Spindle Replacement on our KERN Micro 

It looks like she fly's in from USA, maybe Switzerland, her time definitely costs more than parts shipping.

We called Haas and said we needed a spindle. The guy shows up and the spindle never was shipped. Then they shipped it and said it will be a few weeks before the guy has time on his schedule to come back and put it in. Almost certain it is more of the people we are region locked into dealing with and not the company as a whole.

*scamdemic/plandemic. remember the truckers!

Yeah it shows how little this man really knows about machining. He should have bought a Haas because he doesn't have the experience to run a machine like this.

You are grumpy. You learn by doing!

DiGiCo?

@@johanness6545 Yep. Plus Avid, Yamaha and occasionally Studer.

We have like 30-ish GROB 350s at work where they change spindles every 3-6 months due to high RPMs in aerospace-grade superalloys. It for sure shortens the lifespan of those poor spindles.

​@@coorexzwow, wild.

Trillions

33 billion revolutions if 50 % spindle time last 3 years.

Kern has hydrostatic ways, so it takes very little force to move the mass around. I guess that's all the screw they need, and it's probably oversized as well.

@@vilts This one is not hydrostatic

@@AlMg1SiCu I stand corrected! I thought all their machines were hydrostatic, but seems not to be the case.

@@vilts Just the Micro HD and the Pyramid Nano! The other machines are proof that you can still build extremely high grade machine tools even without fancy hydrostatics or air bearings. Fun fact! The Pyramid Nano has a hydrostatic ballscrew. Look those up if you want to blow your own mind.

its an air bearing spindle

Well there are: -hydraulic drawbar, -oil to lubricate the bearings -air to pressurize the spindle inside, so that chips don't get to the bearings -coolant for the spindle-bearings -air for the tool (e.g. blowing out chips and coolant when changing tools) - external coolant for the tool -through-spindle coolant -Spindle Power-wires -Spindle Encoder-wires -Spindle Temperature-sensorwires -Drawbar Limitswitch-Wires So at least 12 connections for that stuff alone.

Hybrid ceramic bearings, not air bearing.

@@felixm.8910 and in some cases when there is both through spindle coolant and air/MQL, they are run to the spindle in separate lines. In addition to the sensors you mentioned, I'm quite sure that Kern has specified also a dilation sensor (measuring the axial shaft expansion) and a vibration sensor for that spindle. Also, all bearings have their own temperature sensors, and with a high possibility, the spindle shaft is also cooled with coolant.

Theres different levels of „accurate“. The precision requirements this Kern meets at the push of a button are either a big headache or straight up impossible on many other machines

In a Kern service video ? 😅

Buying a used VMC with a 6000 - 10,000rpm spindle is going to be very different to something like a Kern, not sure I've ever seen a Kern for sale used in the UK so something we probably don't need to worry about. Used can be just fine as long as you accept there are higher risks for breakdowns, can make the parts you need to on a machine with some wear in it and then put some of the money that you saved over buying new to one side for those repairs. I have 3 similar capacity CNC lathes primarily for the reason that if one breaks down I'm not completely screwed, all bought used, combined costing less than the cheapest of the 3 new. Lathes seem to be a bit more robust overall though, they don't tend to be doing particually high RPMs compared to VMCs or loads of movement for cutting complex profiles, still, if you can budgeting some money for future repairs would be wise as nothing is going to last forever.

@@robertlees2065 Thanks, that's some really great advice there

They always do rebuilds. Rebuilds are done by Fischer to factory spec and are good as new. The core is always returned and keeping it isnt really an option

Everyone's individual situation is a little different. It's going to change a bit from year to year, and depending on how much travel and labor is needed for the technician to get there and do the job. Also depends on if your core is rebuildable (usually is unless you really smashed it), current currency conversion rates, etc. You just don't want someone in the future to point to a specific number mentioned and whine about why they didn't get Price A when their Price B is based on completely different factors. The price is comparable to a decent new car, but which car specifically and which options on that car depend on the specifics.

Engelbert Strauss

With the ticket price on that machine I wouldn't be surprised if that spindle replacement + labor was upwards of $60 - $70k CAD.

@@TGC32 I think he mentioned the price at some point and maybe I have the price in my head but it was lower than I expected. 60-70cad sounds about right for a new spindle My rebuild is gonna run about 30k isd

I think he said in his podcase it had done just under 10,000 hrs. He's doing about 140hrs/week.

X travel on the left side is extremely limited, so it's likely not possible for most parts he does

@@AlMg1SiCu Interesting. I didn't realize it was asymetric.

@@Nickle314 Most 5 axis machines have about 75% of the work envelope to one side. The one I work on DMG CMX50U is pretty offset. Any machine that has a rotating trunnion table like this one is like that. The center of travel in x is always skewed towards the side the table rotates more. It makes it really tricky when parts are close to the size of the work envelope. You have to perfectly center the part about the work envelope not the table. It gets weird fast. haha

@@TritonTv69420 For some reason I had the impression they were symetric. On the maths front, there is something called Geometric Algebra. It makes the maths suprisingly easy.

Micro HD is, Micro Vario is not.

At least they understood enough basic design to put an electrical fitting where they needed an electrical connection, and not a socket head cap screw that would have been useless in that application. 🤣 There's a lot of different connections there in a tight space. It's likely that the connector used isn't the same as originally designed for, but a running change mid-production. There are several reasons why that might be, e.g. the manufacturer stopped making it or went out of business, or the current favorite: still Covid-backlogged. The engineering supply chain can be very fickle, and sometimes no available replacement is exactly identical. In the vast majority of applications an electrical connector like this would have much more space around it so the physical sizing of the hex just doesn't matter much and its electrical properties are much more important. In a perfect world the spindle designer would have left a circumferential buffer to allow for unforeseen connector changes, but guessing the future of the supply chain isn't exactly 'basic' design. Filing the connector is a bit of a bodge, but compared to the massive engineering costs of a spindle redesign (that would only add to its already sizeable cost), not a bad solution. There's a good shot of it @7:49

usually there's a break in period even for the ballscrews , specifics depend of specifics .

8:15 many 1/10 of 1/1000 of dollars... 🙂

No, but TL;DR the Evo + PyNo are too small and not suitable for his work. The Micro Pro is missing the thermal management system and several other key features. And the HD did not exist at the time of his purchase.

@@AlMg1SiCu oh ok, the pyno makes sense, didn’t know about the other ones and the features. Thanks 👍

Yes they do for all axis accept the z axis cause of many reasons and yes they wear off.

It's cool she was squinting.

Only the Micro HD has linear motors and hydrostatic guideways I believe.

One of the better CNCs you can buy in this world. You kinda need the overengineering for that

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