casting resin parts

[southpier]

what '32 body is that?

[crazyjim]

Anne - you can get started for about $50. I use Smooth-On Oomoo 30 and Smooth Cast 300. No scale, no pressure pot. I buy the Smooth-On stuff from MisterArt. They have the lowest prices that I've found. To make the molds I use old corregated plastic signs. Al over at Ma's Resin sells Aluminite with a discounted price.

I got started in casting when I was building a '57 Chevy that had to have bucket seats front & rear with a full length console. I refused to buy another kit just for the seats. Hence, Crazy Scale Auto Parts began.

[fractalign]

The 32 body is a roadster utility. Ford Australia started producing these back in the late 1920's. It comprised the front of a roadster joined to the back of a pickup.

[southpier]

The 32 body is a roadster utility. Ford Australia started producing these back in the late 1920's. It comprised the front of a roadster joined to the back of a pickup.

so a pickup box will slide into the cut out of the tub?

I always liked the roadster pick up. the roadster that had the trunk lid cut out and a box slid in its place. downhome engineering.

thanks

[kennb]

this is a simple flat casting,,,the tire is the same half cast 2 timre and glued together,,,,,,the backs have been flat sanded for a better fit.

The rims are a 3 part cast for the layered lacing on the wire wheels.the center is still a one off untill I learn how to cast a decent hub that works,,,,

note,,the car is of course scratchbuilt

[fractalign]

I am working on making the passenger floor and the pick up tray an integral unit. As a one piece unit it will slide in a lot easier. This is just one of a number of roadster and coupe utilities that i am working on so i am engineering the floor and the area to fit into all them.

[southpier]

very cool. please post photos as this progresses.

[fractalign]

Will do, once i have ironed out the bugs with this one. I am just in the middle of remastering the body at the moment, cleaning up the inside so that the passenger compartment slides in easily. I want to make sure there are no flaws in the body and that the top lines up properly with the windscreen frame before i remould all the components.

[Wagoneer81]

I've done quite a bit of casting in the past years. The one thing I recommend, especially if you're just getting started, is a slower setting resin. This will allow you time to properly mix the resin, pour it in the mold and work out any bubbles that need removing, if you're not using a presssure pot or vacuum chamber. You've never reached the heights of frustration until you are pouring a 1/350 ship hull and the resin starts setting up in mid-pour. I lost the pour and around $75.00 worth of resin... I've used Smooth-On and Alumilite both. I recommend Smooth-On. This is just a personal opinion, gained through valuable experience....

[shucky]

This is an interesting thread. The original question was vague, but based on all of the replies it proves there are endless opinions from those who have tried their hand at resin casting. It is just "my" opinion, but many people who venture into resin casting overly complicate the matter and make it far more difficult than it really is. But, because resin casting is still somewhat a "taboo" subject where people who do it extremely well are not willing to share their success stories, procedures, and trade secrets ... we wind up with the wild and varying opinions as noticed here in this thread.

If I were to give tips to a beginner (or anyone who wants to cast better cleaner parts) -

1) USE mold release (Price Driscoll comes to mind). This will help your parts pull cleanly and effortlessly from your molds as well as protect the longetivity of your molds. A top shelf mold release is not greasy (READ do not use petroleum jelly!) I cannot believe articles in recent mags published recently even suggest it. I use a paintable mold release which means you do not even have to soak your parts prior to painting. Why anyone would choose to not use a mold release is beyond me. A quick spray every 3-4 pulls will keep your mold in tip top shape.

2) Use baby power to dust your molds prior to pouring resin. Why? It releases surface tension and allows the resin to flow where its supposed to.

3) HEAT. Yes pre-heat your molds to between 140-160F especially if they are very thin 1 piece flat cast molds. Why? Uniform heat throughout the mold will assist the resin in curing properly. The heat also helps the RTV releasing its oils and maintains the molds longer for storage, etc. I actually continue to heat my molds after resin is poured to speed up full cure. Makes demolding faster w/out distorting your parts. Some resin (Onyx from Smooth On does not like additional heat. It actually softens instead of hardens when addt'l heat is applied) Alumilite white loves heat and cures beautifully using this method).

4) This is just "my" opinion. Legos stink for mold boxes. Why? They leak most of the time. Why build a mold box from 20-40+ pieces of plastic (legos) only to have to seal the inside of the box prior to pouring rubber? Again, this was recommended in a recent article and I'm surprised people still do it. Simple way? Express mail boxes from the post office. They are FREE thin cardboard. These are excellent for most smaller mold boxes. You simply cut a length of it, bend at the corners, secure with double sided clear tape and you have a mold box in about 30 seconds. You'll simply use a bead of clay to secure and seal the mold box to your work surface and you have a clean, neat, and leak free mold box in a fraction of the time it'll take to make one from legos. Foam board is also excellent for mold boxes if your looking for something larger / more sturdy. Cut a long strip with a razor blade, score the outer paper layer on the OUTSIDE at the corners, snap at each corner inward, secure with double sided clear tape, run a bead of clay, mold box in less than a minute. Sealed, strong, clean, cheap.

5) Pick a resin that will work best for your application(s). I love quick curing resin for doing small parts and multiple molds in an assembly line type way. Unless your mixing a huge batch or pouring a huge mold that will require more time, there is just no need for longer slow curing resins. I like to belt out parts as fast as possible. So here you should pick what will work best for you and what your doing. Remember very small batches for small parts do not have to be mixed forever and do not require the recommended mixing time.

Good luck to whoever reads this. These are my opinions, yours may clearly differ.

Edited May 15, 2013 by shucky

[Modelbuilder Mark]

I have been using Allumilite for a while, but I would like to find something with a little more working time, and that will settle down into small areas without as many air bubbles. Any ideas folks?

[Chief Joseph]

I have been using Allumilite for a while, but I would like to find something with a little more working time, and that will settle down into small areas without as many air bubbles. Any ideas folks?

Smooth-On's 305 (white) or 321 (off-white). Pot life is about 6-7 minutes with a 30-45 minute demold time.

[Jeremy Jon]

Smooth-On's 305 (white) or 321 (off-white). Pot life is about 6-7 minutes with a 30-45 minute demold time.

I'm considering to try out SO's 310 (white), it has a longer pot life @ 20minutes, and 2-4 hour demold, with same cured strength, I'm thinking this might be even better for some larger volume castings?

Edited May 27, 2013 by Jeremy Jon

[Chief Joseph]

I'm considering to try out SO's 310 (white), it has a longer pot life @ 20minutes, and 2-4 hour demold, with same cured strength, I'm thinking this might be even better for some larger volume castings?

I have used 310 in the past because of its very low shrinkage rate. For large parts with a great mass, shrinkage can be a concern. Most of the time, a rotationally-cast hollow piece is better than a large solid resin casting, but that's beside the point. The downside to that long pot life and demold time is potentially shortened mold life. Resin is destructive to the mold surface, and the longer the liquid/gel resin sits against the rubber, the worse the effect. Smooth-Cast 321 and 305 are a good compromise between good working time, shrinkage, cost, and mold longevity. Very short pot-life resins like standard tan Alumilite and Smooth-Cast 320 might yield more castings per mold (depending on a few other factors), but their high shrinkage and short working time make them unsuitable for my work.

[Modelbuilder Mark]

Thanks for suggesting the 305 or 321. I will have to give give them a try. What is your source or where have you found that offers the best pricing?

I have had good success with Allumilite for my small usages, but the problem I have had as of late, is the resin degenerates quickly in the bottles after opened, and I do not cast all the time. as for the mold life, I USUALLY only need three to 5 pieces per mold, assuming the initial casting goes well. The allumilite also seems VERY thick when pouring as opposed to the videos I watched of the Smooth on being poured. This may help, along with the working time, to get rid of some of the air bubbles/voids I have been getting. I do not have a pressure pot or vacuum pot etc, just try to work it in.

I have used 310 in the past because of its very low shrinkage rate. For large parts with a great mass, shrinkage can be a concern. Most of the time, a rotationally-cast hollow piece is better than a large solid resin casting, but that's beside the point. The downside to that long pot life and demold time is potentially shortened mold life. Resin is destructive to the mold surface, and the longer the liquid/gel resin sits against the rubber, the worse the effect. Smooth-Cast 321 and 305 are a good compromise between good working time, shrinkage, cost, and mold longevity. Very short pot-life resins like standard tan Alumilite and Smooth-Cast 320 might yield more castings per mold (depending on a few other factors), but their high shrinkage and short working time make them unsuitable for my work.

Edited May 27, 2013 by Modelbuilder Mark

[Chief Joseph]

I buy Smooth-On products from The Engineer Guy in Atlanta (www.theengineerguy.com). The prices are usually the same from all the full-line distributors, but I have seen some cheaper prices for the basic items at www.misterart.com. If you're not already using talcum powder on your molds, you should give it a try. The talc helps break the surface tension of the liquid resin and reduces surface bubbles and voids. Nothing beats using pressure, though. Good luck!

[Modelbuilder Mark]

I buy Smooth-On products from The Engineer Guy in Atlanta (www.theengineerguy.com). The prices are usually the same from all the full-line distributors, but I have seen some cheaper prices for the basic items at www.misterart.com. If you're not already using talcum powder on your molds, you should give it a try. The talc helps break the surface tension of the liquid resin and reduces surface bubbles and voids. Nothing beats using pressure, though. Good luck!

hmm, how are you applying the talc? Does it not interfere with the detail?

[Chief Joseph]

You can apply talcum powder the messy way by shaking some onto the mold, giving it a pat or two with your hand, then blowing off the excess. A cleaner way is to put some powder in an old sock and tap that sock against the mold to release the powder. You just need a slight coating of powder on the mold surface-- any excess should be blown out. Does not interfere with the detail at all.

[shucky]

You can simply dust the powder on the mold using a paint brush and shake out the excess. Again, keep it simple. Alumilite white is extremely thin and flows exceptionally well. I recently used Alumilite white that was two years old without any problems whatsoever. Any time I open a fresh batch of resin containers I remove the caps and wrap the threads with Teflon tape. After each use I also cover / wrap the tops with aluminum foil tightly pressing it all around the cap. These steps will increase the shelf life of your resin without going the extra step of an additive.

[High octane]

Not even close.The only stuff on that list that is required is rubber and resin. You can get into resin casting for less than $50. I started with an Alumilite Mini Casting Kit from that national craft store chain who's name I don't like to mention. Cost me about $30, and included enough stuff to make 2 mistakes before successfully copying a wheel to replace one I had lost. As your needs and desires grow you can expand resin casting to include tens of thousands of dollars worth of equipment if you want, but to get started doing small pieces none of that is necessary.

My local Hobby Lobby carries Alumilite products and don't forget to use your 40% off coupons.

[Joeys Models]

Ann here is a cheap way to make mold boxes. I use Glade brand food containers. They come in different sizes and usually cheep. I use them because on the bottom it is marked with the volume of the container. The small round one is about 3 oz and the other is 24 oz. This is helpful in calculating volume for rubber. Also you can just fill it with water and pour it into a cup that you will use to mix your RTV in. I use Smooth-on 1:1 ratio. They have mix cup that have measurement markings on the side! I cut the bottoms of then off. Then invert them and use a hot melt glue gun to glue them down to either a piece of styrene or I use a piece of melamine coated shelving. You can get that at the home centers. Both containers and board are reusable after you pour your rubber. Container will come off the rubber will little problem as it will not stick to the rubber! Just peal off the hot melt and your good to go again. Nice thing about food container is you can get them in different sizes.

Joe

Edited January 11, 2014 by Joeys Models