3D Printing Functional Parts
3D printing is a versatile process that can be used to create everything from desk trinkets to functional parts that can be sold to customers. It would only make sense that the way you approach printing changes depending on what the part will be used for. In this article, we are going to go over the key differences that separate functional printing from cosmetic only type prints.
99% of the advice and habits you will see online are geared toward what we consider cosmetic prints. This would be something that just needs to look good but doesn’t necessarily need to perform to specific requirements. If you are an inventor or tinkerer that bought your printer to create functional prints that will withstand real-world use, then this article is for you. If your main focus with 3D printing is to print cosmetic items such as sculptures or lithophanes, this article may not be as helpful since a lot of the strategies won’t translate well into high detail prints. Regardless, anyone can benefit from reading this article as it will give you a broader perspective of 3D printing as a whole.
At 3DMaker Engineering we specialize in creating functional prototypes and even production parts that are used around the world. We wanted to share our viewpoint when it comes to functional 3D printing to ensure our prints are strong and meet design requirements. Don’t worry if some of the ideas in this article are different than how you may have learned from others—this is to be expected.
It’s important to understand that when it comes to functional 3D printing, looking good comes second to performing good. That doesn’t mean our goal is to make terrible looking parts, but rather we will choose to give up some detail if that means the part will meet our functional requirements. It’s also important to realize that if you are used to printing “lower-end” filament like PLA or PETG, you may need to change your expectations on the amount of detail you can achieve when trying something like Polycarbonate. Yes, you can get great prints from Polycarbonate or Nylon but trying to match something that was printed in PLA will be tough to do.
Temperature Tower Pitfalls:
Go on any 3D printing forum and you will see discussions about temperature towers which are used to tune your printer. Basically, it lets you find the “optimal” temperature to print at based on criteria such as overhangs, bridging, and small feature printing performance. The problem is that the temperature at which the test looks the best is likely not optimal for adhesion strength which is vital for durable parts.
The way we approach calibration is by first defining the temperature we want to print at based on material type (see below). Normally we select a temperature that is at the high end of the suggested range and sometimes above the manufacturers range. We do this because generally the hotter the filament is extruded the better layer adhesion you will get. Next, we will run a simple print like the 3DBenchy and make changes to our print settings, however, we very rarely adjust the hot end temperature. Instead, we change things like retraction, print speed, z-hop, and coasting to make improvements. It’s also important to not get too hung up on trying to make your calibration print perfect. We have found that if we can get our machine to print a 3DBenchy with decent quality, most of our functional parts will print flawlessly. Also, when possible, we design most of our parts so that they are optimized for 3D printing by limiting features like steep overhangs and long bridging. Below are the temperatures for common filament types we suggest you print with for functional prints:
After reading through our suggested temperatures you will probably find that they are much higher than you are used to printing with. While you may lose a little detail at these temperatures, it is vital for maximum layer adhesion. The goal is to ensure that the layer lines are not the weak point on the part.
Printing at 100 mm/s is awesome--it looks impressive and you save time. The drawback is that many filament types will have poor layer adhesion because of it. This is because filament that passes through the melt zone of the hotend too fast will still extrude but it does not have time to fully melt. This means that the plastic is extruded “dry” and is cooled off before bonding to the previous layer. For most plastics, we like to keep print speeds around 45 mm/s. Sometimes we will even lower speeds to 30 mm/s for certain nylon and polycarbonate filament. These plastics are known to melt slowly and may benefit from passing through the melt zone at the reduced speeds.
It doesn’t matter if you only print PLA and PETG, you NEED an enclosure. This doesn't mean you can't get a good print without one but if you are serious about 3D printing, it is an invaluable tool. Printing in an enclosure has four main benefits:
1. The first one is obvious--it lets you print materials that won’t print successfully without one such as ABS, Nylon, and Polycarbonate. Printing these materials without an enclosure almost guarantees you will get warping during your print.
2. The second benefit is that you will have more consistent results from print to print whether you’re printing PLA or Polycarbonate. Since print performance is so dependent on ambient temperature, you could run two identical prints in a row and end up with vastly different results. By controlling the ambient temperature on every print, you will eliminate one major source of failure. You want to be able to be confident that once you have a working program that you could call it up on your machine 6 months later and get the same result as last time.
3. The third is increased layer adhesion. By keeping previously layers closer to their glass transition temperature, it allows new layers being deposited to fuse together better. It is very difficult for two layers to bond properly if the previous layer is already solidified and at room temperature.
4. The final and most important benefit of an enclosure is that it helps to reduce the number of particulates being released into the air as your hotend is melting filament. Most people know that filament such as ABS releases hazardous particulates into the air, however, even PLA puts out a small amount. Even an enclosure without active filtration has the ability to lower the number of particulates drastically. If your budget allows for it, we recommend adding some type of filtration into your enclosure.
While you can make your enclosure as elaborate as you want, we have found that Creality Enclosure is a simple solution for smaller printers such as the Prusa MK3 or Ender 3. One of the things that we love about it is its ability to easily collapse, saving on space when you aren't using it.
Adding a bigger part cooling fan and modified fan shroud is probably the most popular upgrade everyone adds to their printer. Every time we go on a forum it seems like someone is always coming up with the next “bigger and better” cooling fan setup. Of all the habits we see in the printing community this is the one that makes us cringe more than any. We call these “upgrades” the layer adhesion killer.
We have a print farm with a large number of machines ranging from desktop to industrial style printers. Guess how many have upgraded part cooling fans--ZERO. To add to that, we rarely even turn on the stock cooling fans except during bridging. Blasting molten filament with air right as it comes out of the nozzle shock cools it and caused it to solidify before it can bond with the layer below it. Even with PLA we generally only run the fan at most at 50% and leave it off for almost every other filament.
There is a lot of debate about whether filament really needs to be dried or not. Some swear by it, others say it’s a scam. After a decade of printing we can tell you with certainty that filament absolutely absorbs moisture and it affects print quality and strength. Engineering grade filament is even more more susceptible to absorbing moisture and must be dried before your first print.
There is much misconception that when you take a new roll of filament out of a vacuum-sealed package that it is already dried. This is only meant to prevent more moisture from being introduced during storage and transport but the filament has already absorbed moisture while it was being extruded and waiting to be packaged at the factory. As mentioned, engineering-grade filament is more sensitive to moisture and the two that are particularly prone are Nylon and Polycarbonate. It is almost certain that when you open a new roll of those types that they will need to be dried before printing.
One of our own learning experiences came years ago when we tried printing Nylon for the first time. This is supposed to be one of the toughest filament types in existence but we were left with a part that literally crumbled in our hands. Layer adhesion was so poor that you could peel away the layers like an onion. We spent weeks tweaking temperatures, speeds, and flow rate but nothing seemed to produce a usable part. Finally, we read an article about the importance of keeping filament dry and we were willing to try anything. It was like magic; our very next print was rock solid with much less stringing. It was night and day difference. So, for anyone who thinks drying filament is a myth, try printing nylon or polycarbonate out of the package without drying first.
For more information, check out our page on how to dry filament
There are many different filament types that are great for functional parts. It really is a case by case basis depending on your requirements; however, we recommend becoming familiar with ABS. In our experience, it is a great general-purpose filament that works for most of the projects we work on. It’s easy to print, has great physical properties, and the price is extremely affordable. If you have heard other say that it is hard to print, keep in mind that most of these people were trying to print it on an open machine with a glass bed. In an enclosure with a proper build surface such as PEI, ABS becomes a breeze to print with excellent print quality.
For more information, check out our page on material properties
Not all infill is created equal. There is everything from triangles, honeycomb, and one of the more recent types: Gyroid. We won’t go over each one but have found gyroid to be extremely strong. The issue that most infill types have is that they may be strong in one direction but if you apply a force perpendicular to the pattern, they tend to become very weak. Gyroid is a shape that is equally strong in X, Y, and Z which means it is one less thing you have to worry about when determining your print orientation.
Heat Set Inserts:
One of the quickest and easiest ways to take your prototype or functional print to the next level is by using heat-set inserts for threaded holes. One of the drawbacks of every filament type is they tend to not hold screws very well. If the screws in your part will be removed and reinserted multiple times, it gets even worse.
Heat set inserts are typically made of brass and are pressed into a slightly undersized hole using a soldering iron. The insert heats up and melts the plastics which allows the insert to drop into the hole. After the plastic solidifies you have a metal thread that almost appears to have been injection molded in place. Not only does this give you part a professional appearance, you no longer have to worry about threads being stripped from over-tightening.
As mentioned, 3D printing can change depending on its end-use. The good thing is that many of the concepts are the same which makes the transition easy. The key takeaway is that layer adhesion is king and don't be afraid to print hot. It's easy to take the easy path and lower the hotend temperature to solve some of your issues but try to avoid when possible. By following the concepts in this article you can be confident that your parts will be able to handle anything you throw at it!
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