3D Printing & Imaging
The Theta 3D Printer: 4 Extruders On A Polar Coordinate System



Traditional 3D printers, as well as most CNC routers, laser cutters, and most machine tools where the programmer doesn’t want to go crazy trying to get his or her head around the underlying code, work in the XY coordinate system.* This “theta printer,” as seen on Hackaday.io, eschews that paradigm and instead uses a rotational, or theta, axis and an R axis. This “R” tells the printer how far away from the center the extruder head is. That would be interesting enough, but it also uses not one, but four extruder heads.

This setup has several advantages, including that one can print with several types of material without negatively affecting performance. As each extrusion head is separate, the mass of each is smaller than if several were combined on a single XY gantry setup. Precision can also be improved, especially towards the center of the rotary table.

On the other hand, one would have to assume that more extruders and motors on a machine would equal greater expense, and possibly more maintenance issues. Either way, it’s a really innovative design, and you can see it in action below. I only see two extruders in action here, but this shows another advantage, in that it seems to be quite modular. Also, at least two identical parts can be printed at the same time with different materials.

*Yes, lathes work differently. Don’t derail my thought process!

0 thoughts on “The Theta 3D Printer: 4 Extruders On A Polar Coordinate System

    1. Sorry, but we saw at least three different printers “claiming” the 4D capability at MakerFaire last June.

      This is neither unique nor really new. The single biggest problem is maintaining Z accuracy with a rotating platform.

        1. Tom, you keep claiming z accuracy problems, but yet don’t detail why rotating z platforms are more inaccurate than Cartesian ones. Rotational platform stability and accuracies have been solved, just look at the hard drive manufacturers’ many patents on the subject. This design may not have the answer, but to say rotational platforms are inaccurate is just plain wrong. They are no more inaccurate than a Cartesian platform. The Cartesian platform has the advantage of being further developed, that’s it. Mathematically, the 2 systems in the z axis are the same.

  1. Sorry, but the accuracy issues inherent in any rotational system make this little more than a cute idea.

    We saw a couple of these at MakerFaire this year and the out put was crap.

    1. you’re not sorry. don’t say sorry when you’re not sorry. it’s called lying.

      rotational stuff isn’t inherently inaccurate, they just have a different type of accuracy. it’s rotational, rather than cartesian, that’s all. gear down the rotations and you can have all the accuracy you like.

      1. No, I was at MakerFaire, running a booth for a couple of schools just like the last five years – no lie there

        Rotational, especially with a chip-board bed is inherently less accurate in the Z axis – no lie there. Just watch a record on a record player push the tone arm up and down.

        The samples we saw at MakerFaire, were in my opinion, with Six years of printing under my belt, crap.

        No lie, just my opinion.

        So based on your rather childish response, I am guessing that you have a financial stake in one of these companies which would make you a:


        1. Not a shill, I just know that the tone arm of a record player has absolutely nothing to do with how flat a rotating platform on a 3D printer can be. There are no inherent accuracy problems on a rotating platform, it’s just that the resolution of the print is radial rather than cartesian.

          1. No, I don’t a financial interest in this printer. Stop asking profoundly stupid questions and stop making profoundly stupid statements. I’m telling you that you’re wrong because you’re wrong, not because I have any interest in the printer.

          2. Neither the question, not the questioner is “profoundly stupid”.

            Nor are my observations about the printer.

            On the other hand you insistence on personal attacks and adolescent vitriol are slightly amusing.

            “You are wrong because you are wrong” is a masterstroke of logic and incisive wit.

            Samuel Johnson, The Bard, and even Mark Twain would cower before an intellect such as yours!

            My god man do the people from the Nobel Prize Committee know who you are? Perhaps the Pulitzer team?

            Keep writing bub, you are making a mark here (kind of like the one you leave in your skivvies).

  2. first ……congratulations nice job !
    about the accuracy discussion ….i think that this printer could have the same accuracy as Cartesian 3d printers but in case of cylindrical and spherical prints i think this printer has the preference (if it is well calibrated )


Jeremy is an engineer with 10 years experience at his full-time profession, and has a BSME from Clemson University. Outside of work he’s an avid maker and experimenter, building anything that comes into his mind!

View more articles by Jeremy S Cook