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Design sketch for unbreakable joints in doll fingers

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Re: Design sketch for unbreakable joints in doll fingers

Post by life-is-plastic »

impressive work Koen ... incredible what you're able to achieve on such a smll scale 8O

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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

pygmalion2 wrote:I have a similar design for Katie's hands.
Unfortunately they have not eliminate the finger poke through's.
Yours is a much more elegant design than mine. You need to address the problem of bonding the metal
to the silicone skin.

Image
Did you make those joints yourself? They look really good! I absolutely do not think that my design is more elegant. It is mere that I had to come up with another solution than yours because in scale 1:6 joints like yours would become too difficult to make, too weak and would not maintain to hold position when used frequently.

As for the bonding I may have an elegant solution for you. Unfortunately I cannot post it because is of commercial value. But when you are not a professional and only need it for your own doll and when you are still in the process of making the hands, then PM me and I will tell you more.

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

grafx wrote:This is a great design!. I am making my own 58cm silicone doll as a hobby. I was wondering if you had any advice on how I should pour the silicone into my mold? Do I only pour from the top? But how will the silicone go down to the fingers and toes? Or do I push it in with pressure from the feet and hands. I want to make a single pour body. I seen your website and the dolls you have all lined up after they we poured. The look very nice, you dolls are smaller then my 58cm doll I am trying to make so it should be easier for me I think since I am working with a bigger mold. Thank you for any tips you can give
Hi grafx,
From your question I suspect that you have little or no experience in working with resin or silicon. If so, I strongly recommend that you first make some tests before you start making the body mould. Make a small size test mould (!) that contains a similar kind of complexity (like narrow passages, dead ends, air entrapment parts, obstacles and such. For instance: a bend arm with hand) and experiment on it. Pouring silicon or resin for complex parts like small silicon dolls with skeletons inside is really very difficult.

There are many ways to pour liquid silicon in a mould. All have they pro's and cons. But in general I can say that for small dolls pouring from the top is only recommendable when the pouring entrance and the more narrow passages will not obstruct the air vent unless the liquid silicon that you use is really thin fluid.

I have listed for you some of the parts that influence the pouring:
- what the viscosity of the silicon that you are using after mixing?
- do you have a vacuum chamber, a vacuum pot or no vaccuum at all?
- do you have a hard mould or a soft mould?
- do you have a transparant mould or not?
- is it a single or multi-layer cast?
- what is the pot-life of the silicon ( the time that the silicon is still pourable)?
- can you access the areas that you expect to contain airbubbles to remove them?
- Do you have a facility for rotation moulding?
- Are there obstruction parts in the mould (like a skeleton)

My advise is:
- make tests
- make a pouring plan and think about every possible obstacle (and how to overcome it)
- make a back up plan in case problems like leakage or airbubble entrapment occur

Sorry that I do not have a straight answer for you. But when you have a plan on paper (with sketches) I will be happy to check it for potential pitfalls.

Good luck! :)

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

Hello Koen
Could you please weigh in on this idea.
Doll will be midsize of 130 - 140cm. Plat silicone.
Silicone will be degassed.

See attached pic:
2 wire finger armature.
Each joint will have coils of small wire wrapped around the armature wires. Each coil will be connected to the other by the single wrapping wire. I see no need to cut it each time.
Each wire wrapping will have epoxy resin pushed into it to make it solid.
There will be a molding support rod stuck in the end of the armature. I will have to coat it w/ release and remove it before the epoxy cures.

The hand armature will be placed in the mold and the support rod will be pushed from the outside of the mold into the finger armature. When silicone has cured, the rod will be withdrawn. I think the idea of having to push a finger wire end cap in or out of the end of the finger harmfull. This way only a small hole will need to be filled.

Do you think it's a good idea or feasable to pour shore 30 silicone through a funnel and tube to fill the fingers and hands? The main part of body would be shore 20.

Thanks
RK
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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

rubherkitty wrote:Thanks!
You must be a microsurgeon or watch maker in your non doll life. All too tiny for me. Maybe a full size hand I would attempt!
Hi RK,

I will let you into a secret. I am really not that handy. For the making of that small stuff I have an assistent whose fingers are a lot smaller than mine. But obviously this has to stay between you and me. Reputations you know. A lifetime to build, seconds to destroy :wink:

Image

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Image

I am chewing on your last post. I have some ideas for you that might be helpfull, but first I want to make some tests for this in my workshop before I will answer to you.
For your last question I need to know if you intent to make a multi-cast ( pouring the hands and body in the main mould in one cycle) or do you have seperate mould for the hands?
I also would like to know if you use a soft, a hard or a skin mould (thin layer soft mould in a hard shell).

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

That's a wonderfull helper you have!
Does she fix lunch too?

This is all study at this point.
I'm not certain what mold style I will use. Fiberglass is looking best.

Basic plan.
With mold halves open, pour soft silicone for breast, butt and stomach. Install skeleton in back half of mold while this 1st pour is curing. Let silicone cure until tacky.
Assembly mold halves and stand upright. Hope silicone stays in place!
Pour harder shore silicone into the hands via funnel and hose. Immediately pour medium shore silicone into main body and arms. I am assuming this final pour will not displace the silicone already poured into the hands.

I tried to experiment a little w/ this finger armature idea, but could not find the proper weight of wire in my buildings.
I just moved my entire work shop and still trying to get organized.

Thanks
RK
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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

Hi RK,
As you know I have PM you some ideas about the hand armature. As for your idea about the support. This is good. In fact this is almost a necessity. The chance that the armature will not stay in place when not supported is very big.

The idea to pour the silicon with a funnel through a hose is basically a good idea, but it very much depends on the viscosity (thickness) of the silicon and the diameter of the hose. Because most types of silicon are really thick and sticky, the pouring through a hose may cost too much time and because a lot of silicon will stick to the hose it will be almost impossible to predict how much silicon will reach the hands. My guess is that you will need a hose with a diameter of a vacuum cleaner. But a hose with this diameter will be too big to pass the elbow joints.
I think that for the hands it is better to create special (closeable) entries in the mould near the hands and use a large type of syringe to fill them.

Still I think that your idea to use a funnel and a hose is useful. Because I can reasonably presume that you do not have either a large vaccuum chamber to degas the mould after pouring the silicon or a rotation device to rotate the mould during the hardening of the silicon, entrapped air will cumulate in the highest parts of the mould (neck and shoulders). To remove this air you can create a flow with a funnel and hose in the chest which will drive the airbubbles on the shoulders to the top of the neck.

As for your idea to fill the breasts and butt first, I fail to see the relevance unless you want to make them softer than the rest of the body. When you intent to make them softer it is recommendable to make tests first because there is definitely a risk that the breasts will slip from the mould under their own weight. For the strength, look and feel I think you will probably need to cast this in 3 layers. ( nipple-skin-breast).

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

Thanks, I appreciate all your help!

Regarding a funnel pour.
I had thought about pouring the hands via a small access hole at the inside of each wrist. The sprue would be trimmed off. Then I thought it would be easier to just use a funnel and 3cm hose, but I totally forgot I'll have a skeleton in the way!

I will be building a vacuum chamber out of a new 250 PSI steel tank I have. It will hold a 5 gallon bucket or a taller bucket of same diameter. From my studies, it seems you only need to degass the silicone in a bucket prior to pour.

Regarding multi pour.
Yes, I want the breast, butt and stomach to be softer silicone than the main body. The hands and feet will be harder than the body. As the breast will be on the small side, I will not pour them with a gel core.
The professional makers pour some of the body parts with the mold open then close it up. Hopefully the silicone is sticky enough to stay in place. Suction may help too.
I have attached a googled pic of the outer breast skin and gel core that has been poured and is under cure before the mold is assembled for final pour.
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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

rubherkitty wrote:Thanks, I appreciate all your help!

I will be building a vacuum chamber out of a new 250 PSI steel tank I have. It will hold a 5 gallon bucket or a taller bucket of same diameter. From my studies, it seems you only need to degass the silicone in a bucket prior to pour.
The expansion of silicon when put under vacuum after mixing is appr 500%. The foamy silicon is very thick and tough . If you make more silicon than there is room in your bucket it will be very hard to degas it because the breakage of the bubbles will take a very long time. There is however a trick. But for this you need a moveable vacuum pot. When you toss the silicon around in the bucket while under vacuum (you need to be able to shake the entire vacuum pot for this and the bucket needs to be clamped in the vacuum pot) then the airbubbles will instantly break. This way it is possible to degas up to 2 gallons of silicon in a 3 gallon bucket :idea:

But as for the pouring, while pouring air will be enclosed. This is unavoidable. The pressure in the lower parts will make the airbubbles go up relatively quick, but in the higher parts it will take several minutes at least.
As mentioned: air will cumulate in the shoulders you will need to make a plan to solve this :roll:

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

Thanks

I did not realize it expanded 5x. I've seen videos where it looks like 2x, but I think they must be breaking the vacuum and degassing in multiple stages. My cylindral tank stood on end will hold a 22 US gallon container w/ room around it.

I can weld a hunk of steel on the side of the tank and vibrate the tank by hammering the hunk of steel w/ my air chisel. Or attach a electric motor w/a offset crank chucked in. Many way to make vibration.

The mold can be mounted on a stand so it can be swiveled during the pouring operation. Mildly vibrated too.
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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

Vibration will not break the bubbles :!: . You really need to stretch them. By twisting the bucket vigorously and constantly a quarter turn (approximately) and back the airbubbles will break because the foam is relatively heavy and reacts in slowmotion to the twisting which results in the stretching of the bubbles over the limit of the cohesion of the silicon.

As for the mould, like mentioned above vibrating does not have any noticeable effect. The silicon fluid is simply too thick and will absorb the vibrations. Swiveling is good and bad. The swiveling in (extreme) slowmotion will have some effect provided that the mould is not completely filled. It will help airbubbles to move fatser, but it may also set free airbubbles that were entrapped in corners of the skeleton.
When fully filled up there will not be any flow in the mould. ( except fot the airbubbles that sloooooowly make their up to the shoulders).
As mentioned in my previos post the best it is to generate a local flow in the silicon near the shoulders by pumping around silicon with a funnel and hose. Or wait with filling the shoulders untill you are certain that all air from the legs, body and arms has reached the surface and then fill the final part with a funnel and (pre-filled, airbubble free) hose which you stick at least 10 cm in the silicon.

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

Thanks
I understand now that vibration will not agitate the silicone enough to break the bubbles. Sounds like the chamber will need to be mounted on a swivel base. Can do!

I was thinking in regards to pouring the hands, making a threaded bung in the epoxy resin/ fiberglass mold for a threaded plastic plug. Maybe make the same thing in the top of the shoulders to either add silicone or let air escape? Will detract from the appearance though unless trimming will help.
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Re: Design sketch for unbreakable joints in doll fingers

Post by Koen »

rubherkitty wrote:Thanks
I was thinking in regards to pouring the hands, making a threaded bung in the epoxy resin/ fiberglass mold for a threaded plastic plug. Maybe make the same thing in the top of the shoulders to either add silicone or let air escape? Will detract from the appearance though unless trimming will help.
In order to be sure that the top of the bung equals the inner surface of the mould properly you can better make a non-cylindric wigshaped opening in the mould, wax it and fill the hole with resin to create a perfect fitting plug.
As for the opening in the shoulder; unless an airbubble happens to be straight under the opening no air will escape there. If you want remove the air in the shoulders by making ventilation shafts you have to make so many that you will end up with shoulders that look like a lawn because there is no way to predict exactly where the air hit and will 'stick' to the shoulders.
When you make injector holes on the far ends of the shoulders then you could effectively drive out the air to the neck. But as describes earlier there are other ways to achive the same effect with less effort and markings to the skin.

Koen

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Re: Design sketch for unbreakable joints in doll fingers

Post by rubherkitty »

Thank you.
Very good ideas.
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Re: Design sketch for unbreakable joints in doll fingers

Post by kiralove »

Awesome concept so are hands a big problem on these dolls?
Kiralove

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