[N4NV]

Has anyone ever seen an automatic tool changer for a Bridgeport mill with R8 collets? I have looked at some quick change tooling and it looks like an automatic system could ge adapted.

Vince

[ViperTX]

Tormach....I believe still offers one...

[N4NV]

I checked their web site and they do not have one listed.

Vince

Tormach....I believe still offers one...

[philbur]

I have the Tormach system. It is an excellent quick change system but is not designed for an ATC.

I think you will have extreme trouble with an ATC for R8 collets. How would you hold the cutter in the collet until it was drawn into the taper of the spindle, how would you ensure repeatable of the Z-axis location when there is no fixed axial relationship between the cutter and the collet. Lining up the drive key with the collet keyway will also be a bit of a challenge but is probably less of a problem than the other two points. It's never good to say never, as somebody will always prove you wrong, but an ATC for R8 collets is a challenge not worth tackling in my opinion. R8 tool-holders might be another proposition however.

Regards
Phil

Tormach....I believe still offers one...

[N4NV]

http://www.royalprod.com/product.cfm?catID=11

Royal Products makes a quick change system where the R8 collet stays in the spindle, you only change a tool holder. The problem with adapting their system to automatic would be lining up the spindle. That may be possible if you had some type is system that could sense the spindle position.

I have seen other automic systems for smaller mills that did not require indexing the quill.

Vince

[ViperTX]

Oh, I remember Joe Vicars.....for some reason I always think Tormach.

[philbur]

I did say never say never. I've just looked at my Tormach quick change. The tool holder shank is parallel so you would need to add a guide taper to the told-holders to assist with alignment during entry into the collet, and some form of positive assist to eject. The positive eject could possibly be achieved with a spring, internal to the collet. The tool holder also needs to be pushed positively into the collet as you activate the drawbar. This could be achieving with some kind of spring assist under each tool in the carousel.

The Royal products system looks like it could solve some of the problems relted to the paralle shank, looks expensive though. The beauty of the Tormach system is you can make tool-holders on a small lathe, no precision tapers to be ground.

Get the CAD system fired up and go for it. When you have developed a proven system please send me the drawings.

Regards
Phil

I have the Tormach system. It is an excellent quick change system but is not designed for an ATC.

I think you will have extreme trouble with an ATC for R8 collets. How would you hold the cutter in the collet until it was drawn into the taper of the spindle, how would you ensure repeatable of the Z-axis location when there is no fixed axial relationship between the cutter and the collet. Lining up the drive key with the collet keyway will also be a bit of a challenge but is probably less of a problem than the other two points. It's never good to say never, as somebody will always prove you wrong, but an ATC for R8 collets is a challenge not worth tackling in my opinion. R8 tool-holders might be another proposition however.

Regards
Phil

[philbur]

The Royal Products QC.

It's not clear how the tool holder is drawn into to spindle with sufficient force to ensure the tool-holder taper is rigidly held. I don't see how a locking ring is going to make it. So it looks a bit light weight with respect to maximum radial loading. And look at that price. At those prices it's probably a better bet to change your spindle for a proper quick change system compatible with ATC.

Regards
Phil

http://www.royalprod.com/product.cfm?catID=11

Royal Products makes a quick change system where the R8 collet stays in the spindle, you only change a tool holder. The problem with adapting their system to automatic would be lining up the spindle. That may be possible if you had some type is system that could sense the spindle position.

I have seen other automic systems for smaller mills that did not require indexing the quill.

Vince

[Hood]

A guy called Peter Renolds was working on an auto toolchanger for a Bridgeport, not sure if hes made any progress as his site still says the same as the last time I looked, might be worth an email.
Heres his site http://www.zoomt.com/products.htm

Hood

[daedalus]

for an example of using tormach, you could take a look at littemachineshops tormach based automatic toolchanger for the seig minimills.
http://www.littlemachineshop.com/pro...ProductID=2937

Philbur, if you dont mind could you give a bit more detail of the problems of using tormach with an atc, as i was considering putting something together like the littlemachineshop one, and would like to know if there are problems im missing.

[NinerSevenTango]

I see a problem with that one immediately --

The cylinder is pushing on the drawbar to compress the belleville washers in order to release the collet. The washers have to be sized for enough force to hold the tooling when the cylinder is released. The problem I see is that all of the cylinder force has to be resisted by the spindle bearings. I'm not sure if they are rated for that. My thought on that is that it will probably require a mechanism that squishes the washers to release the drawbar without putting the load on the bearings. It can be done with only a little more complication.

--97T--

[daedalus]

would a suitable solution to that problem be having a mechanical stop for the piston set to only compress the belleville washers sufficiently to release the collet?

[ViperTX]

Okay, I found Joe Vicars ATC....it's not for R8, but it may trigger some ideas.

http://home.insightbb.com/~joevicar3/default.htm

[philbur]

Based on the level of detail given the main problem I see is that the Tormach tool-holder has a 19.04 mm parallel shank and the R8 collet has a 19.05 mm parallel bore, with a very narrow entry bevel. The tolerance/repeatability for x/y location of each tool-holder in the carousel will therefore need to be something like < +/-0.05 mm. One possible solution is to add a short entry taper to the top of each of Tormach tool-holders shanks. Further, because of the parrallel shank, the tool-holder will not self-eject when you activate the draw-bar because the draw-bar is acting on the collet not the tool-holder. You will need a mechanism to either physically push or pull the tool-holder out.

The possible overload of the spindle bearing by the draw-bar could be overcome my having a semi-floating (in the z-axis) air cylinder that engages against a flange arrangement on the spindle when activated. This would mean that the cylinder is transferring the pushing load to the end of the spindle, not through the bearings. The z axis float of the cylinder would be controlled by a spring or springs that would hold the cylinder down, out of engagement with the spindle flange when not activated.

There are possibly many more issues in the detail of the system as drawn, it’s not possible to see if they have been solved. It would be nice to see a video of a working system, if there is one. I would not even buy a set of plans based pure on what I see on the web site, it looks like work in progress to me.

Regards
Phil

for an example of using tormach, you could take a look at littemachineshops tormach based automatic toolchanger for the seig minimills.
http://www.littlemachineshop.com/pro...ProductID=2937

Philbur, if you dont mind could you give a bit more detail of the problems of using tormach with an atc, as i was considering putting something together like the littlemachineshop one, and would like to know if there are problems im missing.

[Zumba]

Hmmm.... if you grind the key out of the inside of the spindle, will you encounter any problems with tightening/loosening the drawbar? I'm guessing not, otherwise MT3 spindles would never work.

I'm thinking: grind out the key, use collet chucks, install power drawbar.

Then you're in business.

[philbur]

MT tapers are shallow, self-holding so it has lots of friction to prevent rotation in the spindle. R8 is not self-holding so friction is much less, hence the drive key.

Regards
Phil

Hmmm.... if you grind the key out of the inside of the spindle, will you encounter any problems with tightening/loosening the drawbar? I'm guessing not, otherwise MT3 spindles would never work.

I'm thinking: grind out the key, use collet chucks, install power drawbar.

Then you're in business.

[philbur]

So it might be better to use MT taper tool-holders and spindle rather than R8. Problem is the length of the shank, but you could shorten the shank somewhat, re-tap the end and put in your draw-bar stud. This would then allow you to use the taper for alignment purposes during tool-holder insertion.

Regards
Phil

MT tapers are shallow, self-holding so it has lots of friction to prevent rotation in the spindle. R8 is not self-holding so friction is much less, hence the drive key.

Regards
Phil

[philbur]

Another up side of the MT solution would be that you could use less spring force and a smaller draw-bar cylinder. The down side is if the taper does not engage properly, say due to a small piece of swarf, then you would smoke the told-holder and the spindle while you where having coffee next door.

Integral in any ATC design has to be its cycle reliability. One failure in one thousand (or even one hundred thousand) would probably result in a disaster of some kind unless you introduce adequate fail safe features.

Regards
Phil

MT tapers are shallow, self-holding so it has lots of friction to prevent rotation in the spindle. R8 is not self-holding so friction is much less, hence the drive key.

Regards
Phil

[Willbird]

Most good designs you can REMOVE the key, it is in setscrew form...sort of like a dog point setscrew, nicer than grinding it off :-).

[Zumba]

Phil, why shorten the MT3 arbor? It's already significantly shorter than an R8. Besides, you want the tip of the arbor to be as small as possible to minimize chances of missing the tool.

Good point on taper length... R8 taper length is midgety, probably has much less holding power.

As for swarf, you can use compressed air to blow out the spindle in between each tool change, as with many commercial VMCs. Using a heat treated spindle to begin with would be a good idea.

The biggest possible disaster I can forsee is the Z-axis not aligning with the toolholder (collet chuck) correctly. It would plunge down and probably bend the tool tray out of shape without picking up a new cutter. Then it would continue through the G-Code, without a tool, and the draw bar would rattle inside the empty spindle. Fun stuff.

I guess an even worse case scenario would be if you were cutting a deep, stepped pocket and didn't have a tool in the spindle. The machine obviously wouldn't know that the material that's supposed to be milled away is still there. After awhile, the spindle would crash into the workpiece.

So don't do that.