vulcanized rubber molding and temperature

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aaronr
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vulcanized rubber molding and temperature

Post#1 » Wed Jan 28, 2015 5:55 pm

Previously we wax carved pieces, cast the wax to create a master, then rubber molded the master for production purposes. We used vulcanized rubber for molding and heat 340-350 degrees. Since we got into 3D printing our models a few year ago (with an EnvisionTec and a B9Creator) we do more jobs where we only need 1 or 2 copies cast. So, we have not needed to mold things for a while ... until now

With the cherry resin, is anyone molding the printed model using vulcanized rubber molds?

I know on the cherry material page on the B9 website it says "Printed parts may be used to create vulcanized rubber molds.", but I was wondering if anyone has any success/failure stories to share about molding this material? One concern we have is warping.

Or if others can share what they are using to mold printed models that would be greatly appreciated.

Thanks

Aaron

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akgold
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Re: vulcanized rubber molding and temperature

Post#2 » Wed Jan 28, 2015 6:18 pm

I would give it a try considering the resin cures at around 300 deg f.
But I would cure it first otherwise the resin model will still be pliable and may bend or distort the model.
It needs to be cured to get the hardness for the vulcanizer
I'm so far behind I think I'm First !!

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TAJS
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Re: vulcanized rubber molding and temperature

Post#3 » Wed Jan 28, 2015 6:53 pm

I have had success with the RTV molds on printed models.....

tobyramp@hotmail.com
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Re: vulcanized rubber molding and temperature

Post#4 » Wed Jan 28, 2015 7:25 pm

I have vulcanized several pieces and have no concerns. You may break a delicate model pulling it from the mold, but if you don't need it no problem.

ujd24k
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Re: vulcanized rubber molding and temperature

Post#5 » Thu Jan 29, 2015 12:11 am

You can heat the models around 340 degrees and not problems, so basically you leave it like 30 minutes more time for the rubber fill all the spaces , some times the models become very brittle and break when you are making the cuts in the rubber ,but you have a rubber mold to make another copy ;)

kai
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Re: vulcanized rubber molding and temperature

Post#6 » Thu Jan 29, 2015 7:18 am

The resin (we use 1:1 mix) holds up very perfectly against the regular vulcanizing temperature. We use Castaldo Silicone Rubber (Super High Strength) and vulcanize at 170 C (340 f) without problems. I recommend not to put too much pressure on the model like you would do with silver masters. We made thicker molds (around 1 hour, 10 min vulcanizing time) and had no problems.
As a release spray we used Castaldo Resin Release. I think you can also use any no-stick cooking spray (mazola) or teflon spray.
The braking of the model is actually a nice "feature" as it allows you to cut the mold more precisely, for example the inside of the ring ;)

Kai

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Metalcaster
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Re: vulcanized rubber molding and temperature

Post#7 » Thu Jan 29, 2015 7:42 am

Kai is correct,
Castaldo heat cured silicone works very well for this purpose. Coating the model with their resin release is sometimes very critical. I have been molding Rapid prototypes in Red and cherry for at least 2 years.
Resin must be fully cured or it may bond.

Castaldo offers free samples to try on their website. www.castaldo.com

You can't buy from Castaldo. They only deal through distributors. You can get samples from Castaldo only.
They have a list of US and world wide distributors on their website.

Some suppliers would be www.Contenti.com www.riogrande.com www.gesswein.com

kai
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Re: vulcanized rubber molding and temperature

Post#8 » Thu Jan 29, 2015 9:03 am

I might take this topic away a bit, but I was actually really surprised how well the vulcanizing works. Micro-prongs or even filigree type wire is no problem. We print the model with an adapter to fit the 1/8 metal rods which you can find on riogrande, gesswein, etc. You know before owning the B9C we carved every model by hand (still do a lot by hand, but more for artistic reasons). I thought well you can print, but sure you have to cast,finish the master model and than make the mold. So direct casting was the most important feature for me. But given the great quality of the prints, the workability of the resin (sand it, polish it, patch it) and the compatibility with silicone rubber, there is no need for us do this extra step. Mike could emphasize on this feature a bit more, it is a strong selling point for some ;)

PS: Silicone is also cheaper than VLT rubber and lasts longer

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aaronr
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Re: vulcanized rubber molding and temperature

Post#9 » Thu Jan 29, 2015 2:37 pm

Just posting to say "Thank You" to everyone. The responses were exactly what I was looking for.

Aaron

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Metalcaster
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Re: vulcanized rubber molding and temperature

Post#10 » Thu Jan 29, 2015 3:45 pm

More info on heat cured silicone:

Heat cured silicone requires a clean mold frame. Aluminum or steel frames are fine, but they cannot have had Yellow Castaldo gold or any organic rubber cured in them. If you have cured organic rubber ( this is the old style rubber, still in use, that comes from rubber trees)in any frame, you must remove the invisible sulfur that is left in the interior of the frames.
Usually, the only thing that works well is to bead blast the frames completely clean before using silicone.After having spent the time cleaning the frames, make sure to mark them for "silicone Only" .
If you notice the silicone is not curing around the exterior periphery of the mold or on the flat top and bottom, you are experiencing contamination due to sulfur.

I was the originator of heat cured silicone for the Jewelry trade (late 1970's) while I was working as a design engineer for a large US Jewelry Machinery manufacturer. I did not develop Castaldo's rubber. Theirs came about 3 years after . I do help Castaldo do testing .
The lowest Heat cured Silicone is castaldo's VLT. I run that at about 170 0F ( i have molded Carving wax in it)
All the other heat cured silicones work well in the 310 oF to 350 oF .
Total shrinkage will range between 3 to 5 % for mold, wax, cast and clean up if done correctly.

mredburn
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Re: vulcanized rubber molding and temperature

Post#11 » Fri Jan 30, 2015 5:59 am

Zero D products also offers a low temperature silicone for molding around 165 degrees. I also use rtv silicone to make molds of printed masters.

kai
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Re: vulcanized rubber molding and temperature

Post#12 » Fri Jan 30, 2015 9:01 am

Metalcaster, this is great. I did not know that silicone rubber was used in jewelry in the 70s already. We used Castaldo Gold Label up until 5 years ago and it was really a pain to cut the tiny rubber pieces and pack the mold. I am sure you know :) On the plus side the gold label rubber has a great memory and lasts years ...

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Metalcaster
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Re: vulcanized rubber molding and temperature

Post#13 » Fri Jan 30, 2015 1:19 pm

Hi Mredburn,
Zero D has very good silicones as well. I forgot to mention them. I use their low temperature heat cured material all the time.

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Re: vulcanized rubber molding and temperature

Post#14 » Fri Jan 30, 2015 1:23 pm

Hi Kai,
I grew up on Castaldo Gold making extremely complex rings. Good stuff.probably made a few thousand molds with it. Lasts almost forever.
When I developed the Silicone, I never went back.There are so many advantages to the silicone. Wax does not stick to the mold is a very important one for parts that would normally get distorted from sticking.

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