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Molding in HO, what materials can I use?

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Molding in HO, what materials can I use?
Posted by NWP SWP on Sunday, July 08, 2018 9:15 PM

I'm wanting to reproduce a number of the car that just built, so what materials could I use, I have heard of resin casting but I have heard some negative things too, if I wanted to stick with polystyrene could I order a bunch of pellets heat them up and pour the liquid into a mold to make the cars?

Steven

Crooner, Imagineer, High School Graduate, living with Aspergers, President of the Republica Pacifica micronation,  President of the NWP-SWP System.

Hook'em Longhorns! 

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Posted by nealknows on Sunday, July 08, 2018 9:37 PM

Not quite. The pellets companies use have molds that are put under extreme pressure to form the item. Most molds are some form of metal to withstand heat and force. Back in the 90's I went to a factory that did both injection and blow molding for coolers. 

Your best bet would be to check online at shapeways to see if they have the car you're looking for or maybe upload a file. A 3D printer would probably take days to make one car. 

Good luck!

Neal

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Posted by NWP SWP on Sunday, July 08, 2018 9:44 PM

That's the problem I found with 3d printing the low turn around time, I did some research into at home injection molding machines for hobbyists, the problem is the machines don't have a big enough capacity for the cars, I heard some molds could be made from clay or something like that inside a metal case.

Another thing I could do is look into limited quantity injection molding.

Steven

Crooner, Imagineer, High School Graduate, living with Aspergers, President of the Republica Pacifica micronation,  President of the NWP-SWP System.

Hook'em Longhorns! 

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Posted by tstage on Sunday, July 08, 2018 10:31 PM

Steven,

"Limited quantity" usually equates to large upfront costs.  It's going to cost you chunk-of-change to have the mold(s) designed and machined.  Then you have to pay someone's shop time for injection molding the parts.  If the mold isn't machined properly you'll end up with a bunch of parts that need the flashing removed.  That's NOT a fun way to spend your time.

I would stick with kitbashing for a while until you get a better understanding of what you're attempting to get yourself into, or the revenue it will take to fund this sort of project.

Tom

http://www.newyorkcentralmodeling.com

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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Posted by Little Timmy on Sunday, July 08, 2018 10:47 PM

Let's face it, the only "cost effective" way.... Is the way you just did it.

Keep kit bashing them untill you have as many as you want.

No manufacturer is going to cut mold's just for a short run of 20 or so car's  (making injection mold's cost's thousand's and thousand's of dollar's.)

Casting them yourself in resin mean's you have to make the mold first ( and it has to be perfect or the car's you produce will N O T look right or fit together at all.) Plus, the cost of enough resin to compleate 20 or so car's could run into Hundred's of dollar's quickly.

The 3-D printing could be "Doable", but then you have to wait day's for each car, add shipping to the cost of someone making your car for you and were back to costing Hundred's of dollar's.

I Highly reccommend kit bashing them yourself. As you do , you will get better at it. And you can find quicker, more cost effective way's to do it as you go. Maybe even "Improve" your original car into a few different varient's.

Rust...... It's a good thing !

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Posted by NWP SWP on Sunday, July 08, 2018 10:53 PM

Perhaps I just keep working with the MDC cars or use the Athearn ones or work on scratch building the cars.

I have a few tweaks to make before I go all in.

A few things, where can I find detail parts for these cars?

Also I really don't want to have to cut a pair of drop bottom gondolas every time I make a car (thats not counting the pair of thrall gons) where could I find underframes?

I could try cutting the fishbelly floor runners out of styrene strip.

I also need to work on a jig for cutting the cars more precisely.

Steven

Crooner, Imagineer, High School Graduate, living with Aspergers, President of the Republica Pacifica micronation,  President of the NWP-SWP System.

Hook'em Longhorns! 

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Posted by RR_Mel on Sunday, July 08, 2018 11:27 PM

I do resin casting all the time and the only problems are managing the air bubbles.  There are a lot of resin casting videos on YouTube.
 
The materials are readily available at Hobby Lobby in kits.  In the last two week I purchased a half dozen Shapeways 1:87 scale figures and made molds of each figure.  I cast a few of each one then cut them up to change their looks and when I happy with one I make another mold of the modified figure.  I can turn out a dozen perfect figures in 30 minutes. (30 minutes doesn't include paining)
 
I bought some casting resin off eBay and the listing said 2½ minute work time, they exaggerated, it’s closer to 90 seconds.  That works for figures but too fast for anything larger.
 
I’ve worked with resin casting for over 20 years and once you get the hang of it its very easy.  It does get a bit messy, kinda like working with Plaster of Paris.  Cleanup is messy, I use Acetone and it’s nasty but works the best.  I keep a roll of paper hand towels handy and it doesn’t last very long.
 
If you do try resin casting go with 50/50 mix, the 10:1 mix is hard to get the right ratio.  Too much hardener and the casting is weak and brittle, not enough hardener and it never dries.
 
Here are some of my castings:  
 
 
 
 
I glue them to the head of a pin for painting. I stick the pin in a wooden pencil eraser to paint them, easy to rotate them for painting.
 
Rearranging arms and legs give them a different look, even the head facing a different direction makes a big difference.
 
 
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 

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