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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 411139 times)

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #180 on: September 23, 2012, 06:19:06 PM »
DWalsh: caution about posting drawings . . . the teacher has a big RED pencil  . . .  a corner chair with dunce cap . . .  and possibly a wooden ruler  . .  and a paddle  :o
Do you really see anything wrong with that drawing?
Not at all. Just a joke based on the guys tauting me a few posts back. BR was the actual target, in a sense. I assumed you had read thru there and would get the tease. First rule of plumbing and so on. Sorry it was unclear. No offense intended.   :-X
I wasn't sure if it was a pun or a serious remark.

Seems there are some talented people involved in this thread, a refreshing change.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #181 on: September 27, 2012, 04:06:32 PM »
Making good progress on the ATC.  The whole carousel and "lift" mechanism is working now.  The only major missing pieces are the air cylinder that swings the ATC into position under the quill, the side covers for the carousel, and all the "sensors".  Lots of little details to take care of (like that ugly stack of cr@p on top of the air cylinder in the last photo), but I see no reason this will not work very nicely.  Operating it manually, it very reliably locks onto the tool, yanks it out, and puts it back in.

Regards,
Ray L.
Regards,
Ray L.

Online BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #182 on: September 27, 2012, 07:03:46 PM »
DOn't forget to build (2) (;-) I will send a BIG box.

(;-) TP

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #183 on: September 28, 2012, 07:00:20 AM »
Here is an interesting approach to a power draw bar:

They get by with only 600# drawbar tension, but they have a clamp collar that grabs the spindle nose to transfer torque for high power tooling. R8 is a vexing problam and while it would not be useful with an ATC, I think this is a very clever solution to speed up manual tool changes. Apparently so did the patent office.

Video: (there are several, but this will get you started)
http://www.youtube.com/watch?v=YaiZC93ASJ8&feature=relmfu
Comapny site:
http://mach-1tooling.com/

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #184 on: September 28, 2012, 07:17:33 AM »
Making good progress on the ATC.  The whole carousel and "lift" mechanism is working now.  

Very nice.

The only advice I would offer is to put an upper support on the arm pivot pin. That is a long lever and when you get that carousel loaded with tools, it will put quite a moment load on the pin. Aluminum is not the best choice for the mount, in my view, due to the modulus of aluminum. Your mechanism moves a load vertically at the end of a long arm. This arrangement will induce significant vibration and aluminum has little ability to damp that. An upper support on the pivot pin would address both the moment on the pin and the vibration (bouncing) of the loaded carousel.

An upper support would convert the moment on the lower bracket to compression and put the upper bracket in tension. The pin force would be converted from moment to shear. Moment loads are a bitch to calculate, while shear is easy, so there is an ancillary benefit as well.

edit: one other comment; You probably already have something in mind for this, but just as an observation, the shafts running thru the arm at the carousel would benefit from bellows or a scraper type o-ring to keep the nasties (evidenced by the wall behind the carousel) from jamming the movement.
« Last Edit: September 28, 2012, 07:23:36 AM by simpson36 »
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #185 on: September 28, 2012, 07:18:23 AM »
the trouble with R8 in a manual/semi auto change, is you need soo much more room under the tool to make the change.
The 30 or 40 taper allows you to take the tool sideways a lot earlier than the R8.

Offline simpson36

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #186 on: September 28, 2012, 07:27:40 AM »
the trouble with R8 in a manual/semi auto change, is you need soo much more room under the tool to make the change.
The 30 or 40 taper allows you to take the tool sideways a lot earlier than the R8.

I do not know this for a fact, but my experience with the BT30 taper had led me to speculate that the R8 design has the concentric ring spaced relatively far above the taper in order to prevent the taper from racking due to inaccuracy in the drawbar straightness or thread precision.

If anyone has some reference material on the original R8 design goals, I would really love to see it.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #187 on: September 28, 2012, 11:30:52 AM »
Very nice.

The only advice I would offer is to put an upper support on the arm pivot pin. That is a long lever and when you get that carousel loaded with tools, it will put quite a moment load on the pin. Aluminum is not the best choice for the mount, in my view, due to the modulus of aluminum. Your mechanism moves a load vertically at the end of a long arm. This arrangement will induce significant vibration and aluminum has little ability to damp that. An upper support on the pivot pin would address both the moment on the pin and the vibration (bouncing) of the loaded carousel.

An upper support would convert the moment on the lower bracket to compression and put the upper bracket in tension. The pin force would be converted from moment to shear. Moment loads are a bitch to calculate, while shear is easy, so there is an ancillary benefit as well.

Quote from: HimyKabibble
 
The whole mount bracket, and probably the arm, will be re-made once it's all working.  I already had to modify it once, so it's a little "hacky" already.  Though it is surprisingly strong just as it is.  Also, the small amount of slop/flex it allows is not really a problem, as there will be a tapered pin and socket on the side of the head to ensure precise alignment of the ATC to the head.  I wanted to support the pivot pin with a U-shaped bracket, but didn't have any material large enough to make that, so built what I could with what I had on hand.  Most of the time, when making something like this, I'll do a quick and dirty prototype (what this is), to verify dimensions, fit and functionality, then refine the design, and re-make most/all of the parts for the final "product".

edit: one other comment; You probably already have something in mind for this, but just as an observation, the shafts running thru the arm at the carousel would benefit from bellows or a scraper type o-ring to keep the nasties (evidenced by the wall behind the carousel) from jamming the movement.
Quote from: HimyKabibble
 

The clearances are tight enough I doubt anything could get in there, but I will do something to at least prevent accumulation of crud up there.  Something as simple as a sheet-metal shield, covering the "front" (when parked) and top, would do the job.  It would also be easy to fit lip seals on the top and bottom of the arm.  Note the "main" shaft does not move, only the two smaller "guide rods" move.


Quote from: HimyKabibble
 
Got a nice "bonus" - yesterday PM I spent a few hours tweaking a few of the parts, and adjusting things up carefully.  I was originally afraid I might have to lose up to 1/2" of quill travel, but now have it to where I'm losing only about 1/10", and, with a simple mod to the lower support for my quill drive (just counter-sinking some screws), I can easily recover that 1/10", and lose no quill travel at all (I currently have just a hair under 5").
Regards,
Ray L.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #188 on: September 28, 2012, 07:21:24 PM »
   Made a bit more progress today - only had a couple of hours of shop time.  I rigged up a power supply for the Geneva motor, and did several dozen complete "manually sequenced" toolchanges (pushing a button to power the Geneva, flipping a valve to actuate the lift).  I see no significant problems whatsoever - it seems to work very nicely, even when fully loaded with heavy tools.  I got one half of the guide pin done - a 1/2" tapered pin - mounted on the side of the head, and just need to make the "socket" part that goes on side of the pivot arm.  This will ensure absolutely precise vertical positioning of the forks, and provide a hard stop for the pivot arm.

Regards,
Ray L.
Regards,
Ray L.
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #189 on: September 30, 2012, 03:05:19 PM »
Lots of nice spindle and tool changer activity here.

I keep waiting for someone to set up a SCARA robot to do tool changes.  Ray's got half of an arm on his.  One more arm and the robot is ready.  It can load and unload your parts when it isn't too busy changing tools.  It can make sure the coolant nozzle is pointed at just the right spot for each tool.  Or, it can sweep the chips at the end of the day with a little brush, LOL.

Cheers,

BW
www.cnccookbook.com

PS  Mostly, joking, but a friend has a SCARA and they're remarkably simple and useful.  He uses it to move parts around on his lathe.  For example, to flip them so he can machine the part that had been chucked.
Try G-Wizard Machinist's Calculator for free:

http://www.cnccookbook.com/CCGWizard.html