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Author Topic: BT30 spindle from scratch - with power drawbar and ATC of course  (Read 400220 times)

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Offline poppabear

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #440 on: January 06, 2013, 02:54:10 PM »
:)
Commercial Mach3 & Mach 4, Design/Build/Retrofit CNC and Industrial machines.
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Offline BR549

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #441 on: January 06, 2013, 03:19:15 PM »
IF you wanted slow zones you can use a rotary actuater with a drawbar link. As the rotary arm rotates from retracted to extended position the link geometry SLOWS the tool arm to a stop as the arm reaches Max+ and Max- travel. No jerks at the extents of travel.

(;-)TP

Offline poppabear

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #442 on: January 06, 2013, 07:39:03 PM »
Quote
I personally, like the "KISS" principle, which may be just push a ACME screw with a nut, with a cheap stepper and drive (Chinese drives are real cheap), and/or use cheap AC or DC motors to push the screw and use mechnical Micro switches (or proxes if you have a little more cash), to handle your bang-bang limits. You could even put micros before the end micros, that could be used to cut the speed toward the end of travel prior to the stop micro.

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Offline comet

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #443 on: January 20, 2013, 05:57:37 PM »
If anyone's interested,Ive just made power draw bar for my tool changer,used a stack of belvilles,a 20mm spring collet ala tormach.
 To power it I used 2  50mm dia 20mm stroke air cylinders in parallel,with a bar joining the 2 piston rods, that in turn operates on a pivoted crank arm giving a 3-1 advantage,its got loads of power I can plough a 18mm dia ripper 10mm deep through ali at 250mm pm no problems no slip, good enough for me and most folks I guess ?

My first attempt was a large stepper with a 1.5mm pitch lead screw operating the 3-1 lever I had micro switches, and a logic circuit controlling it.All i can say is it cost me a fair amount of time and money and never really worked reliably, and even with all that mechanical advantage it never really had the grunt.I would advise from my own experience don't go down that route!
 

Tony
« Last Edit: January 20, 2013, 06:06:18 PM by comet »
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #444 on: January 20, 2013, 06:26:06 PM »
If anyone's interested,Ive just made power draw bar for my tool changer,used a stack of belvilles,a 20mm spring collet ala tormach.
 To power it I used 2  50mm dia 20mm stroke air cylinders in parallel,with a bar joining the 2 piston rods, that in turn operates on a pivoted crank arm giving a 3-1 advantage,its got loads of power I can plough a 18mm dia ripper 10mm deep through ali at 250mm pm no problems no slip, good enough for me and most folks I guess ?

My first attempt was a large stepper with a 1.5mm pitch lead screw operating the 3-1 lever I had micro switches, and a logic circuit controlling it.All i can say is it cost me a fair amount of time and money and never really worked reliably, and even with all that mechanical advantage it never really had the grunt.I would advise from my own experience don't go down that route!
 

Tony

Sounds like a very reasonable solution.  By my calculation, you're getting on the order of 1500# drawbar tension (assuming some frictional loss) - not enough for really maximum retention on a TTS holder but enough for many/most machines.  A leadscrew I would not expect to work well - the frictional losses in the screw/nut will kill you. 

I've got a new PDB design I'm building now that will be REALLY cool, simple, cheap, and tiny - even smaller than the impact wrench PDBs.  It's already been proven functionally.  But, it's top-secret for the time-being, because I plan to sell them.

Simpson better get cracking on his ATC! I'm already working on my second one, for my new machine!

Regards,
Ray L.
Regards,
Ray L.

Offline comet

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #445 on: January 20, 2013, 06:43:58 PM »
Himmy, will it be controlled by a single hi/low signal?

  tony
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #446 on: January 20, 2013, 07:33:21 PM »
The little hydraulic intensifier at the heart of this drawbar is the coolest design I've seen for a Belleville drawbar solution:

http://www.sdmfabricating.com/LOD.html

That intensifier plus one small air cylinder is all you need.

Regards,
Ray L.
Regards,
Ray L.

Offline comet

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #447 on: January 21, 2013, 03:56:36 AM »
Well thats nice but OTT, compared to my method,plus Ive a few of my cylinders that I can just add to increase the power.
As far as Bellvilles are concerned Ive used thinner than usual washers and put them in ,in sets of 3 back to back my thinking being that they will be more supple,abit like a leaf spring,seems to work

Tony
Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #448 on: January 21, 2013, 06:41:46 AM »
keep them well greased when you use them stacked, as they tend to rust between each one.

Offline comet

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Re: BT30 spindle from scratch - with power drawbar and ATC of course
« Reply #449 on: January 21, 2013, 07:52:17 AM »
there are belleville washers and then there are disc springs which are the Items that you should use, On vehicle leaf springs its advisable not to grease between the leaves as it attracts grit and forms a grinding paste,or so ive been told! probably a good thing in our application to lubricate though!
Tony