By TURK - 10/26/2018 2:41:43 PM
Hi guys,
Apologies in advance for the somewhat misleading and bizarre thread title. ........ but it's not too far off the result I actually got 
The intention of this thread is to find out what went wrong, or if I did something wrong. Also, it's to find out if the same thing has happened to anybody else.
First of all to put you in the picture .................... I'm working on two ( OffSide & NearSide ) headlight covers silicone moulds for some custom headlights I'm making. My plan was to cast 'Vac-Cast Epoxy Resin' into the silicone moulds to make two headlight covers , that I'll be vacuum forming on my vacuum forming machine. Tooling plugs basically. I've had great success in the past with EC CS25 Silicone rubber in the past, but this time things went drastically wrong.
I first placed an order for 2 x 5Kg silicone + the Catalyst at the beginning of last month. Then realised that I would need in the region of 5100 grams to fill each of the moulds! So 10 days later I placed an order for another 10Kg of silicone. I've got the full EC degassing system so I had to split the pour into 2 parts.
The method I use has always worked for me in the past - fill the mould cavity with dry rice to get the volume, pour dry rice into evenly into x2 10L buckets ( 10L buckets fit perfectly into my degassing chamber ), make a mark on the bucket to the level of the rice ( equal levels = same volume of silicone needed ). Weigh the 10L bucket, minus weight of bucket ( 250g ) gave me 3414grams. Then it's just a case of working out the ratio of catalyst. 5% as it's 100:5 which gives me 172 grams of catalyst. Where did I go wrong? Did I do it wrong somehow, as the result I got was an utter disaster .................... moulds are damaged as are my original plugs 
The very first thing I wasn't happy about! ................ Usually CS25 is white, at least it's always been in the past when I've used it ( but now I realise it's final finish is based on the colour of the catalyst ), as I keep all my moulds and store them for future jobs if needed, these last ones look like crap! The one of the left ( top ) was the first one I did ( white ). The next one discoloured and grey in parts was the second one I did ...................... and no, it's not an indication of a pour mixed silicone/catalyst  >>
De-moulding is usually very easy from the mould setup boxes, as it was this time also, as I always use Melamine wood boxes >>
However ....................... de-moulding my plug from the silicone rubber was an absolute mare! The sides of my plug came away easy enough so I could slip my fingers into the gap, but then I struggled for about an hour to release the plug from the silicone mould! In places, you can see that the silicone has adhered itself to the Pattern-Coat Primer finish on my original plugs, tearing it away leaving Pattern-Coat Primer glued to the silicone surface! I used EC 'EaseRelase' release agent ( even used the special application cloths ) to apply the releae agent. As I was getting nowhere releasing my plug from my mould, I had to resort to spraying water into the silicone mould >>
The image above and this one is Pattern-Coat Primer that's stuck to the silicone! I had to pick it out using a pair of tweesers! You can also see the result of the other silicone pour ( grey patch ), it's now obvious to me that no two orders will despatch the exact same product. The silicone may be white ............... but the catalyst will vary in colour, making your mould look totally different. And garbage in my mind >>
And here's my original plug ............... including some stuck-on silicone where it's been torn while trying to de-mould it! Not a happy chappy I'll tell you. The finish on my plug was like a gloss highly polished finish, now it looks as though the silicone has reacted somehow with the pattern-Coat Primer, and it even feels sticky!!! What on earth has gone wrong? >>
Silicone moulds 'cleaned-up' as best I could after chipping away at the Pattern-Coat Primer. Obviously, this has damaged the moulds so I can't cast Vac-Cast Epoxy Resin into them >>
The whole process ( a very expensive one ), was an utter disaster. So what's next? is this still recoverable? >>
And one more thing .................. As I had a little silicone left over in my bucket, as a test I poured the reminder of that silicone in a Teflon coated baking tray ( a brand new one ) and that too stuck like glue! That's quite worrying! >>
So what's going on? any one got any ideas? where did I go wrong? did I get my ratios wrong? or is there an issue with this particular product? Has any one encountered problems like this in the past when using CS25?
What baffles me is, Teflon is non-stick ( well known ) ............... silicone sticks to virtually nothing, yet I managed to turn into an adhesive! This has left me straching my head, any help or suggestions greatly received.
I'm now in two minds as to continue using CS25 silicone rubber for mould making, as the results seem to be very hit and miss!
TURK
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By TURK - 1/9/2019 8:03:49 PM
Hi guys,
Thought I would post an update on the Quad Headlight Project, but more importantly how I got on with my replacement CS25 Silicone rubber ( thanks Warren ). I think it's only fair that I should share my results using CS25 silicone rubber as everyone has been so helpful, and are probably wanting to know themselves how things turned out. I'm no expert guys, many of you would probably have worked that one out yourselves!
So my recommendation would be ( and that's purely my opinion ), what I concluded was the mould release agent I used wasn't compatible with the silicone. Probably totally wrong!
So, on this attempt I used the 'Mann' Ease Release 200 mould release agent that comes in aerosol can.
This was what I was left with after my disastrous first attempt, the silicone mould was useless and my plug was damaged, the other one was even worst! >>
First thing I had to do was to repair my plugs, as they're basically layer upon layer of Pattern-Coat Primer resin, I had to sand-back most of the previous layers, and then begin to re-apply really thick layers of PcP in the broken areas ( a bit like using Polyester filler ) >>
Because I the headlight design, these will actually be for the headlight covers I intend to use, there's a line ( that I call the 'swagline' ) all the way round the plug, it kind of makes working with the plug awkward, simple things like sanding become quite awkward, but it's needed for making the part structurally sound and adds definition to the shape. So in almost every step of the process I have to add blue painters tape to either protect the swagline or give it form >>
Then the sanding begins ................... If you hate sanding stuff, mould making isn't for you! >>
Lots more sanding later ..................... the 'swagline' is well established, and it's just a case of working the plug till you regain the initial shape back >>
A few more days of sanding, all the while checking your dimensions, you're almost back to where your were the previous month >>
Now it's just a case of working through the sandpapers >>
After the 1200 grit wet & dry things are beginning to look up. It never ceases to amaze me just how good you can get the Pattern-Coat Primer to look. It's like a glass-like finish it's that smooth. And that's without using the 'Pattern-Coat High-Gloss' finish >>
Then it's onto the polishing stage, then a few coats of wax. I got the things so buffed up that I could actually read the wattage of the over-head light reflected in the plugs! >>
Now the plugs are fully repaired, buffed up to a high sheen it's time to install them into my mould set-up boxes. As I need to reduce the hight of the plugs by 30mm ( that will become my 'tooling plugs' for vacuum forming my parts ), I simply glued the batons in place and filled the voids with 'NewPlast' plasticine >>
As the bottom of my mould set-up box will become the top on my actual completed silicone mould, there's no reason to make a pigs ear of it. The edges must be crisp and sharp >>
I'm not going to go through the entire CS25 silicone preparation and pour, as that's already been covered on the first page, as I've already mentioned, the only thing that I did differently was to use the 'Mann' aerosol release agent. De-moulding time - Already things didn't look good!!! the sides of the mould box were well stuck .............. it took quite a lot of persuading to release the sides, no damaged was caused to either the silicone mould or the set-up boxes themselves ( I will need those again in the next stage ) >>
In the end, everything worked-out just fine  well pleased with that >>
The quality of the silicone finish is superb and the definition is bang on. And as intended ( hoped ) the swagline is nice crisp and sharp >>
The next stage will be to cast 'Vac-Cast Epoxy Resin' into these. But a solid block of vac-cast resin isn't what I want or need. For a proper vacuum forming tooloing plug, the tooling plugs have to be hollow. I'm hoping to use plasticine, about 20mm thick ( rolled-out with a pin-roller ) to 'line' the bottom of this silicone mould.
Does anybody see any issues with that method?
I'll be using cling-film as a barrier so the plasticine doesn't stick to the silicone.
My other question, and really my reason for posting this article, PLASTICINE .................. can I put plasticine in a microwave oven to soften it? I've made a 'heat-box' to soften the plasticine, as I need it to be malleable so I call role it into flat slabs., but it takes all day just to soften it just a little! Microwave method any good?
Anybody tried this method? I'd like to hear from you if you've tried this.
And just to finish off ................... The only issue I had ( the silicone sticking to the sides of the mould set-up box ), was due to the fact that the 'Melamine' wasn't actually Melamine at all, but just a cheap finish to make it look like Melamine! When I looked closely at it and picked at it with my finger nail, I realised it was a type of compressed cardboard made to look like Melamine! The junk they make now days, nothing' real anymore!
TURK
T4 Concepts
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