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Ive Looked and looked for an ATC for My currect build and nothing seems to jump out at me, and then i noticed this Kress ATC...http://www.marchantdice.com/forumimages/kress-atc.pdf, i did have a look in the posts but couldnt see any real discussion about it, has anyone any Knowlege????
Rick
Rick,
If you like that design for the Kress then I would strongly suggest looking at Sorotec and their online shop as they have the same tool changer (and have had for longer then Marchantdice, at a savings minus shipping differences of £70 in price over Marchant Dice. It is the exact same unit and they have them for the full range of Kress from what I see. Best of luck and hope this helps.
Michael
Magic, i do wonder why nobody has made a larger unit for a little more money, say er20 or er32. but hey ho that question has been asked before... Thanks for the link ill have a gander...Quote:
Originally Posted by m.marino
Quote:
Originally Posted by Ricardoco
I suspect it's got a lot to do with holding force, balance and liability.
Reading the bit in that manual about bearing/seal replacement, states that if the seals have failed that bad that the holder won't release, then you can pull them out by pulling with 220N of force on the holder. With so little force, I doubt they're using a self locking taper (it takes a lot more than that to release even a MT1 taper!), which means they must be relying on friction to transmit drive. Even an INT/BT/CAT taper takes a good bit of force to knock out.
Also with so little holding force, it won't be able to withstand much force before the holder starts to get pulled out when in use, which is probably why that style doesn't exist for larger spindles.
I would like to see one of the ATCs dismantled, to see how the pull stud mechanism works, and how they've sprung it.
Although having seen a close-up of the tool holders pull stud, it's given me an idea on something that may work in a compact format while still providing a high pull out force...
Yes Please.. (Consider this a Pre Order)Quote:
Originally Posted by m_c
Rick
I won't be building any soon. Got far too many other things to do, but a few doodles would indicate all the bits would fit in, however it would need a good few calculations to see what kind of forces would be involved and if they're acheivable.
Thinking outside the box a bit, use a set of ball bearings that go under a pull stud, that are then forced into place by a spring loaded outer tapered sleeve. The spring could even be assisted in locking by air pressure, as once the tapered sleeve is pulled up, using appropriate tapers it's essentially self locking.
Now for release, you have another set of bearings on top, that also run against a taper, but this taper when moved to release, forces the bearings between the top of the pullstud and another taper above the pull stud.
It would be quite a complex setup, needing hardening and grinding of various parts, and that's once you've figured out how to machine all the various bits to ensure the balls don't just drop out.
This discussion is getting dangerously close to this design:
Rapid Changer
I made a prototype of that just to test the mechanism, but a bit bigger. It holds the holder reasonably well, but since it was only a test I used a random grade of steel which didn't harden much and I didn't grind it. I think it could work, but I doubt the holding force and torque transmission would be that great.
Attachment 6940Attachment 6941Attachment 6942Attachment 6943
I bought some EN19 steel to have a go at making a proper one...
Hey Jonathan, How did you heat the items up for hardening? I only ask since I did some hardening with a blow torch and it was OK but i did some in the furnace and OMG what a difference, as much in common as sun and rain.Quote:
Originally Posted by Jonathan
Chucked them in the chimney if I recall correctly!Quote:
Originally Posted by Ricardoco
next timeQuote:
Originally Posted by Jonathan
, give it a try in a furnace of some description, and dont forget, bright red first time and blue the next and im sure you will be very pleased with the results..
Rick
I've done it before and been pleased with the results - I think this was just a funny grade of steel. The fire was plenty hot enough to get the pieces bright red.Quote:
Originally Posted by Ricardoco
My idea uses a similar set-up to the rapid changer for locking, however doesn't use a constant taper. It uses a small taper to maximise locking force at the locking point, but to avoid needing an excessively long taper, the taper changes into a recess to allow the ball to drop away for release clearance.
Then to avoid needing as much force to ensure a good release, you have a set of balls above the pull stud that are pushed by one moving taper, into another stationary taper to force the holder down.
The tapers are designed such that the release taper doesn't contact the release balls until the locking ball taper has moved away from the balls. Sketches show it would need a taller pull stud than normal to allow room for the two tapers. I'll tidy up my sketches later and scan them in. I'd put them in CAD, but I'll probably not use that option, and I still need to build a router!
Personally, I think a scaled down INT/CAT/BT ATC would be a better option. Mount it to the side of whatever motor you have, and drive it by a belt/gears. It would increase weight a good bit, but you'd have a tried and tested system, with lots of clamping force, and less balancing problems.
one of these to add to the end of an existing R8 or int 30 spindle would be worth making. With a smaller toolholder it could be made to fit inside a fair bit of the existing taper and use the collar as the ejecting face.
My idea sketch is attached. Red hatched bit slides, blue hatched bit is the holder.
Some issues I can think of (in no particular order)-
*)If going for the full ATC route, due to the spring travel needed, a small air cylinder might not be able to provide enough force to release the holder. Could be solved by using a larger diameter, however at what point does diameter become an issue? Alternative, although more bulky option would be an external cylinder with lever mechanism (this would eliminate issue of needing rotating air seals)
*) Lots of bits would need hardened, ground and polished.
Attachment 6954
i2i, if you've got a spindle with a drawbar, there are plenty of ATC options about. Having a hole through the spindle opens up lots of options.