For every injection molding engineering project, numberless hours are spent on 3D modeling, prototyping, and perfecting the product design. Many times, the last step is to prepare your design concept for the injection molding process, so the question is how to start?


How much time does it take to go from the initial concept to the molded part? It is a lengthy and complex process that often intimidates most engineers. So, before hiring injection molding services to produce your prototype, you should prepare accordingly for manufacturability and functionality.

In the article below, we take you step-by-step through the injection molding process from beginning to end. We also offer you some strategies that will help you to save time and avoid potential mistakes accustomed to this complicated manufacturing method.

Mold Design

The initial step of the injection molding process is to finalize your design, which comprises the part and the mold design. The first phase of mold design includes laying out the part and determining how it will be oriented while it’s molding.

This layout offers information regarding mold size and the steel block needed to produce the tooling. You must know the size of the steel block so your vendor can order and ship the steel before the tool design is completed.

When the steel arrives, it’s prepared for machining. The following phase is going over details. You need to complete the core and cavity design (of the mold) and create a bill of materials (BOM) with all the components. After making a 3D CAD model, the 2D drawing is finished after two days.


Material Procurement

When the mold design is finished and the CNC programming advances, it’s time to begin with preparing other materials.

Inserts and EDM Electrodes

At this point, it’s wise to invest some extra money to ensure that the core and cavity inserts that are the correct sizes. It can save you time that otherwise would be spent to grind it down to obtain the right size.

Mold Base

The next material you need to prepare is the mold base. It surrounds the core and cavity parts of the mold. Plus, it absorbs the pressure from the injection procedure. The mold base is usually made of a softer steel than the cavity and core because it’s less expensive.

Off the Shelf Components and Plastic

The next phase is to source all the needed off-the-shelf components such as bolts, screws, and nuts. This is also a proper time for ordering the plastic material.

If the plastic you need is a specialty grade, know that it might have prolonged procurement lead times. So, it’s crucial to ascertain at the start what kind of plastic you want to use and consider ordering it before the product design is finished and the order of the tooling is released.

CNC Machining the Mold

After the material arrives, it’s time to begin with machining the mold. The cavity and core are machined from already prepared steel blocks. The procedure begins with rough CNC machining using bigger cutting tools to cut a rough outline.

Some manufacturers use less precise machinery to do the rough cutting before transferring the inserts to a high-accuracy machine. But, recently CNC machines have become more accurate and cheaper. So, the cost savings from utilizing different machines for the rough and finishing cuts are minimal.

Electrical Discharge Machining

After CNC machining the fine details into the mold components, the finishing touches are next. That demands electrical discharge machining (EDM) to achieve specific geometries that you can’t attain with a CNC grind.

For instance, wire EDM is utilized for cutting gear teeth with sharp inside surfaces and square holes. Afterward, the core, cavity, sliders, lifters, and inserts go through the sinker EDM process using the machined electrodes.

Final Steps

After the mold core, cavity, and other components have been machined, it is time for the finishing touches before the parts can be manufactured.

First, a fit check is conducted. Both halves of the mold, the cavity, and the core, are put together to ensure they line up perfectly. Simultaneously, some precision grinding is performed on the mold parts to verify that everything meets the close tolerances required.

The following step is to give the mold the appropriate finish. That usually means polishing it, or adding different textures if needed. Whether or not the final objective is a polished surface finish, some polishing is constantly needed to remove machining marks and produce a smooth surface.

Finally, it’s time to put the mold together, including the mold core and cavity, the lifters, inserts, and nuts and bolts that hold everything together.