Project ALTius part VII: “Printers for gliders” or “ A delta printer for a (non-)delta wing”

After the early “demise” of the New RC Soaring Digest I was no longer feeling the “pressure” of a monthly issue and I got lazy. The previous part was published after 3 months, this one after 6 months — for the future I hope to do it on a monthly basis.

Probably you are expecting that in this part I will finally start with HAM (my rather stupid acronym for Hardware Assisted Manufacturing — in fact DIY contraptions for building gliders: laser cutters, 3D printers and so on). And I’m afraid I have to disappoint you again: this part is about how to avoid HAM. In other words: how we can use what is available on the market (with a focus on 3D printers of course). More specific: why I recommend delta 3d printers for gliders. And even more specific: it’s an honest and objective (I hope) sales pitch for FLSun SR (Super Racer). And just to make things more interesting: I’ll spice it with a little bit of AI.

There are 3 major types of FDM 3D printers: bed slingers (aka Prusa i3 and derivatives and clones), CoreXY (BambuLab X1/P1 and Creality K1 and so on) … and delta printers. You can also find some cross-breeding like CoreXZ (a bed-slinger but with a CoreXY type of kinematics applied to X and Z axes) but there are few models on the market. And in fact there are not many models for delta printers either (even if they have a history of more than 12 years). And IMHO delta printers have certain advantages over other types.

I’m a little bit lazy today and I’ll ask my assistant Google Gemini to do the heavy lifting — let’s start with some warm up, a simple prompt in order to evaluate what we can expect from the AI assistant in terms of accuracy and verbosity. The whole series is based on the assumption that 3D printing models makes sense — let’s see if Gemini agrees:

Prompt: “Advantages of 3d printing aero RC models vs traditional building methods”

3D printing offers several advantages over traditional building methods for aero RC models: Design freedom and complexity: Complex shapes: Create intricate, lightweight designs that are impossible or difficult with traditional methods like balsa and plywood cutting. This allows for increased aerodynamic efficiency, better strength-to-weight ratios, and unique, customized appearances. Internal features: Print integrated spars, ribs, and other structural elements within the model, reducing assembly time and improving overall strength. Rapid prototyping: Easily iterate and test different designs by quickly printing new versions, accelerating the design process. Material properties and weight: Lightweight filaments: Use materials like nylon, PLA, or PETG, which can be lighter than traditional balsa wood, leading to improved performance and flight times. Tailored material properties: Experiment with filaments offering specific properties like flexibility, strength, or heat resistance for different parts of the model. Consistent density: 3D printing ensures consistent material density throughout the model, leading to more predictable flight characteristics. Manufacturing and assembly: Reduced build time: Automate repetitive tasks like cutting and shaping, saving time and effort compared to handcrafting with traditional methods. Reduced waste: Minimize material waste compared to cutting sheets of balsa or plywood, making it a more environmentally friendly option. Precise parts: Achieve high levels of accuracy and repeatability, ensuring consistency across multiple models. Modular designs: Print parts that easily snap together or integrate with other printed components, simplifying assembly and repair. Additional benefits: Accessibility: Design and print your own unique models, independent of commercially available kits. Customization: Personalize your model with custom logos, markings, or other features. Learning opportunity: Gain experience with 3D modeling and printing technology, a valuable skill in many fields. However, it’s important to remember that 3D printing also has some drawbacks compared to traditional methods: Higher initial cost: Requires investing in a 3D printer and filament, which can be more expensive than basic balsa and plywood materials. Printing limitations: May be limited by the size and resolution of your printer, and some complex designs might require post-processing like sanding and finishing. Material strength: Some filaments might not be as strong as traditional materials, especially for high-performance models. Ultimately, the best approach depends on your budget, experience level, desired level of customization, and performance goals. For those seeking unique, complex, and lightweight models, 3D printing offers exciting possibilities, while traditional methods remain a cost-effective option for simpler designs.

In short: our chatty Gemini thinks it’s a good idea to print RC models (but you have to take it with a grain of salt: “use materials like nylon, PLA or PETG which can be lighter than traditional balsa wood”, in fact these are 10 times heavier). But other things are just spot on. Next prompt:

Prompt: “Best type of 3d printer for printing RC F5J gliders”

There isn’t a single “best” type of 3D printer for printing RC F5J gliders, as the best option for you will depend on your budget, experience level, and the specific features you need. However, here are some factors to consider when choosing a printer: Filament compatibility: For F5J gliders, you’ll want to use a filament that is strong, lightweight, and has good weather resistance. Popular options include PETG, nylon, and carbon fiber-reinforced nylon. Build volume: The build volume of your printer needs to be large enough to accommodate the wingspan of your F5J glider. Most F5J gliders have a wingspan of around 3 meters (10 feet), so you’ll need a printer with a build volume of at least that size. Print resolution: A higher print resolution will result in a smoother and more aerodynamic finish on your glider. However, higher resolution prints will also take longer to complete. Printing speed: If you plan on printing multiple gliders, you’ll want a printer that can print quickly. However, it’s important to find a balance between speed and quality. Experience level: If you’re new to 3D printing, you may want to start with a more user-friendly printer. More advanced printers may offer more features, but they can also be more difficult to set up and use. Here are some popular types of 3D printers that are well-suited for printing RC F5J gliders: Fused filament fabrication (FFF) printers: These are the most common type of 3D printer, and they are a good option for beginners and experienced users alike. FFF printers work by extruding molten filament through a nozzle, layer by layer, to build up the object. Selective laser sintering (SLS) printers: SLS printers use a laser to sinter together tiny particles of powder to create the object. SLS printers can produce very strong and lightweight parts, but they are also more expensive than FFF printers. Stereolithography (SLA) printers: SLA printers use a laser to cure liquid resin into the desired shape, layer by layer. SLA printers can produce very high-resolution prints, but they are also the most expensive type of 3D printer. It is important to do your research and compare different printers before making a decision. You can also read online reviews and forums to get feedback from other users. Here are some additional resources that you may find helpful: Project ALTius: Working within weight and strength limitations for 3D printed F5J gliders “rc f5j” 3D Models to Print

WHAT? Gemini listed my previous piece as a primary source of information for printing F5J gliders (and this looks like some flattering or maybe self-validation — probably I’m the single crazy person in the world to think that a 3D printed F5J glider is a good idea).

And somehow Gemini avoided the question by listing TECHNOLOGY types (FDM / SLS / SLA) and if I give it a more specific prompt “Best type of FDM 3d printer for printing rc f5j gliders” I get more blah-blah and a sales pitch for Prusa MK3s+, Creality Ender 3 V2 and Bambu Lab X1 Carbon (no thanks, I’ll pass). OK, let’s help Gemini focus on the result:

Prompt: “explain the advantages of a delta 3d printer compared to a corexy 3d printer”

Advantages of Delta 3D Printers compared to CoreXY: Speed and Print Quality: Faster printing: Delta printers typically offer faster printing speeds due to their simpler mechanics and lack of large, moving gantries. This results in less inertia and quicker acceleration. Reduced ringing and ghosting: Due to their design, Delta printers have a fixed print head and eliminate wobbly gantries which contribute to these artifacts. This translates to potentially cleaner prints with reduced ringing and ghosting issues. Other Advantages: Smaller footprint: Delta printers often have a smaller footprint compared to CoreXY printers, especially for larger build volumes. This is because they don’t require large frames for X and Y movement. Easy bed access: The open design of Delta printers allows for easier access to the print bed, making it easier to remove prints and handle maintenance tasks. Unique aesthetics: The triangular design of Delta printers is visually appealing and different from the standard Cartesian or CoreXY printers. However, it’s important to consider the downsides: Calibration complexity: Delta printers are generally more challenging to calibrate due to their complex kinematics and interdependent movements. Material limitations: Dual extrusion and filament changes are less common on Delta printers due to the complex movement system. They usually use Bowden extruders which can pose challenges with some materials. Limited build volume: While offering a smaller footprint, Delta printers may have limited build volume compared to similar sized CoreXY machines due to the triangular frame constraints. Choosing the Right Printer: Ultimately, the best choice depends on your specific needs and priorities. If you prioritize speed, print quality, small footprint, and easy bed access, a Delta printer might be a good option. However, if you need multi-extrusion functionality, larger build volume, or prefer easier calibration, a CoreXY printer might be a better fit. I recommend you research specific models and consider your printing needs before making a decision. There are many excellent communities and resources online dedicated to 3D printing that can help you compare models and find the right fit for your projects.

Gemini warned us about the disadvantages (but these are not relevant: calibration complexity is not an issue with Klipper, I don’t need dual extrusion and I don’t care about limited build volume — probably what he sees as an disadvantage for cylindrical shape). We’ve played enough, let’s give Gemini a rest.

Here is MY opinion about delta printers (just some add-on clarification / explanation):

- Delta printers are budget-friendly and easier to build. CoreXY printers are cube-shaped with some additional support structures. To build a modern CoreXY printer like Voron 2.4 you need 18 pieces of 2020 profile, 7 or 8 linear rails (MGN9/MGN12) and 7 stepper motors (6 x NEMA17/1 x NEMA14). For a delta printer you need just 9 pieces of 2020 profile (3 long and 6 short), MAYBE 3 x MGN9/MGN12 (but you can just use 2020 with carriages) and 4 stepper motors (3 x NEMA17 / 1 X NEMA14). The motion controller and the SBC for Klipper are the same but with fewer stepper drivers. - Delta printers are faster. It’s very simple: in bed slingers one stepper motor has to move a very heavy mass (on X axis the printing head and on Y axis the printing bed). In CoreXY printers the printing head is moved by 2 motors (with the exception of the 45 degrees motion where only one motor is active — like in rectangular infill). Guess what: in delta printers ALL 3 MOTORS are working for the printing head movement ALL THE TIME. - Delta printers have better print quality. In bed-slingers and corexy printers the printing artifacts are due to Z axis lead screws wobling and GT2 belts and idlers imperfection and resonances. Due to the symmetric arangements of the A-B-C axes in delta printers (no Z axis woble) and the specific of assembly (the printing head is linked via rigid carbon arms to the A-B-C axis) this issue are mitigated in a very effective way. Just think about it: if you want to stabilize a very high pole or antenna you use 3 wires and anchors. In delta printers it’s a very similar case but you use double carbon rigid arms instead of elastic wires.

OK, we settle for a delta printer: what model to buy? Mainly there are 3 companies: FLSun (budget / consumer), Trilabs and Wasp (pro-sumer/industrial). Forget Trilabs, they were bought by Prusa and are outside of our price range (they don’t list prices on their web site but you can find on distributors prices in the 3000–5000 EUR range). Forget also Wasp — their entry-level Wasp 2040 Pro is 3000 EUR. FLSUN prices are more palatable — under 1000 EUR (in fact even cheaper, maybe inside our budget).

FLSUN flagship product (for the moment) is the V400: D300 X H400 X S400 — a fancy way to say 300 mm diameter x 400 mm height with a 400 mm/s speed with Klipper (in fact 600 mm/s in the last firmare upgrade). You can get one now for 600 EUR (at least I can get one for 600 EUR delivered to my door in about one week). Last year this printer was 800–900 EUR (and it’s still listed on www.flsun3d.com store for 900 EUR but sold out).

The FLSun flagship (for the moment): the V400.

The V400 effector: dual gear direct drive with a Volcano-type hotend.

The next printer in line is Super Racer or SR: 260 mm diameter, 330 mm height, 150–200 mm/s but non-Klipper (probably Marlin). 400 EUR on www.flsun3d.com but I can get one to my door delivered next week for 305 EUR or 330 USD (brand new) from Banggood CZ warehouse. I actually bought 2 FLSun SRs last year: one brand new for 375 EUR and several months later one “used” for 305 EUR (but probably it was just used for a test print). These SRs are my favorite printers — but I have to admit I just “upgraded” both.

What you get for around 300 EUR: a very robust frame; MGN12 linear rails; 10mm width GT2 belts; a very responsive capacitive touch screen; carbon fiber arms; a Volcano-type hotend; a dual-drive extruder with bowden; auto bed leveling and calibration; a textured glass heated bed.

The FLSun Super Racer: the little brother of the V400.

You can use a FLSun SR “as is” and you can even buy a cheap 0.3 mm Volcano-type nozzle (under 5 EUR / USD) for lighter wings. And maybe a larger nozzle (0.5/ 0.6/0.8 mm) if you want to print larger structural pieces (like parts for another 3D printer — but we’ll deal with this on the next part of the series). And after a while you will find that even if FLSun SR is a very capable printer you can still improve it (and in some cases quite cheap). For what (and how) can be improved we can take a look at the differences between V400 and SR:

• nothing we can do about the printing bed SIZE but we can improve the TYPE. V400 has a PEI-covered textured steel sheet. For around 20 EUR you can get a double sided PEI/PET sheet and with a clever trick (glue the magnetic sheet on the back of the SR glass printing bed) you can have 3 types of surfaces to choose from (to better suit the filament).

the PEI steel sheet is a good upgrade for the printing bed.

• V400 has a direct drive extruder. This is a very easy upgrade: buy a cheap ABS 3d printed or even full metal CNC-ed aluminum extruder (and I really mean cheap: you can pay 20–30 EUR including motor or buy the motor sand some gears for under 10 EUR) and 3D print an adapter for this extruder to mount it instead of the bowden tube in the SR effector (https://www.thingiverse.com/thing:5165006):

An adapter for a Mini Sherpa extruder mounted on top of the cage protecting the coldend

• if you want to improve the part cooling you can replace the original dual 4010 blower fans with dual 5015 and some adapters () but for printing with 0.3 mm nozzle this is not necessary)
• if you worry about the additional mass of the direct drive extruder (100–150 grams — depending of the material AB<S/metal and the stepper motor weight) there is a very simple and elegant solution: replace the FLSun steel cage (https://www.thingiverse.com/thing:4911018) and aluminum alloy plate (https://www.thingiverse.com/thing:5155922) of the effector (110 grams in total) with similar 3D printed parts (30 grams). You can even find some combined cage & extruder designs (https://www.thingiverse.com/thing:5223840)
• you can also replace the outdated hotend with a more modern type (Mosquito original or clone, Dragon, Bambulab X1 clone and so on) — you can save additional weight also
• and finally you can convert this 3D printer to Klipper: you can use an existing old laptop with Linux OR an old Raspberry Pi2 OR a new RaspberryPi 3A OR an OrangePi Zero OR an Android TVBox converted to Linux (all these options are in the 20–30 EUR range) OR a more expensive Klipper tablet/pad (for instance BigTreeTeck Pad 7 around 120 USD up to FLSun SpeederPad used in V400 for around 165 USD).

Both my FLSun SRs are upgraded with direct drive with Klipper and are driven by a single Speeder Pad (I could use RPi2 or RPi3 or Orange Pi or other cheap solutions but I preferred the original SpeederPad for the “V400 experience” (for the price of a single V400 from last year I have 2 upgraded SRs and the SpeederPad used in V400).

At this point you will notice that the upgraded SR is costing you around 350–500 USD/EUR and you are still very limited in printing volume (just 330 mm height). And this rises a legitimate question: can we build something better (with a higher printing size, let’s say 800–1000 mm printing height for a full wing segment) for the same cost? The answer is (as you probably guessed) positive. In the last 6 months I’ve worked on 3 different designs (all delta printers):

• a very cheap delta 3D printer (intended to be used in the local RC club for kids)
• ALT0 aka KD2580 (Klipper Delta 25cm x 80 cm) — with 1m MGN12 linear rails and 120cm 3030 profiles
• ALT1meter aka KD25100 (25cm x 100 cm) — with 1.5 m HGR15 linear rails and 1.5 m 2020 profiles

To be honest some of these designs are still WIP (Work In Progress) in some areas, I’m still doing some improvements (in order to reduce costs and complexity of the design) but the initial results are very promising. And of course I will tell you about these designs in the next part.