Posted December 1, 2020

The Advantages and Disadvantages of CNC Machining for Quick-Turn Prototyping

A CNC milling machine working with metal

When a manufacturer requests a quick-turn prototype, they want a delivery that matches design for manufacturing (DfM) specifications within one or two days. The availability of quick-turn prototypes allows for the evaluation of one or several designs while cutting lead times and reducing costs. A quick turn prototype has full-functionality, form, and finish, so customers can experiment with a design, refine the functionality, check the finish, and evaluate different materials. 

Production quantities can consist of one to thousands of units, so it’s critical to choose a production method that’ll deliver the quantity and quality you’re seeking. Computer numeric control (CNC) machining combines the accuracy, precision, repeatability, and scalability required to produce high-quality, quick-turn prototypes. It will meet your requirements for tight tolerances, achieve a wide assortment of finishes, and use certified materials not available with other prototyping technologies. Of course, disadvantages do exist. Here’s a closer look at the CNC machining advantages and disadvantages to consider for your quick-turn prototyping needs.

CNC Machining Advantages and Disadvantages for Quick-Turn Prototype Delivery

Whether your prototype requires milling, tapping, grinding, or drilling, CNC machining offers several benefits for prototyped components.

Advantages

Precision and Tolerance

When it comes to manufacturing your part, you want the final dimensions to match, as closely as possible, the dimensions specified in your CAD file.  Precision occurs in manufacturing through the conformity and repeatability of machine processes. CNC machining provides high precision by consistently reproducing the correct measurements for all values of a machined part.

Precision also defines tolerance—or the allowable deviation of a measurement system from a known or standard value. Tolerance occurs as a plus or minus (+/-) factor that specifies the amount of deviation from a known value. Specifying tolerances allows flexibility in manufacturing methods that can ultimately save time and money in part production. During operation, sensors in a CNC machine provide feedback data for each axis to ensure the machined measurements stay close to the specified value. In some instances, applications may not need total accuracy but always require high precision.

CNC machining offers tighter tolerances than other methods of prototype production. Stereolithographic and industrial FDM 3D printing produce respective tolerances of +/-0.3mm and +/-0.5mm. Depending on the type of metal and the design of the part, CNC milling and turning can produce tolerances between +/-0.025mm and +/-0.125 millimeters. 

Repeatability

CNC machines offer the advantage of repeating precise and accurate tool movements throughout a production run because a programmed code controls all functions. Repeatability occurs when the machine moves to a targeted point multiple times with minimal difference in distance.

As with any machining technology, repeatability measurements also depend on other factors, such as tool wear, the age of the CNC machine, the workpiece materials, and the machine setup. This information can be monitored using advanced software with minimal machinist intervention.

Materials

In contrast to the limited range of materials used for 3D printing, CNC machining provides the advantage of working with various materials, including various alloys of aluminum and stainless steel, plastics, copper, brass, bronze, and more. CNC machining also offers the use of certifiable materials that match different needs, such as hardness, tensile strength, endurance strength, and wear resistance. 

The Brinell or Rockwell hardness number of a material signifies its capability to withstand pinpoint surface loads. While tensile strength represents the resistance of a material to breaking under tension, endurance strength shows the capacity to absorb stress. Wear resistance indicates the capability of a material to withstand friction or to self-lubricate.

Depending on the application, quick-turn prototypes may necessitate lightweight materials that keep the weight of a prototype within the design criteria or heavy materials that can resist high-stress loads. Others call for materials that won't melt, warp, expand, or deteriorate when exposed to operating temperatures. 

Finishes

In some instances, you’ll stipulate a particular surface finish for a prototype. Or, you may particularize the parameters that impact surface texture, such as average roughness or the vertical distance from the peak to the valley of an irregularity. 

CNC machining exceeds other manufacturing methods in that engineers can select from a range of custom finishes that match design requirements. For example, a rotating shaft may require a fine surface texture while load-bearing surfaces can work with a rough, or “as-milled”, surface, which can reduce cost and turnaround time.

Scalability

CNC machining is more efficient at scale than other prototyping methods, such as additive manufacturing. It can repeatedly and precisely machine uniform parts allowing for a seamless increase in production volumes.

In some cases, producing higher volumes of prototype parts quickly is restricted to machining. If you require 10,000 parts made from stainless steel, for example, CNC machining stands as the best if not the only option.

CNC machining can reproduce quick-turn prototypes with greater precision and tolerance—and with custom finishes—in nearly any type of material. Ultimately, it allows you to bring a potentially higher-value product to market faster.

Disadvantages

CNC machining offers many advantages for quick-turn prototyping, but it’s valuable to consider the disadvantages as well.

Cost

CNC machining may have higher costs than other technologies—such as 3D printing—for single-part or very low-volume production runs. Although, CNC machining is cost-effective for higher quantities. There’s more waste simply due to the subtractive method, whereas 3D printing only uses the material that’s needed. 

Skill

CNC machining requires engineers who understand the software operation. A machine shop’s drills, lathes, cutters, mills, and other types of equipment are controlled by software and need machinists who understand how both software and equipment work. Increasingly, machinists enter the job market with this knowledge.

Creating High-Value, High-Quality Prototypes

Overall, the benefits of CNC machining for quick-turn prototypes outweigh the drawbacks when you need a high-quality part quickly, or more than a few components. While 3D printing and CNC machining both rely on digitized designs, CNC machining can reproduce quick-turn prototypes with greater precision and tolerance—and with custom finishes—in nearly any type of material. Ultimately, it allows you to bring a potentially higher-value product to market faster.

To learn more about the advantages and disadvantages of CNC machining for quick-turn prototyping, contact the experts at Plethora. We’re an ISO 9001-certified CNC machine shop that specializes in precision component manufacturing that meets your design and time requirements. Get started today by uploading your design files to Quote My Part, or give us a call at 415-726-2256.
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the-plethora-team

The Plethora Team

The Plethora team is your go-to CNC manufacturer for hardware done right the first time. We have the tools and experience needed to create high quality custom parts quickly and with precision, whether you need a prototype or production run.

Topics: CNC machining, Prototyping

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