertised runout is 5umHas anyone bit the bullet and purchased one of these? If the runout spec is accurate, these could be very good for engraving.

author: Merlysys
author_rank: Regular Contributor
timestamp: January 24, 2018, 02:42:33 pm
content: You will need an inverter with those odd specs75VAC, 1000HzHow much are they?

author: jeremy
author_rank: Super Contributor
timestamp: January 24, 2018, 03:17:35 pm
content: Most of the Chinese VFDs let you set the output voltage iirc. Example:https://www.ebay.com/itm/300W-CNC-Milling-Spindle-W-ER8-Chuck-KL-300-/162289049030Edit: here is a kit listinghttps://www.ebay.com/itm/300W-Spindle-Motor-Water-cooled-60000rpm-1-5KW-VFD-Bracket-Pump-Pipe-CNC-Kit/191871998543?hash=item2cac765a4f:g:euQAAOSwepJXX8Lr

author: Kjelt
author_rank: Super Contributor
timestamp: January 24, 2018, 06:02:47 pm
content: Perhaps take a look at cnczone that forum deals with spindles of all sorts.That said you do know the potential dangers with that kind of speeds?Better build a surrounding safety cabinet.

author: janoc
author_rank: Super Contributor
timestamp: January 24, 2018, 08:57:57 pm
content: You likely don't want a spindle with a collet holder directly attached if this is for a milling machine. These are universally crap because they flex with the milling forces - the bearing is way too far away from the point where the force is applied. Belt driven spindles with the actual spindle being held by a proper bearing are better.Also, 60k RPM is fairly excessive and pointless - about 20k is plenty for what you can reasonably mill on a small cheap machine this would fit in.

author: IconicPCB
author_rank: Super Contributor
timestamp: January 24, 2018, 10:36:41 pm
content: Check with the manufacturer how they measure and specify the runout.Janoc points to some valid issues regarding runout ( as alroeady aluded to in comments about RPM versus runout).Jaeger spindle is an integrated spindle meaning motor and spindle sit o the one shaft supported by bearings either end.Difference is the collet in the Jaeger spindle sits inside a hollow shat within the bearing assembly.Jaeger specify runout in terms of tool tip at 15 mm away from the collet.While the spindle will flex and contribute to runout as a function of RPM, judicious listening to the spindle will allow selection of sweet spot(s) at hgher than 20KRP settings.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2018, 02:01:48 am
content: Looks like it would be fun to play with, but that's also slightly terrifying. I shudder to think what would happen with a catastrophic failure at 60k RPM. There are tremendous forces involved at such speeds, and a huge amount of kinetic energy.

author: jeremy
author_rank: Super Contributor
timestamp: January 25, 2018, 06:20:19 am
content: Quote from: blueskull on January 25, 2018, 05:58:14 amIsn't that what protective earth is for? Surely one would earth the outer case of the spindle and the machine frame?Quote from: IconicPCB on January 24, 2018, 10:36:41 pmProblem is, I don't trust themAlthough they are some of the best, I'm not sure I'd ever be able to afford a jaeger; even their smaller ones cost more than my car is worth.Quote from: Kjelt on January 24, 2018, 06:02:47 pmI am well aware of the dangers. Frankly, even a 20k rpm machine should be in an enclosure IMO.

author: IconicPCB
author_rank: Super Contributor
timestamp: January 25, 2018, 11:49:06 am
content: there isnt much to fail in the spindle.It is a deep bar squirrel cage rotor. If that rotor fails.. nahh only a paper mache rotor would go tits up in such a catastrophic way.In any case the spindle would be housed in an external clamp providing additional protection.

author: ikrase
author_rank: Regular Contributor
timestamp: February 07, 2018, 06:39:35 am
content: 60 thousand RPM?Makes me wonder if it's time to start building DIY turbomolecular pumps for high vacuum.(FWIW, the part of the turbo pump that contains the motor does not need to be ultra-high-vacuum compatible.)(the smallest standard size of turbopump, the 50 to 90 L/s pumps which have an inside diameter of about 65 mm and are about 150mm tall, spin at around 80 thousand RPM, with a respectable low-speed mode closer to 50 thousand RPM.)

author: rx8pilot
author_rank: Super Contributor
timestamp: February 07, 2018, 06:45:19 am
content: Quote from: janoc on January 24, 2018, 08:57:57 pm60k is not even close to excessive for engraving and small hole drilling. The smaller the tool, the faster you have to spin it. I am looking at a 90k air spindle for my CNC, but it is too slow. The drills I am hoping to use are designed for 120k RPM for best life.

author: janoc
author_rank: Super Contributor
timestamp: February 07, 2018, 03:44:54 pm
content: Quote from: rx8pilot on February 07, 2018, 06:45:19 amYes, but that also assumes that your mill and spindle is actually rigid and aligned well enough that the bit doesn't shatter into thousand pieces at such speeds.The spindle the OP has linked to is typically found on the cheap AliExpress CNCs (like this one:https://fr.aliexpress.com/item/1000W-MACH3-Control-Diy-6040T-Mini-CNC-Machine-Working-Area-57-5-x-37-5-x/32720516377.html- even though this one is one of the better ones) - which are far far from rigid and well trammed. Plus it flexes, so the runout will be a killer. There even 20k RPM is pushing the limits, IMO. That's what I have meant.

author: 691175002
author_rank: Regular Contributor
timestamp: February 07, 2018, 04:16:43 pm
content: Chinese spindles of this type are incredibly common for hobby level CNC builds, although typically people use the 24K versions. They are sufficiently reliable and fairly well built, but of course the run-out specs are a lie and the AC bearing pack is going to be of a very low grade. Great for typical hobby cutting with small endmills.QuoteThis is a big problem because if I have a correct understanding of your objective the spindle is the least of your worries. Micromachining isn't just limited by the spindle, any errant motion will snap the bit instantly. Everything from the toolholders, linear guides, ballscrews, servos, and machine frame must be chosen for zero play and high damping.Look at something like thehttp://www.minitech.com/GX for an example of what micromachining requires.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 07, 2018, 04:53:31 pm
content: Quote from: 691175002 on February 07, 2018, 04:16:43 pmI totally get it. My machine is 5,000 lbs and the motion control is suitable for entry-level micro machining - end mills down to about .010" if the RPM is available and the programming is perfect. It is true that the slightest imperfection anywhere in the rotating assembly is a show stopper. Any un-commanded motion in the workpiece is a show stopper. 60k RPM is not a place where cutting corners will have a good result.As a reference - the 90k RPM spindle I am looking at costs about $5,000. It's runout is lower than I can even measure in my shop, in the low 'millionths' territory while rotating [verified of course]. It goes into a larger ATC spindle like the one on my machine which is trammed extremely well. That level of precision is suitable for extremely small tools. Not sure what to expect from this eBay option - but obviously it will not be that good. My guess is that for engraving and drilling, it would allow fairly small tools to survive a reasonable amount of time when it is new. I would not have much expectation that it would last very long though where the TIR just grows and grows until it becomes a tool killer.The runout spec claimed is probably from the spindle that they copied to make this one - which is near the claimed spec. At least not while it is spinning at 60k RPM. I don't know of anyone hobby or professional that has the capability of measuring 50um (or whatever the claim is) while it is rotating. That requires some fancy non-contact laser metrology to confirm. So - if no one can prove it, why not exaggerate it, lol

author: Marco
author_rank: Super Contributor
timestamp: February 07, 2018, 05:54:59 pm
content: Quote from: rx8pilot on February 07, 2018, 04:53:31 pmDoes it need to be fancy? An interferometer seems like something you could DIY relatively easily.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 07, 2018, 06:11:25 pm
content: Totally out of my range of understanding. All I know is that the only systems I have seen doing metrology in the low millionths non contact seem to be rather expensive.Short and misplld from my mobile......