CNC Machining

3 tips for reducing costs on CNC prototyping

By June 3, 2021
CNC Prototyping Hero

For a precise and versatile manufacturing method, many designers and engineers turn to CNC machining. This subtractive manufacturing process uses computer-controlled rotating cutting tools, such as drills and end mills, to carve away at a solid block of material. CNC machining can create excellent components using various materials including plastic, fiberglass, and metal.

Thanks to its rapidity and versatility, CNC machining is often used to manufacture prototype parts. CNC machining is an excellent method for creating functional prototypes of metal parts. However, there are certain design decisions that can add preventable costs to your parts.

Costs of CNC prototyping — and their solutions

Here are some of the main cost drivers of prototyping with CNC machining and how to reduce them.

Material selection for CNC prototypes

CNC rapid prototyping requires a large block of metal, commonly known as a blank, from which the component will be carved using CNC machining tools. Choosing and obtaining the right CNC material for your blank is an expected cost and naturally, some materials are more expensive than others. Material price can vary based on region, accessibility, and other factors.

As a general rule, metals are more expensive than plastics. The machinability of the metal also affects the cost of the prototype — less machinable materials take more time, tools, and money to process, which in turn increases costs. Also, consider your component’s properties and its future applications, like how hot it will get or if it needs to be rust-proof. Be as accurate as possible and don’t overshoot. For example, if plastic can supply the strength you need, use that material instead of steel to cut down on costs.

Some metals are easier and faster to CNC machine and are therefore less expensive to manufacture. Most CNC machining rapid prototyping is done with aluminum alloys, like Aluminum 6061, although other CNC machinable steels like 303 SS can further save costs. Even if your final component design doesn’t require a machinable material, it can be beneficial to prototype with these inexpensive materials. Material choice also plays into machining time — machinable materials, such as acetal, will be machined faster due to higher tool speeds.

cnc machining pieces and metal bits
CNC machining has the power to produce incredibly fine tolerances with a very high level of accuracy.

Setup and machining of CNC prototypes

Before you can begin CNC rapid prototyping, the CNC machine itself must be prepared. This includes programming toolpaths, collecting and assembling the equipment, and gathering the necessary materials. CNC machining also requires proper time to produce effective components — you must cut the material, exchange tools, load the component in and out using these tools, and more.

There are two time-consuming machining tasks that are easily avoidable: programming toolpaths and material removal. Simpler parts will be easier to program, thereby decreasing the time it takes to create and execute a programmed tool path. Reducing the amount of material that needs to be removed also reduces the time a part takes to machine. Designing parts to minimize unnecessary material removal can create a blocky appearance but results in a part that is more cost-efficient and faster to machine.

Laser engravings, silkscreening, part identification, finishes, and other cosmetic additions are cost-effective for high-volume production runs but pricey for CNC rapid prototyping. If you’re CNC prototyping a part for function only, or another short-term or single-use purpose, hold off on these cosmetic and aesthetic decisions until after prototyping is complete. Opt for an “as-machined” finish, which means there is no final CNC finish, for the most cost-efficient option when CNC prototyping.

Design complexity of CNC prototypes

If your prototype’s design is straightforward, it will be easier to build and cheaper to manufacture. However, many prototypes require complex shapes that must undergo testing before being manufactured in high-volume production runs. CNC prototyping unique, interesting geometries will increase manufacturing complexity and costs.

Similar to complexity, tolerances drive up the price of CNC manufacturing. CNC machining is designed to support incredible precision and can produce components with extremely tight tolerances that don’t allow for much wiggle room. But the tighter and more precise your part tolerances, the more you’ll have to pay during prototyping.

CNC machining has the power to produce incredibly fine tolerances with a very high level of accuracy. While super-tight tolerances help create consistent and functional components, fine tolerancing standards are often not necessary for CNC prototypes. Adhering to fine tolerances will increase CNC machining costs during rapid prototyping. Use medium, coarse, or very coarse tolerances to reduce CNC machining rapid prototyping costs.

CNC rapid prototyping with Fast Radius

Even though CNC prototyping is important, you shouldn’t have to break the bank to perform this essential manufacturing step. Prototype with inexpensive, easily machinable materials to save manufacturing time and costs, and wait to add on cosmetic features like finishes or ID engravings until you’re ready for high-volume production runs. Also, use standard tolerances as opposed to specialized ones. Want to save even more? Connect with a seasoned manufacturing partner.

Fast Radius is dedicated to helping you create cost-effective CNC prototypes without compromising quality. We hold ourselves to the highest manufacturing standards and will help you do the same when it comes to your parts. At Fast Radius, our team of experts can guide you through every step of the prototyping process, making sure you’re satisfied with your prototype and final product. Don’t wait — contact us today.

For more CNC prototyping best practices and ways to save on CNC machining, visit the Fast Radius resource center.

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