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Messages - simpson36

511
Feedback is that people really like to see the raw materials and not just the finished parts. Also, mock ups seem to be popular. It would be nice if there was more participation in this thread instead of my e-mail, but in any case, here are some mock ups of the mechanisms for the arm and the carousel. I am most likely going to use the same gear box for both, although the carousel will be driven by a smaller BLDC servo and a Coplet Accelnet drive.

To Hood; incidentally, the Copley does have the configurable roll-over feature. I have not had time to check out the rest of the related feature set that you described, but it looks like it may be the hot setup for the carousel. The Mitsu J3 has a special anti vibration capability that should make it a good choice for the uber accell/decell of the arm.

http://www.youtube.com/watch?v=8JkFqzwlyiI

The Mitsu motor can blast over 6K RPM momentarily so with the 50:1 worm gear drive the swing should happen in about 1/4 of a second give or take. Any of the 6 tools should be reachable in less than 1/2 second with the little BLDC servo motor. I *might* be able to eliminated the pneumatic release of the tool from the carousel, so I think I am on target for sub 5 second tool changes and be well back from the maximum speeds.

512
(;-) Are yous guys building tool changers or PITCHING machines.
There is definately a security breach around here somewhere . . . .

513
Better late than never . . .

514
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

THX!  At this point I am not considering the ATC design to be proprietary and there is nothing in it (thus far) that is beyond the capabilities of a competent DIY. I may be inclined to share the drawing of the final design claw and pod. Not a promise at this point, but I don't see a patent in the ATC so far, and I am doing it on my own dime, so no NDA on that part of the project.

The current pod actually works perfectly. My concern with the first prototype was the potential for jamming. The current gripper arrangement does not tend to jam, but it needs to be a little more bulletproof. More robust. Probably the interlock lever's 'beak'  should be hardened, which would put it out of DIY.  I have already refined that design a bit from what is in the photo and the areas that need to be stronger can be handled with different materials, but I don't want to spend any more time on it for now since I have a new method in mind. Something of a hybrid between the two approaches. See my response to Ray (Kabibble) for a description.

515
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.

My bad. I have the lever in the photo upside down . . or backwards, depending on the perspective. It works exactly as you surmised. The 'beak' if you will, pokes thru the hole at the top and interferes with the ball holder descending into the body, this preventing the tool release. The 'tail' reaches down to the bottom of the body and is spring loaded. The spring is not in the photo because those parts are not here yet. The spring goes in the bottom of the pivot slot just below the pivot pin (also not in the photo).

The claw engages the slot on the adapter and then in the last 1/4" or so of travel, it pushed in the tail of the lever, thereby removing the interlock and allowing the air cylinder to release the tool.

You are uber observant, so I will presume your next question will be why is there a 'tooth' on the 'beak'. The 'beak' is retracted, the plunger is then pushed in (down) by a small air cylinder. The plunger not only 'releases' the ball grip, it also physically ejects the adapter about .060". The next action in the sequence if to the arm to descend with the toolholder in-hand, so to speak.  At this pint in the sequence there are two options:

1) let the plunger up and lower the arm simultaneously and the plunger will raise all the way to the snap ring stop. It will then need to be depressed again by the air cylinder in order to return the tool

2) lower the arm first and then let the plunger up. When the claw is lowered from the pod, the lever re-opens via its own return spring and the 'beak' pokes back into the chamber. Letting the plunger up at this point results in the 'tooth' catching the top edge of the plunger and holding the gripper in the 'open' position. 

In the second configuration, the tool is returned simply by the claw raising the holder into the pod. The claw re-compresses the 'tail' as it raises the last 1/4" or so, thereby releasing the plunger and locking the holder into the pod.

Hopefully that all made sense.
 

516
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 . . .


517
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 . . .

518
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.

519
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.

520
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.