CNC VS. 3D Printing: What to Choose?

CNCvs3DPrinting

These two manufacturing processes are becoming more and more controversial. With the recent trend in the manufacture of parts using stronger materials, increasing demand for 3D printing instead of CNC due to the advantages of reducing costs and time.

By bringing a piece to the Eiger software, you can see that you’ll get it the next day right away for a fraction of the day’s worth. Well, it doesn’t seem like a lot to think about choosing a 3D printer.

But is it really all good? From the article “CNC vs. 3D Printing: What’s the Best Way to Make Your Part?” written by Markforged, today we would like to summarize the advantages and disadvantages of the two production processes to be the basis for considering the technology for the production for everyone to decide.

Physical considerations

Appearance

  • Size

Both work processes limited by tool size. In the case of CNC, the tool diameter dictates the smallest negative production properties that can be created (cutting of meat workpiece). In the case of 3D printing, the nozzle diameter determines the smallest positive productivity that can be produced (adding the workpiece).

The nozzle diameter for 3D printers is between 0.25 mm and 0.8 mm, and the minimum size is four times between 1.0 mm and 3.2 mm.

  • Surface

With the right tools, CNC machines can produce a much smoother surface than a 3D printer. 3D printers are capable of producing parts that fit and finish in one. For parts that require extra smoothness for assembly with other precision components, CNC machining may be more suitable.

  • Deviation Standard

Some of the best composite 3D printers can hold dimensional tolerances up to +/- 0.005 and generally have compliant surfaces. For a snug, fit press, the durability properties of a 3D printed part can be further improved after printing. Anyway, it depends on other part properties. While it may be easier if we use all production machines, results may vary depending on the machine, material, and shape of the part.

  • Reinforcement

Non-structural parts are easy to use for general 3D printing. Also, structural parts that are subject to significant physical loads can be produced with both fiber reinforcement or by using CNC machines.

The continuous fiber reinforcement can improve strength more than other 3D printed parts, but composite parts are stronger in the X, Y-axis than in the Z-axis, and do not show isotropic properties of metal parts.

Operating environment

  • Temperature

3D printing and CNC are capable of producing both metal and polymer parts. So the choice depends on which process you want to mold the material.

The forming temperature of a specific metal often related to its melting temperature. Pure metals tend to soften strongly at about half the absolute temperature melting point (melting point in degrees F plus 459). The conventional alloys can push the range higher. In some cases, it is up to approximately 65% of the melting temperature.

3D-printed composites and polymers have lower temperature limits than metals. Typically, Markforged materials should not use temperatures higher than 150 ° C.

  • Moisture

Some polymers absorb moisture and may lose strength with prolonged exposure to moisture. Therefore, it may be necessary to have a coating with a coating such as Liquitex. Then, moisture will generally not affect the aluminum but can cause iron to rust.

  • Chemical

If your part subjected to any chemical substance, first check the material for chemical compatibility. Many metals are suitable for a wide range of chemical applications, but it is also important to check product compatibility before new materials or environments are introduced.

Nylon material made by Markforged is chemically resistant and is unaffected by most petrochemicals, but not suitable for use in acidic or alkaline environments.

Economic considerations

  • Internal production

If parts are needed immediately, without interruptions, and you have machines, operators, materials, and clamps, then you should use CNC to manufacture the part. But if there is a very urgent job or can wait for a part, 3D printing can get you parts immediately the next day. Also, free up operator time for other important tasks.

CNC machines tend to have the ability to remove materials faster than 3D printing. Their dimensions often do not affect time constraints. So CNC is more likely to remove material. But if the parts/stock quantity is very low (high level of material removal) 3D printing may be a better option.

With 3D printing, the size of the workpiece affects time. The larger the components, the longer it will take to manufacture. If the parts fit in the palm of your hand, then the part is usually obtained within a day. Therefore, if smaller parts required, 3D printing is often faster than machining. As with CNC, you have to spend a lot of time pouring stock materials, writing G-code, finding holders, setting up tools, and doing the job. So you can spend time right here with 3D printing instead.

  • External Production

Most external manufacturing processes require at least several days between part inspection, file generation, quotation submission, inspection, and purchasing, as well as delivery and lead times. The factory, which may cause excessive delays in the process. In this case, 3D printing may be a reasonable way to verify the compatibility of parts or parts that finished, ready to use, or have parts ready for the next day while permanent parts are being cut.

How much do you want?

When you divide the cost of parts from low-volume machines, most of the costs come from programming and set-up time, as the time required for conventional metal cutting is relatively short. Generally, expanding throughput can be achieved by setting up large sizes to automatically cut additional parts. But as parts complexity and number of features increase, the programming time and the number of settings required may also increased.

The price of a CNC per unit can be adjusted to accommodate hundreds or less of thousands of items per month because programming and settings can be reused.

With 3D printing, file programming (file separating) takes place in minutes. Also, the complexity of the workpiece has little effect on the file programming time. Although the unit cost and initial capacity are low, the unit cost is not greatly affected by the large volume and production expansion. This can be done by bringing more machines online.

How much budget do you have for equipment and operators?

CNC machines can be automated when setting up properly, but full-time training and programmers typically contribute to a more successful production. The machines are not easy for owners to service, and they require expensive maintenance planning.

3D printers can be easily run automatically. The operator only requires little training and programming is easy with software. They are generally easier to service and have much lower maintenance costs.

CNC machines and 3D printers come in a variety of prices based on their features and print quality. In general, it’s easier to own a 3D printer with a lower investment than a CNC machine.

Upfront and operating costs of additive manufacturing low volume make the 3D printer suitable for low-volume applications such as prototyping and tools. However, when scaled to higher volumes, subtractive manufacturing usually cheaper.

Summary

Changing machines is not as easy as changing a one-to-one process. Plus, 3D printing can’t solve all your productivity problems overnight. Cost-effective production for 3D printing is low volume production and subject to material and process limitations. On the other hand, CNC machining is often more economical when it comes to high throughput and most of the hundreds per month.

It doesn’t mean that we have to switch to either CNC machines or 3D printers. The two technologies can work together and sometimes rely on each other, because 3D printers will not replace CNC, but instead lowering operating costs for businesses and industries.

If anyone still has questions, needs advice on applications, materials, pros and cons, and various technologies. Contact us for service at Septillion Co., Ltd. Tel. 02-865-2688 or Email info@www.septillion.co.th