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The ambitious claims of 3D printing technology to revolutionize the way we do almost anything has the potential, but the technology is not quite there yet, at least not in the near future. This is because we imagine a world made out of 3D printers. You’ll often read about how 3D printing is used to build homes, aircraft components, or even guns. But the uses are limited and aren’t always clearly defined.

You may see some of the highly inspiring, artistic yet functional objects promoted by metal 3D printing advocates, but you won’t find anyone talking about the efforts, cost, and build time that would have gone into developing that object. There are investments happening, however, to enhance the reliability of industrial 3D printing in terms of operation and print quality. Even so, the technology is still not at a stage to replace the traditional machining processes. In fact, machining still has a long runway, and 3D printing can be seen as a good complement to it.

There are multiple reasons to actually not consider rapid prototyping as a replacement to machining:

1.Part Strength

It is possible to develop the most complex-shaped object through 3D printing, but when it comes to strength, a part machined from a metal block is likely to possess more strength. This is because the layer-by-layer printing technique cannot maintain a strong bond between layers in the z-direction, resulting in strength inconsistencies across all directions. Numerous advancements have tried to overcome this challenge, but there is still a lack of substantial data on life expectancy of products developed through metal 3D printing. Developing market-ready products would then lead to risks of premature failure.

2.Speed

There is a phrase often associated with 3D printing– develop parts quickly. But this is not true, especially when there is a need to develop products in masses. Metal printing technologies use vector technology to create part volume. This means the laser or deposition head needs to touch every point in the part in which a material required. This puts a limit on the material being added in an hour, even if the printing machine is fast. The build time as such will be even longer for larger parts, and the same amount of time will be required each time the new part is developed, keeping the technology inefficient for mass manufacturing.

3.Surface Finish

A major chunk of research in the 3D printing space is focused on improving the surface finish quality, but the results are still not satisfactory. 3D printed parts often require secondary finishing process performed through machining to remove the rough surface layers, smooth out the holes, chamfers, and surface features. The problem with the secondary refinement process is it increases the chances of parts losing details and tolerances.

4.Cost

There are numerous opinions all over the internet about how 3D printing can save material when compared to traditional machining and injection molding techniques that require additional tools. But there is relatively little information on the high percentage of failures during the part build process and the amount of material that is scrapped. Besides, the cost of raw materials is much higher when compared to the cost of buying a billet. Building a part then with 3D printing can cost the same as that of machining and at times even more if there is no proper understanding of the design requirements for additive manufacturing.

5.Modeling Requirements

Most people believe that 3D printing requires a 3D CAD model of the object and with just a push of the print button, the printer will convert that model to a physical object. This is not true. 3D CAD models for rapid prototyping are different, and there are multiple factors the need to be considered when modeling a part to be printed.

For instance, the model is required to be watertight, with no gaps or space between the surfaces to avoid build failures.
Special care is required when defining the tolerance values between the mating parts so they can fit properly once developed. Apart from this, resizing holes, maintaining the resolution of the STL file, and the balance between part strength and density are other important factors that will eventually define the print quality.

This blog is not to disappoint all the 3D printing enthusiasts but to cut through the hype clouding the importance of traditional machining in today’s manufacturing environments. There is no doubt that 3D printing is going to bring tremendous advancements in ways we manufacture products, but it is an evolutionary process consisting of smaller advances. 3D printing technology is not in a state today to replace machining, but is a complement to it, and this is how most manufacturers today perceive it.

A hybrid manufacturing approach, in which a product maybe partly developed with 3D printing and partly through machining is what sounds more meaningful and promising. Taking the best of both the worlds not only provide distinctive advantage to manufacturers, but will also help in integrating new processes and technologies to prepare for the future.

About Author

Kashyap Vyas is an engineer at TrueCADD and holds a master’s degree in thermal engineering with several research papers to his credit. He covers CAD and CAE topics for the engineering industry. His contributions are primarily focused on encouraging manufacturers and suppliers to adopt virtual product development tools to build efficient products with reduced time-to-market.

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