The Advantages and Disadvantages of CNC Machining for Prototype Design

The Advantages and Disadvantages of CNC Machining for Prototype Design

CNC machining had its time as the marvel of the manufacturing world. It may not be so new and shiny anymore compared to methods like 3D printing, but it still offers plenty of benefits.

There are numerous reasons that businesses utilize CNC machining in various industries around the world. Today, we’ll be taking a look at how and why CNC machining is used for prototyping. There are many other methods of production available with all of the technology that’s in use today, and CNC machining continues to be a top choice.

You’ll learn why so many rely on freelance CNC programing services and when it’s a good fit for a project. Before you know it, you’ll know if CNC machining is right for your situation or not.

What is CNC Machining and How Does It Work?


CNC machining is a process where parts are made by using strings of code to manipulate a machine tool with a very high level of precision. Today’s CNC machine tools range from simple tabletop units for home and hobby use all the way up to enormous specialized multi-axis machining centers that may be larger than rooms in your home.

At this point, CNC machining has been a standard tool in many industries for decades. The earliest CNC machine tools were developed well over half a century ago. These first specimens looked quite different from modern CNC machine tools, but the concept was the same.

Essentially, CNC machining allowed more consistent levels of accuracy during high volume production. When CNC machine tools were becoming more common, most companies and job shops were relying on large numbers of highly skilled machinists to operate manual machine tools. While these machinists were very good at their jobs, there was always the potential for human error. CNC machining significantly reduced this room for error.

Today, many industries rely on CNC machining in some capacity. Metal and wood are commonly shaped using CNC machine tools. Some rely on CNC directly as their method of choice for production. Others utilize high precision parts for their processes, such as machined molds and parts for progressive dies.

Benefits of CNC Machining for Prototype Design


As mentioned earlier, when CNC machine tools began to become widespread, they were replacing manual machine tools. The same people were operating them, but now someone had to create CNC programs. The introduction of CNC machining created a new role in the job shop, but it also allowed machinists to operate more than one machine at a time. Previously, this was unthinkable, when only manual machine tools were in use. CNC machine tools allowed for a tremendous increase in productivity.

In addition to the significant boost in overall productivity and work potential per employee, CNC machine tools allow a higher level of precision to be maintained during high volume production. This results in a higher yield for companies and fewer hours wasted by scrap parts. It’s still very possible to make scrap parts when using CNC machine tools, but it is far less likely in many scenarios. The machine is going to do exactly what it’s told to do, so long as the program is accurate, then all is well.

Today’s CNC technology and machine tools are so advanced that it’s possible to have little to no human intervention in some cases. Just set up the material and come back when the program is finished. This depends on a number of factors, such as the machine tool that’s being used as well as the geometry and features of the part.

Common Applications of CNC Machining Today


In some cases, CNC machining is the production method of choice because it is the most convenient. To clarify, many businesses already have their own CNC equipment or existing relationships with job shops that utilize CNC technology. They would rather continue to have parts made with this method simply because it’s what they’re used to.

Most of the time, CNC machining is chosen because it offers a higher level of precision than many other methods. It’s nothing special to hold tolerances of plus or minus .001” with CNC machines. Some shops and workers can hold tolerances even smaller than this, but many machined parts require tolerances in the plus or minus .005” to .010” range.

Materials are another driving factor for many when choosing CNC machining. For example, if you need 10,000 of the same part and it’s made of plastic, there are several ways you could go about having them made, such as hiring an injection molding designer. On the other hand, if you need 10,000 parts and they require a high level of precision and must be made of steel, then machining is really the only viable option.

CNC machining is typically only thought of as appropriate for short production runs. This isn’t necessarily true. In some situations, CNC machining is an appealing option for high volume jobs as well. In high volume scenarios, specialized fixtures or other tools may be made specifically for the job to optimize production speed.

Factors to Consider with CNC Machining for Prototype Design

Just like other types of manufacturing, there are numerous factors to consider when deciding if it is the best method for your project. Whether these matter or not is determined by the specifics of your situation. Let’s take a closer look.

Braun electric screwdriver design and prototype by StephanStrydom


Production volume can be one of the most significant factors when deciding if CNC machining is right for your project. In low and medium volume scenarios, CNC machining shines. This is one of the things that make it an excellent option for prototyping design services and drafting services. You won’t have to deal with large minimum order quantities for parts. Setup costs tend to be low as well, as long as your part doesn’t require a highly specialized method.


There are few materials that can’t be machined with the equipment that’s in use today. That being said, if you’re making a metal part that needs a higher level of precision, then CNC machining is likely the most appropriate choice.

This wide range of potential material choices is useful when prototyping for other reasons as well. Let’s say you’re building an early prototype, and you only want to examine a few specific qualities of this iteration. You may be able to save some money by choosing a different material for this prototype before going back to the material that will be used for the final product.


CNC machining has long been the method of choice for making high precision parts. When you’re in the prototyping process, you don’t want to leave things to chance. You wouldn’t want to examine why a part of your product failed only to find that it was given too much tolerance on the blueprint. With this method of manufacturing, you can specify tolerances that are close enough to be precise without making the tolerances so small that costs go through the roof.


Geometry can be a significant factor in the cost of making a part with CNC machining. While the part may not be incredibly complex, it could have a design that necessitates several setups on multiple machines. This will increase the amount of time it takes to make the part and the total cost of the part as a result.

Some shapes that may appear complex can be made rather easily with certain CNC machine tools. This aspect of your part should definitely be noted, even if it cannot be changed. This is one of the main areas that Design for Manufacturing will examine if you choose to utilize it.

Changes and Revisions

This is another area where CNC machining has an advantage over many other methods. Let’s say that you have a part made for your new product. When you put it in the prototype, you realize that somehow the need for a small hole was overlooked. In a situation like this, you can probably just have the hole put in instead of tossing the part in the scrap pile.

The same goes for more formal design changes. Since parts are often made one at a time, changes can be made from part to part if necessary. This kind of flexibility is fantastic during prototyping. Perhaps you have three different ideas for a part of your product. You know all three of them could work, but they’re very similar and one may be significantly better. You can have one of each made so that they can all be tested.

If a design needs to be updated because of a new prototype iteration or a new weakness has been identified during production, it’s easy to go straight to making the latest version. You won’t have thousands of obsolete parts sitting around either.

Production Speed


CNC machining has been overshadowed by 3D printing services when it comes to making single parts as quickly as possible. However, the production speed that CNC machining offers may be plenty for your project.

If you happen to be working with a job shop that has the material you need on hand and ready to go, you may get lucky and have your parts in a matter of hours or days. There are even some job shops that specialize in fast delivery times for prototype parts.

Making Designs CNC-Machining Friendly and DFM Basics

If you’re going to utilize CNC machining for prototype development, then there are some things to consider during the design stage. By implementing changes during the design stage, you’ll be able to reduce production costs and lead time later.

One of the best things you can do is get a DFM analysis. DFM stands for Design for Manufacturing. This school of thought examines areas of a part or a product’s design that can often be changed to reduce costs without compromising on quality. Things like the shape of corners, the way pieces fit together, symmetry, and the way fasteners are used are common areas that will be examined in a typical DFM analysis.

Formal DFM analysis services can be a little challenging to find. If you can’t find a specialized firm, then the good news is that there are plenty of mechanical engineering services and designers that are familiar with this concept. By working with one of them during the design stage, you can reap many of the same benefits, perhaps without paying for it as a separate service.


CNC – This is an abbreviation for Computer Numerical Control. CNC information, typically G code, is used to tell automated machine tools what to cut. The amount of information in the CNC program will depend on what machine the program is for and what software was used to generate the program. Some simple CNC machine tools may only offer automation of two axes, but more advanced CNC machine tools may have the capability to operate the movement of three axes or more.

G Code – G code is a programming language that is the standard for CNC machines. All machine tools have their own library of G codes and a program for that machine must give it the correct G codes. Some are practically universal, such as G01 for a straight cut, while others can vary between manufacturers or even from machine to machine.

M Code – M codes can also be found in CNC programs. G codes are used to tell the machine the direction and length of a given movement, whereas M codes are used to control other aspects of the machine’s function, such as changing tools, turning coolant flow on or off, and other variables that are independent of the actual cutting path.

Stock – When talking about machining, stock is your material. Since machining is a subtractive process, it begins with a piece of material that is larger than the finished piece. Stock is removed from the piece with any number of setups or operations until it is complete.

Iteration – In the context of prototyping, an iteration is a new version of the design. Designs for new products often go through several iterations making improvements with each round before reaching a final version that’s ready for full-scale production.

DFM – DFM is an abbreviation for Design for Manufacturing. This is a process that is used to optimize the mass production of parts or products. A DFM analysis will take many factors into consideration. Each element will be evaluated to see if a simpler or more efficient option may be available to reduce costs and complications.

Machine tool – The term machine tool refers to a machine with a specialized function for working with material, such as a mill or lathe. Other types of CNC machine tools exist as well, such as wire EDM, conventional EDM, surface grinders, and CNC machining centers. A variety of other tools are CNC operated also, like lasers and waterjet machines.



Rates for CNC machining vary widely based on a number of factors. Some materials are quoted with higher rates because they decrease the life of cutting tools or require other unique factors. The specific type of CNC machining that’s involved plays a significant role here as well. If the part is something that can be completed with a single setup on a CNC lathe, then it is going to be quoted at a much lower rate than something that requires multiple setups on three different machines.

Machine shop rates can vary by location as well. In addition to varying by all of the factors mentioned so far, the size of the job shop or company affects the rate as well. This factor can be harder to pin down because it’s not necessarily the same trend across the board. The best thing to do is to get quotes from several shops. This will give you a more accurate idea of how much things should cost. From there, you can make a decision to either prioritize price or quality.

From a customer perspective, the ideal scenario is to get the best work for the best price. However, this scenario isn’t found often, so decide whether price or quality is more important. To give you a general idea, rates may be as low as $30 per hour in some shops, but they can be over $100 per hour. There’s a lot of range here, so investigate your options and go from there.

Is CNC Machining Right for Your Prototype?

If you’re considering CNC machining to develop your prototype, then it’s very possible that you’re on the right track. In fact, you can take the next step right here at Cad Crowd.

When you utilize our pool of vetted CNC machining professionals, you can be sure that the process will be as smooth as possible. Our standard procedure for projects protects both your privacy and your rights. A non-disclosure agreement is used to cover the privacy end of things, and you will keep all of the intellectual property rights of your project.

If that sounds better than trying to sort through job shops and independent CNC machinists yourself, then it’s easy to get the process going. Start today by getting a quote.

Research Advice

There are quite a number of highly detailed resources available if you want to learn more about CNC machining. There are specialized websites for those who just want to learn more, as well as some that are for hobbyists and those who make a living as machinists. While they can be initially overwhelming if you’re just starting to research the subject, these sites can offer a vast wealth of knowledge.

Many books and classes on the subject are available as well. Books and articles are excellent resources for becoming familiar with CNC machining as a whole. Just a little working knowledge on the subject can go a long way towards keeping communication efficient if you’re outsourcing this kind of work.

It’s also a good idea to do some additional research on materials. If you’re already set on using a specific material for your part or product, then this is simple. If you haven’t decided on the material yet, then you may just find an option that’s even better than what you had in mind.

When it comes to prototyping, this is a rather broad subject as well. Some of the most beneficial topics for you to research maybe things like iterative design, DFM, and various manufacturing methods. This knowledge will help to make the process smoother for you. Find out how it works today.