Tilting 3D Printer for 90 deg overhangs?

Hi everyone,

altough I am new to the forum, I am building and using RepRap 3D Printers for about two years now.

I have always hated the problem with overhangs and never liked to use support material. But after listening to a mathematical student, who developed the idea of rotating the objects during the print to overcome the problem, I had a slightly different idea: why dont we tilt the whole printer.

I found some ideas where people wanted to tilt the build platform but none where the whole printer is being tilted. Is there any project like this out there?

I have seen printers printing vertically, so theoretically it should work. To reduce the hardware complexity, I would use a polar coordinate printing system like the R-360 or the PiMaker. I also think that tilting it about 45 deg into both directions would be sufficient for many/most cases.

Now I would like to know what you think about this idea?

Edited 2 time(s). Last edit at 12/13/2013 07:50AM by Fabricate.

Printers can print upside down and sideways. Bottomline: gravity has nothing to do with it. Plastic forces are an order magnitude above gravity. You still have the 45 degree restriction. So regardless of layer orientation the edge of one layer can not extend more than one layer height off the previois layer.

You can tilt the nozzle and do some angled slicing to solve the problem. You would need a 4DOF+ printer like the Sextupteron. [youtu.be]

I do not think, that gravity has nothing to do with the 45 deg angle of printing.

But I think I should make a little bit more clear, in which scenario I see a benefit for such a printer. Of course it will not solve all the overhang or bridging problem, but it could solve some.

I am thinking about printing a sphere with just one perimeter, without infill and without support material. I would cut the base of the sphere, so that it can stick to the build platform. Then I would tilt the x axis to about 45 degrees and start the printer until it gets to the center of the sphere. As the whole sphere rotates on the build platform now at about 45 deg, it is important for the new layers to cool down quite fast (after the built platform has rotated at about 45 degrees). Now, when the print reaches the center/middle of the sphere, I would tilt the x axis to -45 degrees and continue the print until it reaches the top.

I think you are right that there might be also some other difficulties (especially at the top of the sphere), but I think this concept would allow us to print at more than 45 deg.

That will work.

Some thing like this?
If now can you provide a picture.

Spherical Induction Motor
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Gyroscope
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Quote
nicholas.seward
That will work.

Great!

As I understand the problem with the overhangs at the moment (if I understand it correct) is that there are two forces: Gravity and some kind of sticking force between the individual layers of plastic. If the angle between gravity and the layer sticking force is to much (assume over 45 deg), layers start to fall down. So my idea is to reduce this angle by shifting gravity a bit !

As I figured out now, just tilting one axis is only sufficient if the object is completely symmetrical (ie. rotational). Otherwise you would always need two tilting axis (along x and y), no matter which type of machine you have.

@A2: nice movies, but my idea is different. I am trying to make a small sketch of the idea as soon as I can, at the moment I have just a rough concept on a sheet of paper. Any sugestions which tool is best suited for designing a complete machine. Atm I am quite familiar with openscad.

FreeCad
[www.freecadweb.org]

Windows download page, there are other OS supported go to home page for list:
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Description
FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is 100% Open Source and extremely modular, allowing for very advanced extension and customization.

FreeCAD is based on OpenCasCade, a powerful geometry kernel, features an Open Inventor-compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt. FreeCAD runs exactly the same way on Windows, Mac OSX and Linux platforms.

Solve Space (This has a lot of potential. I am going to try to use in on my next project.)
DesignSpark Mechanical (Haven't tried but looks good.)
OpenSCAD (Amazing but there is no GUI.)
sketchup (For completeness

FreeCAD is workable but I would rate it below the top three options I listed.

Whether you believe me or not, gravity doesn't come into play here. (much, it is a second or third order effect.) The 45 degree restriction is relative to you nozzle. As a quick test tilt your printer at 45 degrees and print an inverted cone with a 45 degree overhang. I am sure the top side and the bottom side will be almost identical.

Thanks for the hint with FreeCad, looks great. Unfortunately, I have already startet to design a sketch witch OpenSCAD.

I just illustrated the example of the sphere in the two different stages. But the process is not ment as a strict 2 (or even 3) stated tilting feature but as a continuous movement between -45 deg and 45 deg.


This image shows the process at the beginning of the print (the lower half of the sphere). The picture is a little bit misleading becaus the print is exactly at the center of the sphere and therefore the tilt should be zero (horizontal).

This image shows the process close to the end of the print (the upper half of the sphere).

I hope the pictures make the idea a bit more clear.

Oh, I thought you meant tilt the nozzle relative to the platform. This is unlikely to work for the reasons I have stated above. When one layer sticks out far from another layer regardless of gravity then it will curl. For a thin shell print like this at some point the plastic will curl so far that the nozzle can stick the next layer to it.

So, now I corrected the error in the first pic. Here is how the idea should look like.

Start of the print:


In the middle of the print:


At the end of the print:


Is this going to work?

The idea to try it first hand with a tilted printer is very nice, I will give it a try. But I am not shure if the 45 deg cone is the right test object, I will think about it.

Edited 1 time(s). Last edit at 12/13/2013 12:00PM by Fabricate.

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nicholas.seward
Oh, I thought you meant tilt the nozzle relative to the platform. This is unlikely to work for the reasons I have stated above. When one layer sticks out far from another layer regardless of gravity then it will curl. For a thin shell print like this at some point the plastic will curl so far that the nozzle can stick the next layer to it.

So what you mean is that tilting the nozzle relative to the platform will work, while the idea with tilting both at the same angle will fail at some point.

Now two more questions arise: can we shift the overhang angle at which the print starts failing with this idea at a much higher point (lets say 60-70 degrees)?

And what if we assume that we have the same layer hight as the nozzle diameter. Is there so much difference between putting the layers on top of each other (i e the nozzle forces the new molten plastic down onto the older layers) and putting the layers besides each other?

Quote
nicholas.seward
Printers can print upside down and sideways. Bottomline: gravity has nothing to do with it. Plastic forces are an order magnitude above gravity. You still have the 45 degree restriction. So regardless of layer orientation the edge of one layer can not extend more than one layer height off the previois layer.

You can tilt the nozzle and do some angled slicing to solve the problem. You would need a 4DOF+ printer like the Sextupteron. [youtu.be]

Your design of the Sextupteron is great. How did you design and animate it? Have you achieved to tilt the nozzle while it stays perfectly in place?

So, what should always work (under all the assumptions above) is tilting the whole printer and the nozzle, like this:

Beginning:


Mid-Print:


End:


This way support less printing a hollow sphere should work fine, right?

You don't need to tilt the printer though, just the nozzle.

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I was looking for a video that shows upside down printing in more detail. Interestingly there is no video that is much longer than just a minuteor two! I guess there might be a reason for that, but I am not sure what it is.


Anyway, I think I found a nice test object that can test the potential of a tilted printer:


Sadly I have to repair my hotend before I am able to test my hypotheses. I am sharing the source just in case someone wants to start experimentint, too.

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bobc
You don't need to tilt the printer though, just the nozzle.

This is great as it simplifies the whole thing ! Is there anyone working on tilted nozzles? I mean the perfect solution would be if the nozzle could stay at the same position (x,y and z) while it is tilted!

I have a "secret" project that is call Tilt-n-Twirl that is functionally the same as what you have assuming you don't tilt the whole printer. I am going to utilize the arm joint technology from GUS Simpson.

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nicholas.seward
I have a "secret" project that is call Tilt-n-Twirl that is functionally the same as what you have assuming you don't tilt the whole printer. I am going to utilize the arm joint technology from GUS Simpson.

Wow, the GUS Simpson has a very cool design. Actually I don't like delta printers that much (small build size compared to the huge height) but your design is much better!

Please let me know when your Tilt-n-Twirl Hotend isn't secrete any more! I am so looking forwared to this design. I expect it to be as awesome as all your other designs !

It isn't really secret. I just have no time or money to make this project a reality. I am working on a few other things that are secret that will make it easier to take on this project. I don't want to discourage you from going after this design. I will try to mock up the geometry that I was planning to use to see if that helps you along your path.

BTW, I use Autodesk Inventor for my modeling and animations. It is very expensive.

Quote
nicholas.seward
It isn't really secret. I just have no time or money to make this project a reality. I am working on a few other things that are secret that will make it easier to take on this project. I don't want to discourage you from going after this design. I will try to mock up the geometry that I was planning to use to see if that helps you along your path.

Yeah, this would be great!

I just remembered this 6dof printer.

Here is the geometry that I am thinking of. This is in the XZ plane. I would drive the elbows like Wally. I would add a stepper to tilt the effector. I would also put a turn table to do the "Y". Some related discussion.

Also I flipped my new printer upside down and also set it on its side during a print. This proves to me that (gravity forces) <<< (plastic forces)
[youtu.be]

Sorry for my late reply but I was quite busy the last weeks.

I did some experiments with some test objects and it turns out that gravity has some influence on the overhang problem but the main force is the one that is pushing the molten filament out of the nozzle. Tilting the printer for 30 degrees resulted in a marginally better result (I guess you could print 1deg more overhang with 30 deg printer tilt).

So I guess the only thing that helps you with overhangs is a tilting hotend (eg. 4DOF or even 5DOF printer). Maybe a tilting printer might also work well for other materials than plastic, but atm I am just working with plastic filament. I am going to build a small prototype for a 4 (or maybe 5) DOF printer but I am wondering if any one else has done that before (as I am not a mechanical engineer). I see some huge potential for this approach, but you will need a new slicer (or maybe a gcode preprocessor). Besides the overhang problem, you could tilt the hotend for making the top of round-shaped objects more smooth (eg. some anti aliasing for 3D-Printing ;-) ).

@nicholas: Your design looks great and I really love your work on the delta printer, but I have to admit that I am used to the linear movements of the prusa mendel and I don't understand the rope concept 100%.

I have designed some other small x-carriage upgrades that will allow to tilt the hotend while the nozzle stays perfectly in place (altough I have to admit that I am not shure where the center of rotation should be: at the center tip of the nozzle, one layer height below the center of the nozzle [I think this is correct] or in the center of the new laid plastic-tube).

My first idea was this (just rough sketches, as above):




You simply use a stepper and gears, while the hole thing rotates on two roller bearings.
Drawbacks: maximum of 30deg tilt in both directions, heavy, maybe not very stable.

My second approach was to use some kind of (rc) servo instead of the stepper motor (the quater-circle indicates the servo) and let a circular shape glide in some v-shaped bearings:




Pro: more stability and less weight (servo should be much lighter than the stepper)
Cons: so many bearings needed, maybe not enough stability

My third approach was to use some kind of bushing instead of the bearings:




I think that this will give you the best stability, but I am not shure if you can get the friction low enough for the servo. I am going to build this last version in the next months and I will use PLA for the bushings (and if it is not smooth enough I will try some wax).

As I said before, I am not a mechanical engineer, so all your help is greatly appreciated ;-) !!!

Edited 1 time(s). Last edit at 01/10/2014 06:13AM by Fabricate.

I liked your first one the most. Here is another idea to add to your mix. [youtu.be]

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nicholas.seward
I liked your first one the most.

Why? It limits the tilting angle to about 30 deg in each direction and adds a lot of weight to the axis!

Quote
nicholas.seward
Here is another idea to add to your mix. [youtu.be]

This is a very nice concept! I think I applied the same principles but took all the parts above the extruder because it is not a good idea to have parts below the tip of your extruder ;-)

I changed the design of the printer a little bit, here are some pictures how it should look like:

We are actually developing a 5axis 3D printer that solves a lot of the issues that you're referring to. The most difficult part of the build was figuring out how to feed the filament with all the ranges of movement. Nicolas Seward has some very interesting input and if anyone can figure out a way of thinking outside the box, it would be him.

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@REPRAP SQUAD: I would be curious what your 5-axis geometry is. I have the 4-axis design I talked about above and the 6-axis Sextupteron but I don't have a great 5-axis solution unless you count a hobbled Sextupteron. I want symmetry and 5-axis motion. It seems like those two things don't go together.

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REPRAP SQUAD
We are actually developing a 5axis 3D printer that solves a lot of the issues that you're referring to. The most difficult part of the build was figuring out how to feed the filament with all the ranges of movement.

It is nice to hear that someone else is also working on a 5 DOF printer! I would like to have a look at your printer design. Do you have a project-website or a github folder? How far has your 5DOF printer progressed?

Quote
REPRAP SQUAD
Nicolas Seward has some very interesting input and if anyone can figure out a way of thinking outside the box, it would be him.

Yea, this is so true! I love his design of the Sextupteron, can't wait to see it in reality !!