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How to Combine 3D Printing with CNC Machining
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How to Combine 3D Printing with CNC Machining

3D printing has changed the way companies think about prototyping. With the powerful function of add-on manufacturing, it is simpler than ever to transform digital 3D design into physical objects. The starting cost is low, the learning curve is short, and the results are often consistent and satisfactory. But not everything can be printed in 3D. Some shapes and materials are still more suitable for other manufacturing processes, such as CNC processing or injection moulding, while many commercial 3D printers simply cannot produce parts with the tolerances required for practical applications.

What are the advantages of 3D printing and CNC processing?

performance

CNC

3D printing

materials

It is mainly used for processing metals, and also for processing cork and hardwood, hot plastic bags, acrylic acid, styling foam and wax. Each material requires different cutting tools.

Metals, ceramics, waxes, sand and composites

speed

CNC machine tools can remove materials faster than 3D printers in processing parts. However, a lot of process planning and settings are needed, especially when multiple processing steps are needed, parts usually need to be repositioned.

One-time forming can be achieved, which means that it does not depend on other manufacturing stages except post-processing. Batch manufacturing (such as SLS and SLM) can be achieved for many processes.

complexity

Bottom cutting, tools, internal features and gaps are all constraints that must be considered when complex designs can be implemented with a 3D printer. The order and orientation of parts must be taken into account in the processing process.

Complex designs can use 3D printers to achieve secondary constraints. Forming direction, feature size and model size are usually the main limiting factors.

accuracy

Accuracy is determined by the geometry of the cutter, because all the cutters are rotating and have radius of the processing angle.

Small feature sizes are usually the diameter of a material conveying mechanism (e.g., a nozzle for DM or a nozzle for material injection).

The learning curve is short, and the results are often consistent and satisfactory.

But not everything can be printed in 3D. Some shapes and materials are still more suitable for other manufacturing processes, such as CNC processing or injection moulding, while many commercial 3D printers simply cannot produce parts with the tolerances required for practical applications.

What are the advantages of 3D printing and CNC processing?

For some projects, the answer lies not in the manufacturing of additional materials or traditional processing, but in the middle. Combining these two processes is easier than what you think, and it can provide great advantages


Produce shape features smaller than tool size, such as thin walls smaller than tool diameter. Compared with the surface quality of 3D printing, CNC processing surface is better.

Or machine spot diameter control (such as sintered laser or UV light source). The thickness of FDM printing layer is 100-200 microns, and the resolution of material jet printer can be as low as 16 microns.

geometry

CNC machine relies on the point-to-point processing technology of predetermined tool paths to remove materials. Therefore, the surface that CNC machine tools can reach is limited, and there is no need to adjust parts. It can be used to process very large and very small parts.

The suspended surface of the model needs to be supported, which increases the printing cost and time.

Process

Operators or engineers are required to consider tool selection, spindle speed, proximity, angle and cutting path. These factors have greatly affected the quality of components and construction time.

Once the model is uploaded and the direction, thickness and support position are selected. Most AM machines can print complete parts without any manual intervention.

So, when do you process your 3D printing parts with CNC? What should you do?

When should 3D printing parts be processed?

Although 3D printing and CNC processing are generally considered to be diametrically opposed processes, they can actually be combined to produce good results. Firstly, the part is printed in 3D and then processed by CNC to reduce or modify some areas.

1. Urgent time

When substitutes (usually injection moulding or similar) take too much time, companies should consider CNC processing of their 3D printing parts. Although the sequential process of 3D printing and CNC processing involves many steps, the combination method is usually faster than creating and utilizing die tools.

The combination of 3D printing and CNC processing also allows for mobile adjustments to the product or prototype, since it is easier to modify digital files than to modify injection tools.

2. Accuracy is the key

The accuracy of 3D printers is increasing year by year, but many industries require critical end-use components to have tolerances that are currently unattainable on 3D printers.

By combining 3D printing with CNC processing, the required accuracy can be achieved, while still taking advantage of the advantages of 3D printing, including low cost and complex internal geometry. High-end 3D printers can usually achieve a tolerance of +0.005 inches, while CNC machines can compress them to ±0.002.

Things to Consider in Processing 3D Printed Parts

Combining the process of 3D printing and CNC processing requires two kinds of practical expertise, and some measures can be taken to ensure the smooth manufacture.

1. Notes

In order to get the best results in CNC processing of 3D printing parts, it is very important to specify exactly what needs to be done. This should include specifying which areas require strict tolerances and allowing the mechanic to work properly. When these tolerances are specified, the machinist may recommend some design adjustments to the 3D printing parts to make the work easier.

2. Consider

These recommendations may include instructions for the use of excess materials. Since CNC processing will effectively reduce the quality of components by cutting off certain parts, additional materials may need to be printed to make these adjustments. If the number of layers is insufficient, the processing may not produce the correct size.

3. Location

The areas of the 3D printing parts to be processed should be properly positioned so that the tools can reach.

Hummingbird finds that 3D printing is an important complement to traditional processing methods. Its main function is not to replace but to supplement. Therefore, the combination of 3D printing and CNC is a very good form.


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