What you need to know before choosing the filament and model export settings before printing.
In the last article, we left a file on the 3D printer to be created. In theory, it should have just printed out in a couple of hours and - “Voila!… here is our print”. That is what was supposed to happen but unfortunately, “Houston – we have a problem”.
As you can see from the picture, the print has started to lift off the build plate, and this is also affecting the print quality. This was unexpected when we printed it, but was caused by the model getting cold on that side of the build plate. We were taking pictures and kept opening and closing the door of the printer, obviously letting in colder air. Some 3D printers do not have doors but are very susceptible to breezes in the room.
This failed print meant a couple of hours and all that printer filament wasted. (Get used to this kind of thing. Until you work out all the issues, you WILL have blown prints, and even then, prints will sometimes still fail.)
So, the solution was obviously to NOT open the door here, but there are also a few other “tricks” that can be used to fix this. We will come back to those later.
On to the next print to try again. This time we used a different printer to see what the difference would be. We expected the print to come out, but again, problems came up.
What is going on here? This was very unexpected for a number of reasons. For those of you who cannot see all of the problems here, we will point them out.
You will notice that there is a thin plastic “skirt” around the print this time. That is actually deliberate and a setting used to help models adhere to the build plate. In this instance, the skirt is way too thin and actually makes it harder to get the model off the build plate.
There is also quite a lot of stringy plastic material coming off the model at various places. This is typically an issue with the heat and the pressure in the extruder.
Lastly, the tops of the model have broken off, and inspection showed that there were distinct laminations in the print. The tops broke off along these laminations. Hmmm... a little investigation is required as to how these problems occurred.
Not to worry. The good thing about all of these problems is that they are all well-known and solutions are easily discovered. Let’s look at a few of the more common ones.
- Printer Calibration
- Build Plate Adhesion
- Overhang Support
3D Printing is a precision manufacturing process. When building models, the tolerances are measured in divisions of a millimetre. For a typical machine metal lathe, the accuracy is about 0.002mm. For an industrial 3D printer, it is about 10 times that figure at about 0.02mm. For a typical desktop 3D printer, the precision is about 0.02-0.05mm. These are very small precisions and they have a tolerance of about +/- 5%. This tolerance is due to shrinkage from cooling and is unavoidable, however, 3D printers can be programmed to take it into account in very high precision builds. The point of all of this is that with precisions that are so small, it doesn’t take much for a printer to be “out” for it to make a big difference.
The build plate
The build plate is the surface on which the printer extrudes the molten material to form the print. Some cheaper 3D printers just have a rough surface to make the plastic stick, but most reasonable printers have a heated build plate to help the material adhere and make a solid base for the print. Anyone who has melted plastic for any reason knows that hot plastic can be “sticky” and very difficult to remove while hot. When this plastic cools, it becomes hard and stiff so that it can be easily broken off the surface. This is the way most builds are removed from the printer when the print is finished. Simply waiting for the build plate to cool and often the print will just become unstuck. Sometimes a little “gentle persuasion” is required with a scraper or sometimes a very sharp blade. This often depends on many factors including the material printed, the material the build plate is made from, and if any “surface” or “texture” is part of the build plate. Some build plates are deliberately textured to help models stick and blades can damage this surface.
Some build blates are flexible and can be easily bent or flexed to help remove models. The type of build plate is dependent upon the printer.
The two pictures here show a flexible build plate and a glass build plate. As you can see, the glass build plate uses some extra “assistance” to stick down models. We will stick to normal-style heated build plates for now.
There are three main things that need to be correct when getting prints to work with the build plate. The first is that the 3D printer must be properly calibrated. The printer does not need to be calibrated EVERY time you use it, although, if you use it irregularly, then it may be worth it if there is a chance it can be easily knocked or if there are temperature extremes.
Calibration involves first making sure that the build plate is level at all points. This is normally automagically done by most modern 3D printers, but it can also be done manually. It is fairly obvious that if the plate is not level, then precision is immediately lost in the print. HOW you would level the build plate is normally in the printer’s manual or online. We will assume you have successfully done this bit.
The next calibration is to get the extruder nozzle set to the correct distance away from the build plate. This is also often done automagically by the printer, but again, methods are available to do this manually. Ideally, the correct distance will be set with a feeler gauge but methods of dubious accuracy are encouraged on the Internet. The “paper feeler” method is a common one that comes up in searches using a sheet of printer paper instead of a feeler gauge. If you buy or have access to a 3D printer, feeler gauges are only a few dollars and are much more accurate. The extruder nozzle must be at the correct distance from the build plate so that sufficient material can be extruded at the correct pressure so that it will stick to the build plate.
As you can see, there are some differences with the nozzle position to the build plate, and obviously, if the first layer is the foundation for the whole build, then getting it right is very important.
The next most important thing about 3D printing is getting the temperatures right. For now, we will assume that we are not using any fancy filaments, just normal old PLA. We will be discussing filaments later. PLA likes to have a build plate temperature set at about 60°C. This makes it sticky enough so that it will actually adhere to the build plate under normal circumstances. We say “Normal Circumstances” because not all printers are the same and individual printers, or the environment they operate in, can be quite different (but “normal” for those circumstances).
So how do you set the temperatures? Well, remember on our initial prints we went with default settings? If you need to adjust the settings then open up your friend Cura.
Open Cura and go to the drop-down arrow in the top right.
From the menu that drops, go to the second menu in the top right.
This will drop yet another menu, but this is the one we actually need because we need to set it to Basic. As long as this is set to Basic, Cura will only show the minimum of potential settings and new users shouldn’t get too confused.
One very strong word of warning about changing the settings of Cura. If you change the settings, Cura will REMEMBER them for next time. If your print has gone wrong and you don’t remember which settings you changed, this can cause much grief!
If you do “get your settings lost”, then the easiest and probably best way to fix it is to delete the config files. When you restart Cura, it will then recreate new files. You might have to set your 3D printer up again but this is normally a trivial exercise unless you have been really hitting the Internet and tweaking the settings hard!
Now, we are ready to actually change some of the critical settings for our build. Let’s just make sure that we are in the Standard Quality Profile.
This will make the default resolution of our build 0.2mm. This setting will affect the basic speed of the print. A finer setting will slow the print down but give better resolution, a coarser setting will be faster but the resolution will be worse. Sometimes it will not matter because some prints just do not get any better than a particular resolution setting, and sometimes you just want a quick and dirty print to see if something will work or for a destructive prototype. Either way, after a little use, you will get the hang of what initial profile setting you want with experience.
Setting the temperatures in Cura is fairly easy. Just open the material section and type in the temperatures you want. The only question is: How do we know what we want? Great question – let’s find out.
The roll of PLA (Poly Lactic Acid) filament here is a fairly standard roll from the Jaycar website.
It was actually the first one we found and costs about $40 per 1kg roll – about right for generic PLA, some are cheaper and some more expensive.
The important data about PLA is usually found on a data label on the roll and typically includes the four highlighted data points. Here is how to decode what all this stuff means.
Best Printing Temperature
This is the recommended printing temperature for this material to get the best results in most 3D printers.
One of the good things about the 3D printing industry is that right now, there are not that many hardware manufacturers, and they all use the same hardware, more or less, so a de-facto standard has been created by the industry by necessity. While the exact temperature for an individual printer may vary for best results, the recommended temperature should get consistent results. If PLA is extruded and it is too cold, it may not stick to the previous layer and form a good bond. Also, 3D printers sometimes will print across gaps in the build. If the temperature is too cold then the material will break and leave a gap, which may not be wanted. If the material is too hot, the material may join the gap but then sag under its own weight. Both of these conditions are obviously bad and lead to poor-quality prints.
This is the recommended temperature to make the material stick to the build plate.
Not all 3D printers have either heated build plates or heated print chambers. This is not necessarily bad but can cause inconsistent results. The Artillery Sidewinder X1 that we used for our test print has a heated build plate, but is in a glass enclosure to keep out any drafts. We were opening the door to get some pictures and this caused drops in temperature that made the build distort. As a general guide, the hotter the build plate, the better the material will stick to it. When the build plate cools, it will release the model, so the build plate temperature is normally maintained throughout the print.
This is an interesting number and can have a huge effect on a number of different variables, including the actual time it takes to print a model, the quality of the model and the strength and other properties of the model.
The material in the extruder is heated up and layered down, and new material is fed into the cold part from the spool. There are a number of limitations to how much material can be fed into the extruder and also how much comes out, and obviously variables that affect this. The print speed is how fast the material comes out of the hot end of the extruder. Some of this is dependent upon the temperature of the material, and some of it is dependent upon the pressure of the material being fed in.
The temperature part is fairly straightforward. If the temperature is hotter, then the material is “runnier” and will come out faster. The pressure part is more interesting. The hot end is “fed” from the spool, and this pressure can be changed.
This makes a difference because sometimes the extruder will come to the end of a line of printing and stop, but the pressure of the material inside may still squeeze out, even though the printer thinks it has stopped. This can lead to blobs of unwanted material on the model that can build up and degrade the precision of the print. This can be stopped by turning off the pressure before the end of the print is reached and the remaining pressure squeezes out and stops just in time for the end. This setting is often called the Coasting setting.
This is obviously affected by the temperature changing the runniness of the material. It can be a fine balance to juggle this temperature and pressure and settings are available to change it, but also the actual speed of the print has an effect. There is also a fan cooling setting that can affect how all of this stuff interacts.
Each 3D printer will have an optimal and recommended speed for printing. This will be based on tests done by the manufacturer on many machines. There will always be some variability between machines and these optimum speeds will be the ones that are optimum for 90% or more of the printers of that type. There will always be an outlier in the data, and this is when people will start experimenting. If you have ever heard of overclocking a computer then this is the 3D printer equivalent – tweaking settings to get the absolute maximum out of a machine.
If you change the printing speed of the printer, it MAY work. It may NOT work either. If you fiddle with the settings, you may GET it to work. It’s all up to you. Sometimes, some people, for quite valid reasons, will change all this stuff and have success. The Print Speed Range is the speed that the manufacturer thinks everything will still work within reasonable limits. At the end of the day, however, Time is Money and Speed Sells! Just because we cannot afford a Sports Car, doesn’t mean we don’t WANT one!
This one is tricky! As far as we can tell, this is the fastest speed that the filament will come off the reel without being damaged. While we can see this would be a useful thing to know, we are not sure why it is important enough to be on the reel. After a thorough search on the Internet, including some of the major filament manufacturers (some of whom put this on their filament like eSun), and asking a few questions of dubious “experts”, we came up with this explanation.
Movement speed doesn't really matter for domestic 3D printers, however, some industrial 3D printers are about 4-5 times faster than these machines, and this particular requirement does actually matter. Also, not all filament is the same and can be brittle before it is heated and extruded, so movement speed does make a big difference.
Build Plate Adhesion
Now we get to build plate adhesion techniques, and what they mean and affect. Some models that are 3D printed will quite happily stick to the build plate without any help. Others, you just about have to nail them down before you start or they will not work. This is where the build plate adhesion settings come into effect.
Build plate adhesion is some extra material laid down on the build plate to help the model stick.
It is usually either set to None, Skirt, Brim or Raft.
None is pretty obvious.
Skirt is one or more lines around the model that checks bed levelling and if the material sticks to the build plate at all.
Brim is like the Skirt but it actually joins and becomes part of the model. It is easily removed by trimming in post-processing.
Raft is literally a raft of material that is laid down on the build plate that the model is built onto. It takes time to lay down a raft which will add to the build time, but on the other hand, if the model is going to stick at all, it will with a raft.
Infill is also one of the most important settings we will need to know about when 3D printing anything with a bit of volume. One of the things that Cura does when it slices the model, is asking how much and what type of infill to use. This is important because it will drastically affect the outcome and strength of the print.
Cura actually has settings for how thick the walls of a model are, but it doesn’t care (usually) what is inside the model. This means that there is no support for a model on the inside – just a shell.
For some models, this is not an issue because they are perfectly capable of maintaining their shape and integrity. Other models will simply collapse in on themselves or have no strength and break easily. The important thing to remember is that NOT ALL MODELS NEED TO BE SOLID. Many models just need enough internal support to do what is needed with them.
SOME models need to be solid. Printing solid models will take much more time as more filament will be extruded into the model. This is the main reason we use Infill instead of printing solid – to save time. Another really important thing about solid models is the DIRECTION of LAMINATIONS. The best way to see why is to watch this video on YouTube where this crazy guy prints bolts horizontally, vertically and at a 45° angle then strength tests them:
Getting back to Infill. The amount of infill percentage is basically how much of the empty space you want to fill with internal structure for support. So, 5% means that much space and 100% means solid. The other thing to set is the shape of the infill. This can be important because different infill has different strength properties. The best example of this is when using square infill, pressure directly down on the walls of the square will be resisted easily, but pressure on the corner of the square will often make it distort.
As you can see, there are many types of Infill available in Cura, so which one should you use? Well, experience will tell you after time, but that doesn’t help right now. As a Rule of Thumb, the engineer inside us says that triangles are the strongest structure so we normally use them for all of our models. Hexagons look nice and are similar to triangles. There is a great deal of research going on about infill and more information and advice can be found with your ‘Google Goggles’. Just search for 3D print infill and up it pops.
The last thing about infill is how much you need. This is one of those “How long is a piece of String?” questions. Depending on the model, and the strength requirements, and the material, the amount of infill needed will typically
be between 15-40%. 20% is a good compromise for testing, but it really is a bit of a guessing game until you get some experience.
The last of the basic settings to know about is support. You have probably worked out by now that as you lay down layers of material with the extruder that it needs to stick to something. It will not just hang in mid-air. This is not quite true.
Depending on the model, the material, and the settings (Have you noticed that EVERYTHING is dependent upon these parameters?), the extruder can cross small distances of open space and join together two points. The two points are relatively small, however. Overcoming this problem is where support comes in. You have probably guessed already that a support is a 3D printed structure that is used by the printer to support parts of the model so it can be printed.
The main parameter of the support is the overhang angle. This is the amount of angle that the printer can still print and not have any support. This will vary with our good friends (model, material, settings). The overhang is a problem with shallow angles, so support will be generated for a part of the model hanging out the side and not so much vertically.
There are two methods of generating support for a 3D print. The easiest way is to let Cura do it for you, and this will work reasonably well. The other way is to build supports manually as part of the model. You want to WHAT! WHY!
WHY would you want to generate your own supports when Cura does it for you? The reason for this comes back to other settings. Cura is very conservative when it builds the supports, and it is possible that it may create supports that are just not that important and the print will work without them. The biggest issue with 3D printing is that it takes time, and as we all know – time is money. If you have a model that needs support, but you can customise that support so that it is more efficient and needs less printing time, this will save overall time. You can customise the settings to work with these custom supports. You can even use custom and Cura generated supports to get the best of both worlds. Ultimately it comes down to efficiency and time.
The model of the SR-71 test print in yellow needed to be supported in the test model in green as it was at an angle of 60º overhang. You can see the support generated by Cura here on the green model.
While it looks fairly robust in this picture, the support would have come away fairly easily by trimming and a little post-processing with sandpaper. The reason we did not bother was because the printer had an error that caused the top of the Moai head and the monolith to not be printed. You can also see the infill we used on the Moai head.
The plan with this article is to also talk about some filaments available, but before we do that, there are just a couple more things we want to mention about troubleshooting your prints. The first thing is probably the most important. Almost ALL failed prints that are not caused by the actual individual printer calibration, can normally be fixed by tweaking the correct settings in the GCode through Cura or other slicing software. The second thing is that while there are many, many, different 3D print problems, the most common ones are easy to fix. A list of common issues can be found on the Ultimaker website here:
The two examples of problems shown here are stringing and blobbing. While these may be fixed by tweaking temperatures, they might also need more tweaking through the Cura software to a setting called coasting.
Coasting is when the pressure is reduced in the hot end by retracting the filament and allowing the print head to lay down material from the residual pressure of the material in the print head. When tweaked correctly, there should be exactly the right amount of material left to finish exactly where the print needs to stop with no further leakage. It is an experimental setting in Cura but can be very useful. Now, on to filaments.
There are literally thousands of different filaments available on the market, all of different materials with different properties. So, where do you start? Well, the best place to start is with the safest and easiest filaments to learn, and then go exotic when you have done a little research and know what you are getting into. A little like learning to sharpen a knife – practice on mum's kitchen knives before you attempt to re-sharpen that thousand-year-old Katana sword.
As you have probably worked out by now, not all 3D printers are the same. They have different specifications and capabilities. The best place to start with filament is using the printer manufacturer’s recommendations, then branch out. The main difference with various filaments from a practical point of view is the change in temperatures or the hot end and build plate, the speeds that can be used, and the OHS issues of toxicity of the filaments or the solvents and cleaning products needed to use them.
While there are many types of filaments that base-level 3D printers can use, the most common filament in use is ABS, closely followed by PLA. Yes, more three letter acronyms!
Most 3D printers available for maker use will be printing in some kind of plastic. Plastic is typically referred to by its constituents or chemical names of some kind. Since us mortals would struggle to say: Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl), we just use a shortened version of it to remember more easily - (Poly (ethylene terephthalate) or PET.
A list of common filament types is shown here.
This list can be found here with a full explanation:
Obviously, there are many different types here and they all have different properties. As we said earlier, ABS is the most common plastic filament in use for 3D Printing, closely followed by PLA. Either is good for general purpose use, both cost about the same. PLA is marginally more friendly to the environment than ABS.
As a general guide to the different types of filaments available, this list is very helpful. It can be located with a whole heap of extra information on this website:
This article does not even scratch the surface of the types, colours or anything else in the filament world. The information out there is endless and expanding rapidly. We have only covered the basic types, and even then, without any depth, but for a beginner to get started it should at least whet your appetite. The only other thing really to know about filaments is that they come in any colour you can imagine (All the Pantone colours and many more). They also come in some exciting colour mixes and metallic look filaments, especially the ones mixed with Silk. A few examples of which are shown on the next page.
DISTINGUISHING FEATURES FOR DIFFERENT FILAMENT TYPES
Aesthetics: Engineering PLA filament can create great visual prototypes with the added option of post-processing such as painting or being able to be sanded to create great models.
Ease of use: Engineering PLA is the easiest material to work with that does not have unique workflow requirements.
Heat resistant: ABS has got high heat resistant properties which is useful for functional prototypes
Wear resistant: ABS models do not scratch easily and can last long if stored properly.
High Elasticity: Very flexible and can stretch.
UV Resistant:Many models degrade if left out in direct sunlight, PETG is the main exception in 3D printing.
Water Resistant: PETG models can be used to store liquids or be submerged without degrading.
Chemical Resistant: PP is highly resistant to chemicals and cannot be combined to anything apart from itself.
Fatigue Resistant: PP models do not break easily from repeated flexural forces.
CARBON FIBRE FILAMENT
High Strength: Carbon is added to a base filament to increase strength and rigidity in the final model.
Low Friction: Great for models that require movement without degrading.
Elasticity: Elastic parts like phone cases and grips can be made with flex
Soluble material: HIPS dissolves in citric-based acids.
Impact Resistant: HIPS is high impact resistant and can withstand forces for various functional applications.
Soluble Support Material: PVA dissolves in water and is used for complex geometric models.
Some of the metallic filaments are stunning and the multicoloured filaments really can add that WOW factor to some models.
3D printing is changing and improving every day and some of the creations that amateur and professionals alike are coming up with are simply stunning. We were inspired enough by our recent short course to do some investigation and play with the machines. We really are literally a few months ahead of new readers who have not used this tech before. Our advice is to get inspired, like we did, and give it a go. 3D printers can be bought for around $500 and up in Australia and they open up a whole new world of possibilities.
In the next article, we will be starting a new making for beginners topic on laser cutters. If you thought 3D printing was fun, laser cutters are really cool!