Tag Archives: molded part

Making a Molded Part

mold making

I recently noticed some jelly-like blob soaking in the shop sink. What? It prompted a discussion with, Tom, one of our model makers, about making a mold for models. I grabbed the camera, took some pictures, and wrote the process down in a notebook. Here’s what I came up with:

model making

Choosing the object you want to make a mold of, you determine where you want the “mold line” to go. This is the seam that will need to be disguised after the molding takes place. Using clay, you make the mold line on the object, then place it into a well sealed custom box and pour rubber up to the mold line and let set. After that half dries you peel off the dried rubber and reposition the object in the box in order to pour rubber on the other half. You peel the hardened rubber off the other half and now you have two rubber pieces that fit together with the cavity in between them representing the object you want to mold.

The rubber mold is sprayed with mold release and again placed in a special box to keep it rigid, the  two halves forming a whole. An opening, called a gate hole, is created where the resin will be poured in. Air holes are made in the rubber mold as well, where hoses or straws will be poked through to allow air bubbles to escape during the hardening process.

model making

Resin is mixed with hardener and then poured through the gate hole via a tube. The box is then placed in a pressure chamber to compact and press the resin into all of the nooks and crannies of the cavity. When the resin has hardened, the box is opened, the rubber mold peeled off and the molded part is then rinsed off in the sink.  After that the mold lines are smoothed over and the molded part is ready to be primed and  painted.

pressure pot for mold making

model making

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.