At OmkBoxes, our design and engineering team does a wide variety of prototyping with an equally wide selection of materials. One of our specialties is plastic prototyping with design for manufacturing in mind. Depending on the specifics of a project and what the client is trying to accomplish, creating a prototype might best be accomplished with CNC machining, 3D printing...or combining the two to create a hybrid model. Let’s discuss the basics of prototype production, as well as the merits and disadvantages of each.

Benefits and disadvantages of CNC machining prototypes

CNC (Computer Numerical Control) machines are electro-mechanical devices that manipulate machine shop tools using computer programming inputs. By using CAD software such as Solidworks, it is possible to transform a stock piece of material (like a block of plastic) into a finished product by means of a controlled material removal process. CNC machining is a little bit like sculpting: beginning with a block of material and removing it as necessary (also known as “subtractive manufacturing”).

One of the biggest benefits of using CNC machines to create a prototype is that it is possible to create a “Looks Like - Works Like” model. As the name implies, this type of prototype is a showpiece that is intended to wow the client while showcasing what a final production part would look like and work like. Most of our clients require fully functioning prototypes to ensure that design and functional objectives are met. Many of the projects we are approached with are enclosures

If a client comes to us and requests that we prototype this enclosure, our design and engineering team can CNC this model from a stock piece of polypropylene plastic. However, doing this can be expensive in labor, time, and cost...which is one of the disadvantages of CNC machining for prototypes. This is especially relevant when it comes to the low quantities of parts that are usually desired.

What about 3D printing for prototypes?
3D printing is an “additive manufacturing” process (unlike CNC machining, which was earlier described as subtractive manufacturing). Basically, parts are created through the sequential addition of small pieces of material to create a larger finished product. The process involves the interpretation of a Computer Aided Design software file (such as a Solidworks 3D file) and is capable of producing complex, novel, and scalable parts in a matter of hours. At Creative Mechanisms, we use state-of-the-art Fused Deposition Modeling (FDM) machines to 3D print prototypes when appropriate.

One of the advantages of 3D printing is the fact that parts can rapidly be created with relatively little human labor once you are past the design phase; this decreases costs significantly when it comes to time and labor. FDM prototyping is often used to determine whether or not the engineering concept has any flaws that require redesign. Multiple prototypes can be generated based on iterative design improvements in a relatively quick time span and at a relatively low cost of production using 3D printers. Unfortunately, one of the drawbacks to 3D printing is that there are limited materials that can be utilized to create parts. For instance, there is no proper way to effectively 3D print polypropylene.

3D Printed ABS + CNC Machined Polypropylene = Hybrid Model for Prototypes Case Study