Automatic Solid Dispensing

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CoryG

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Feb 9, 2012, 2:07:07 PM2/9/12
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Has anyone worked with automatic solid dispensing mechanisms before
that might know of a cheap method that can be used reliably? So far
researching the subject the standard methods seem to be:
-Screw Dispensing (a screw sits inside a container with a powder and
turns to dispense the powder)
-Vibration Dispensing (a rod goes through a container holding a power
a vibrates the end which double as a cap) to tap out powder
http://www.youtube.com/watch?v=_NAPsMxadGo&feature=related
-Air Pressure Dispensing (a tube with a paper filter on the end is
used to suck powder into and blow it out at the desired location)
http://www.ebay.com/itm/BioDot-DisPo-Adjustable-Mass-Powder-Dispensing-Kit-/170675114107?pt=LH_DefaultDomain_0&hash=item27bd07907b#ht_500wt_1413

My take on it so far is that air pressure would be a mess or very
costly to use something like the biodot solution (I'm putting together
a method of mixing the ceramic powders for my super capacitor printer,
but would like to be able to use variable powders for automated lab-
work as well). I've seen a couple of methods that employ glass
bottles with a cap that has some gearing mechanism inside so you can
pick bottles housing different powders off a rack, then spin the
bottle within a holster to dispense pre-loaded powders and have a
scale built into the holster to meter by - the solution seems like the
ideal method for versatility, but I can't seem to find any of the
bottles for sale without the machine they plug into - does anyone know
of a source for them? Alternatively, does anyone have thoughts on who
might be able to manufacture a few hundred caps for glass bottles with
a Teflon screw or similar inside?

Chris

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Feb 10, 2012, 9:06:35 AM2/10/12
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I have worked with two different types of solid (powder) dispensing
systems.

They were for not for biology applications. Both were 'homemade' but
were in lab situations and was impressed with the accuracy.

The first employed a screw and a vibration slide. This was for a
production line that dispensed powder into hundreds of vials a day. A
screw would dispense gross amounts of a powder on the a vibrating
slide (v shaped) and at a slight downward angle. The slide would
vibrate and dump powder into a container at that end of the slide.
The container that it was dispensed into was on a scale. The slide
would vibrate until the correct weight was reached.

The second system was an air pressure system. It is not so relevant
to you application as you suggest its quite messy. The output of the
air nozzle looks like a paint sprayer and powder coats everything in
its path.

Chris

On Feb 9, 2:07 pm, CoryG <c...@geesaman.com> wrote:
> Has anyone worked with automatic solid dispensing mechanisms before
> that might know of a cheap method that can be used reliably?  So far
> researching the subject the standard methods seem to be:
> -Screw Dispensing (a screw sits inside a container with a powder and
> turns to dispense the powder)
> -Vibration Dispensing (a rod goes through a container holding a power
> a vibrates the end which double as a cap) to tap out powderhttp://www.youtube.com/watch?v=_NAPsMxadGo&feature=related
> -Air Pressure Dispensing (a tube with a paper filter on the end is
> used to suck powder into and blow it out at the desired location)http://www.ebay.com/itm/BioDot-DisPo-Adjustable-Mass-Powder-Dispensin...

John Griessen

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Feb 10, 2012, 10:58:09 AM2/10/12
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On 02/10/2012 08:06 AM, Chris wrote:
> The slide would
> vibrate and dump powder into a container at that end of the slide.
> The container that it was dispensed into was on a scale. The slide
> would vibrate until the correct weight was reached.

Sounds like the vibration on the low slope V-chute averages
lumps in the screw output and makes the falling powder
amount vs. time more linear, less noisy.

Chris

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Feb 10, 2012, 6:27:32 PM2/10/12
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@John yeah that seemed to be the general gist. I did not make the
powder system but was in charge of overhauling the robot that grabbed
the weight out containers. A screw drive seems to be limited by the
volume of powder contained in the screw. Once it dropped on the slide
it would tend to spread out so you could get finer resolution. There
were still lumps in the powder but some of the larger ones would
breakup by the end of the slide. If I can remember correctly there
were a couple of screens along the slide as well that help to breakup
really large chunks as well.

Chris

John Griessen

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Feb 10, 2012, 8:03:05 PM2/10/12
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On 02/10/2012 05:27 PM, Chris wrote:
> If I can remember correctly there
> were a couple of screens along the slide as well that help to breakup
> really large chunks as well.

Hmmm.... you could make one screen be the shaken weight so as to
create a positive sifting action...

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