ECHO Slope Wing

[Yotaman1985]

Thanks Jure, Ive been trying that but when I slice it with a plane or line or anything, the whole part disappears even though I have keep both parts selected. They also aren't hidden from view because the seperate parts dont show up in the parts list so not sure exactly whats going on. Im guessing its not liking it since its and airfoil thats swept and lofted

 

[OribaSJ88]

Doing it by hand is only really needed if you want to print in vase mode, which is how the foaming filaments print well.

Look at Geode's planes and most other 3DP planes on RCGroups, they almost all use the slicer's infill options. The Slingshot that MOM is using is also using slicer-based infill.

The thing that bugs me about the SoarKraft models is that they have hand-drawn internal structure while still not being vase mode compatible. IMHO it makes the design too sensitive to differences in slicer versions and a wide array of settings and filaments.

And yeah, I have found that doing anything to the model in the slicer (like cutting it up to make it printable) is a terrible experience.

I will concede that I've never printed a SoarKraft plane but I took a lot of inspiration from how Waynesie designed them and, to a lesser extent, how they are modeled. The control he exerts over every feature of the model, by not relying on slicer infill, is very impressive. I wish I knew how to achieve that!

Design for 3D-printed aircraft of any kind is a long discussion in and of itself. It has its own learning curve and I can't do it justice here. Different designers approach it in different ways. I don't profess to be anything more than an experienced hack. Looking at some of the available designs that some have offered is the right--the essential--place to start. Geode's designs would be a good starting point to have an idea of the work involved.

Making 3D-printed prototypes to evolve the aerodynamic design before committing to molds makes sense to me because I've already developed my "3D printing bag of tricks". And, there's no one bag of tricks. Without that experience, it would require a whole new learning curve unrelated 3D printing for mold making. There's a lot of good discussion over on RCG, but it's a big pill to swallow. I'm still learning and banging my head against the wall on things I don't fully understand.

In the briefest of terms, turning a solid model of a sailplane into a printed design starts in the whatever 3D modeling program you're using. It's important to always have in mind how the slicer is going to "interpret" any feature that you model. I never use the slicer to cut up a part for printing. The 3D model drives the slicer. If I don't see what I want when I slice, I fix the model. I rarely adjust slicer parameters to fix. The line width and layer height you plan to use for the printing are kind of "golden feature sizes" that need to be kept in mind when creating the 3D model. Things that are too small/thin will not print well or at all. A good example is the trailing edge of any flying surface. Newer slicers treat this differently, but a good rule of thumb is that the trailing edge should be twice as thick as the line width you plan to print with--typically 0.4mm for wings and such. Modeling the control surfaces and the hinging is another can of worms. The thin walls we print also creates many other challenges that affect the strength and durability of the finished model. This is only scratching the surface.

I can see why the modeling and 3D printing of the molds was a more straightforward place to start. It brings a new way of making the mold to the art of making molded sailplanes. It avoids lot of what I mentioned above because the 3D-printed pieces for the mold fall into more "common" types of printed parts. They can have thick walls and relatively high infill. Those two things makes everything more straightforward for printing.

Whichever way you guys decide to go, it's a cool project. I wish you guys the best of luck.

Ollie

 

[zeo0nie1]

The control he exerts over every feature of the model, by not relying on slicer infill, is very impressive. I wish I knew how to achieve that!

totally, agreed.

 

[Yotaman1985]

Sanded down my molds today and sprayed the first layer of high build primer on them. Waiting for them to cure and then Ill wet sand them and do at least one more coat/wet sand. I have some more work to do on the molds now that they are painted and I can see more defects. After the primer stage is done and the molds are ready, Ill be coating them in an epoxy coating resin and then wet sanding and polishing that.

 

[thenated0g]

Just showing the facets that show in the print. Very easy to remove with sanding. Actually was very impressed with how easy pla is to wet sand quickly to a nice finish.


Top half parts getting glued together with Gorilla glue. Very easy cleanup with a scraper and than some light sanding.


Marking the trailing edges with silver sharpie. Before sanding it was getting hard to find the lines.


Vertical stab molds sanding and filler/primer applied. Wet sanded to 1000 grit.


1st coat primer on bottom half


"fixing" the alignment holes

 

[jakem]

Very Cool!! I've done a bunch of 3d printed molds with pretty good results. I've tried that xcr stuff and it was a pain the ass to sand. I've had really good luck with 3d printer uv resin. I wipe it on one tiny layer at a time, hit it with uv and repeat. I've found it the best way to keep the airfoil. Also the mold(pla) will move around. You can look at it in the morning and its smooth and come back later in the day and you can feel the seams. I started gluing the molds to aluminum extrusion to try and keep them straight which seemed to help.

Will be following you guys to see the final product!!!

 

[Yotaman1985]

Well, I had a setback as I learned about PLA and sun/heat. I let my molds get too warm while trying to dry the filler primer and the molds after wet sanding and they warped bad. The top mold also started spiting at one of the seams so going to have to reprint them and try again...

 

[thenated0g]

Bottom mold:
i did the 2 in 1 primer as seen in the previous pics and that came out great. Super nice finish. The problem was when i went to add the XCE resin on top it was not happy. Tons of areas where it would just totally leave the area. So empty spots of resin across the whole thing. It did this on the top part and the two halves of the vertical stabilizer mold. In later applications i noticed it does the same thing with sharpie lines. Does NOT like it.

I tried spreading, adding more, removing some. Ended up wiping as much off as i could.
I sanded it back down to 400 and used a different type of epoxy, "150" thick epoxy from usacomposites. This had no issues going back on asside from some "bubbles" ill talk about in the top mold area.

Top mold:
With the issues between XCR and paint, and the fact that the pla is so quick and easy to wet sand to a nice finish, i went straight to XCR resin on the pla, but a very light coat. This had zero chemical issues over pla, except where i on purpose went outside of the part area and crossed my silver sharpie lines.
The only issue im having is a lot of little tiny bubbles, super tiny, raised maybe 1mm off the surface raised of the surface. Hot gun and lighter had zero effect. So i sanded just the surface defects down and did a second light coat.
im wondering if i need to degas or if this is some physical effect of the pla?

I checked the second coat of XCR this morning and while it is doing the same thing, the second coat has significantly less surface issues. So im going to sand it down to 1500 ish and using some self destructing polishing paste to get it ready for making parts.

 

[Wayne]

Ahh, the chemical fun stages have begun. Seems like this is always the biggest headache, figuring out what chemicals will work with any other materials. Sadly this can be the biggest stumbling block. Everytime I changed a paint or anything in the mix it was a risk that I was going to have some fun new challenge.

 

[thenated0g]

Exactly. Was talking to @Hawaii Sloper last night about getting a bunch of different spray paints and making board with them all on it, labeled and than cover with the epoxy and see what happens.

 

[thenated0g]

Started working on the v2 molds i want to try with ultracal 30 mold making concrete stuff. I have used it before, it makes a super nice finish.

So instead of 3d printing the mold i will 3d print a positive part that i can than make a mold from.
I took the model @Yotaman1985 made and sliced it nose to tail and placed it on a base. This form i will screw down to a board and hot glue a dam around it before pouring the ultracal 30 or building up with epoxy/fiberglass.

 

[thenated0g]

I added holes for alignment pins, which i will 3d printer later so i dont need supports. I also added smaller holes for wood screws.

Since it wont be under vacuum i can make it much lighter and significantly faster to print out.

 

[Wayne]

I think this may well be the better direction.

How hot does the ultracal 30 get when curing? That is my only concern.

 

[Yotaman1985]

Looks great Nate. I am in the process of reprinting the mods with a bunch of revisions from the first ones I printed. Hoping to have one side printed out by the weekend and then will start prepping it to get back to where I was before my set back.

 

[thenated0g]

I think this may well be the better direction.

How hot does the ultracal 30 get when curing? That is my only concern.

Good point Wayne. I had planned for this a few weeks ago and forgot about it.
My original plan was to print this in petg as its just above what ultracal hits. Guess i need to order some petg.

Im still not close to doing this mold as i want to pull at least one set of parts off the ones im doing.

 

[Wayne]

Also, watch out, not all PETG is the same. HF can be different than normal, etc.

 

[thenated0g]

Your not supposed to let ultracal 30 get above 120f and i think pla deforms around 130...so could work.

 

[thenated0g]

oh interesting, this may be just fine no matter if it gets too hot:

"While it does heat up rather quickly, it is already very firmly set by the time the temperature starts to rise. You should have no problem with removing the tool from the glass before it gets too hot. It will be soft but nowhere near like anything that would change shape. "

 

[Red]

This is an awesome project. I'm sure you know this already but I want one hahaha

One of the great benefits of composite construction is the ability to get a razor sharp trailing edge. In the future you might consider adding a trough or ditch right at the trailing edge to make this easier to achieve. This allows the cloth to "pinch" tightly at the TE, gives the extra material a place to go and gives a high definition edge to trim to after the part is cured and released from the mold. If you don't allow clearance for the cloth in the mold with this or some other feature, the mold will be held open some amount leaving a more blunt trailing edge. Of course this may not be important to you in which case please disregard, but I thought I would mention it.

You can see I also have a feature around the LE for cloth runout as well. This was important to me to preserve airfoil fidelity.

 

[jure]

...
So instead of 3d printing the mold i will 3d print a positive part that i can than make a mold from.
...

this brings you to an earlier suggestion I made:
to use the 3D printer to produce a positive plug , and from this plug make the negative mold(s).

as the plug will not be designed to fly , you do not have weight or structural constraints ,

you have one objective : a solid and accurate plug