Perfect silicone translucent switch covers

[Northern Lights]

Perfect except that air vulcanizing DAP clear silicone seal is too soft and does not support itself very well to replace factory caps or seals, the method is sound but a better silicone is necessary.

But my point is how to make them. I make molds and cast plastisol for fishing lures!

click here X to see BIG wigglies.
I jointed another forum all about that. www.tackleunderground.com . I learned how to make better molds and copy patterns.
TU taught me this, its long, pics too. this link is for you fishing guys...

This thread inspired me to make up a casting system for translucent silicone switch covers that can be mixed with GID pigment.
Transparent Mag switch covers?

You will have to find your own silicone but here is how to mold it.

Use a straight sided container as you will need to flip the half of the mold over. Blue the switch covers to be copied down using glue that will allow you to pull them off. I used Locktite vinyl and fabric glue.
Coat it with a release agent, spray cooking oil works but I like vasoline. I found the silicone was not sufficient for the silicone sealer, it stuck in this case. I recomend heating vasoline and brushing it on.
You can use plaster of paris (pop) but I prefer Durham Water Putty (dwp), DAP makes a product like dwp too. I use dwp as it copies fine detail very good. I copied the knurling on switch covers and the cat head from mag covers.
Mix the dwp as thin as crème, it must pour. You can slow the reaction by using ice water and or adding 1-2% vinegar by volume.
Use a small brush and paint the surface of the switches with the mix so when you pour in the rest of it there are no bubbles.
After you pour in the rest, shake, rattle and roll it. Use a vibrator if you like, and settle it sending the bubbles to the top. This material sets, does not dry, a chemical reaction occurs and crystals of the plaster form in it. Excess water just dries out later.
Next morning flip it over and remove the half of the mold.
click here X to see BIG view
Clean up the cavities and replace the covers to their proper positions in the mold and clean off their surfaces. I also used a drop of white glue on the edge of the cover in a spot or two to hold it in place for the next step. A second side will be made so use acorn nuts in 3-4 places for index points. Drill a recess into the mold and set the nut into it with glue. Make sure it is even or above the surface at the shoulder of the nut or the next layer of dwp will lock the pieces together. The nut sticks up providing a pin to index the mold on. Put the mold half back into the container. You can use silicone to glue and seal the top edge to the container to prevent the second layer of dwp from going down the sides of the first half. I have also used Vaseline to do that.
I did not do this on my first mold but there is a weakness to the mold where the caps that have center buttons inside them connect and it likely will break off. Those are the caps typically on clickies. Coat the whole works with release agent, again Vaseline with a brush works good. A coating, do not leave globs. For the center of the clickie caps that have the buttons inside use some JB Weld, work it in and fill the cavity and build a hump up so the next dwp pour can anchor to it. You can put in a pin or two into the epoxy using thin brad nails sticking up to get a better hold into the dwp.
Now mix up the second batch of dwp and work it in the same way, paint the models with the stuff to avoid air bubbles. Once the mold halves have set remove the entire mold. Gently separate the halves. Wait a day for the set to take place so you do not break it. You can also put a screen on the surface of the dwp when you first pour them to reinforce them like you would a concrete foundation.
Once you have the mold apart you remove the models, the originals. Cut a moat around each cavity to accept excess sprue when you make the covers. At this point I built wider skirts on the clickie covers by using a Dremel and enlarging the skirt like you would with a router tool. You could carve your name into cover at this point. I put in air vent channels between the moat and cavity. I found that is not necessary.
click here X to see BIG view
Coat the mold with a solution so 10% white glue and water, this seals the mold and preserves the detail. Blow off excess with air, leave not drops or puddles and put it in the oven at 200 degrees for 40 minutes and let it cool to room temperature before removing. You could cast switch covers now but it is best to allow the mold to harden another day.
To make a cover coat it all with vasoline, fill the cavities with silicone, air dry vulcanizing type, maybe a two part RTV is out there that will work. As I stated the DAP makes good looking covers, it comes in caulking tubes but is too soft to support itself in actual use. Press the mold halves together and a day later separate.
click here X to see BIG view

Cut off the flashing with scissors. You got it.
click here X to see BIG view
A two piece mold insures a copy of the original. CAPTURED WAS THE KNURLING AND CATS HEAD! Pressing the mold together extrudes the excess silicone and you get universal thickness to the cap this way.
Did you know if you add a few drops of water to air dry silicone seal it acts as a catalyst and it hardens in minutes, not over night? But it leaves a milky look to it and can easily have bubbles in it that way. Not good for making covers.
I do not sell covers and will not. My sole purpose in this project was mold making as that is another hobby. It worked.

 

[flashlife]

Another silicone to try is GE RTV108, available from Mouser:

http://www.mouser.com/Search/Refine.aspx?Keyword=590-RTV108-85ML

This is also an air(moisture) cure silicone but it has a Shore A 30 durometer hardness.
I couldn't find the hardness of the DAP material for comparison.
RTV108 cures clear(translucent) and smells like vinegar (acetic acid) while curing.

A good mold release for these materials is a 10% solution of dishwashing liquid ( like "Vel") in water,
ie 1 part Vel to 9 parts water.
Rinse the mold with the solution and allow to air dry.
The detergent film which remains will prevent the RTV from sticking to the mold.
Just don't disturb the dried film before you pour/inject the RTV.

We used this stuff back in the 70's for Mil-Spec and NASA projects...it's durable as hell when cured.
Parts sealed with RTV108 are possibly floating thru space even now, from the Viking program, still orbiting Mars.

 

[Sabrewolf]

Another silicone to try is GE RTV108, available from Mouser:

http://www.mouser.com/Search/Refine.aspx?Keyword=590-RTV108-85ML

This is also an air(moisture) cure silicone but it has a Shore A 30 durometer hardness.
I couldn't find the hardness of the DAP material for comparison.
RTV108 cures clear(translucent) and smells like vinegar (acetic acid) while curing.

A good mold release for these materials is a 10% solution of dishwashing liquid ( like "Vel") in water,
ie 1 part Vel to 9 parts water.
Rinse the mold with the solution and allow to air dry.
The detergent film which remains will prevent the RTV from sticking to the mold.
Just don't disturb the dried film before you pour/inject the RTV.

We used this stuff back in the 70's for Mil-Spec and NASA projects...it's durable as hell when cured.
Parts sealed with RTV108 are possibly floating thru space even now, from the Viking program, still orbiting Mars.

One of the problems i have seen over the years with an air-cured silicone
is the acedic properties of the drying agent. It attacks components on
circuitboards and causes corrosion Is this Not the case with the stuff on
Mouser? And, The reasons for myself choosing the 2-Part was for a
vacuum capable curing when i shove the project in my vacuum chamber.
That is really only for getting ALL the bubbles out
A shore hardness of 39A is perfect for button making. But you can
actually make the stuff Much softer by mixing Less Catalyst with the
base product. It feels tacky, but is perfect for potting electronics.

 

[Northern Lights]

Another silicone to try is GE RTV108, available from Mouser:

http://www.mouser.com/Search/Refine.aspx?Keyword=590-RTV108-85ML

This is also an air(moisture) cure silicone but it has a Shore A 30 durometer hardness.
I couldn't find the hardness of the DAP material for comparison.
RTV108 cures clear(translucent) and smells like vinegar (acetic acid) while curing.

A good mold release for these materials is a 10% solution of dishwashing liquid ( like "Vel") in water,
ie 1 part Vel to 9 parts water.
Rinse the mold with the solution and allow to air dry.
The detergent film which remains will prevent the RTV from sticking to the mold.
Just don't disturb the dried film before you pour/inject the RTV.

We used this stuff back in the 70's for Mil-Spec and NASA projects...it's durable as hell when cured.
Parts sealed with RTV108 are possibly floating thru space even now, from the Viking program, still orbiting Mars.

The plastisol that I generally use for lure making does very well on a mold coating of 50% white glue and water. The dishwashing liquid solution may soften the elmers coating. If one was to use the mold for RTV and use the dishwashing I would think the elmers solution should be left out of the process. That is no problem, as you would not be using plastisol in the switch mold anyway.

 

[flashlife]

One of the problems i have seen over the years with an air-cured silicone
is the acedic properties of the drying agent. It attacks components on
circuitboards and causes corrosion Is this Not the case with the stuff on
Mouser?(Edit: RTV108) And, The reasons for myself choosing the 2-Part was for a
vacuum capable curing when i shove the project in my vacuum chamber.
That is really only for getting ALL the bubbles out
A shore hardness of 39A is perfect for button making. But you can
actually make the stuff Much softer by mixing Less Catalyst with the
base product. It feels tacky, but is perfect for potting electronics.

The material gives off acetic acid while curing, and since it cures by absorbing moisture from the air, it may not cure properly in a fully enclosed mold. That said, if you blow air across it while curing, that will disperse the acetic acid fumes, and prevent most all the corrosive effects. It should NOT be used for potting electronic assemblies in a closed mold, it needs access to air moisture to cure. It's OK as a PC board sealant that you coat the board with and allow to cure in the open air. In fact, we did this in the industry, making the RTV less viscous by diluting it with VM&P naphtha ( read Zippo lighter fluid) to get a thin pourable conistency. The diluted goo may be painted or sprayed on and the naphtha evaporates from the thin film quickly, leaving the RTV film to air cure. We had no corrosion problems in sealing PC boards this way.

A 2 part-silicone like Dow Corning Sylgard 104, is clear, Shore A durometer 40, and won't stick to anything. We also vacuumed it to remove bubbles.
Since it uses a platinum catalyst, it's easily 'poisoned' by certain materials, such as amine-cured epoxies...it just won't cure in contact with them. BUT, it's fairly brittle...which is wierd for a flexible silicone, but in fact, it's easy to scratch and tears easily. Dow Corning Sylgard 184, has great strength, 40 durometer, and won't crack or tear...but, it's BLACK. Bummer.

The Sylgards are great materials, and if you can find one about 40A, thats clear, and won't tear, you're in business. They're a little pricey though.
DC recommends that you NOT mix less-than-recommended curing agent to get a softer Sylgard...it screws up the chemistry and they may have a tendency to "revert", ie come-uncured and get very gooey.

BTW, the 10% Vel solution makes a great release for Sylgards also.

Bottom line, The RTV108 MIGHT work OK in your closed plaster (Durham's)
mold, IF you moisten the mold before you coat it with the release agent, and pour/inject the RTV while the mold is still damp. The RTV will get its moisture from the damp mold. After you de-mold the parts, let them post-cure in air at room temp 'til all traces of acetic acid are gone...your nose is a great parts-per-billion detector here. Once cured you have to allow them to "age" in air to get all the acid vapors out. If you're not sure they're 'done', throw a handful in a zip-lok bag, wait a few hours, open the bag and sniff. Vinegar smell ?...then they need more time under the fan.

We used a 'wet' trick in the 70's to get air cure RTVs to cure in an enclosed mold, by stirring them with a wet popsickle stick. The wet stick disperses enough moisture into the pooky to allow it to cure 'firm' and de-moldable, but not 'hard'. An air post-cure allows them to fully cure.

There are also other air cure silicones that liberate alcohol rather than acetic acid while curing, these are totally corrosion free...don't recall the names though. Sorry.

 

[flashlife]

The plastisol that I generally use for lure making does very well on a mold coating of 50% white glue and water. The dishwashing liquid solution may soften the elmers coating. If one was to use the mold for RTV and use the dishwashing I would think the elmers solution should be left out of the process. That is no problem, as you would not be using plastisol in the switch mold anyway.

Yep, I'd say omit the elmers if you use the detergent release, the detergent WILL soften the elmers. BUT, I wouldn't commit a production run using the new detergent release without trying it 2 or 3 times in trial runs.

Since I never tried 50% Elmers as an RTV release, it might work OK too. If I recall correctly from other experiments, elmers white glue will cure instantly if exposed to an acid solution. You might try coating a glass microscope slide, scrap of aluminum, etc with your elmers release, let dry as normal, then dump some vinegar on it. That would simulate it being exposed to the RTV vapors. If all goes well, I'd then try a few parts in a scrap mold.

Experimentation is at least 65.375% of engineering.

 

[flashlife]

Nothern Lights,
I just re-read your original post and would like to mention a trick that I've used.

I used to make N-scale railroad landscapes and the mountains were made from Scott paper towels coated/dipped in POP or DWP. These plaster-wet towels were just draped over a flimsy cardboard frame and sculpted into 'mountains'. Once cured, a good strong mountain using 3-4 layers of plastered towels would support my body weight ( ~ 160 lbs) !! Since paper towels are easier to form and manage than metal screen, they might work well to re-inforce your molds.

I'd say, pour the 1st layer of POP (DWP) that will hold the parts details then add a couple of layers of dipped paper towels then fill'er up, and finally add a layer of POP-towels to form a durable outside surface on the mold.

When dipping the towels, you want the POP to be about the consistency you said above (cream) and the towels should be just damp (wet, then squeezed out) so they won't suck the water out of the POP. I used to just lay the damp towels onto the POP surface then knead it with fingers to get it fully covered, then flip it over and repeat, then drape the POP dripping towel over the form.

This gave a 'mountain' that was simply a shell of POP/towel 'composite' about a 1/4" thick, but really strong. Also, paper towels are cheaper than screen wire.


Wow...three posts in a row...I'm done.

 

[Northern Lights]

YES, that would be easier than metal or fiberglass screen. I will use the method next time.
Thank you, that was unique and new to me.