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R8 Spindle Speeder - new member

vmipacman

Cast Iron
Joined
Nov 21, 2014
Location
Virginia, USA
Hello, It's good to finally be a member. I have frequented PM for years and spend a lot of time on the forum but usually can find the answers to my questions by searching. I finally have a question I would like to ask and get some different perspectives on. This is pertaining to spindle speeders.

I have been needing to use as small as a 1/32" EM on my CNC kneemill. For the last couple projects most all of the tools have been smaller than 1/4" and I am struggling with the max RPM of the bridgeport. 4500 rpm is still very slow for such small tools and I hate running the machine wide open for hrs at a time. I searched for a high speed spindle option but could not find one for an R8. I have designed a spindle speeder/multiplier instead that I think could be used when I need higher RPM's. I considered several other methods such as air or electric spindle or gear drive but felt this had its own set of benefits. My plan is to build this for myself, but was hoping I could get some input on this concept. I guess I am also trying to gauge whether this is a common issue others encounter and how they solve it, i.e. is there a larger need. If spindle speed on bridgeport's is a common issue, is there an aftermarket solution I have overlooked? (Everything I have found is several thousand dollars and designed for a CAT40)

Pros:
-1:6 ratio
-timing belt drive, dampens vibrations and easy to maintain
-power taken from main spindle
-maintains original zero
-easy tool change
-ER20 collet

Cons:
-Run out, TIR of main spindle is compounded with run out of speeder. Hope to achieve .0002-.0004" TIR on the speeder assy alone.
-Deflection, I expect 1/4" EM max in aluminum.
-Loss of ~.5" Z travel due to torque clamp

Usage:
I would use this for 1/8" tools or smaller. Engraving would be a good use. Expected max rpm would be around 20K. Not meant to replace an actual high speed spindle, just provide a stop-gap measure if you must use a tiny tool on a bridgeport.

I look forward to your replies. Thanks, Paul
spindle assy.jpg
 
You'll need super precision angular contact bearings in your spindle. Your drawing shows what would appear to be plain ball bearings, due to the simplistic construction of the high speed spindle and its housing. Angular contacts require more components and more complex construction details.

Plain ball bearings will permit your spindle to float way too much, be noisy at 20,000 rpm and probably will overheat.

I would also be concerned about all the additional rotating mass that you have to spin with the countershaft speed up. Little timing belts may not handle the start up jolt very well. I'm also hazy on the engineering of timing belt speeds, but those belts sing like a high speed zipper when you run them really fast :D
 
If spindle speed on bridgeport's is a common issue, is there an aftermarket solution I have overlooked? (Everything I have found is several thousand dollars and designed for a CAT40)

I did a Google search "R8 Spindle Multiplier" and came up with lots of hits ???
I did not investigate further,but it looks like they are out there.
 
I like your design. For the most part I think it's pretty good if your bearings are very good.

However I think the yuasa is hard to beat for the price and it's very well proven.

Also, anything driven by the r8 is going to orbit, magnified by the overhung distance. For that reason I think you would like a design that is not driven by the rotating spindle. -Which brings me back to the router motor option.

I might think about a motor running a belt drive to the quill like an old dental drill. maybe a 9mm timing belt with a piece of extra long pulley stock and let the belt walk along the pulley. that might get you a couple inches of z.
 
One might even make the case for a complete system built with that sort of 'packaged spindle'.

There are now tons of choices - including air and water cooled. Some are right economical...a decent design could provide for swap-out and upgrade of the spindle itself.. precision long-nose or short. Design it with all it needed to do its job...

And then....attach to the aft-end of the ram, just as BP did for slotter or cherrying heads.

Or to any OTHER mill, horizontal as well as BP. One could see more 'leverage' in going to the effort if the 'gadget' ended up more universal as to where one could use it. That's how BP itself got started, after all...

Bill

that's right smart.

spin the turret around and use or make make some servo controlled linear rail or box way slide etc and put a decent router spindle on it. this gets you past the crappy cnc quill drive some turret mill cnc conversions have.
 
Thank you for the comments.
You'll need super precision angular contact bearings in your spindle.
I absolutely agree. I did intend to use precision angular bearings but the model does not show them. McMaster is just so easy to drag and drop parts from. I should have caught that before taking the screenshot. I am not sure about the missing complexity to use the precison bearings though? I have it setup with matched bearings (model aside), spacer, and preload nut. I need a way to lock the nut (like a setscew) and some shims possibly but what else would you recomend? One other thing, I planned to have the R8 taper ground insitu after the bearing cartidge was assembled and preload set.
I did a Google search "R8 Spindle Multiplier" and came up with lots of hits ???
I'm sorry but I did not... Lots of pictures of homemade offset spindles, some super high speed air driven spindles for VMC's, did touch on the Yuasa!, and several pictures of a Tormach unit (not sure the taper). Lots of hits, but not many that really fit the search.
Are you aware of the Yuasa speed multiplier (not sure of the ratio)?

Here's one on eBay. No connection to the seller.

Yuasa Speed Multiplier R8 Milling Machine | eBay
Only vaguely, Thanks! I looked a couple weeks ago and did not see one. I did not know they could be had as readily as that. Do they still make/support them? Or when did they go out of production?

However I think the yuasa is hard to beat for the price and it's very well proven.

Also, anything driven by the r8 is going to orbit, magnified by the overhung distance. For that reason I think you would like a design that is not driven by the rotating spindle. -Which brings me back to the router motor option.
I am not sure I understand your comment completely. The two comments seem to contradict one another. I understand and completely agree that any runnout would be magnified. Does the Yuasa deal with this issue differently so as to make it a very well proven design?

Thanks
 
Thank you for the comments.

I absolutely agree. I did intend to use precision angular bearings but the model does not show them. McMaster is just so easy to drag and drop parts from. I should have caught that before taking the screenshot. I am not sure about the missing complexity to use the precison bearings though? I have it setup with matched bearings (model aside), spacer, and preload nut. I need a way to lock the nut (like a setscew) and some shims possibly but what else would you recomend? One other thing, I planned to have the R8 taper ground insitu after the bearing cartidge was assembled and preload set.

You need a locknut on top of the spindle to retain the bearing inner races and the spacer, otherwise the spindle will just work its way out. Then you could set the preload with the cap. I see you have something rather skinny drawn there, it looked more like a dust cap than a nut, but as long as you know it needs to be there.
 
Could you use a miniature air die grinder (1/8" collet capacity) in a bracket held coaxial with the quill? They can spin up to 50k RPM but can be throttled back to about 30k. The other accessory needed is a miniature sign to hang on the spindle switch "CAUTION -TURNING SWITCH ON WITH DIE GRINDER MOUNTED MAY RESULT IN PROFANITY".
 
I have a $3k / 60k rpm air spindle and I have accidentally turned the spindle on with it. profanity does ensue.

luckily it's fed with a push lock air hose fitting that rips the hose out, but not until it's ripped the filter/regulator off the side of the mill and thrown it on the floor.

<$100 air handpieces are not up to cnc engraving duty for long.
I wanted to pack a cheap handpiece one up inside a cat40 toolholder once, but it was not nearly good enough for .010" endmills so I bought a $3k air spindle.
http://www.airturbinetools.com/spindles/specs/602js.html
 
FWIW, the input shaft on Tormach speeder fits into a 3/4-in R8 collet in the spindle; Tormach specifies that their collet, which has a flat nose, be used. The output shaft spins at 3x the mill spindle speed.

Mike
 
This person is looking for the most cost-effective solution, otherwise a KERN might be the right answer (lol).
For milling a lot of materials and for very small end mills, you will still want a spindle speeder on a CAT 40 Machine, even one with 20k RPM.

Dan
 
This person is looking for the most cost-effective solution, otherwise a KERN might be the right answer (lol).
For milling a lot of materials and for very small end mills, you will still want a spindle speeder on a CAT 40 Machine, even one with 20k RPM.

Dan

Well Dan, thanks for digging up a 5 year old thread to let us know!
 








 
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