Spherical slicing

Hi!

I'm currently building a BB-8 robot, and I want it mostly 3D-printed, without any post-printing process (sanding/painting): I like the 3D-printed look

I already printed the dome, and I'm now working on the body. The inner frame is a combination of 3D-printed parts and laser-cut parts. Next are the body panels, which are sphere portions. I could print them flat, but it would require a lot of support, and use variable layer height to get a decent finish, which is very time consuming.

Another way (also time consuming, but much more interesting) is to modify my 3D printer to be able to print on a tilt-able spherical bed (with 2 more axis) so it is possible to always print perpendicular to the surface. I have ideas for the mechanic, and as I'm using a Duet board, there is no problem to drive these 2 additional axis.

As it has already been said (several times), building/driving a 5 axis 3D printer is easy, but generating G-Code for such printer is muuuch more complicated. But...

...In my case, this is not a true 5 axis 3D printer, as I don't plan to be able to print complex shapes: I only want to print a spherical part, with a pre-defined radius, on a spherical (3D printed) bed. In fact, by implementing a new Kinematic in dc42 RRF firmware (which is now very easy, thanks to his new Core-XY architecture), I think it could be as easy as printing on a flat surface. From a slicer point of view, it would require to parse the part along the sphere, instead of parsing it along the X/Y plane. Then, all X/Y moves would be converted by the firmware to X/Y/Z/A/B moves.

What do you think? Am I totally wrong? Would it be something very complicated to implement in Slic3r, for example?

Any advice/comment welcome.

Thanks,

Edited 1 time(s). Last edit at 07/05/2019 03:02AM by fma.

---

Frédéric

far easier just to vacuform something over a spherical base...

Isn't this basically eggbot?

would you need X and Y? Surly A,B and Z can get to any point around a sphere.

Well, when I said build a printer, it is more adapting my CoreXY. And the problem is I don't have enough room to only use A,B, Z; this would require to have the rotation point matching the radius of the sphere, but if I do that, the bed will collide with Z rods. So, I need to use shorter radius for A and B rotation, so I need to correct with X/Y.

But, as said, the machine is not the problem: the slicer is.

I had another idea: if I modify the stl, so I transform the sphere to a plan, then I should be able to use a standard slicer. I can even avoid building a new kinematic, and rather post-process the G-Code file to move X/Y/Z/A/B according to X/Y coordinates (I have to compute the normal of the original point to move A/B ). Don't know if I am clear...

Edited 2 time(s). Last edit at 07/05/2019 12:31PM by fma.

---

Frédéric

Ok, I started to work on that idea. I think I successfully mapped the sphere on the plan : [wiki.logre.eu].

I'm now working on the kinematic (post-processing the G-Code file).

Edited 2 time(s). Last edit at 07/09/2019 12:53AM by fma.

---

Frédéric

Mmm, in fact, it is complicated to post-process the G-Code, as the new axes are not linear. It is better to implement it in the firmware, and split moves into segments, as it is done for a Delta printer.

---

Frédéric

First results are encouraging!

[wiki.logre.eu]

Note: the french page contain more informations, and photos:

[wiki.logre.eu]

---

Frédéric

Perhaps you could try
Spiralize contour in Cura

Configuration >> Extrusion >> Spiralize Contour

Is it not just what other slicers call 'vase mode'?

---

Frédéric

I uploaded a short video showing a spherical print:

[vimeo.com]

---

Frédéric

Nice