- 1.3D Printing Part 1: The What and Why
This is the first in what will hopefully be a series of articles on 3D printed fittings. In this article, I’ll delve into what 3D printing is and why we’re using it to produce our fittings.
3D printing. You don’t have to look hard to find all kinds of hype about how it’s going to revolutionize manufacturing of everything from pencil holders to houses. Imagine, anything you could want at the touch of a button in your very own home! Right. Unfortunately, most of what’s said isn’t grounded in practical reality, and in the end is just hype. Well, hype with a lot of grainy yoda figurines mixed in.
But 3D printing actually is revolutionizing manufacturing processes. It’s just doing it behind the scenes in small areas where it can compliment, rather than replace, traditional manufacturing methods.
Before we dig deeper into 3D printing, let’s take a quick look at the standard manufacturing method for plastic fittings.
Injection molding is the dominant manufacturing method used for 95% of plastic kite fittings in production. In this process, heated plastic is forced at great pressure into (usually) steel molds. Parts made this way generally have a very high surface finish and level of detail. While there are limitations to what geometry can be molded this way, it is by far the best process for mass-production of plastic parts.
The downside to injection molding? Tooling costs. A set of molds for a part costs thousands of dollars for a very simple part, and adding complexity can send the costs up from there. That’s not a big deal if you’re planning on making a lot of the same part, but when was the last time most of us needed 20,000 of anything? Unfortunately, the demand for kite fittings is not growing. Tooling doesn’t last forever, and much of the tooling that started life during the boom years of kite flying is nearing end of life. It’s tough to justify the investment required to re-build tooling, so those of us who rely on those fittings are out of luck.
Injection Molding Pros:
-Very high quality of finish
-Inexpensive, but only if volume is high enough
Injection Molding Cons:
-High tooling costs require substantial investment
-Limitations on complexity
-Once tooling is made, design changes are next to impossible
With that out of the way, let’s get back to 3D printing.
3D printing refers to a few different types of additive manufacturing techniques. This is done by building a part up out of a lot of very thin layers of material. There are a variety of methods for printing and even more acronyms, but we’ll focus on two methods in particular: Fused Deposition Modeling (FDM) and Stereolithography (SLA). Both of these methods share the major benefit of 3D printed parts – the ability to make very small quantities in a cost effective manner. Tooling cost is very, very low. What this means is that it is practical to produce fittings in low volumes, so fittings can be tailored to specific purposes rather than trying to be one-size-fits-all.
FDM – Fused Deposition Modeling
The most widely used process for small 3D printed parts is FDM. This includes the vast majority of desktop or hobby printers. FDM printers extrude plastic through a heated tip to build up a part layer by layer, kind of like building a log cabin. This is the fastest and most economical method of printing, but has a few major shortcomings.
First, the surface finish is not good. Remember all those grainy Yoda figurines? That’s FDM. Just like a log cabin, all the ridges show through. This also means that the level of detail is low. Not good for small parts like kite fittings! The second problem is structural. The bond between layers of filament is not nearly as strong as the plastic itself, so the material has ‘grain’. Much like wood, it’s got a weak direction. Last but not least, FDM has certain limitations about how parts must be printed that must be integrated into a design from the start.
I tested a number of different ways of using FDM early on in my experiments with printed kite fittings. At the end of the day, the finished product just wasn’t good enough. For small parts like kite fittings, there are just too many compromises.
SLA – Stereolithography
SLA printing works quite differently. The plastic used is a photopolymer as opposed to a thermoplastic. In it’s raw form, the material is a room-temperature liquid. The resin hardens when exposed to a lightsource. The printer works by focusing a light beam on the part suspended in a bath of resin, hardening wherever it touches. After printing the part has to be carefully cleaned and then post-cured in a UV chamber to finish the chemical reaction started by the printer. The end result is a monolithic part with consistent material properties and a fairly good surface finish. Not quite injection molding smooth, but without the pronounced ridges of FDM. This process is substantially more expensive than FDM, but the end result is a high quality, consistent, and functional product.
SLA is used for producing finished products in a number of industries. I am using engineering resins and printing with a machine that was initially developed for industrial printing in the medical field, in particular printing custom hearing aids. Some other SLA machines are optimized for printing even more intricate parts such as jewelry casting patterns.
I’m not going to make up some marketing bullshit to push 3D printed fittings as the be-all and end-all solution for manufacturing kite fittings. 3D printing is never going to replace injection molding. An injection molded part will always have a higher surface finish than a printed part, and in large quantities can be significantly less expensive.
But what about parts where there isn’t enough demand to make it worthwhile for someone to invest thousands of dollars in tooling? The reality of kite making in the 21st century is that that scenerio describes just about every part we use. 3D printing fills that void.
But printing goes farther. Imagine a world where you could design a kite without having to design around what’s on the shelf. Think of the options that would open up! Thanks to 3D printing, that day is here.
That’s enough rambling for tonight. Next post I’ll dig into the process of designing a custom fitting, from concept to finished product.