Author Topic: 60KRPM Spindle  (Read 8090 times)

Offline PK

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60KRPM Spindle
« on: February 28, 2016, 01:53:22 AM »
Been chipping away at this one for a few months. It turned into one of those projects where you had to fix this, before you could change that, before you could upgrade this bit etc.. With dodgy hacks a tempting option at every stage. 

I managed to avoid the dark side and do most things properly...

Still more to go but I had it making swarf today...

Offline raynerd

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Re: 60KRPM Spindle
« Reply #1 on: February 28, 2016, 03:57:07 AM »
Hi PK, really interesting because my brother in law and I currently have some G10 stuck to the bed of our CNC router and we still haven't cracked a suitable cutting speed and feeds or cutter.

We have recently purchased some 'chip breaker' titanium coated end mill advertised for cutting PCB. We tried some cheapo £2 cutters off eBay and it literally rounded the sharp cutting end within a few minutes! I'm interested to see how we get on with these.

Your diamond burrs look to be going through this like cheese! What profile are your burrs? My spindle is 10,000 to 29,000 rpm idle. Is your 60k rpm necessary for the feeds you are using or necessary for using burrs in grp.

Great post and I hope to learn more!

Offline Spurry

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Re: 60KRPM Spindle
« Reply #2 on: February 28, 2016, 04:56:01 AM »
....... currently have some G10 stuck to the bed of our CNC router and we still haven't cracked a suitable cutting speed and feeds or cutter.

How thick is the G10 you are trying to use? What is the maximum diameter of cutter you can use for the job? Never had a problem with G10 on my cnc machine with max rpm of 24k.

Pete

Offline PK

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Re: 60KRPM Spindle
« Reply #3 on: February 28, 2016, 05:14:09 AM »
So the cutters we use for composites all look a bit like this:
http://www.ebay.com.au/itm/1-NEW-IMCO-1-4-250-SHANK-CARBIDE-BURR-DIAMOND-CUT-DRILL-POINT-USA-E413-/371562711422?hash=item5682dd097e:g:bQsAAOSwbqpT16NT

I've got them from 12mm down to 1.6mm and have run them on spindles at 10KRPM, 20KRPM and 60KRPM and usually at full depth.
Our big router has a 3.5KW spindle and hapilly runs the 12mm tool at >500mm/min.

For the 3mm cutter I calculated about 0.02mm per rev but ended up running at half of that because the motor started to load up. I really suspect that the problem was that I couldn't clear the swarf out quick enough. In any case, 0.02-0.05mm/rev is a good conservative feed rate....
The cutters don't last very long, you'll notice wear after a few meters. The little ones snap, the bigger ones burn.
Again, go nuts trying to blast the dust out to make 'em last..
 

Offline PekkaNF

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Re: 60KRPM Spindle
« Reply #4 on: February 28, 2016, 05:43:29 AM »
What spindle is that? Aircooled? How many hours you have been using it? What seems to be proper speed range?

Pekka

Offline DavidA

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Re: 60KRPM Spindle
« Reply #5 on: February 28, 2016, 06:45:24 AM »
PK,

..With dodgy hacks a tempting option at every stage. ..

Specialty of the house here.

Dave.

Offline PK

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Re: 60KRPM Spindle
« Reply #6 on: February 28, 2016, 07:07:06 AM »
What spindle is that? Aircooled? How many hours you have been using it? What seems to be proper speed range?
Always with the questions....

It's a 60,000RPM spindle (obviously), 300W and about 50mm diameter
It's water cooled and has an ER-8 collet. Less than 15minutes run time on it to date, but that will change soon.

I bought it for two reasons:
1. I did some 3D machining of MDF vac forming plugs last year, lots of fine cuts at 20KRPM... Those jobs took anything up to 6 hours to run on the big router and getting a decent finish was a hassle because the toolpath was only using the very tip of the ball nosed mill. The idea is that 6 hours at 20KRPM=2 hours at 60KRPM and this is good!

2. We sent a design off to be 3d printed as a final check before we had injection mould tooling made. When the prototyping company heard that these were t o be IM check parts they flatly refused to 3d print them and insisted that we let them machine them from ABS on their 5 axis machines. The parts came back absolutely perfect! I've had parts SLS and SLA printed before and they never looked anything like these machined parts. I could have easily sold them as finished product.  So the intention is to add a couple of axii to the mill and try to find some 5axis CAM software so that I can do this at home.

Offline PekkaNF

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Re: 60KRPM Spindle
« Reply #7 on: February 28, 2016, 09:14:16 AM »
Interesting. So plan is is to run it falt out max speed and very little reason to run it on any slower speed? Reason is that I considered making a little PCB etc. mill and no matter how I calculated I was returning back to TEFC 24k rpm units as a starting point. I never started because I really didn't have much experinece on those, but I got the impression that they were happy on fairly narow speed/load curve.

I would think that water cooled has somewhat better speed/load envelope to work with. Therefore I wasked about speed range. That is not ofcourse any problem if it can be and is run narow speed/load envelope.

Edges of that GRP looked nice. Swarf did not seem to come out even with vacuum, but were easily blown out.

Milling MDF is a pain. Sealing MDF for molding is a pain.

Pekka

Offline PK

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Re: 60KRPM Spindle
« Reply #8 on: February 28, 2016, 04:49:55 PM »
Interesting. So plan is is to run it falt out max speed and very little reason to run it on any slower speed?
Yep, an ER8 collet just cant hold a carbide tool that needs a slower rpm...
I do intend to give PCB milling a go. I made some engraving bits to do it. Again, all the info I could find described it as a slow process so more RPM=more feedrate=more good.

Offline JHovel

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Re: 60KRPM Spindle
« Reply #9 on: February 29, 2016, 09:02:00 PM »
PK, looking very good!
Can you give me a little more detail on the spindle please?
The video shows you setting the VFD frequency to 600Hz. That equates 36krpm for a 2-pole motor.
Does that spindle have a stp-up gearbox? Or does your VFD and motor allow 1000Hz operation?
Very interested!
Cheers,
Joe
Cheers,
Joe

Offline PK

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Re: 60KRPM Spindle
« Reply #10 on: February 29, 2016, 09:09:43 PM »
PK, looking very good!
Can you give me a little more detail on the spindle please?
The video shows you setting the VFD frequency to 600Hz. That equates 36krpm for a 2-pole motor.

I've configured the VFD to show calculated RPM. It's actually running at 1KHz.
The spindle is only 300W but the drive can do 1.5KW so switching losses at 1KHz don't result in excessive heating..

This is the setup I bought
http://www.aliexpress.com/item/0-3KW-Water-cooled-Spindle-Motor-60000rpm-75V-4-5A-1000Hz-ER8-D48-120mm-GDZ48-300/2052012943.html?spm=2114.30010308.3.1.Ob5ZwG&ws_ab_test=searchweb201556_1,searchweb201644_4_505_506_503_504_301_10020_502_10001_10002_10017_10010_10005_10006_10011_10003_10021_10004_10022_10009_10008_10018_10019,searchweb201560_2,searchweb1451318400_-1,searchweb1451318411_-1&btsid=09d57ead-ee38-404d-9042-e2d731a059ab

Although I didn't pay that much. Go looking for 60KRPM spindle and you'll find lots...


PK

Offline PK

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Re: 60KRPM Spindle
« Reply #11 on: June 05, 2016, 07:03:21 AM »
So I used it in anger a bit today. Total of about 2.5 hrs of spindle on time.
The job was cutting a mold tool from some machinist wax we made a few years back.
Its swinging a 3mm two flute ball nose at 49KRPM and there's enough chip loading that you can hear it start to slow down a little during the roughing pass (3mm DOC, 100% step over 2000mm/min).

All worked a treat!