What Is Precision Molding?

It’s all about how you build the tool to build the part.’ ~ Alan Lipman, CEO Romar

Precision molding is the process of molding either silicone or plastic in a particular way, with a very high degree of accuracy and tolerance, to ensure repeatability in long machine runs.

As specialists in precision molding, we are able to mould these materials to achieve the required result, using the most cost effective methods.

With over 50 years experience in building precision moulds, we have the technical, engineering and creative expertise required to meet every precise standard. Romar is acknowledged and applauded worldwide for producing injection molded components of the very highest quality and precision.

Our experience in molding has seen products ranging from precision miniature components with micron dimensions to large components weighing in excess of 16kg.

If you're ready to collaborate with a team that understands the precise requirements of precision moulding and micromoulding, let Romar provide you with an innovative, end-to-end design and manufacturing solution. Contact Romar today.

What is metal casting?

Metal casting is the process of making objects by pouring molten metal into an empty shaped space. The metal then cools and hardens into the form given to it by this shaped mold. Casting is often a less expensive way to manufacture a piece compared with machining the part out of a piece of solid metal. There are many metal casting methods to choose from. What type of casting is most efficient depends on the metals used, the size of the run, and the complexity of the casting.

Before starting a production run, it is helpful to know some of the terms and methods from the foundry floor.

Casting terminology

Casting mold

A mold is a cavity in a material that receives liquid metal and produces a cooled object in the shape of that cavity. Molds can be simple. The forms used to create ingots of metal are like loaf pans, with the metal simply poured inside and left to cool. Most molds are for more complex shapes and are based on a pattern. The pattern imprinted into a split mold. Half of the pattern is imprinted on one side of the mold and half on the other, and then the halves are clamped together before the mold is filled. By making the mold in two parts, the pattern can be withdrawn before filling. These molds can be made with a horizontal split

Cope and drag

In horizontal molding, the top half of the mold is called the cope, and the bottom half is called the drag.

Swing and ram

In vertical molding, the leading half of the mold is called the swing, and the back half is called the ram.

Molding cores

If a mold is supposed to have internal spaces or holes, a core is often made. These cores are shaped like the internal space. The cores are usually held in place by extending past the casting and being held in place through core prints, which suspends the core like a bridge between two banks. The empty spaces around the core will fill with metal, and the core will be removed from the final casting, leaving a hole where it once was. If the core is very long, it might be supported by chaplets to prop it up. These are usually made of the same metal as the final casting as they sit in the space that will flood with material and become part of the final casting.

Dimensional tolerance

One of the important factors in choosing a casting method is dimensional tolerance. Dimensional tolerance is the variation acceptable in the size of the final product. Metal shrinks when cooling, and the type of casting influences by how much. If a product needs to be precise, a client may want a casting method that produces near net casting. This means that the product is very close to being the right size when it is shaken out of the mold.

Surface finishing

Another consideration is surface finishing. How granular, bumpy, or rough can the surface of the casting be? What is acceptable for a cast iron pan is not acceptable for a wedding ring. Very smooth metal surfaces are usually created with machining, which is an extra cost: if shiny and smooth is a desired outcome, choosing a casting method with a finer finish may reduce machining costs.