Okay, first off, I've been building this spindle for a few months already, but only got a buildlog on a Swedish forum, then I thought wny not share this build with you guys too!
For you who wounder, I work as a tool maker for mold injection, that's why I have access to all the machines.
Oh yeah, almost forgot, I'm making this spindle because milling spindles really fascinate me. I have a small chinese bench-top mill that I re-built to 99% and made a new BT30 spindle for (that was ~1½ year ago.) But the design and my job wasn't that great. (Because I didn't have enough knowledge and not access to good enough machines) But with the first spindle I learned a lot, so now move on to the next one!
Let's start with a section view of the spindle design. I might make some minor changes to the design through out the build tho.
Attachment 244004
Manufacturing time!
When the spindle is done, I need to measure the run-out of the tool taper somehow. So I started making a "test bar". I used Uddeholm Stavax for the test bar because it is a rust-resistant tool steel which can be tempered.
I lathed the shaft to nominal diameter + ~0.4mm, which will later be removed with the cylindrical grinder. Then I turned the part around and lathed the tool taper, bored and tapped the hole for the draw-bar.
Attachment 244006
Attachment 244008
Then I started making the rings which will offset the angular-contact bearings(for added stiffness) and also the rings to adjust the pre-load in the back roller-bearing(the bearing have a tapered seat on the axis, so the harder I tighten it on the bearing seat the less clearance it will have, or in my case, preload.)
The rings are made of Uddeholm Orvar Supreme(2242), it is a good "all-round" tool steel.
Attachment 244010
Attachment 244012
Latheing a small part for the gripper.
I made this out of Orvar, too.
Attachment 244014
Now, let's get serious and start making the spindle shaft!
For the previous small parts I used the smaller lathe, now for the shaft i used the heavy-duty one! I actually like the smaller one better, but for this job the bigger one is better suited.
This, too is made of Orvar, quite a big chunk of tool steel!
Attachment 244016
Attachment 244018
Some hours later...
Annnnnd it's done! Well, operation 1 atleast. :P
Attachment 244020
Attachment 244022
Turning the shaft around and boring out the shaft.
Attachment 244024
Making the labyrinth-seal for the front-bearings. I made the play around 0.2mm/side.
These 2 are made of Stavax, because it is rust-resistant.
Attachment 244026
Attachment 244028
I lathed the front-lid for the spindle and drilled the holes for mounting. But I accidentally f*****-up.(got the hole and head clearance off-center to each other) To fix it, I used the sinker-EDM(sure i could've fixed it in the mill/drill-press, but it looks muuuuch better EDM'ing it! ). Cylindrical ground a electrode for me to use.
The front-lid is made of Stavax too, for it's rust-resistant properties.
Attachment 244030
Attachment 244032
Attachment 244034
Attachment 244036
Attachment 244038
While the sinker-EDM was running I made the drawbar in the lathe.
It is made of Uddeholm Impax Supreme.
Attachment 244040
I sent all the Orvar and Stavax parts off to tempering! Now there around 52HRC hardness. Nice!
Attachment 244042
Now the precision work begins! For higher parallelness, I began with grinding the magnetic table.
Attachment 244044
Attachment 244046
Surface grinding the parts to tolerance on both sides.
Attachment 244048
The spacer rings between the front AC-bearings need to have a really tight parallel tolerance, I measured the parallelism against a flat-surface and a 1µm dial-indicator. I measured the parallelism to 2µm on the bigger ring, on the smaller one it is 1µm. Yeah, I'm happy with the result.
Attachment 244050
Then off to the cylindrical grinder.
Attachment 244052
Mmmmmmmm... Ground parts!
Attachment 244054
And they fit, too!
Attachment 244056
Attachment 244058
Attachment 244060
Attachment 244062
Measuring the axial-play in the labyrinth seal, turned out perfect!
Attachment 244064
Some ground and "to be ground" parts for the gripper assembly.
Attachment 244066
Time to grind the spindle shaft!
First of all, I started grinding the tapered bearing-seat for the roller-bearing and measuring the taper in the measuring machine.
Attachment 244070
Attachment 244068
Some hours later, it was finally done! And my god it is beautiful.
Attachment 244072
Next up, the test bar! Ground in a single clamping to get 0 run-out.(or atleast verrrryyyy little run-out)
Made a short video confirming this.
https://www.youtube.com/watch?v=I8nkFkNeFhU
Attachment 244074
Ground some small parts for the gripper.
Attachment 244076
I bought a roller bearing and some lock-nuts for the spindle.
The roller bearing is a SKF NU 208 ECKP-C3, (I wanted a bearing with lesser play, but the only one they got was with C3 play, oh well.) This bearing is kinda special too, because of it's tapered bearing seat (1:12 taper).
The nuts are SKF KMT 10 and SKF KMT 8, high-precision locknuts.
I already got 2x SKF 7210 BEGAP AC-bearings from my previous spindle build, I'm re-using those.
Attachment 244078
Time to grind the thread for the lock-nuts! Yes, I said grind...
Attachment 244080
Attachment 244082
Attachment 244084
When the ATC is in progress, you want a stream of air to clean the taper, made a small hole (~1.3mm) through the drawbar to get that stream of air.
Attachment 244086
Attachment 244088
Just for fun, I tried mounting the AC-bearings and the spacer rings and check the run-out of the bearings.
Yeah, I'm quite happy with the result.
https://www.youtube.com/watch?v=JG0BBG3qgeU
Attachment 244090
Ground the tool taper - check.
Run-out of the bearing seats was around ~1-2µm.
Feels like the run-out of this spindle is going to be really minimal. My guess/hopes are around 10µm, 200mm out from the taper(that's the length of the test bar).
Attachment 244092
Attachment 244094
Time to sinker-EDM the large hole in the spindle for the drawbar assembly.
Attachment 244096
Attachment 244098
Attachment 244100
Attachment 244102
And sinker-EDM the thread to hold the gripper assembly in place.
Attachment 244104
Attachment 244106
A huge chunk of Uddeholm Impax, will be the spindle housing! Raw material weighs 23.3kg!
Attachment 244108
Attachment 244110
Attachment 244112
First tempo done. Should weight around 16-17kg.
Attachment 244114
Did the next tempo in the CNC-mill. Milled in the height and front diameter +0.2mm saved for grinding.
Also drilled 2 holes thru the whole housing, those holes will be used as starting-holes for the wire-EDM.
Attachment 244116
Ground 2 electrodes to sinker-EDM the space where the gripper opens.
Attachment 244118
Attachment 244120
Made some drive dogs, they are made of Impax.
Attachment 244122
Milled the electrodes for the "drive dog track" for the spindle.
Attachment 244124
Attachment 244126
Attachment 244128
Attachment 244130
Milled and sinker-EDM some drainage tracks for the front-lid, so liquids don't enter/get stuck in the labyrint seal.
Then I polished it.
Attachment 244132
Attachment 244134
Attachment 244136
Attachment 244138
Time to fit the roller-bearing. Right now there is ~0.07mm radial play in that bearing, but I want a preload of a few µm. That's why the bearing seat have a 1:12 taper, the harder I tighten the nut the more the inner ring expands. That's why I need a spacer ring, ground to tolerance beneath the roller bearing so I don't over-tighten the nut and get too much preload.
I used a dial indicator with 1µm resolution to check the radial clearance in the bearing, then I tightened the nut more and more until I got a pre-load. Then I measured the distance beneath the bearing with gauge blocks.
Attachment 244140
Attachment 244142
Lathed, ground and sinker-EDM the gripper, All that's left is to split it in the wire-EDM.
Attachment 244144
Just for fun, I assembled most if the stuff I could. I can promise you, this is a sturdy piece of metal!
Attachment 244146
Attachment 244148
Well, that's a few months work up til' now, hope you like it so far!
I'm going to start wire-EDM earliest next week.
If you have any questions or design improvements(It might be a little late for that now but one of the reasons I'm making this spindle is to learn something), feel free to tell me!