Lowest percent fill settings?

[Elbot]

What's the lowest percent fill settings possible? What have you done to test the limits of your printer? I'm thinking about doing one the following to print a RC plane with for light weight. I don't want to stick a mylar skin on the plane. I want it to be 100% printable with almost zero assembly afterwards. It should take a 7 year old child 10 seconds to put together; 
A. 5% with 1 extra shell and 0.2 mm layer heights.

B. 5% with 0 extra shell and 0.2 mm layer height.

C. 5% with 0 extra shell and 0.1 mm layer height.

D. 2% with 1 extra shell and 0.2 mm layer height

E. 2% with 0 extra shell and 0.2 mm layer height

F. 2% with 0 extra shell and 0.1 mm layer height.

[Cymon]

Uh, I've done zero infill with 0 extra shell. Even took off the top and bottom fill layers. Do I win?

[Andrew Plumb]

I've been taking a different approach. To get my prints as light as possible I design the wall thickness to be even-integer (2,4,6,etc) of the nozzle diameter - 0.4mm in the Replicator case. Then I zero out the fill.

I'm not sure how well printed PLA or ABS will stick directly to Mylar, but you might be able to adapt my PLA-on-tissue-paper approach to the task: http://www.instructables.com/id/3D-Printing-PLA-on-Tissue-Paper/

Andrew.

--

"The future is already here.  It's just not very evenly distributed" -- William Gibson

Me: http://clothbot.com/wiki/

[Elbot]

No, I don't want to use mylar. That's the whole point of this. I want to use the printed part directly on the model with zero assembly time and zero fuss. Ideally, you just pluck the plane off the Replicator and it flies, but the Replicator's HBP is too small for that. Plus, you can't print electric motors and microchip controllers... yet (with current technology) with a Replicator.

Yeah, you always win Cymon. I luv your stuff on Thingiverse. Hmmm... maybe I can print totally hollow stuff with 0% infill as long as I'm mindful of the 45 degree overhang rule. However, if I am NOT mindful of that rule, what is the lowest infill I can do and what settings should I do it with? If possible, I'd like to print complete wings for airplanes at 2% fill.

[Andrew Plumb]

On 2012-11-04, at 10:56 AM, Elbot wrote:

No, I don't want to use mylar. That's the whole point of this. I want to use the printed part directly on the model with zero assembly time and zero fuss. Ideally, you just pluck the plane off the Replicator and it flies, but the Replicator's HBP is too small for that. Plus, you can't print electric motors and microchip controllers... yet (with current technology) with a Replicator. 

Yup, same goal; different compromises.  By printing the skeleton directly onto paper I'm able to keep things light enough to single-print an almost-complete plane.  I trim off the excess paper, snap the v-tail into position, add some LEGO-weight to the nose and it's ready to sling-shot/rubber-band launch.

On a related note, I just received my Plantraco DSS-2 kit last week and have started taking measurements and doing some OpenSCAD coding over the weekend. 

[Cymon]

So your concern is support? Because it seems to be your seeings would vary greatly on the geometry of the part. I haven't had a chance to test this but I feel like the placement of the latice fill is actually independent of the geometry meaning you could move the part 0.2mm to the left on the build platform and the latice would shift inside the part, or in other words the latice wouldn't shift with the part. But like I said, I haven't had a chance to test it. But if this is true it's not merely about infill but also about placement.

But generally I use 10%.

[Elbot]

ok, i'm gonna conduct a test and report back to the forum / group. gonna answer the question, "what's the lowest infill you can get away with if you want to print an airplane's wings. I wanna build a snap together rc plane. that one currently featured on thingiverse is WAY too complicated. I can't easily build it and a 7 year old child certainly can't do it. I wanna build one that will snap together in 10 seconds or less. Almost pluck it straight from the printer and it will fly.

[Dan Newman]

Have you seen

http://www.thingiverse.com/thing:32845

It's not R/C but using components from Plantraco you could make one.
Indeed, clothbot, aka Andrew Plumb, aka the chap who did the above
cited thing, just mentioned getting the component kit DSS-2 from Plantraco.
So, if you wait a little longer there may be a new version of Thing 32845
which is R/C. Should work pretty well indoors too. (I have one of the
original Butterflies from Plantraco circa 2005.)

Dan

[Andrew Plumb]

On 2012-11-05, at 12:51 AM, Dan Newman wrote:

On 4 Nov 2012 , at 9:23 PM, Elbot wrote:

ok, i'm gonna conduct a test and report back to the forum / group. gonna

answer the question, "what's the lowest infill you can get away with if you

want to print an airplane's wings. I wanna build a snap together rc plane.

that one currently featured on thingiverse is WAY too complicated. I can't

easily build it and a 7 year old child certainly can't do it. I wanna build

one that will snap together in 10 seconds or less. Almost pluck it straight

from the printer and it will fly.

Have you seen

http://www.thingiverse.com/thing:32845

A better fit to his own goal of 3D-printed-plastic-only may be the Bukobot Fly that I derived my variant from: http://www.thingiverse.com/thing:22268

If he splits it into parts, scales up the XY dimensions (leave height/thickness unchanged) and designs in snap-together mechanics (LEGO-compatible is useful that way) it may be a large enough airframe to support more robust electronics.  The Plantraco kits (like the DSS-2 I'm using) are likely too fragile to qualify as "easy to build", at least as a first-learner kit.

[Elbot]

Great idea, but sadly it wouldn't work very well. I just took a look at the Bukobot airplane you pointed out and here's my thoughts;
1. air has a small amount of viscosity, so the Bukobot fly doesn't have to have a perfect airfoil shape and it will still fly. Same goes for a paper airplane. The Bukobot fly has a very rudimentary airfoil that is not a true airfoil shape. It is just a cylinder laid flat with a plane behind it.
2. everything "flies". it is just a matter of power to weight ratio. However, the Bukobot fly, if scaled up, due to lack of proper airfoil would have a horrible glide ratio. That would mean that it would take way too much power to be a simple and inexpensive rc plane. I could strap a rocket to it and it would "fly" but "Buck Rogering" is not my engineering style. I enjoy making stuff that is extremely simple, inexpensive, but can still do the same job that a less elegantly engineered product could do.

Plan of action;
1. make airfoil
2. print it
3. test structural strength to failure
4. reprint it
5. wind tunnel test
6. repeat process as many times as necessary

This will probably take a whole year to complete....

[Elbot]

electronics are going to be extremely simple. no control surfaces at all. 2 motors; one left and one right. You control motor speed independently on two sides to change flight direction. all my rc planes are built this way. This setup simplifies the build and the learning curve to learn to fly it. It is also very inexpensive so if you lost the plane (I have lost all my planes) it wouldn't sting as much. it is very easy to lose a plane if you fly in extremely windy conditions.

everything i make is inexpensive and simple, yet totally functional.

[Andrew Plumb]

On 2012-11-05, at 12:16 PM, Elbot wrote:

electronics are going to be extremely simple. no control surfaces at all. 2 motors; one left and one right. You control motor speed independently on two sides to change flight direction. all my rc planes are built this way. This setup simplifies the build and the learning curve to learn to fly it. It is also very inexpensive so if you lost the plane (I have lost all my planes) it wouldn't sting as much. it is very easy to lose a plane if you fly in extremely windy conditions.

everything i make is inexpensive and simple, yet totally functional.

Cool!  I've only flown RC ornithopters to date, so very different design goals and flight conditions. :-)

Going with something like a DelTang Rx31d or Rx41d on the electronics side?

[Elbot]

No, the Deltrang is $42 USD. That's expensive if I'm paying that for just the electronics, not including the motors and batteries. It would sting if I lost that due to windy flight conditions. I pay less than $30-60 for el cheapo components boxes from China that includes;
2 very high power motors
1 x radio control box
1 x 2 channel radio receiver
2 x nicad batteries
propellers, wheels, and assorted foam pieces.

Every time I go to China, I come back with a whole suitcase full of el cheapo throwaway stuff.

[Elbot]

BTW, I didn't know that RC ornithopters exist! The power to weight ratio must be ENORMOUS as the glide ratio for any ornithopter must be dismal due to animals having a large body in relation to the wing size. Also, the mechanics of the flapping wings must be really a bear to make due to complexity. Kudos to you!

[captchemo]

So, are you more concerned with weight to strength ratios, or bridging the skin during the print (in regards to the fill issue)?  I don't have a lot of experience with RC planes, but at these smaller scales, wouldn't the power you get from the modern motors now available for RC compensate for a "little extra weight" from the extra fill?  Especially if the airfoils are generous.  I apologize if that is a sacrilegious statement...;) 

I think it's an awesome project.  I've stayed away from Andrew's stuff (so far..) and I really wanted the Flying Towel after seeing it in action at MK Detroit this summer.... I'm trying to scale back my hobbies right now, and RC planes are very high on the Oh Yeah, Gotta Do That list.

[RocketSled]

On Tuesday, November 6, 2012 9:26:45 AM UTC-5, captchemo wrote:

So, are you more concerned with weight to strength ratios, or bridging the skin during the print (in regards to the fill issue)?  I don't have a lot of experience with RC planes, but at these smaller scales, wouldn't the power you get from the modern motors now available for RC compensate for a "little extra weight" from the extra fill?  Especially if the airfoils are generous.  I apologize if that is a sacrilegious statement...;) 

I think it's an awesome project.  I've stayed away from Andrew's stuff (so far..) and I really wanted the Flying Towel after seeing it in action at MK Detroit this summer.... I'm trying to scale back my hobbies right now, and RC planes are very high on the Oh Yeah, Gotta Do That list.

I'm an avid RC flyer, airplanes and helis. All my models are electric.  The smallest fully aerobatic model I own is a 12" span biplane called a "Beast", a semi-scale Pitts-12 stunt plane.  The radio gear is integrated on to a single PC board that's about 1" x 1.25".  The board has the spread-spectrum receiver, two servos and a brushless motor speed controller.  It weighs 6.4g.  There are also two other servos, one each for left/right ailerons, that weigh a scant 2.3g each.  The airplane is mostly foam, so it has a flying weight of only about 72g.  But this plane is designed for "3D" flight.  It has a much > 1:1 power/weight ratio, the plane can "hover" on the prop like a helicopter.  The power system would easily fly a model weighing 4x as much.  ~280g, or 10Oz, that's a lot of plastic.  I bet you could print a flyable plane in the 12-15" wingspan range on that budget.

I've been thinking of this kind of project myself.  But I had been thinking to print just the airframe, and cover it with thin foam sheet.  More involved for sure.  Maybe not necessary.  RepG will tell you how much plastic it needs for a print.  It'd be easy to see how much of a budget you have to work with.

[66tbird]

I'm also an avid RC nut and a printable airplane using the vapor brick has come off my board. I'm just not ready to give it up yet. It is possible, and it does work, its sub 25gr and it's sporty as heck. 

[Elbot]

Yup. I just printed out an airfoil made of ABS foam from my Replicator. It is just as light as RC hobby foam but much stronger. I am testing it now. As soon as it is thoroughly tested, I will post it on the web for all to download.