Discussion in 'Replica Props' started by darienvader, Dec 27, 2005.
What are your thoughts on the TASKÂ™ 15 liquid plastic from Smooth-On for making helmet casts?
I use task for tooling patterns. It is very hard and can handle very high heat. I thing its a great plastic. It is a flash cure plastic so you have very little time to work with it before it flashes over.
This may be an issue when pouring a large pour like a bucket
I was thinking more along the lines of a rotational cast. Build it up in thickness.....
I think his concern is how fast you can mix and pour. Task has a pot time of 6 minutes, so how much material can you:
1)Pour two parts together
3)Pour into a rotating cast
In 6 minutes? That would be how quickly it build up.
Just by glancing, Task 3 might be better. You get a 20 minute pot time with a 90 minute demold.
What I was actually refering to is the fact that its a flash cure. The plastic goes thick in a blink of an eye compared to the slow steady thickening of a plastic like smooth-on smooth-cast series.
The cure of TASK locks the shape in in less that the time they state on the working time. Also the larger the volume the faster the cure.
In a situation like this I would say a slower cure is better for roto casting. The plastic has more time to find its place. Task however is still an excelent choice for durability.
Well since you seem to have a working knowledge of the product, do you think a thin layer of Smooth-Cast for the details backed by TASK might work? Kind of like the gel coat before you start laying Fiber when you make a FiberGlass item?
Speaking of smooth on, can anyone tell me on how fast their shipping usually is?
They usually ship through the closest distributor to you that carries that product or product line. So I guess it depends on the particular distributor. I've been very fortunate and see most deliveries arrive within 3 biz days of placing original order.
There is a problem I can see with mixing 2 different resins even if the first is cured. The resins all give off an oil and would act as a release agent. Although the shape may lock it in place, it may be brittle.
I suggest going with a slow cure TASK. Also are you machine roto casting or doing by hand rotation? By hand may not have enough g-force to get a good press up.
Thanks all for the response; great input. I'm used to the Smooth-On 300 series which also has a short pot life, but for something as large as a helmet, I'll probably go with the TASKÂ™ 3 based on the input given here. Thanks again.
I agree, bad idea to mix your resins. Casting resins won't stick to themselves so you basically have shell inside a shell but no bonding occurs. The other problem is that some products cause the second resin to cure improperly or fail to cure at all..........so be careful.
I'd search for a resin that has slower cure rate too.
I've used Task 15 for helmets in the past. It is an excelent rotocasting resin as it slowly gels over starting about 6 minutes after mixing until about 12-15 minutes after mixing. This gives you plenty of time to poor in and start turning it.
It cures to a very strong slightly flexible finish that my only, accedental, strenth test is it can be knocked from a table and hit concrete without any noticable damage what so ever.
Only problem I've noticed is that it claims demold time of 1 hour but I always give it at least 3-4 hours otherwise it is still a little bit flexable and hasn't 100% cured.
I've been using Smooth-On's products for 4 years now. They make some great stuff. Seems like it takes 2 days to process my order and 3-4 days to ship it to me. Sometimes if I order it on a Saturday or Sunday I can get it on Friday. I've got an order of Smooth-Cast 305 on the way to me right now, in fact.
Please tell me you're all taking the proper health precauions when working with urethanes.
If you don't know what they are, I'll be happy to send you the patented "Gordon Rant" about their use under proper conditions.
You all sound like you know what you're doing, but for those newbies who might not...
-Gordon (helping you all NOT to get TOXED OUT) ; )
Can someone explain what a rotating cast is?
Rotational casting, ie: roto-casting refers to rotating the mold (either by hand or machine) while the material (in this case: resin) cures. This leaves hollow shell rather than a solid block.
In the example described above, resin is mixed and poured into a mold. The mold is rotated by hand while the resin cures, thus coating all the sides. The resin will thicken as it cures and stick to the sides of the mold without running off. When there is a nice even coat on all the interior walls of the mold, the resin will kick off and solidify. After a few hours, the resin has cured and you can remove the piece. If done right, you have a hollow shell for a helmet. If done wrong, you will have real thin areas and big blobs in others.
This is how I make my helmets. I use 1000 grams of 3 minute kick resin. This works great, but not in summer when the ambient temperature kicks the resin too fast.
think chocolate easter bunny.
you think its a nice solid piece of chocolate when you look at it.
once you sink your teeth into it , its hollow.
the cheap buggers.
Thanks for explaing.
This casting stuff is gonna be a lot more complicated than I thought.
I use Easy Cast
They have a resin that has a plastic feel and look
I live in the Washington, DC area (Smooth-On is in Pennsylvania). I order on Monday and get my products on Tuesday or Wednesday. It's the fastest service I've ever had. Well, them and ULine (www.uline.com) for purchasing shipping boxes.
Be careful with Smooth-On Crystal Clear. I'm sensitized to it and get a violent skin rash if I touch it. I cover my skin and use a respirator when employing this material. (It's generally recommended that you do this with all urethanes.)
Of all the urethanes, CLEAR urethanes are the most toxic. They kick out massive amounts of isocyanate gas when they cure. WATER CLEAR urethanes will kick your butt faster than you can imagine.
I still have memories of my boss looking for all the world like Quasimodo after a particular giant tooth-brush molding project his reaction was so severe. His face literally puffed up like a popover.
It took him over a week to get back to normal. But he can't even be in the building when we cast urethanes now, he's THAT sensitive. He'll end up coughing up a lung if he stays.
I personally know three guys who went to the hospital when they were trying to rotocast a 3 foot tall CLEAR Coke bottle. They had a heated rotocasting room to help it kick off, but they didn't vent the space to the outdoors so all that fume-age ended up in their shop. They all pretty much just passed out and had to be ambulanced to the hospital. It wasn't pretty. They failed the job and didn't get paid in the end.
Like I said earlier, I'll be gratified to horrify you further if you care to know the tales. I got plenty.
How would these materials fare for a prop that's actually supposed to be plastic, like a replica toy? Would they be able to handle abuse like regular injection-molded plastic, or would they be far too brittle to be handled normally?
Most importantly, though, would it have the final appearance of an actual, mass-produced plastic item?
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