G0704 Spindle Mods and balancing ... Very cool!!!

[lcvette]

Ok. So I have been battling terrible vibration problems for some time with my spindle and pulley drive setup and a while back I had drawn up plans to change from the timing pulley setup to a multi rib poly v type pulley as they seem to work really well with higher RPM and run very smooth and have long life spans. My spindle finally got bad enough to require another set of bearings so I figured it's now or never.

So I went ahead and started the project this week. And have finished the pulleys as seen below. I used my G0704 setup like a Lathe to make the pulleys and used a SVVCN neutral Lathe tool holder with a 35deg diamond Point to cut the grooves which are a 40deg angle. It is tight in there and a cringed a bit on the G0704 when it made its final pass bit it worked out great in the end. I was able to keep run out to .001" which I think is significantly better then the previous timing pulleys used. I designed the spindle pulley to drive the quill barrel to keep the load on the spindle as close as possible to the larger body and keep any twist from occurring from driving it at the top.

While working on this project I started using Instagram.. I know I know.. I'm a late comer bit better late then never and conveniently enough happened to be the perfect time. I found a G0704 owner who may be on here as well?? his call sign on Instagram is @bens.Benz if you are on here I can't thank you enough for your ingenuity and to others reading, I recommend following him as he is quite the inspiration with this platform!

He used a phone app called "vibration monitoring" which uses the phones accelerometer to show imbalance from vibrations and a balancing ring added to the spindle just under the retainer on the bottom of the spindle to dial in the balance of the spindle while fully installed and under its own power. Very clever indeed. He used a jewelers scale with .01g divisions and an excel spread sheet available for download by searching "Conrad Hoffman Balance" on Google, showed up as the top result for me.

He ran the test with the ring rotated at 0, 120, 240 degrees (120degree increments) and exported recorded data from the vibration monitoring app into the spreadsheet and with some trial and error and removing discretionary weight as defined by the spreadsheet from the balancing ring (measured on the jewelers scale for accuracy) was able to balance his spindle so that it was silky smooth and quiet even at 13,000rpm!!!!

Maybe he will come in here and explain any items I missed, I will let him know I started this thread.

Linked below is his Instagram post.

https://www.instagram.com/p/9myfKxRz0U/

https://www.instagram.com/p/9myfKxRz0U/

Hopefully it works, never tried linking to Instagram before. I plan on documenting my efforts to replicate his work once my Belts and bearings arrive and will update e this thread with my progress!

Below are the pulleys I made as well as a short video of the last bit of groove cutting performed on the G0704 in transformer Lathe mode...lol. Sorry the video is so short but I didn't think to film it until it was almost done cutting. I used the J series groove profile since it was a little lighter weight then the automotive K series and was able to get a 6 groove in no problem and shouldn't have as much problem with the belt weight adding to vibrations. In retrospect and in future designs I think I will grind a custom tool from HSS and make a dual ratio setup, bit with the 12x12mm SVVCN tool it would have added ~.25" height from being able to get the tool on the smaller diameter step of the pulley. So once I finish converting my new 3 in 1 17x31 Lathe mill combo I may have a go at making a dual ratio drive. For now I just want to eliminate vibrations and noise and finally be done with bearing failures.

So here you go!









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[Fastest1]

Very cool. I now have a vibration app too! I learn something all of the time. I never understood or have used Instagram as it seemed like just another reason to dislike people. Interesting. I would like to see Ben's approach to the spacers he mentions.

[lcvette]

Yeah Instagram was not on my radar for a long time, I knew what it was but didn't k kw there were so many machining people in there using it. Very cool feeds to follow and share with everyone..lol

What spacers are you referring too? Must have missed it.

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[Fastest1]

I just got back from Benz's Instagram page or whatever that is. Lots of videos showing many aspects of his machine and mods. The spacer is his approach to installing the bearing without the drive tube. Or that is what it appears.

[lcvette]

Yeah, just found it, that is exactly what he is doing... Sounds like what Chris is doing.. I think while I have the drive tube out to replace the upper bearings I'm going to turn off the gears to remove some of the weight, i'm sure they add to the imbalance of everything. Think I'm going to add on a trigger wheel for spindle feedback as well, the output from my BLDC driver is not very stable and jumps around alot. Maybe I will make it with some extra meat and balance the barrel before putting the spindle in and then put the spindle in and balance it.. Should be nice and smooth after that.

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[Fastest1]

I have the Bench Top Precision kit. It replaced that tube with a seemingly well made version without the gears. Something in the assembly vibrates.
My theory is the least parts the better. I am curious as to why Benz made the adapter, or maybe the bearing wasnt available in the correct OD/ID? Same thing, less parts the better. Might be cost?

[lcvette]

He mentioned because he couldn't find a bearing with the speed rating he needed.. Usually larger bearings have lower speed ratings because the balls move exponentially faster the bigger the farther away from the centerline they get. He spins that thing to 13,000rpm...lol insane..

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[lcvette]

Ok, so my bearings arrived finally so that is good!

This evening I removed the quill barrel and chucked it up in the Lathe... Man the material between the two gears was so far off from being concentric to the centerline its not even funny.. .035" off center.. I imagine that was my biggest culprit of vibration.. So it is now cured and all is nice and concentric and the entire quill barrel is all concentric to itself to about .0002 which should be perfectly fine for 6500rpm max.

I can't believe how nice it is to have a Lathe mill combo beside the G0704 to work on mill parts when its torn down..lol.

I'm waiting on a live center that I ordered that is delayed in shipping. But when it arrives (crossing my fingers its tomorrow) I'm going to chuck up the spindle with the top hat for the power drawbar installed, and skim turn it to be perfectly concentric to the spindle, then I'm going to make a draw bar that fits snuggly through the top hat so it will stay concentric. And Chuck up each belville and ream them to fit the new draw bar (just a light cut to have them fit without any gap over the drawbar).

Then I'm going to install the top hat, bellvilles and drawbar on the spindle with a collet installed and tighten it down and skim cut the outside of the belvilles.... Hopefully after all that the whole rotating assembly from top to bottom will be concentric and it should be closer to balanced and require very little discretionary weight to final balance once installed.. Maybe finally it will be silky smooth and quiet.

Here is a shot of the freshly turned down quill barrel!!



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[Eddard_Stark]

Thanks for starting this thread.....Upon reading OP I signed up for Instgram so I could follow the machinist community (have heard several positive mentions in forums I frequent; balancing video put me over the top)

When I convert my G0704 this is on the list of threads to reference.

[lcvette]

Thanks! And yeah I am amazed at Instagram.. It's my new favorite...lol

Definitely balance the spindle, it is a good way to enjoy higher RPM without destroying bearings and making better part finishes for sure!

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[lcvette]

Well, nothing super exciting to report today.. Out of 3delayed packages, 2 could have helped me today and of course the one that made a break for it and showed up, a set of soft jaws is useless for this project.... Lol

I machined the flats and drilled and tapped the quill barrel and pulley for the holding screws.. That was supposed to be a simple job, but of course a tap broke.. Sure wish I had the cnc mill running, I hate tapping, thread milling is the only way to go for me anymore.... Todays whole project that took 5 hours of work and repair could have been banged out in under 5 minutes on the CNC with he barrel chucked up in the 4th axis.. I don't miss the days of converting in a manual mill, but I am glad to have one..

So I am trying to decide the best way to fix the motor pulley to the motor. The motor has a keyway, but I have no way (that I Know of) to make a key way in the pulley. Any tips and tricks appreciated here.

I don't want to drill through the ribs of the pulley and use a set screw, I prefer to use a retaining bolt in the end and the keyway for quiet operation, (can hear when the belt goes over the drilled holes on pulleys).

Any thoughts on how to broach without a broach? I have considered using really small drill bits and drill the key way and then finish it with a square edge file. Anyone tried that before?

Chris

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[pippin88]

Square file and some patience

[Fastest1]

Simple, broach with a lathe and a tool holder. I did it as a joke just because it became obvious 1 night. Like this

[lcvette]

That's awesome... Only problem is all I have is insert type tooling.. Lol.. Except I do have a cutoff blade that I never use since getting a insert type.. Will have to see what the width is..may have to cut the width and a couple passes with it thought.. Will have a look tomorrow

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[Fastest1]

Buy a piece of key stock and sharpen it.

[lcvette]

Well... Duh... KISS..lol. Why did t I think of that?

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[lcvette]

Ok, finally had some time to wrap up the quill barrel mods.. Hope to have the mill back together tomorrow to make the new motor mount parts!! Then install the new motor and Drive and electrical components and do the balancing for everything. Then make the new spindle index optical pickup case and install.

Then finally I will begin the z axis linear rail conversion.. Lots to do bit hopefully when its done the mill will be tighter and more powerful then it ever has been. Can't wait to see the part finish after its completed!



Above is the spindle index pulse disc with a slot for the optical pickup to trigger the index pulse to mach3. There is a formula used to determine the slot width but after several hours of research and asking questions on the mach support forum it was explained that the formula is for the minimum slot width and the bigger it is the more likely you are to have a stable signal to mach3. So I decided to use the formula and then make the slot angle two times the minimum to be safe. It was suggested I make it a half slot half disc for 50% of spindle rotation triggering, but it seemed like overkill and would be much harder to balance so I decided to try twice the formula angle. We will see how it works.



And in this picture, everything assembled and ready to be installed into the head. The index disc was made with a .0015" interference fit, heated and pressed onto the freshly turned will barrel. Then the new deep groove Nachi bearings were installed again with heat and the shop press. Then to eliminate the imbalance of the retainer clip, i opted to turn a ring spacer out of aluminum to press over the upper bearing and be proud .010". Then the pulley was pressed into the quill barrel and against the upper bearing spacer. To retain the pulley, two flats were previously milled into the remaining portion of the upper gear and a hole was drilled through the center of the quill barrel and through the pulley hub. I then tapped the drilled holes for 1/4-20 threads and used two stainless steel button head socket cap screws to secure the pressed in pulley. These screws hold the pulley and maintain the upper bearing to the quill barrel very slick design I think..

And the finished product is a very concentric and balanced quill barrel drive assembly that should last for a long time to come and not introduce any vibration. We shall see how far out it is during balancing!

[BTP]

Fastest1, I believe you have one of the early spindle nuts. The vibration you are referring to is the backlash between the male spindle splines and the bearing carrier female splines. For fitment reasons, this is inevitable. This has since been corrected with a simple o-ring design on the spindle nut. The o-rings compress against the inside wall of the bearing carrier which eliminates the vibration entirely.

Here's a picture of the new spindle nut.

[DonKes]

Why don't the mfg's use an even number of slots to help balance.

More accuracy.

Don

[lcvette]

What is that spindle nut? Mine doesn't look like that.. Crap I need to get a new one I guess. Looks like those o-rings also would seal metal from getting down into the bearings that might come from the top from the splined shaft.

Thanks for posting that up!!

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