"How much of mold making is arcane art?" Topic

I tried several times to come up with a title that fit, so, I had to settle for this.

Except for one brief stint at piracy where I found out it was a LOT of work, and did not give me good figures (and before I repented my evil ways), I know about as much about mold making as the next guy. which is not much, nd totally intuitive.

When I was designing tooling for die cutting fabric, I had some "rules of thumb" for how close parallel walls could come, how close curves and points could come, etc.
I sense there is the same bits of "arcane" knowledge involved in mold making.

Theoretically, all plastic models should fit together. Yet, we see praise for kits that DO fit together, and often read about the need for filler.
Mixed media, resin and metalm resin adn plastic, plastic and metal often have "issues" also.

Where does the "intuition" and "I've been doing this for a while, and we have to make the frammis plane a bit longer so the whosis will fit" come in?

Just idle cutiosity on my part.

Then, maybe, you can explain why riders so seldom fit well on the saddle.

I've always had good luck with plasticine and cardboard (for the dams). Dupont RTV (red stuff), an old dental tool for imbedding the "master" figure in the plasticine and a sharpened brass tube for making vents to remove air pockets.
You have to look at how the metal will "flow" into the cavity the master represents.
Arcane art, or patience and practice; the latter I think.

There are " tricks of the trade" one picks up from older mold makers and experience . When I visit resin shows I look at how pieces were cast it gives me more insight . there are classes you can take from resin and rubber companies , but I never met any one who did .
There is a science to it , about the flow of resins and metal .and an art , hiding joints, and seams .
Dave
One of the moldmakers Alternative images productions

John asks: "Then, maybe, you can explain why riders so seldom fit well on the saddle."

It has to do with the metal shrinking in the third dimention……depth of the casting in relation to how it is put into the mold. Take the horse master- laid on it's side. The ribcage (from left to right) would represent depth I am talking about. Metal shrinks back upon itself when it cools. The extra flows back in the way it was introduced into the mold. This can be corrected by applying centrifical force that forces the metal to remain against the cavity walls , longer. This "force" allows the outer shell to cool and solidify- the still viscous interior is slower to seep back into the gate.

Of course, when casting for production, most companies just set and forget spin time based upon the size of the figures in the production run. Of course, horses are "thicker" than foot (or rider) figures and get run for the same length of time regardless of mold contents.

To prove the theory to myself, I ran the old Smog the Dragon (IIRC the name) from old Heritage which contains some pretty hefty and think body pieces. I first ran them for the same time and pressure as the rest of the mold (wings, head, jaw, tongue, etc. Body halves fit like crap!

I then ran the body half mold for 3, then 4 then 5 times longer. By 4 times longer, the fit had improved considerably. By the 5 times longer, it fit perfectly!

Towards the time I left GFI, I was having 15mm and 25mm horses run (x3 time longer for 15mm; x 5 times longer for 25mm) and fit was awesome. This meant that we had to plan runs of nothing but horses, but "I" feel the quality to the customer was well worth the extra time!

John, I hope that answered your toungue in cheek question! />)

Best
Tom Dye

Oh, yes Tom.
I like to think that there is as much voodoo involved in mold making and casting as there is in steel rule die cutting tool design.

As for horses, I bet it helps if you don't mold the saddle on both the rider and the horse.

Well, from a plastic injection standpoint there are several things that could get overlooked. First, consider how much shrink is involved. For polystyrene you might have 0.004 to 0.006 inches of shrink per linear inch. So you need to design the part at 1.004 inches to have it end up 1.000 inches. Also you need to worry about uniform thickness. Having a mixture of thin areas and think areas could cause the piece to warp as well. If a part is designed too thick you could have sink marks left in the part. You can find tricks around some of these, it just takes digging to find something that might work.

So after you are done with the parts, you need to think about how the parts a arranged in the mold and how balance the cavities of the mold will be filled. I have a couple of book about mold design, so you can pick up some of the knowledge if you don't mind shelling out the cash.

Don't misunderstand me.
I am NOT looking for "practical advice" so I can go into the business. Oh, no.
I just want to know if there are "things you have to know" to get it right.

I had a pen plotter that I used to make shape check gages for my die cut parts. Unfortunately, it was off by a small percentaage in the "Y" or travel dimension. It was spot on in the "X" direction.
So, (in CAD) I had to block the plot along with 100mm calibration lines, and insert it at 1.001.
I love this kind of "seat of your pants" stuff.

Well, John, Many times I felt like the weather or how I got up in the morning had something to do with the success of casting for that day! I once had a caster that talked to the molds as he was casting……damn if it didn't seem to work!

Yes, dumb as these things may sound to the average Joe, sometimes there is no other explanation for why one day is "better" than another…..

Tom

Even some professionals don't get it right.

I've got a number of production aircraft, in 1/300th scale, with badly skewed wings.

They never should have been sold, they are so bad.

Appears to me they put them in the mold, incorrectly, or didn't think about the effects of spinning on the thin mold, resulting in them being diagonal to their fuselages, instead of square.

A shame.

In all honesty, should a self proclaimed figure recaster be getting help on his mould making?

Repentant.
And not about to try it again. Too much work and too messy.

Rapier. I have always believed that an informed customer is a better one. It also keeps honest manufacturers on their toes to keep the quality up within available resources. I do not condone recasters! Most don't have the means to own the equipment required to do it right. Besides, it follows the same concept that guns don't kill people, the people who use them that way do. Gamers can posess some basics of casting and moldmaking, but most, like John, walked away more appreciative of what it takes to produce a good, quality piece and would prefer to buy it.

Regardless, anyone can obtain the knowledge of HOW miniatures are made; doing it oneself is yet an entirely different matter! Its always good to hear of yet another one removed from the market and shut down, slapped with fines and with a ruined reputation in the industry.

I have worked with half a dozen mold makers in the white-metal casting end. No two have the same technique. I have learned valuable things from all of them, but I do not make molds the way they do. Frankly, I do not make molds with a single style. I am -very- careful with master molds containing original sculpture. I want the greens to survive. Any mold maker I have worked with will tell you how protective I am of my greens. On a production mold, the priorities are different. You are looking at ease of extraction and mold wear issues, and a cast metal production master that will stand up to a considerable amount of abuse short of throwing it on the floor and stomping on it.

As for resin… I am usually amazed by what can be done. I have resin kits of the Hunley and the Turtle that I could not hope to duplicate. I do silicon/resin molds/ castings for game prototypes for my current employer on a semi regular basis, using what I was taught by the late master modeler Jack Wendt, but production casting is vastly different from doing a handful for prototyping.

Richard Kerr
Gray Cat Castings/Gray Cat Studios
Evil inventor of 3D card board Ogres

Dye4minis, trouble is we only have his word that he is redeemed.

It's a bit like a failed burglar asking you for details of your locks because he couldn't open them last time.

RAPIER, Maybe for you that seems to be the situation. I have good friends in PA. that game with John and despite his TMP facia, I have been told many times he is a real gentleman. How smart is it to question the integrety of customers? I mean, what would the next step be?…..have them sign an agreement not to cast their own before the sale is made? ( Which is impractical, insulting and would probably backfire as enforcing it is hard in he first place with existing laws.) (Suggestion was just Tongue in Cheek)

In the USA (and I presume in the UK as well) a man is presumed to be innocent until proven guilty.

I don't think you have to worry about John pirating figures….but would be very disappointed if my faith was misplaced.

Best
Tom Dye

The single best book on the subject I have ever seen, indeed the only really good bock on the subject, is Principles of Centrifugal Rubber Mold Casting by Gonicberg. Long out of print, but copies can be obtained by either inter-library loan or spending 150 bucks.

If it isn't in there it truly is arcane lore.

Depends if you are making a production mold or just a simple two parter for drop casting. Making production molds for use with casting machines IS an arcane art requiring specialist equipment. Molds for plastic figures are even more so – leave it to the experts

Just doing my personal master mould for the 6mm Ottoman Levant infantry I have sculpted up over the past few weeks. I use a cold cure method as I am not needing mass production (Peter at Baccus can do that, although many of the poses I have sculpted I think will simply get squished in the hot mould press).

As you will appreciate there are different moulding techniques. I think we all develop our own tricks and neuances how to get them to work and it does seem at times like a black art practiced on some general principles, which may or may not work depending on which way the wind is blowing.

Hope to be casting later this week and am quite anxious already about a few of the poses in particular.

Back in the 70s, I was just getting into minitures after about 10 years as a boardgamer.
Somehow I met a guy who did a LOT of recasting. He made it sound like the most natural thing in the world, regularly pirating (not the word he used) Scruby figures and selling them to museums as dioramas. Or, so he said.
Then, I bought an RTV kit and tried it myself. It was VERY messy, and I never made a good gravity mold that gave good castings.
So, I threw it all away.

Only later did I "thik about what I had done". It came with develoing my own sense of ethics.
I can see, a little bit, the "But they are SO EXPENSIVE!! Waaaah!" side of the argument. This was back when metal; figures wee skyrocketting past the $.30 USD mark for a 25mm figure. It was also annoying to keep placing the same order for the same figures! Hey, why not cast my own?
But, it is hard to get it right, other peopel do it better, and they deserve the fruit of their creativity.
And, as that great moral philosopher Mick Jagger sang, "You can't always get what you want."

…. the arcane art.

Well the Ottoman Levant infantry are generally not working too bad. 10 casts in and getting about a 90% cast rate of the 18 masters (with mainly 2 models causing 'issues'). A few extra air holes here and there, widening of the pour hole, and going for a quick pour seem to be working best…

… or it may be the music I was listening too, and the current Lunar pull in the context of the solar flare 17 days ago.

Part of the reason I am trying to develop my own sculpting skills is to fill in that gap of "You can't always get what you want."… now its more "You can't always sculpt what you want."