Tag Archives: molding and casting

3D Printed Mold for Casting

KiwiMill has an Objet 3D printer to make scale model parts efficiently, accurately and with greater detail.

When the printer is not in use for model parts, it’s available to customers for rapid prototyping services. Not only can the printer create parts with very quick turn around and accuracy, but it can be used to create a tool for molding and casting multiple pieces.

Here is a 3D printed mold created by our designer, Mike, that will be used to cast multiple parts. It incorporates gating and venting in the design.

Creating a mold using a 3D printer saves time. Traditional molds require a Master to first be created, and then the mold is made from this initial part. 3D printing the mold means there is no need for a Master. The mold is created with a 3D drawing, then “grown” in the 3D printer. It comes out ready to cast its first part. In this sense, 3D printing the mold eliminates entirely the molding step as it is traditionally known.

Once you have your 3D printed mold, different materials can be cast in it – from very rigid, to soft and flexible.

Yet another technology tool for Model Makers to make use of, and for our customers to take advantage of.

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Model Maker’s How-To: Molding and Casting Model Hands

model hand

Model Maker Joe recently shared the process by which he created a total of 300 model hands for a client in the medical field:

We had a customer contact us with the need of a class room training aid to use in a practical exercise, measuring gout build-up on a hand. I was initially tasked the job to produce 100 realistic hands with gout build-up at designated locations, using particular dimensions for the bumps.

First we set out choosing a hand model. Then I brushed on a platinum-cure silicone rubber (hardness: 10A, tear strength 102 ply, 1000% elongation at break to guarantee a stretchy, nearly untearable glove) over the model’s hand in thin (this rubber is very thick and traps bubbles) layers.

After achieving a desirable thickness, I shelled the mold with plaster cloth while still on the model’s hand. I made this exo-shell in two halves (palm and back) so that I could pull the mold out.

creating hand mold

After the plaster cloth was dry it was time to separate the two halves of the shell and release the model’s hand from the silicone glove.

molde maker hand mold

The next thing for me to do was pour a master by putting the glove original in its shell and banding the two halves together. After putting the unit in a standing base (resting on its finger tips, wrist up), I poured a polyurethane casting plastic (hardness: 70D, tear strength 3000 ply, 7.5% elongation at break) with some black tint and put it under pressure.

casting model hand

When the plastic was cured, I peeled the mold back to reveal the master. It revealed many small nodules around the finger tips and palm (most likely do to sweat) that I cleaned off. After the master was cleaned up a bit, another member of the team built up specific (height, width, length) gout swells out of Bondo, per the customer’s request, at particular locations on the hand.

casting model hand

After the art work was done I repeated the same steps above to make three working molds, but this time the polyurethane plastic was tinted with a flesh color.

We shipped the client an initial quantity of 20, and upon their review, found the hands too hard and life-like for their studies. We needed to re-tool and come up with a new game plan – a softer plastic or a fast curing rubber.

molde hands

I came up with the idea of a two part silicone mold. A hand cast out of a softer material might not hold up to being pulled out of a glove mold and the cast piece would have to be fully cured (no short cuts).

mold for model hands

Meanwhile another team member was preparing a new master cast by brushing some blackened polyurethane plastic over one of the previous working casts, to even out the skin texture. After that cured, he fine-tuned the gout buildup back to customer specifications and tolerances.

When he was done, I built three two-part molds (fingertips down, wrist up) and begin production casting of my next 80 pieces. This time I used a polyurethane casting plastic (hardness: 80A/30D, tear strength 2264 ply, 233% elongation at break) with the same flesh tint.

pressurized pot for casting

This plastic had a 90 minute demold time, but with the two-part design I was able to turn the mold (pull the product and pour the next piece)  in 60 minutes. These pieces came out of the mold with no flash and very little seam line.

casting hands

The customer was very impressed and the molded hands did what they needed to do. The client ordered 200 more castings.

molded and cast model hands

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Model Maker’s How-to: Casting Cars

KiwiMill model makers recently designed a car model to be used for a sales display. The models will be used to showcase automotive paints for Hyundai. We chose to cast these from a carved resin master made from our original computer drawings.

A generic car body was created in Rhino 3D by one of our designers.

A  CNC milled resin master was created from this drawing.

CNC router model car

A negative mold  of the core was made from the master.

mold for casting car model

 

 This core was inserted in the mold to create a hollow space in the cars when cast.

mold for casting car model

 Three molds were made to cast the cars.

mold for casting model cars

pressure pot for casting model cars

 

 

 

 

 

 

 

 

                                The molds were put in a pressure pot for a smooth cast.

pressure pot for casting model cars

 

130 castings were created.

casr model cars

The bottoms of the casts were sanded smooth.

grinding car model

 The resulting cars will be painted various colors by our client, but here is one we painted.

 cast model car

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