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Archive for Homebrew_PCBs.
Thread
2003-12-02 by bsjoelund
2003-12-03 by mpdickens
> Hi,Hello Bengt,
>
> I�m looking for small/miniature tool changer for PCB
> drilling.
> Any links - pictures - ideas ??
2003-12-03 by Dave Hylands
> -----Original Message-----http://www.c1tracking.com/l.asp?cid=5511
> From: mpdickens [mailto:md30022@...]
> Sent: Tuesday, December 02, 2003 9:37 PM
> To: Homebrew_PCBs@yahoogroups.com
> Subject: Re: [Homebrew_PCBs] Homebrew Tool Changer
>
>
>
> --- bsjoelund <tecnoconsult@...> wrote:
> > Hi,
> >
> > I´m looking for small/miniature tool changer for PCB drilling.
> > Any links - pictures - ideas ??
>
> Hello Bengt,
>
> This is robotics and robotics is as much an art as a
> science. Further, robotics can provide humbling
> experiences as well as be exceptionally rewarding
> (Both experiences the same time...). For drill bits,
> excluding the ability to position the head of the
> drill (The head of the drill is called a chuck in the
> America. I don't know what they call it elsewhere...)
> at the correct latitude/logitude/altitude, you going
> to need quantity-4 servo motors and quanity-1
> sensor.(I don't think you can change a drill bit with
> less than four motors and one sensor). Three of the
> motors *must* have a high tork and all motors must
> step in fine steps.
>
> Some drills have keyless chucks and some have keyed
> chucks. This example assumes a keyed chuck:
>
> Motor A: Pushes the key up to and into the chuck.
> Motor B: Adjusts the key to fit the gears of the chuck
> Motor C: Rotates key to tighten/loosen the chuck
> Motor D: Rotates what is known as a "lazy susan"
>
> A lazy susan is a round table that in this case has
> holes in it that the drill bits sit in (Standing up)
> The drill bits are changed over the lazy susan.
> Further, the lazy susan rotates.
>
> It would work like this:
>
> The drill head has no drill bit in it. The drill head
> now moves over to the lazy susan. The head is lowered
> down to the lazy susan directly over the desired drill
> bill. Motor A pushes the key up to and into the chuch
> while Motor B is *slowly* rotating the key. Once the
> gears on the key catch with the gears on the chuck
> (This is a predetermined distance plus or minus a
> small distance. The gear catch is also monitored by a
> senor that measures tork. Further, They make chips
> that measure tork), Motor A stops and Motor B
> continues to turn the key to tighten the chuck (This
> is a predetermined number of rotations for each drill
> bit and size. Also, tightening is monitored by
> another tork sensor). The sensors are "fail safes" for
> the both distance and tork which is predetermined,
> but *estimated*. Once the prodecure is complete your
> good to go. Reverse the processes to take the bit out
> of the drill head/chuck.
>
> What you want to do requires very fine motor steps
> combined with software that does not glitch during the
> process. This process definately is an embedded system
> thing and should be automomous: In other words, the
> drill files should be handed to the embedded system
> and the computer that hands the embedded system the
> drill file should stay out of the process (Which
> greatly simplifies the software. Further, this makes
> debugging MUCH MUCH MUCH easier...)
>
> If I were going to do this, I would look at:
>
> A.) Existing products and how they work mechanically.
> B.) Tape libraries for extra idea's and inspiration.
>
> Figure everything out that you can before purchasing
> anything, spinning the first wrench or writing any
> code. Also, draw schematics of how it's going to be
> buildt and how it will work. Flow chart the software.
> Keep damn good notes while
> building/programing/testing.
> Keep rescipts from your purchases in case you buy the
> wrong part and want to return it. Do business with
> small to medium size companies while prototyping. Cut
> a deal with them that you can return anything you
> don't need if you have not used it and it's not
> special order (Anybody who will not cut this type of
> deal, don't do business with them. Don't fall for the
> 15% restock BS fee. There are too many companies out
> there that will work with you the right way).
>
> Good luck and best regards
>
>
> Marvin Dickens
> Alpharetta, Georgia USA
>
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