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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 400212 times)

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Offline budman68

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #200 on: October 01, 2012, 11:49:36 AM »
That is a great video, Bob thanks for sharing.

Looked like a wreck was just about to happen at the end there though! lol!

Dave
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Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #201 on: October 01, 2012, 12:00:20 PM »
Bob;

Thanks for the links. The retention of the holders in the carousel is not an issue. On mine, the BT tool holders will be completely enclosed in a sealed pseudo-spindle and released via an simplified ball gripper. Credit for the ball gripper idea goes to Mr. Hood. The 'pods' (my fancy name for the carousel mounted holders) each gave a positive mechanical lockout on the gripper that prevents release until a mechanical interference is withdrawn.

As to the speedy littel dual arm gizmo, it *appears* that there is a stud retaining the holders in the arm. It is hard to figure out exactly what the camming is doing even pausing the vid, but there is only a ridge to fit into the holder grove on one side of the arm pocket  . .  if that made any sense.  The stud "I think* must retract to release the holder. So . . if I have that observation correct, then the holders are positively locked into the arm socket by that retractable stud. This is what I was referring to as a 'positive mechanical retention', or 'interlock'. Something that prevents the arm letting go of the holder until some specific action it taken.

Ray;

Centrifugal force is not the problem. The claw already surrounds the holder. The problem  is the sudden decel at the end of the arm sweep in the direction where the claw opening leads the motion. The sudden stop generates thru inertia, a force greater than what the claw spring can hold. If I noodled over is long enough I could probably increase the spring pressure, but there is a point where I would need hydraulics to get the darn thing on the holder in the first place, so I abandoned that whole method, even though it is by far the preeminent method used in almost all of the DIY videos that I studied. The industrial stuff is just too friggin' fast to actually divine what's going on.

Critique; the tiny dual sided arm that Bob linked to has one major drawback that you should fix if you do build one; the cam is exposed. I would fit a bellows on that thing or I don't think it will perform very long. In my working life, fault analysis was my specialty. You might be surprised how many machine failures were caused by poor design relative to keeping foreign matter out of the mechanisms.

« Last Edit: October 01, 2012, 12:10:41 PM by simpson36 »

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #202 on: October 01, 2012, 12:01:37 PM »
Possibly the forum itself, as I noticed many "lag" times when I'm here. Heck, even if I'm changing threads to look at something else, it lags for a bit.

Give it another go and I can delete it if it gets messed up for you.

Dave

THX, Dave. Will try again on next post.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #203 on: October 01, 2012, 12:33:36 PM »
Dave, here is a SCARA robot loading and unloading a lathe:
Not my friend's setup, but similar.  The thing I like is the SCARA's have such simple geometry and construction.

Nice, but this is the one I want for changing material in my  machines:
http://www.youtube.com/watch?v=lTGOjWv9fcQ&feature=related

OK, state of technology . . and I found this quite some time ago . . here is the most amazing demonstration of robotic dextrerity I have come across to date:
http://www.youtube.com/watch?v=-KxjVlaLBmk&feature=related

Quote
Ray, yup, make the centrifugal force work for you.  Use a stronger spring in the extractor too!

Nope,  centrifugal force is not the problem  . . and stiffer springs cause as many problems as they solve. See my response to Ray on this.

Offline Hood

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #204 on: October 01, 2012, 01:28:19 PM »
Credit for the ball gripper idea goes to Mr. Hood.

No credit to me for the idea, Balding Engineering or whoever made their toolchanger for them is where the credit is due, I only pointed it out ;)

Hood

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #205 on: October 01, 2012, 02:01:48 PM »
No credit to me for the idea,  . . . . I only pointed it out ;)

That is what I credit you for; bringing the idea to my project. If you gave me a Cream Crowdie , I would thank you, even if you did not make it yourself . . . .  unless there was already a bite out of it when you gave it to me . . . . in which case . . .

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #206 on: October 03, 2012, 11:43:50 AM »
Here are the components of the first prototype carousel tool holder pod using the ball gripper arrangement. It works fine, but I have an idea for a simplified variation on the concept that I will try before committing to this one. It is still a ball gripper, but with a snap in / snap out mechanism that has an adjustable retention pressure. The device still has a mechanical safety interlock and therefor cannot release a tool inadvertently.  Should do the same job, but be much simpler and does not need an actuator to release the tool. We shall see . . . .  

The components are laid out in the photo as an 'exploded view' and they go together in the order shown. The only thing that is not visible is an o-ring groove at the bottom where the adapter is pulled up into the taper. Since there is not a separate hardened sleeve, the gripper is actually a chamber inside the body. Challenging to machine, but I was unable to get a clear photo of it.

Air cylinders, worm gear drives, raw materials, a variety of springs, special fasteners and other assorted components are arriving for the ATC project, but I am getting short on time to work on it before I have to address other priorities. I may get a new claw made, but probably that will be all for a while.

Now to try this thumbnail photo attaching again . . .

Offline derek

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #207 on: October 03, 2012, 11:53:36 AM »
Do you sleep?
Thats looking great.
I disassembled my ball gripper after about 800 tool changes and there were no signs at all of wear or distortion. Starting to test my spring forks to work out those details. Even if I stall on the tool changer (I won't) changing over to the BT30 and air drawbar was the best mod I've made to this mill since I converted it to Mach. Manual tool changes are so… Civilized :)

Again amazing work your doing.

Derek
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #208 on: October 03, 2012, 11:53:48 AM »
Steve,

I don't understand the black lever at the bottom of the photo.  I'm assuming this is a positive lock, that prevents the ball gripper from coming down and releasing the tool, but it's not clear how it fits.  I assume the pivot goes into the slot on the side of the housing, but where does the "tang" on the RH side go?

Regards,
Ray L.
Regards,
Ray L.

Offline budman68

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #209 on: October 03, 2012, 11:58:04 AM »
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Now to try this thumbnail photo attaching again . . .

congrats  ;)

Dave
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Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)