Automatic Tool Changer with Pull Stud Tooling without changing R8 Spindle

I'm in the process of designing an Automatic Tool changer for my Charter Oak Automation RF45 mill. I am going to design it with the original R8 spindle as I am finding the NMTB 30 tooling harder to find in my area. plus it doesn't lend itself to automatic tool changers. I am also designing new R8 tooling similar to what David Decaussin did, It is R8 Taper with a CAT V Flange. I am including a model of what I have so far.

Very nice subscribed...

The Cat R8, as Mr Decaussin calls it, is on my project list as well. Matter of fact, I made a couple tool holders some time back to test my taper setting on my lathe. I have the ball grip for the pull studs made as well and have tested the fit of the various parts to the spindle. I backed off of the project waiting until I could afford a heat treat oven to properly heat treat the various parts involved. I have that now and am preparing to jump back into the project sometime this winter. I recall my design of the complete QCTH system being hung up above the spindle in regard to an air cylinder or another option. I never took the next step of designing a tool changer. I'll gladly watch your build and wish you success on it. Are you intending to incorporate drive dogs on the spindle and notch the tool holders for them? I did on mine.

Bob

Very nice looking forward to see how it works !


was thinking of making a large collet for my NM TB30 and work with that to make my tool changer .

I've been using BT30 tool holders in the original NMTB30 spindle that came with my IHCNC. These are designed to be used with removable pull-studs, but I just extended the manual draw bar a bit and they've been working very well. The tool holders are readily available and not too expensive. Has anyone looked into modifying the spindle with a power draw bar and clearance for a grabber at the top of the taper?

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Originally Posted by ksanalytical

I've been using BT30 tool holders in the original NMTB30 spindle that came with my IHCNC. Has anyone looked into modifying the spindle with a power draw bar and clearance for a grabber at the top of the taper?

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I tried to purchase a NMTB30 spindle for my IH mill to play with and look into doing that, but never got one bought. I like the longer taper, but that small diameter at the top is a problem and you're correct that it would need to be enlarged. Getting the gripper in the R8 is doable, but I wouldn't want to try it on that little area. My original thinking on trying to change to a NMTB30 was the outside of the spindle most likely would look exactly like the R8 version I have today, so opening up the smaller area would be possible.

One thing that needs great attention to, is that area has to be exactly concentric to the taper. You don't want the gripper pulling the top of the tool holder off of the center of the spindle. It could be opened up to match the same size as an R8 taper spindle and be made to work I think, but it will certainly take away from the length of the taper of the NMTB30. probably leaving it the same as a standard R8 taper in length. So I came away from my cursory look at it thinking just use what I had in the R8. Like I mentioned above, I've made a couple sample CatR8 tool holders with included pull studs. Pretty much just like Mr Decaussins versions. The taper is short no doubt, but no shorter than what the TTS style tool holder seems to be. I've added drive dogs to the end of the spindle to help the taper out.

The part of the design I'm working to today that I don't like is the gripper. I'm using 3 hardened balls, 1/8" or 3/16", i don't recall exactly right now. That's all built, but not installed. I would like to have gripper fingers there instead. But at this point I'm uncertain if I'll make that move. The ball gripper hasn't failed as it's not been used on my mill. And I've seen plenty of them in use, so it must work ok.

I do think there's a market for a better spindle for these machines. Not a high dollar, high speed, cat 40 kind of deal, but a spindle that offers a QC tool holder feature, maybe having the tension springs built into it along with the gripper. For a belt drive spindle under CNC control, the quill isn't needed, just a bearing housing holding the spindle that locks into the mill head. Consequently, the splines on the spindle aren't needed either. Leaving the splines off the spindle greatly simplifies the making of the spindle. I don't think the current replacement NMTB30 is that spindle though. Back when I started on redoing my mill with QC tooling, making a spindle was a bit daunting and still is somewhat today. But I've made replacement spindles for two older lathes and made a D1-3 spindle for a 4th axis in the recent past and am not as intimidated by the task. One isn't on my to do list though.

Bob

I did a little what if in my cad program this morning taking the NMTB30 dimensions and removed enough taper length to achieve a 1" diameter like the R8 tool holders have to give room for a gripper. I'd done the same thing a couple years ago, but had forgotten the exact results. That takes a bit more than 1" off the length of the taper measured along the tools center line. Making it mostly the same as the taper length of an R8 tool holder. And I'm hard pressed to think more than that is needed for these small horse powered machines. Add a couple drive dogs to the spindle and I think it's a fairly capable combination. Now more meat at the taper end of the spindle to add those dogs would be an improvement.

Bob

not to get further off topic but couldn't there an adapter ( collet ) made for the spindle with the correct taper of the NMTB30 and use the same style thread and end of a holder . this is a quick drawing of a 1/2" collet just to represent the holder/collet

I guess I got no idea what the need for a collet or adapter is. But I do have a suggestion for the draw bar. I personally don't think the little hardened balls are going to work for pulling in the pull stud. I started out with that very same idea, but now have work toward gripper fingers instead. My problem with the balls was one of accuracy. In order to keep from pushing the pull stud out of alignment with the spindle center line, they would need to contact the ramp on the pull stud in exactly the same place. I felt a lot had to be right for that to happen with little room for error. With fingers, or pedals as I hear them called, I think they are more forgiving as they provide a means to turn the holding feature all in one operation yielding a uniform ramp to match the ramp on the pull studs. In addition, they add way more contact area than any number of balls ever could.

It doesn't take much web searching to find stated problems with the ball type grippers, and that was what started my rethinking them. I was able to keep the outer cylinder that had the ball cage inside it and use the ramp in it to close the fingers on drawing in the tool holders, so the only changes I made was to replace the ball cage and balls with he fingers and add a shoulder bolt to the bottom of the draw bar to array the fingers around.

Attachment 262580

Bob

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Originally Posted by RustedOut

I guess I got no idea what the need for a collet or adapter is. But I do have a suggestion for the draw bar. I personally don't think the little hardened balls are going to work for pulling in the pull stud. I started out with that very same idea, but now have work toward gripper fingers instead. My problem with the balls was one of accuracy. In order to keep from pushing the pull stud out of alignment with the spindle center line, they would need to contact the ramp on the pull stud in exactly the same place. I felt a lot had to be right for that to happen with little room for error. With fingers, or pedals as I hear them called, I think they are more forgiving as they provide a means to turn the holding feature all in one operation yielding a uniform ramp to match the ramp on the pull studs. In addition, they add way more contact area than any number of balls ever could.

It doesn't take much web searching to find stated problems with the ball type grippers, and that was what started my rethinking them. I was able to keep the outer cylinder that had the ball cage inside it and use the ramp in it to close the fingers on drawing in the tool holders, so the only changes I made was to replace the ball cage and balls with he fingers and add a shoulder bolt to the bottom of the draw bar to array the fingers around.

Attachment 262580

Bob

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Just out of curiosity, what material are you using for the gripper fingers? Heat treating will be necessary for longevity and reliability so material choice will be crucial. I've done both Cat-R8 and BT30 with the ball stud gripper which worked very well. My component were made from 304 SS and seemed to work quite well.

D2 for the gripper fingers, the rest of the parts in that area are from 01. And yes, heat treated. I have my own oven for that.

What I really don't like about the balls is the contact area or lack of it. Just doesn't seem right to me. The wear points are so small they have to wear faster than something with more contact.

Bob

I've been working on my Cat R8 tool holders and have one end of 15 or so of them done and about a third of those nearly done with the end mill bores finished. I had to work out the process to be able to turn them 100% on my lathe and that's working well. I'm getting low runout numbers on the actual tools sticking out of the tool holders with the worst being .0004" tir 3.5" from the gauge line of the longest tool holder. I'm measuring half that or less as they get shorter, so I'm pleased with that.

But one thing has been bothering me as I get these finished. That is how far the actual cutting end of the end mills are ending up from the gauge line. I wish I had made the tapered ends longer so the pull stud could be farther up from the gauge line so I could shift the end mill bores up into the taper. Mine all start at the gauge line as the end of the pull stud ends there. And there's nothing in the spindle that would prevent that other than my spindle sleeve. My sleeve is a exact copy of Mr Decaussins other than changing what was needed for my selection of pull studs and fitting it to my draw bar diameter. There is inches above the gripper area that could have been used. But I don't think inches were needed, maybe just 1/2" shift on the pull stud. That could have been accomplished by just making the taper longer and the spindle sleeve shorter. You can see in one of my shortest tool holders the large diameter flat at the top of the taper. No real reason for that other than following what Dave did in his design. There wouldn't be any more engagement of the taper as there is no more taper in the spindle.

Attachment 268072

That being said, I'm wondering lately how tough it would be to modify an existing NMTB 30 spindle to make the features needed to to make gripper fingers function. That's probably above my pay grade though. I don't think I'd want to be modifying any existing NMTB 30 tapered tool holders either to shorten them and add the pull stud there unless I was turning the rest of the tool holder features afterward. I'm cutting my tapers first along with the gripper section of the tool holders, then flipping the tool holders and holding them by the taper in my lathe spindle with a heavy draw bar through the spindle. So, in theory, if I could have modified an existing NMTB 30 spindle, then made the custom tool holders to fit that with the shift of the pull stud and end mill bores as mentioned above, there would be more taper to be engaged. That would be a good thing. But I'm not changing course on what I'm doing, just thinking out loud about the results.

So native34, how goes the design of the ATC? You get any further than a concept? Not that I'm going to build one, just always interested in what others are doing with these mills. I got my hands full with the Cat R8 stuff for now.

Bob

I haven't been able to do much on it lately, as I'm working fulltime and back in school fulltime as well. I'm hoping to get some more accomplished on this over the spring break and have a working prototype done by June/July.

Hi Bob,
I am interested in the CAT R8 tool holders I ordered a couple from DD and wondered how yours are coming along can you give me any information as to which size pull stud your using?
The amount of Bellville's needed, and if you have experienced any slippage etc.
Are you grinding the tool holders after Heat treating? etc.

Any info would be helpful. Also if your running Mach3 I have developed a ATC Screen set and Macro unlike anything else Ive seen.

Be Safe Sam
www.cnc4xr7.com

Not sure I'm the Bob you're speaking to, but I do have an update on the Cat R8 tool holders. I never did like them that much better than R8 and I eventually gave up on them after making a bunch of them. Never even put them into service as I attacked other areas of my mill that took me nearly forever to finish. In the middle of that, I bought a NMTB30 spindle, designed a new spindle housing to use angular contact bearings on the bottom end and built it. In the middle of me flip flopping on Cat R8 or not, I started buying BT30 tool holders. Now I have about 40 of them and most of the old R8 stuff is gone. The never used and some never quite finished Cat R8 are sitting in a box looking for a new home. I went with BT30 45 degree pull studs for the Cat R8 holders, the 12 x 1.75mm ones. So all the Cat R8 tool holders got threaded for those. I think the only thing I didn't do was to finish the end mill ends of them. I even built a lathe fixture to do that along with a draw bar to pull them into it. I never did heat treat them either as that would be the next step when I was bailing on them.

Went to a lot of work to end up not using them I guess. But I like where I'm at now. I'm not running pull studs on the BT30 tools, just a threaded draw bar. I've tested repeatability on the BT30 tools and they repeat less than .0004" in multiple tool changes over days just indexing from my home switch. I think I could have gotten to the same point with the Cat R8, just decided to go another route.

I've also moved on to Mach4. I like it better than I did Mach3. Had to learn a bunch of new stuff though to get it up and running. And that took forever too. But now the mill runs better than ever before. Even added a chip enclosure to it. Next step is the 3 phase 3 hp spindle motor. I'm slow if it doesn't show.

Bob

Thanks Bob,
For the information I am currently using TTS tool holders But have been debating the CAT R8 option as a ATC is in my future plans so a PDB will be used.
Pull out is my main concern with the TTS system.
Be Safe,
Sam

Yeah, I never got excited about TTS, thinking Cat R8 a better choice. Especially if one added drive dogs to the spindle, that was part of my plan. What I ended up not liking about Cat R8 was the short length of the taper vs BT30. Another plus to BT30 was the drive dogs. And once I got my first BT30 tool holder, Cat R8 was history.

Regards
Bob