Looking for a generic "delta printer" reference



  • After having a delta printer for a few weeks, I'm finding that it's slightly (heh) more complex than a cartesian printer. There are a lot of delta specific variables at work, such as "delta radius", "arm length", and so on. These variables all seem to interact and influence each other to a large, yet subtle, extent. (I realize that my last sentence is an oxymoron, but it seems appropriate.) While the duet auto calibration does it's best to automate those variables, I'm finding myself with a need to better understand what's going on.

    Rather than post a million questions that have undoubtedly been asked hundreds of times before me, I was wondering if anyone knew of a good (free and online) resource that might give a good overview of the variables, math, etc involved with delta printers.

    Perhaps, "Everything you never wanted to know about your Delta Printer, but should anyway" ... or ... "Understanding a Delta Printer for Geeks"



  • The reprap.org page is a good place to start:

    https://reprap.org/wiki/Delta_geometry

    adavidm



  • http://danalspub.com/DKcalc/?he=655&ve=1500&dr=720&lr=1000

    This may help understand. Play with the sliders on the left, while looking at the section on the right that shows Marlin firmware setup.



  • @adavidm said in Looking for a generic "delta printer" reference:

    The reprap.org page is a good place to start:

    That was great. While it didn't make the direct connections I was hoping for (such as the direct relationship between delta radius, arm length, and a flat build plane) it (and links from it) provided the formulas that let me put the dots together. After reading that, I feel I have a much better (if still not complete) grasp of what my delta is and should be doing.

    I think every person who has a delta should read that and look at the formulas. Only then can someone really appreciate what the duet board is actually doing. That, in turn, would lead to people being able to better troubleshoot problems. "X0, Y0, Z0" might be trivial on a Cartesian... On a delta, it's quite a bit more complex.

    @danal said in Looking for a generic "delta printer" reference:

    http://danalspub.com/DKcalc/?he=655&ve=1500&dr=720&lr=1000

    This may help understand. Play with the sliders on the left, while looking at the section on the right that shows Marlin firmware setup.

    While useful and neat to play with, it doesn't really tell me WHY things work.

    In the first week of having a delta, I was satisfied with someone telling me "use arm length of 375 and delta radius of 208." I printed a nice dragon figurine and some flexi-rex's for kids.

    In the second week, I was good knowing what the "arm length" and "delta radius" meant. I printed a cat mask for my daughter, a cap for a squirt bottle I use for alcohol, and had fun printing massive overhangs that my previous printer couldn't handle.

    Since then, for troubleshooting and just because I'm engineer, I've wanted to know how those numbers actually work to put everything together. Seeing the math helped me a lot. Since that second week, I haven't printed much of anything as I've been having first layer issues...

    I recognized the first layer issues as looking like a build plate leveling issue I'd have on a cartesian with manual leveling screws; but in a circular pattern. I felt like I was going in circles. (heh.) A few hours with a piece of paper showed that my nozzle was too high in the center of the plate and almost grinding the build platform towards the edges of the plate.

    That led to google searches and trying to understand how my "delta radius" could be wrong on a printer that auto-calibrates the delta radius and the only M665 parameter that doesn't get calibrated is the arm length... Which led to realization that I should be able to put nearly ANY value as the arm length and the duet will still spit out a delta radius that results in a flat build plane (but possibly printed parts that are sized incorrectly.)

    At that point, I realized that I didn't know what I was doing and how all the stuff actually worked. Hence, the question in the first post of this thread.

    Now that I better understand it all, not only am I a happier person, but I think I can attribute my issue to a single FSR acting up under my build plate. I don't (yet!) completely understand the math used for the delta auto-calibration, but it seems reasonable that it would be somewhat reverse of the math used to calculate carriage positions for a level build plane - so if the level build plane isn't as level as assumed (because an FSR is triggering erratically), it would throw off the calculated values...

    Wow.. I type too much. 😉



  • Using Chrome, load the sizer, right click (almost anywhere EXCEPT the printer graphics area) and select "inspect". Navigate to "sources" and "deltacalc_de.js". All the WHY is in the code... particularly the "positionXxxx" and "calcXxxxx" modules. 🙂

    0_1540254010024_c29e64b9-87bb-47a0-b3fe-b15553c4b7e2-image.png


 

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