Jump to content
Model Cars Magazine Forum
BDSchindler

Rubbery/Flexible Resin Castings

Recommended Posts

question for those that know more about resin than I do...I rec'd some parts that I ordered and one of them (an engine) is quite rubbery and flexible.  All of the pieces of this engine are.  The rest of the resin parts I ordered are rock hard, as I am used to working with.

So whats the deal when resin is delivered rubbery and flexible?  This isn't normal, is it? 

Was it not given enough time to cure? 

Will it cure hard if I leave it out and/or put it in a paint dryer under low heat?

Will it still hold paint and will the CA glue still hold it together?

I emailed the resin caster about it and waiting on a reply but wanted to gather some info from the resin experts out here.

Thanks!

Edited by BDSchindler

Share this post


Link to post
Share on other sites

Even if all the parts are from the same caster (which I assume from your post), it's impossible to make a blanket statement.

Improperly catalyzed (mixed in the wrong ratio of resin to "hardener") will probably never cure completely, and no amount of baking or wishful thinking will fix it...probably...but it's worth a try.

BUT...there ARE resin systems that are designed to remain flexible, and a caster could have possibly oops-ed and made your parts from that.

Without having in-hand EXACTLY what you have, and experimenting to find out what the actual reality is, all the opinions in the world aren't worth the paper they're printed on here.

Your best number one course of action is to get a definitive answer from the person who made the stuff, and preferably, get hard-cured replacements from him.

Share this post


Link to post
Share on other sites

From my experience when the resin goes bad it won't harden. I also notice fresh molds can have the first few parts soft an uncured. In this case I throw out these parts, not sell them to people. I wish there was a way I could inform those buying resin about quality. This is why I got into casting parts after I was burned. Don't ever buy from a caster with bubble voids or pimples on their product images. Even more so don't deal with casters that use the kit plastic for the product image cause there resin is so bad.

Share this post


Link to post
Share on other sites

Thanks guys.  The good news is that the resin caster did not bat an eye and is sending a replacement as soon as they can.  Although it would have been better to have double checked the quality before shipping, I am happy with the fact that he is going to replace it without questioning.

Share this post


Link to post
Share on other sites

Aside from sprinkling it with Viagra, you will have a time painting said parts. Get the info from the caster or get replacements!

Share this post


Link to post
Share on other sites
2 hours ago, George Bojaciuk said:

Aside from sprinkling it with Viagra, you will have a time painting said parts. Get the info from the caster or get replacements!

 

57 minutes ago, jaxenro said:

Not even Viagra makes soft resin hard

Related image

Share this post


Link to post
Share on other sites
On 7/15/2019 at 10:00 PM, ScottH454 said:

From my experience when the resin goes bad it won't harden. I also notice fresh molds can have the first few parts soft an uncured. In this case I throw out these parts, not sell them to people. I wish there was a way I could inform those buying resin about quality. This is why I got into casting parts after I was burned. Don't ever buy from a caster with bubble voids or pimples on their product images. Even more so don't deal with casters that use the kit plastic for the product image cause there resin is so bad.

I actually ordered 2 Coyote engines.  One was the one that ended up being flexible and uncured but the other one was rock hard.

So I started cleaning up what I thought was the one good casting and realized 2 things...

  • These were not pressure cast as there are pinholes galore
  • Definitely cast from a plastic kit engine.  There is a hole in the block just above the where the oil pan mounts (although poorly filled with resin) that on a plastic kit would allow a metal axle to pass through and there are mounting tabs on the block for the parts to mount to but the same void is not there on the part to be mounted.

I emailed the Resin Caster and told him not to send me the replacement Coyote engine but instead just refund the money for it.

 

Coyote.jpg

Share this post


Link to post
Share on other sites

The biggest enemy to resin is humidity.  Here are a couple of photos of a vacuum chamber I built some time back.  It was built out of a ten inch piece of PVC pipe I found in a dumpster at work.  I added a interior LED light to better see what is going on inside.  I use it to de air silicone before I pour it into a mold box and to remove humidity from my resin material.  If you have attempted to try to make your own parts and the resin grows and starts to look like foam in a can it is full of humidity.  Resin can reach a 160 degree temperature and the humidity will start to boil and foam up.  After some time I bought a dehumidifier.  After it was in use for 24 hours, the bucket was full.  I could not believe how much moisture can still be in an enclosed shop even using air conditioning and also live in a dry state.  A big problem with parts you may purchase that have dimples or warts on them might actually be from the silicone mold not having been de aired first.  A silicone product may say that it does not need to be vacuumed but this is a CYA statement on their part.  Many times I mix, vacuum and pour and vacuum again even on molds that are not very tall or thick, however you want to view it.  Humidity and room temperature can effect the silicones ability to cure.  I pour a small amount of silicone over a part with lots of detail like a wheel or grille or a dash and vacuum it.  A small bubble can trap in detail crevices causing the part to come out with a wart on it.  A small bubble can form just under the surface of the silicone next to a part too.  Once pressure is applied that small area will get pushed in and a part can come out looking bad but to the eye the mold can look like there is no problem and from experience that can be frustrating to learn.  Sometimes once the mold is inspected the problem is obvious but once it sets for awhile it can look normal again, A Jeckyl/Hyde affect.  A air bubble tapped in silicone can be affected by normal air pressure too.  if you notice a bump, stick a exacto knife blade in it to relieve the air pressure.  The tubing you see has a drain valve attached to it.  I usually just hold my gloved thumb over it so the vacuum draws down.  The material will start growing and you want to make certain it does not go up and over the top of the container making a big mess.  The front clear cover is about a half inch thick.  I use a Robinair 2 stage 15500 vacuum pump.  You can buy a 2 stage from Harbor Freight, but you should buy the warranty too, just to be safe.

vacuum chamber 1.JPG

vacuum chamber 2.JPG

Edited by Greg Wann

Share this post


Link to post
Share on other sites

Well, the good news is that the resin caster was very good about and refunded the entire purchase, not just the one engine as I requested.  That was pretty up front of the guy to do that, in my opinion.

Share this post


Link to post
Share on other sites

Glad it worked out. I don't think I would even try resin casting here with the humidity levels we have. Some days the air is so thick you can almost chew it

Share this post


Link to post
Share on other sites

We've had 60+ humidity and 80+ temps for days, there's no way I'd try pouring resin right now. I don't have A/C so it would be fighting a losing battle for me. 

 

Share this post


Link to post
Share on other sites

BDSchindler, as I mentioned before I don't have a "Coyote" engine ready. I do have the kit with the engine used here but like you see it had a hole through the block. However, I do have a "426" shown that is available on eBay. At the least, you can see the quality comparison in the photo. You can see more of my work at action-modeler.com. Nothing goes out with pimples, voids. or flash an is always in-stock when listed.

IMG_1029.JPG

Edited by ScottH454
Found the kit engine in question.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...