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Dec 09, 2017, 06:02 PM
Retired CAD guy
birdofplay's Avatar

What about those darned Mating edges ?

Is it just my dumb old thumbs or paranoia about my Super glue setting up before I get things lined up ?

I've printed several 3dLab designs, AeroFreds lilSchtik, Balfor's Fuse, and Carletto's Gasb 1 & 2.

They are all a works of art and took insane amounts of CAD time to create.

But, All of those wonderful designs give me fits when assembling.

I have tried gluing little pieces of scrapped prints on the insides to help align edges
but, I always manage to disappoint myself.

So my question is ...

Why not put in a little more effort make those edges more ...
Self Mating
easily aligned

It would turn all those Works of Art and thousands of hours of effort intoTrue Master Pieces !
Last edited by birdofplay; Dec 09, 2017 at 08:01 PM.
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Dec 09, 2017, 09:49 PM
Laughs at un-boxing videos...
basicguy's Avatar
I always make a joiner. My technique is to cut the fuselage back a half inch or so on each piece, then put in a offset surface on the inside finally thicken the offset surface and combine the two joiners to make it bridge. There is probably a better way but it is what I have figured out.

Here is the joiner for the fuselage I uploaded .

If you want to make the sections removable glue one side and use a few screws on the other side.

You are right Bob, at least for me, there is a lot of time even on my simple designs.
Dec 10, 2017, 05:08 AM
FDF - Front Door Flyer
derfred's Avatar
It has to do with the process, at least in my case. You design, export the meshes and then slice the meshes, the tabs would have to be added after the meshes had been sliced and its not easy to design over meshes.

On my next one I will start thinking about this at an earlier stage and define where the bodies will be sliced for printing leaving the alignment feature in those places.

I was thinking about a simple solution to this, the 3dlabprint method works fine and its clean but in my case it would require me to draw over a mesh and I donīt want to do that, probably its not even possible so I was thinking about leaving a piece of tube on each one of the parts then use a bit of filament to align the parts.

Making a kind of step interlocking or rectangular or triangular dovetail would be a good way to align, as a lego like system would, the problem would be the above or if you could solve the design issues you would then need to add supports to the prints.

My next plane will be a Klingberg wing, 2 meter span. Bob, you can count with an alignment system on that one

Klingberg wing:
Last edited by derfred; Dec 10, 2017 at 06:20 AM.
Dec 10, 2017, 09:06 AM
Retired CAD guy
birdofplay's Avatar
Basicg & Derf

Totally agreed doing redesign using the STL's.
Very messy and sometimes the results do not come thru as expected.

It appears that 3dlabs have in most cases attempted to do some alignment tabs.

But, again I have to point out that aligning 1 perimeter edges
is NOT easy nor in most of my cases clean, let alone pretty .

Edge rework is Not something to be undertaken lightly
especially when considering designs with as many separate parts as ... Oh ... Say
the new Dusty Agplane from 3dLabs
It's like around 60 individual parts.
It's another beautiful, intricate, thoughtful, design ,
but, wheeeew , lots of edges to align.

I have a Larger format 3dPrinter with a 400mm Z volume. FT-5
That feature alone allows me to "Sometimes"
edit two STL parts together and print them at the same time.

But that is only a partial solution.

With a Carbon 3d printer it might be possible to pull the whole thing out of a puddle.
However the cost of one of those is staggering.

I envision a edge that is slightly tapered on one side
which allows the mating part to slide into place and SEAT perfectly.

Will it add weight ?
I presume so.

Will it save weight and time due to rework and fill time.
Likely !


1. There is likely a Parametric CAD out there that could possibly make all those "edge treatments" an easy to do task.
Or ...

2. Something like a "Utility" or Custom Command in the Current CAD's that just processes the HIGHLIGHTED "Edge Lines"

Regardless, Thanks for the Responses
Last edited by birdofplay; Dec 10, 2017 at 09:11 AM.
Dec 10, 2017, 09:20 AM
Suspended Account
a slower setting CA will get u past ur issue..
Dec 10, 2017, 11:54 AM
Retired CAD guy
birdofplay's Avatar
but wouldn't it be nice to have things aligned all the way around those edges ?

Here's a pic of what I was considering.
It took about anhour to do just this ONE test and ...

Yeah It looks sort of nice,e but I managed to NOT create manifold edges so it won't print.

That's the part about these designs that drives me crazy.

I am missing something salient about the process.
Dec 11, 2017, 08:51 AM
FDF - Front Door Flyer
derfred's Avatar
Instead of those faces try to draw solid bodies with just 0.2 or 0.3 mm thickness.

But still that would be drawing over a mesh that is something Iīm not inclined to do.
Dec 11, 2017, 09:14 AM
Retired CAD guy
birdofplay's Avatar
I made Solids all the way along that edge but then I realize the need for clearing some
interference's and did some Splitting of those Solids which MUST have resulted in
"open ends" .
I should have done Solids Difference which leaves the solids CLOSED on the cut faces.

However, I've spent W A Y too many hours fiddling with that effort already.
I can't imagine all that effort for EACH "edge" treatment.

I/we have to figure out a better approach and attack strategy.
Maybe even better "tools" .
Dec 11, 2017, 09:37 AM
Laughs at un-boxing videos...
basicguy's Avatar
Yes better tools, especially for us non-engineers.
Dec 11, 2017, 12:10 PM
Retired CAD guy
birdofplay's Avatar
And for those of us who cannot afford those tools , whatever they may be.
Dec 20, 2017, 02:19 AM
Registered User
dpot's Avatar
i use a use a offset serif on joints on PLA it gives a stronger joint and found that but joints can brake and glueing PLA is not easy ABS is easier but that will brake next to a joint anyway.
with rhino you can edit STL ferley easaley.
Dec 20, 2017, 02:32 AM
FDF - Front Door Flyer
derfred's Avatar
I think that will not print very well Have you tried it?

I was thinking about other solution that doesnīt requires supports.

Half tube on one side, half tube on the other side and a piece of filament or a custom made printed part to join the half tubes.

These tubes are put in place during the design phase when the fuselage is still one piece at the approximate place where you know you are going to split later.

When you then split the large objects you get the halves.

You can put 4 or 5 or you can put 25 its up to you.

Or you can put round section tubes or you can put rectangular section tubes and print small pieces of plastic to make the joint.
Dec 20, 2017, 04:04 AM
Registered User
dpot's Avatar
there is a bit of cleaning up to do with supports but it give a very strong good joint but i could do a separate print for the joint then i could just print the outer shell of the fuz then add after
Dec 20, 2017, 04:53 AM
FDF - Front Door Flyer
derfred's Avatar
Looks good. The separate joint looks simpler to design and print. Its a good idea.
Dec 20, 2017, 08:35 AM
Retired CAD guy
birdofplay's Avatar
Using a slip fit is great for new designs.
Basicguy has done so in some of his.
The alignment holes is another good way to go .

Having a larger format printer means I will be trying to
COMBINE as many parts "as Possible" for printing together
which will reduce the number of joints all together.
I'll be trying this on the Dusty Ag g plane.

Still I need to Experiment with those pesky 3dlabs files
to see IF I can come up with a methodology to develop better joints , where needed.

Dpot, I agree that rhino does allow for some Mesh editing , I have to say it's NOT FUN.
Yet I still have NOT found a NICE, yet free, mesh editor.

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