Thanks all for several interesting ideas. I am currently reviewing
responses.
most of the equipment and the control software for ball pick and place
from several bins of balls has been designed and built and tested, but
is not yet mounted on the machine or tested all together. I think the
difficult part of pick and place is done.
I have considered the following approaches to glueing balls into the
cavities.
1. a. dispensing a hot melt glue into cavities (exact method to be
determined)
b. placing balls where desired (possibly only partially in
the indentation)
c1. pressing down on the balls with a heated plate or iron
(more efficient and elegant)
c2. heating in oven then pressing down. (less equipment)
The only obvious problem seems to be dispensing hot melt glue onto the
cavity walls.
Using equipment made for reprap experimenters might work if I can find
a clear hot melt glue in the thin diameter form factor.
Moving small rods of material seems easier than variable viscosity liquids.
Dispensing the small ammount needed (aprox .01 - .02 cc) seems much more
difficult using much larger diameter glue sticks.
2. dipping the boards
The problem is surface clean up. The wood surface should remain
appealing without coating the ball tops with anything.
if dipped and dried before placing balls. The surfaces could be
sanded after drying. What liquid clear adhesive can I activat after
drying, method?
3. dipping the marbles
How can one remove the glue from the top surface of protruding
marbles without causing problems to the surrounding wood surfaces?
4. I will give some thought to dispensing and smearing liquid adhesives,
or heated hot melt adhesives with brushes or flaps.
craig
On 10/9/2012 9:52 AM, dave wrote:
> On Tue, 2012-10-09 at 08:24 -0400, Bruce Layne wrote:
>> I have a suggestion that's maybe not quite as snarky as Charles'
>> suggestion, but still in the direction of "maybe you're optimizing the
>> wrong problem."
>>
>> If I were placing approximately 10,000 marbles or less, I probably
>> wouldn't try to develop a method of having the machine do it. I'd make
>> relatively minor changes to optimize the operation for manual assembly.
>>
>> I have an EFD 1500XL fluid dispensing system. It has a couple of
>> operating modes, but in this case, it's basically a syringe full of
>> epoxy with a regulated air supply that can be applied over the epoxy to
>> precisely dispense it through a needle. Press the foot pedal and a thin
>> bead of epoxy is dispensed as you move the tip of the needle around the
>> upper rim of the concave pocket. Release the foot pedal and a slight
>> vacuum is applied over the epoxy in the syringe to keep it from
>> dripping. The positive pressure can be adjusted for the flow rate you
>> want, and the vacuum can be adjusted for the fluid pull-back you want
>> for your application. It's now a one handed operation, leaving your
>> other hand free for placing marbles. You can buy a used EFD on eBay,
>> probably for <$100, use it for this project, and then sell it for what
>> you paid for it.
>>
>> Dispensing epoxy is a bit tricky, because it's curing in the syringe,
>> and the viscosity is changing. The trick is to use a slow epoxy with a
>> 6 hour cure rate, and that should give you a 1-2 hour working pot life.
>> You might need to bump up the dispense pressure slightly toward the
>> end. Slow epoxies tend to be watery. If you want thicker epoxy to give
>> you a little more time to place the marble, you can mix in materials
>> like cabosil to increase the viscosity to make it easier to use on
>> vertical surfaces, and use a larger bore needle.
>>
>> I recommended this approach because we often tend to focus our
>> efficiency efforts on making the machine do all of the work, but many
>> times, the fastest CNC throughput is achieved by an appropriate division
>> of labor between the machine and the operator. For example, if the
>> machine was a blur-of-motion SCARA assembly robot that could place all
>> of the adhesive and marbles in five seconds, that's five seconds added
>> to the cycle time. If the operator is placing the adhesive and marbles,
>> all you'd need to do is keep up with the machine's ability to make the
>> holes and there would be no increase in cycle time. Basically, if
>> you're trying to maximize the rate of production, it does you no good at
>> all to devise some clever method for the machine to dispense epoxy and
>> perform a pick and place operation with the marbles, if that leaves you
>> standing there watching the machine with nothing to do but juggle your
>> marbles.
>>
>> However, if you have issues with operator fatigue or quality that can't
>> be addressed with precision dispensing tools, or you simply have a hobby
>> interest in solving the technical challenge of getting a machine to glue
>> marbles into holes, then by all means, go for that technical solution
>> and post a YouTube video. I love stuff like that! Andy had some great
>> suggestions in that vein, as usual.
>>
>>
>>
>>
>> On 10/09/2012 07:41 AM, charles green wrote:
>>> suggestion: consider alternate method of celebration.
>>>
>>> --- On Tue, 10/9/12, craig <cr...@facework.com> wrote:
>>>
>>>> From: craig <cr...@facework.com>
>>>> Subject: [Emc-users] Gluing little balls
>>>> To: emc-users@lists.sourceforge.net
>>>> Date: Tuesday, October 9, 2012, 2:52 AM
>>>> I have a CNC related problem.
>>>>
>>>> I am making small decorative personal gifts using thin wood
>>>> (5-6mm - 1/4
>>>> inch thick) and 6mm diameter colored glass balls (small
>>>> marbles).
>>>>
>>>> A pattern of shaped holes is cut in the wood with a small
>>>> cnc router
>>>> using 2 tools. A 1/4 ball nose mill cuts to
>>>> approximately 4mm depth. A
>>>> 3/16 tool then cuts the rest of the way through he wood.
>>>> additional
>>>> surface patterns may also be cut.
>>>>
>>>> The balls are then glued into the holes with a clear
>>>> adhesive (
>>>> currently a thinned clear caulking compound).
>>>>
>>>> The resulting items are interesting viewed directly or
>>>> back-lit.
>>>>
>>>>
>>>> The problem:
>>>>
>>>> The marbles are currently glued in by hand.
>>>> Painting the glue into the holes, placing the ball
>>>> and pressing it
>>>> down gets tedious.
>>>>
>>>> I would like to automate this process by replacing the
>>>> spindle with
>>>> other equipment.
>>>>
>>>> I can automate the pick and placement of the balls. (
>>>> spheres may be
>>>> the easiest item to pick and place)
>>>>
>>>> But I have not found a good way to automate the gluing
>>>> process
>>>> inexpensively.
>>>>
>>>> suggestions? Thoughts?
>>>>
>>>>
>>>> Any help would be appreciated.
>>>>
>>>> Craig
> If you are going to do a lot of these then some level of automation is
> desirable unless you enjoy being bored.
> So: Tube dispensers to place different colors of balls; just like ink
> cartridges. Insert balls from back side of board then dispense a small
> amount of non-viscous adhesive in the center of the ball and it runs to
> the perimeter of the hole where surface tension tends to keep it in
> place.
>
> I must say this is an interesting application. ;-)
>
> Dave
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