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udirn1

udirn1

Electrical
Apr 17, 2009
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Hi all
i hope fhis is the correct place for this kind of questions..
i have a project where i need to glue a capsule or a tablet which is round shaped to a round shaped plastic mediator.this whole assembly at the end will be clinked to an handle to preform a certain task.the problem i have is with properly attaching the capsule to the mediator.the capsule is made of condensed powder and its like an alka zeltser tablet that you are all aquainted with.i undetstand that i need to use an elastic glue to attach it to the plastic surface but the problem is that in all my experiments so far the tablet either broke or detached from the mediator after a while leaviln a thin layer of the material where the glue was placed.i undetstand there might be an issue here of forces going from the plastic mediator fhrough the capsule and thus breaking it....so if the pladtic rxpands a bit immidately it transfers this gorce to the capsule and breaks it or cracks oit.
my questions to the experts here are ad follows:
1.how would you recommend best attachment between the capsule and mediator to have minimum breakage.
2.the diameter of both capsule and mediator are the same.would yoi recommend decreasing or increasing one of them vs the other to reduce the forces described above?

would appriciate any adviSe
ron
 
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me·di·a·tor
ˈmēdēˌādər/
noun
noun: mediator; plural noun: mediators
a person who attempts to make people involved in a conflict come to an agreement; a go-between.
 
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Mediator is also used as a material that mediates or acts like a medium between 2 materils.hope i am clearer now.
 
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Gather a sheet of nylon net around the capsule, forming a crude bag. Tie the bag to the mediator, whatever the hell that is in your world.

Nylon net is cheap, comes in colors, and is available at any fabric store.


Mike Halloran
Pembroke Pines, FL, USA
 
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Sounds like you have a major increase in stiffness at the same point in your structure as a major reduction in strength. Always a likely trouble spot. Is it possible to isolate the two transitions?

Could you glue the tablet onto a metal disk (weak/stiff onto strong/stiff) then glue the disk onto your mediator (strong/stiff onto strong/flexible)?

A.
 
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It sounds like your adhesive should be much less stiff than either tablet or its holder - maybe something like an adhesive foam tape. Alternately, look at ways of keeping the the tablet in compression, maybe with a circular rubber o-ring around the periphery (tablets, like concrete and other ceramic-ish stuff don't like tensile or shear stresses).
 
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Udirn1:
If it is actually a capsule, I would use/try a blob of the gel (gelatine, whatever it is), of a fairly thick consistency, which makes up the outer skin of the capsule to glue the two together. If it is a tablet, maybe grind up a tablet, mix that grinding with a little glue and take a small ball of this to bind the two together. Both of these approaches may have to be done in some sort of a mold or a press, until the glueing component cured, dried and hardened. Would some form of epoxy work, at least to the extent that the tablet material had shear and bond strength near the glue joint. You could drill the tablet, and insert and epoxy a fine wire in the middle of the tablet. Could you form the tablet right around the plastic handle, like a popsicle. You’ll just have to experiment with this, it’s a fairly strange requirement/request.
 
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Thanks all.
I have upoaded a few pictures to give you a beeter understandin of this issue.
the capsule needs to be exposed as it needs to touch a second surface during the process.
I have uploaded 4 pictures as follows:

1. Broken capsule residue on mediator

2. Assembly of capsule and mediator glued together and place on the wand

3. Stand alone casule and stand alone mediator (prior gluing them together)

4. Assembly of capsule and mediator after glue process.

As I stated above the problem I am facing is after I glue the capsule to mediator some capsules detaches from the mediator.

Any advise would be helpful.
Thanks guys

 
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Well, if you are stuck with that configuration, then using as much glue (creating as much bond area) as possible is about your only choice. I.e., spread the glue over the entirety of the cup/mediator surface and up the side walls.
 
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Are you allowed to make modifications to this mediator and this capsule? Seems to me that more glue surface would be good, but also, making the surfaces rougher or even adding texture would help the gluing.

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What glue are you currently using? Clearly the first improvement is to use more bonding area. 3 spots of glue will be far weaker than a large area bond. Tablets are made by compacting powder together and are usually intended to break-up easily.
The glue must be compatible with the substrates. Solvents or water can weaken the tablet, as might the acetic acid released by RTV silicone. A hot-melt glue would probably be best for this application. Heating the tablet before bonding can help improve the bond for hot-melts.
 
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Could you mold the mediator with an array of ~6 undercut fingers extending 'upward' so as to surround the capsule and allow someone to 'snap' the capsule into the mediator fingers with no adhesive?


Mike Halloran
Pembroke Pines, FL, USA
 
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