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Jul 27, 2017, 10:42 PM
one man's trash
Discussion

Design and printing tips?


Hey everyone, I am currently working on a 3d model of an OV-10 Bronco. I will be giving the model out for free when it is finished. I am attempting to design the airframe with inspiration from 3dlabprint's wonderful styles. I have just "finished" the outer portion of the model, with mounting points for 9g servos. I am in the process of adding channels for the wiring and finishing off small things before I skin and lattice the model from it's (current) solid state. The model is meant to be as scale as I could make it with the software that I use (designspark mechanical - 'cause it's free), and it was made from multiple scale drawings.

There is still a lot of work to be done before it is ready to print, but I thought I would share and seek advice while I am still designing the model. I plan on making a skin of the solid model and filling the inside with a type of lattice structure. In the example spitfire part from 3dlabprint on thingiverse, it looks like the models are 0.4mm thick for both skin and internal latticework. This is how I am planning on structuring my design. The main fuselage/cargo bay will be thicker, but it's not clear how thick just yet.

A list of what is left to be done:
-add channels for ESC and servo wires from booms to fuselage
-design and add motor mounts ( I have a few 1806 laying around so they will be for 1806)
-skin the solid parts and add internal latticework
-split model into printable size files
-decide on and incorporate a method of securing printed parts together
-add LED mount points

I wish I could test the aerodynamics of it, but I lack any capable software and cannot afford any that I've seen The airfoil was made to the scale drawings so hopefully it's great

I do not have much formal training in CAD but I have about 8 years experience designing and printing. This is the most complicated project I have undertaken so far, but I'm hoping for the best!

If anyone has any suggestions or comments, I'd love to hear them! I am open to design changes, so long as I'm capable of doing it.

Attached are pictures of the model and the prospective lattice shapes.
Thanks for looking!
Last edited by DengisKong; Jul 27, 2017 at 11:24 PM.
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Jul 28, 2017, 03:40 AM
one man's trash
Something like this
Jul 28, 2017, 08:46 AM
Registered User
DengisKong
That looks very interesting.
Is there any particular reason why you have chosen to build up the internal structure in a series of curves?
My understanding is that a printed skin is sufficiently strong to take the required loads but being so thin requires adequate support, particularly when under compression, to prevent buckling.
Your support design appears to leave quite large skin areas without internal support or am I missing something?
Jul 28, 2017, 12:01 PM
Registered User
Rudix's Avatar
Quote:
Originally Posted by DengisKong
Something like this
I like your structure! A really interesting project and a nice subject to model! If you ever want someone to do some test prints I would be more than happy to help!

Keep up the good work!
Rudi
Jul 28, 2017, 01:31 PM
Registered User
Very nice work! It's great to see how someone else is approaching the "design problem". 3DLabPrint sure set a high bar for the rest of us to follow

When I look at your wing drawing it appears you are using a separate spar - am I interpreting your drawing correctly?

Thanks!

Rob
Jul 28, 2017, 03:49 PM
Internet Pilot
fATAL's Avatar
You can't afford xflr?
Jul 28, 2017, 04:41 PM
one man's trash
@Quorneng - There is no particular reason the supports were made with a series of curves as it was thrown together in a few minutes to do some test printing. As you noted, there are large bare areas that will need some more support if they are going to make a durable model.

@Rudix - Thanks, buddy! I'll let you know as soon as I have a working printable prototype I'll need some test pilots for sure!

@Stangrob - The internal channels you see are for the servo and esc wiring. I have been toying with the idea of inserting a spar in the wing but haven't come far enough in testing to determine if it's needed or not.

@fATAL - I did not know about this program before... thanks, buddy! I just barely afforded it, lol


I did a couple test prints of the servo slot and wing tip with internal structure. The parts look pretty good, although the interior structure is not quite as robust as needed. I also had to increase the output precision of my modeling software as the first model was a little crangled (the software was set to allow 0.5mm deviation in exported model vertices). As the walls of the wing and the internals are ~0.4mm thick, these thresholds were not working. Some of the support areas turned out very strong, but there are some bare areas (as noted by Quorneng) that need more structure.

I'm hoping to not only get my design in the air, but also to present guidelines and modeling techniques for others to learn from my experience.

Will update soon!
Jul 28, 2017, 05:49 PM
Retired CAD guy
birdofplay's Avatar
For designers the Low sloping Curved interior is to make PRINTING work better.

Horizontal stuff tends to , umm, NOT WORK well , if at all, without supports and
supports on the Interior would NOT be removable.

As it is the 3dlab stuff leaves "some" strings and adhesion's.
Maybe that's just my printers' problem or some errant settings on my part.

More of an issue for me has been the lack of good alignment of stacked mating parts.
I have been hoping to do a better job of the matting surfaces with
the addition of some continuous "lips" for better alignment and better gluing surfaces.
I also want to try some of the NEW Raptor PLA as I have been noticing lots of
temp warping due to Sunny exposures.
That happened to my Cessna and my Spitfire.
So I have stopped 3dptinting RC models until a good cure has been identified.

This project does look like an interesting one.

hang in there and keep u the good work.
Aug 29, 2017, 09:06 PM
Registered User
rajazo's Avatar
Beautiful work.
A couple of advice about the bronco :
the twin boom produce lot of twist on the central part of the wing. Maybe needs more stiffness on the trailing edge section.
A good idea will be use a separate external section of the wing (outside the booms) one with original proportion and other longer to improve the the performance.... Bronco has to short wings and 3d printer is not the lighter material.
Aug 29, 2017, 10:39 PM
WJH
WJH
B747-400 First Officer
WJH's Avatar
PLA's... The natural color, with no pigment, seems to be the strongest. I love printing more conventional stuff with ABS. So much better than PLA, but trickier.
Aug 30, 2017, 12:41 PM
Laughs at un-boxing videos...
basicguy's Avatar
I really like the Bronco. Glad that someone is printing one.
Aug 30, 2017, 01:07 PM
Retired CAD guy
birdofplay's Avatar
OK it's expensive , but has anyone tried and or compared the MakerGeeks Raptor PLA ?

It's SUPPOSED to be higher temp resistant and possibly better for
my poor warping and distorting Model parts.

I'd have tried it but they don't take Paypal.
I wrote a couple of days ago about that issue and some others but NO REPLY YET !

sigh ........
Aug 30, 2017, 01:28 PM
MorganTech
Try Push Plastics, they have some great HighTemp PLA. I've been using it on the 3DLabPrint airframes with great success.
Aug 31, 2017, 08:34 AM
Retired CAD guy
birdofplay's Avatar
THANX, I just did ! bookmarked em too ! ;>}

Simple easy ordering using PP. refreshing

Got a roll of CLEAR Hi-Temp PLA with the free shipping as a test order.
we'll see how it go's !

They appear to be a good source with USA made products.
Sep 05, 2017, 06:49 AM
MQ-5B Driver
Doug Cronkhite's Avatar
I wish I had your 3D skills.. I really want to design and print a wingeron slope glider.. The 3D printing stuff opens up a lot of possibilities..


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