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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 400614 times)

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Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #140 on: September 21, 2012, 01:36:25 PM »
Very cool ! I saw these at IMTS.
I especially like the part load/unload gripper set up as a tool.
Thanks Hood,
Russ


Yes and the beauty of the basket changer is nothing rotates round so having air lines to things liike grippers dont pose a problem.

Hood

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #141 on: September 21, 2012, 01:52:17 PM »
Steve,

Like Terry, I too question the real-world value of a super-fast toolchange time.  I can't imagine that it would save more than a few minutes per day at the cost of significantly increased complexity, and opportunity for disaster, due to higher speeds, and generally higher precision required.  I think you can quickly get to the point where doubling speed will take 10X the time and 2X the cost, to make it as reliable as a slower, simpler machine.

Re: the speed of a Geneva, this, too, I think is a bit of a red herring.  Perhaps a high-speed Geneva will always be a bit slower than a max-performance direct-driven mechanism, but I think the overall difference in toolchange time would still be small.  I'm running mine VERY conservatively, and it runs under a second per tool pocket.  So, even with a 24-tool carousel, max seek time would be 12 seconds.  I'm sure I could easily double that.  Beyond that point, you have to start worrying about the tools flying out as the thing moves.  The biggest job I ever did only used about 12 tools, and that one took hours to run, so an additional 3 minutes in seek time would be lost in the noise.

I'm not sure if our posts 'crossed in the mail' or if you misunderstood. My setup will not be 'super fast', just fast. And even that is a subjective term. I think the only number I mentioned was 5 seconds, but really I won't know what it will tolerate until it is running and I can push it to failure.  What I don't want is 20 second tool changes. Seconds add up when you are multiplying them by orders of magnitude. If you doubt that, just run Vectrix generated peck drilling code for 30 deep holes . . . . ::)

Quote
Certainly doing a variable-tool-size chain-driven machine is quite do-able, but, again, at considerable cost in terms of complexity.  You'd have to not only program each tool length, but now the "pocket" width as well.  And, setting up a job will mean a fair amount of disassembly/re-assembly to move the tools to their required positions.  Or, have pre-configured slots of different sizes, but then you have to deal with mapping tool numbers so each tool lands in an appropriately-sized pocket.  My biggest tool is a 4" face mill, so I just sized all the pockets accordingly.

The jury is still out on this and I have not really thought it thru. Thanks for you observations. Every comment helps.

The idea probably falls apart without a smart servo drive that can find the tool spots on its own. I had in mind just a certain number of 'small' spots and 'wide' spots. You put your 4" face mill in an existing wide spot and your 1/4" drill in a 'small' spot. The only disassembly would be to alter the ratio of small to large to suit your typical jobs. The position of the tools can be defined as a distance from 'home' and could be calculated easily thus; 3 wide spots x 4" and 2 small slots x 3"; that tool is at 18". All you would need is a table of tool positions stored in the drive or the controller.

It would just be a way to shoehorn a couple more tools on a belt which may be all you need for a specific job. If I build in the capability, that doesn't mean it has to be used. Even if the slot width was variable, they could all be set the same, so no harm no foul . . . .  IF it turns out to be easy to implement. If it does result in a lot of complexity, then I would agree with you that it may not be worth the effort, but I don't know that yet. Certainly the tool postions could be completely random and be probed, but that is most likely over the doable-but-not-practical line.

The chain belt option is a definate, but variable spacing is just a discussion point at the moment.  



Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #142 on: September 21, 2012, 02:10:27 PM »
Steve
Heres a site that  gave me  ideas  when I was dreaming about how I was going to do mine, now I dont have to (assuming I buy the Chiron ;D ) May give you some food for thought, I especially like the hinge down holders.
http://www.miksch.de/en/tool-changing-systems.html

Hood

Couple things, Hood;

First, thanks for the link. But a full half second for a tool change? Please . . . way to slow . .  :D    OK seriously cool stuff. This is pretty much similar to what I have in mind . .  except on a whole different level.

Second, on their 'magazine', they seem to be linking individual tool 'pods' to each other rather than attaching them to a separate chain . .  interesting . .  and so much for the variable slot width  idea . .  :-\

Third, since you won't need that old Beaver mill, you can just put it in a big box with a ribbon . . my address is . . . . .   ;D

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #143 on: September 21, 2012, 02:14:03 PM »
Ha ha well afraid I like my Balding Beaver so its staying. Have to get rid of the Bridgeport and one of the manual lathes to make room though. Sad day in a way as I had to sell my CBR600 to buy the lathe when I was starting out and kind of have a soft spot for it even though I rarely use it.

Hood

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #144 on: September 21, 2012, 02:15:56 PM »
Second, on their 'magazine', they seem to be linking individual tool 'pods' to each other rather than attaching them to a separate chain . .  interesting . .  and so much for the variable slot width  idea . .  :-\

Could you not make up double width pots for such situations?
Hood

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #145 on: September 21, 2012, 02:47:42 PM »
Could you not make up double width pots for such situations?
Hood
Now that's creative thinking!  8) I suppose you could indeed . . so long at the 'double wide' could get around the corners.

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #146 on: September 21, 2012, 02:56:16 PM »
Could you not make up double width pots for such situations?
Hood
Now that's creative thinking!  8) I suppose you could indeed . . so long at the 'double wide' could get around the corners.
Surely a man of your proven capabilities could make it hinge ;D After all the pot itself will be the same size, just the lugs out each side would be longer.
Hood

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #147 on: September 21, 2012, 03:06:13 PM »
Picture worth thousand words:

This it the first prototype 'pod'. There would be 6 (or more) of these bolted to the outside of the turret wheel or to the chain belt

The body survived the cut, but the lever is being replaced by a modified design to be more 'jam proof' . . most likely the coil spring will be replaced as well. Note that the tool taper is completely covered and protected and that the tool cannot release from the pod without the catch being retracted (by the claw on the arm).

The pod body is a little complex, but the entire part; OD turn, flat one side, drill and counterbore two 1/4" mounting holes, center drill, 3/4" drill thru center, taper bore center, drill and tap latch pivot mounting hole, can be done with a single setup and a single program on my InTurn™ 4th axis . .   provided I had a working ATC . . . Catch-22.



Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #148 on: September 21, 2012, 03:11:21 PM »
Looks a nice design however may just throw out another idea. My friends Beaver mills changer uses balls and a small spring  in a similar fashion to your drawbar. There is a small air cylinder above the tool release position so when the correct tool is in position and the clamp is gripping it the cylinder pushes down on the spring and releases the  pullstud, I thought it was quite a nice idea and the spring pressure needed is small so any old valve spring would be more than enough.
Hood

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #149 on: September 21, 2012, 03:14:20 PM »
Heres a video of a similar setup that CNCIT on the forum has oon his Beaver mill, you can quite clearly see the cylinder/spring setup.
Hood