Hoss ATC Project

[hoss2006]

Found these spring washers at MSC Direct that look very similar
to what the LMS power drawbar uses.
I think 3 pairs would give plenty of force to hold the R8 tools.
6 washers = almost .100 deflection and 1044 lbs used like this ()()()
Might even be able to use the stock X2 drawbar instead of making a custom one.
Have to give it a try.
Hoss

[RedDog22]

Hoss if you stack the springs in a series. You will not get the load you mention. You'll only get the load of a single washer but the deflection of all 6.

Parallel Stack - (((((((( - Force is multiplied by the number of washers while deflection remains constant to one washer.

Series Stack - )()()()( - Force is constant to one washer while deflection is multiplied by the number of total washers

Series and parallel - ))(())(( - Force is multiplied by how many washers are in a parallel group. Deflection is multiplied by how many total groups there are.

Hope this helps you out. Should be a good footing on the ways to use them.

[RedDog22]

Any chance you can tell me how much room you have to work with? I could try and find a good washer and how to stack them.

You'll need to be able to preload them to 600 pounds and still have the .1" of total deflection left to get the tool out. Guess that explains why they needed the 1000psi to get the tool out. Since you'll have to overcome the 600 preloaded pounds to get that final deflection.

[hoss2006]

Way to go Red, make me have to think
After eyeing the LMS PDB a little closer, I see they do stack 6 washers in series.
Did some research on the Belleville Spring Washer.
If you want to get out the slide rule check here.
The deflection I think I'll need is about 1/8 inch.
One turn of the drawbar to tighten the collet (per LMS instructions) = .050.
That leaves .075 to release the tool.
MSC Direct has these spring washers that will give 936 lbs of force (1674 lbs flat) and .132 total deflection
for (6) 1.750 OD washers stacked in series like the LMS. I think. ()()()
A bit pricier than the 1.0 OD ones.
I'll have to peek at the Matsura at work, Dave said it uses spring washers to retain the tools but 60,000 lbs worth.

[RedDog22]

I didn't do the math or anything. But as long as the .050" of pretensioning is enough to load the washers to 600 pounds of force, you're fine.

Have you given McMasterCarr any thought on the washers? Found these specs...
Minimum Inside Diameter .630"
Maximum Outside Diameter 1.250"
Thickness .089"
Overall Height .111"
Load 979 lbs.
Deflection at Load .011"
Flat Load 1,914 lbs.

Also, don't forget. You're not limited to 6 washers like what LMS is using. You can use 4, 10, 50 if you really wanted. And you don't need to have .050 to load 600lbs either. Maybe you need to turn your drawbar nut 2 turns in before its loaded. Just as long as its loaded and still has enough deflection left to drop your tool holder from the collet.

[ataxy]

ah i am sure alot of people where waiting for this one and i am one of them, cant wait to see how it will turn out hoss

[hoss2006]

Ok, think I'll order these Belleville washers from MSC (I already have an account).
They are metric but I get the most for my buck.
ID=12.2 mm (.480 in) just the right size to fit the drawbar.
Load=2910 N (654 lbs)
Deflection=.41 mm (.016 in)
A pack of 10 is only $6
Gives me plenty to experiment with.
I figure stacked in series ()()() should give 654 lbs with .096 in total deflection.
or
stacked series/parallel (())(())(()) should give 1308 lbs with .096 deflection.
or
()()()()=654 lbs, .128 deflection
should be able to get one of these scenarios to do the job, Eh Red?
Hoss

[RedDog22]

I forgot to ask. You said you think it will take.125" of travel to loosen the the collet enough? Or that only a guess? If it does truly need that. You'll need to calculate what it will take to preload the washers to 600 pounds. And then still have another .125 of deflection left.

654 pounds wont be enough. Because you'll need to have them basically compressed all the way(to reach the 600). You wont be left with any spare room to loosen the collet.

But both of things go with how much space do you truly need to get the tool holder out? And how much minimum force do you truly need to hold your tool in place? Until you know its all guess work. But that is the great thing about using Belleville washers in a spring stack. You can flop them around, add more, use stronger ones. All to get you where you need to be.

[hoss2006]

I figured (guess) .125 for load on the washers and enough left to release.
May only need .010 or so to release
We'll see, let the experimenting begin.
Hoss

[RedDog22]

Awesome. I cant wait to hear your results. One last thing. Normally when you loosen the drawbar you have to give it a wrap to get the collet to let go of the tool holder. Any ideas on how to get around that? Or do you think it wont even show itself?

[hoss2006]

When you loosen the drawbar by hand, it's free to move up away from the collet
because there's nothing to stop it. So then you have to tap it to release the collet.
With the cam and lever being depressed by the air cylinder against the top of the drawbar, the only way it can move is down against the spring washers.
It pushes the drawbar and collet together, releasing the tool. Voila
Hoss

[RedDog22]

After reading your answer I cant believe I even asked it. lol Thanks for answering. I'm not sure why I was thinking only the spring stack was being pushed on...