Carbon: Is 3D Printing Ready for Mass Production?

It is no secret that the additive manufacturing revolution is one of the driving trends of Industry 4.0. Consequently, there’s a shift into a new mindset with a broader range of possibilities on how we do engineering. Traditional manufacturing capabilities tend to have rigid boundaries that can significantly limit our options to satisfy requirements efficiently in terms of costs, times and simplicity, from the initial planning of a project all the way to production. In contrast, 3D printing offers more design freedom, waste reduction and bridging solutions between design and manufacturing, streamlining processes like never seen before. However, additive manufacturing is not perfect. Three characteristic factors challenge all 3D printing technologies when it comes to shifting from prototyping to end-use production, these are:

• Slow and impractical for large volume production
• Mechanical weaknesses due to anisotropic structures
• Limited material possibilities to work with

Now, this is where Carbon’s revolutionary technology, CLIP, comes into play. Carbon DLS (Digital Light Synthesis) printers are praised thanks to their unique ability to print an incredibly wide range of functional polymeric parts 25 to 100 times faster than traditional AM processes. These rates enable molecularly continuous compositions. In other words, isotropic layer-less parts.

So, is additive manufacturing ready to take that decisive step from prototyping to mass production? This is the question we want to answer in this article.

Background

What if a resin printer could print a part continuously without slicing, without steps? Sometimes, the most incredible ideas, rather than being born from complex academic deliberation, simply come from pop culture fiction. In this case, that memorable scene in Terminator 2, where the antagonistic T-1000 rose from a puddle of liquid, was the inspiration for CLIP (Continuous Liquid Interface Production).

The idea came from the brilliant mind of Dr Joseph DeSimone, Carbon co-founder and current board chairman, also currently a professor of chemical engineering at Stanford University. After the 2015 Science Magazine publication about what would become Carbon’s foundation, the Continuous Liquid Interface Production technology, DeSimone amazed the world by printing a whole part incredibly fast while delivering his ten minute TED talk. Click here to get access to the original paper and here to watch the TED talk.

From there on, Carbon became a leading AM company with a successful history in offering solutions for the automotive, aerospace, construction, engineering, manufacturing, and medical industries while working closely with recognised brands like Ford and Adidas.

Understanding CLIP

First of all, the CLIP technology is a resin photopolymerisation process. But you might ask, what makes it unique? The best way to understand this is by evaluating the limitations of other resin processes like,for example, stereolithography. SLA printing processes consist of repetitive cycles, layer by layer, with four discrete steps:

1. First, the cured resin sticks to the bottom of the tank
2. Then the platform rises to separate the part, enabling the uncured resin to refill the gap. A big issue here is that this separation leads to peeling and vibration forces that can significantly affect the quality of the part and progressively wear the bottom surface. The higher the velocity at which the platform pulls up, the higher will be these effects in intensity.
3. To properly recoat the surface, additional components like blades are needed to push the resin back into the printing area
4. Lastly, a repositioning step that significantly adds to production time as the platform descends to start a new curing cycle

For these very reasons, DeSimone points out that 3D printing is in fact 2D printing but stacked slice by slice. Now, in contrast, CLIP is a continuous process where the platform constantly rises without sticking to the bottom. As a result, CLIP can print at a rate of 300 mm to 1000mm per hour, which in comparison is 25 to 100 times faster than layer by layer processes. The simple fact that the cured material never touches the bottom is the key to how Carbon printers swiftly produce a consistent monolithic part, similar to injection moulding results. How is it achievable? The key lies in oxygen.

Printed test probes proved consistent performances regardless of printing orientation.

The Dead Zone

Unlike the typical mechanical engineering culture of additive manufacturing, Carbon’s core innovation comes from the criteria of molecular scientists instead. Therefore, it makes sense that carbon, the building block of organic matter, the chemical element of boundless possibilities, is the simple yet elegant name chosen to represent this brand.

CLIP harnesses the way in which light and oxygen work in polar opposite ways. Basically, while UV light enables the photopolymerisation process, oxygen impedes it. The great innovation here is that if we can incorporate and control an oxygen input into the resin tank, we can tune how the print cures to an optimal point.

And, how do they do it? Just like with contact lenses, the window at the bottom of the tank is made out of a transparent material, which is oxygen permeable. That interface of uncured resin that impedes the forming object to stick to the bottom and allows the resin to flow freely beneath is what they call the “dead zone”. By tightly controlling parameters like photon flux and resin opticals, the “dead zone” can be maintained at a constant thickness of tens of micrometres, or to have an idea of scale, about a third of the width of a human hair.

In comparison to today’s polymerisation standards, this technology seems to be flawless. However, this technology currently faces some limitations that open room for Carbon3D to exploit the potential of the CLIP technology further. First, every resin has distinctive curing times, which limits the overall printing speed. Secondly, the rheological or flow properties of the resin restrict the speed at which the dead zone recoating happens. So, one of the main R&D challenges Carbon3D faces lies in improving their resin formulas. We’re eager to see what we might get from Carbon3D in the near future.

Carbon3D DLS Printers

Now that we know CLIP is a continuous instead of a discrete layer by layer process, how do light projection works in this case? Just like many printers in the market, Carbon3D printers use a DLP projector to reflect the cross-sectional shapes of the object. But the most exciting aspect to it is that rather than a series of images, the projection is more like a movie. It is fascinating to perceive printing speeds in terms of frames per second instead of slices per minute. So, instead of adapting the image of each slice to a specific layer height setting, in this case, it is only a matter of playing a video.

Carbon printers combine CLIP’s oxygen-permeable optics with a fine-tuning of programmable resins and DLP projection in a process they named Digital Light Synthesis (DLS). With this company’s proprietary one-part and two-part resins, DLS printers can offer a vast range of material solutions for end-use applications. Available choices range from elastomeric and rigid polyurethanes to silicones and epoxies, thermally stable cyanate esters, and certified medical-grade resins.

Last but not least, we want to point out that high-end printers like these are not affordable at all. Acquiring industrial machines implies risky factors like upfront costs, depreciation and obsolescence. Considering this, Carbon has a unique approach to future-proofing by promoting a lease by subscription model as an alternative to purchasing the machine. For more information, click here.

The L1 vs the M2 Model

Currently, the printers Carbon offers are just two models, the L1 and the M2. Despite being few, they fulfil particular production purposes. To better understand where the differences lie, let’s briefly compare these models in the table below.

We can spot two critical parameters that distinguish these printers; it all comes down to XY resolution vs L1 build volume. As Carbon’s workhorse, the M2’s superior XY resolution makes it an ideal choice to produce smaller parts with intricate geometries and fine details. In contrast, the L1, with its larger format, is geared more towards moving further into high-volume production.

And with that in mind, we return to our question: Is additive manufacturing ready to take that decisive step from prototyping to mass production? Are these machines up to the task?

3D Printing as a Legit Alternative Injection Moulding

After many decades of existence, injection moulding remains the most reliable process for consistently producing high-quality polymeric parts in high volumes. Nonetheless, injection moulding is also very problematic. Besides restricting design freedom to a high degree, tooling implementation involves significant upfront costs, extensive lead times and many risks. Among the main costs associated with tooling implementation, we have tooling amortisation, prototyping, design, setup fees and inventory waste. In this fast-paced system, recurrent schedule delays in meeting time to market expectations can lead to significant market share losses against competitors. For further information on Carbon’s take on these issues, read this article.

The idea is to have as efficient, flexible and leaner production as possible, and some of the potential 3D printing to offer solutions lies in:

• Lower upfront costs
• No tooling design requirements
• More design freedom
• Rapid design iterations and prototyping
• Production on demand
• Fewer inventory costs

But again, additive manufacturing has been struggling for decades to pass the threshold of producing with end-use quality and in high-volume like injection moulding does. Thankfully, Carbon offers the opportunity to explore the possibility for mass production with AM benefits, and they already have a history of success in this matter.

A History of Success

Perhaps the most representative case of high volume 3D printed consumer products are the Addidas 4D midsoles, where engineers applied Carbon’s distinctive lattice design approach. But, it goes way beyond consumer products; it is already happening in other industries like the automotive and medical. Companies like Ford and Lamborghini are implementing and approving Carbon 3D printed parts for their assemblies. In parallel, Resolution Medical could rapidly respond to COVID-19 critical demands for nasopharyngeal nose swabs by leveraging Carbon 3D printing.

One particular case that truly caught our attention was the production at scale of a trailer-tow connector cap for Ford Super Duty trucks. The company responsible for this was Aptiv, in close collaboration with the manufacturing company Fast Radius. The issue started when Ford required to change their previous cap model, which didn’t fit in the new assembly design. Aptiv had to provide a new iteration with very tight schedules. Taking into consideration that the traditional approach of retooling for injection moulding implied extensive lead times, they decided to take the additive manufacturing route. However, quality requirements for automotive parts are rigorous. In this case, they had to meet the following criteria:

• Material performance: Can it seal electrical components at 105 C and approve the Production Part Approval Process (PPAP)
• Repeatability: Is it possible to produce 1000 parts consistently and fastly enough?

In the end, they could meet material quality standards with Carbon’s EPX 82 resin. But the most compelling result is how they managed to reduce the time of production by 50%, as seen in detail in the image below.

As we can see from the timing tables, we can conclude that the key benefits of implementing additive manufacturing into production over traditional injection moulding are: Firstly, not even having to worry about tooling design and, secondly, being able to sample design iterations very fast.

For more information on this case, click here.

Further Info

If you want to explore more production solutions, SolidPrint3D is here to help you. For more information, please call SolidPrint3D on 01926 333 777 or email on info@solidprint3d.co.uk.

To further read on related topics, we suggest the following articles:

• A Guide to Resin Printer Technologies: SLA vs DLP
• Insert Moulding, Overmoulding and 3D Printed Prototypes