Jittering X-Axis On Arcs and Circles, I NEED YOUR THOUGHTS!

Hi all,


I have been on a calibration crusade, printing night and day all using all kinds of settings on all kinds of objects.


My machine has started to "jitter" quite predictably and repeatably while drawing arcs and circles…


This causes a ribbed pattern on the outside of all rounded and circular objects. This problem seems to get worse as I drop my width/height ratio. (I could be wrong, I am about to test this)


I just did a test print of a circular object (the x-axis ldler cover) without any filament and the jitter still happened. The jitter is coming from the movement of the X-Axis on the circles and arcs. Strangely, it seems to handle large circles and very small circles fine, but for all circle sizes between tiny and huge, the X-Axis turns into a real jitter monster! The X-Carriage can wobble terribly when provoked!


Oh yeah, that reminds me /*COUGH COUGH Make triple linear bearing X-Carriage official! Come on JM!; Mr. "I have it and use it on some of my production machines," But that's for another forum post… You know I love you JM


Back to the matter at hand; I have a few current thoughts as to the cause and possible correction of the Jittering:


1. I have been dialing down my W/T in an attempt to get a very nice and smooth top surface. My current Width/Thicknes ratio is very low (1.3). Is this so low that the printer is attempting to print a line thinner/smoother that it is capable of? (I only achieved a surface smoothness I liked with a W/T of 1.4; but now my arcs are perfect squiggly lines!)


-> I will prove/disprove/fix this by dialing the W/T until the wobble goes away (if it works that way…) and then try to dial-in the smooth surface by dialing down the extrusion multiplier.


2. If #1 does not work, then I will assume that there is a build problem occurring, and I need to tighten belts or what have you. This seems unlikely though seeing as how the problem is perfectly reproducible. (It draws an interesting embossed sin-wave into the sides of my objects.)


Looking forward to your thoughts!

Sounds like you are trying to make thick lines with a nozzle that is too small. That means you are trying to compress the filament lengthwise, which is like pushing a piece of string, it squirms from side to side and makes a sine wave.

Try reducing the filament width and keep to W/T ratio above 1.5, which may mean you need to reduce the layer height as well.

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[www.hydraraptor.blogspot.com]

Sounds to me that you are using Sprinter or some other old firmware without look ahead. Try Marlin or the experimental branch of sprinter.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
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Do you have a picture of what your circles look like? I tried printing some simple 15mm cylinders to stest my circles and I might be having a similar issue. The sides are alightly wavy. On straight prints my Prusa is doing very well

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Ryan
Quality Engineer & Hobbyist
thingsandtrains.blogspot.com

Hi all, I will see if I can post some pictures. After visualizing the RepRapPro Huxley STLs I was printing in KISSlicer, I can plainly see that the "rounded" edges are actually stubbly little sharp lines. My printer was simply following these sharp little edges.

I would love to try Marlin or Sprinter V2; but I am using the RepRapPro Melzi board and I am not sure how compatable this board is with those firmware options. If anyone has any advice for getting Melzi to run those firmwares, I would love to hear it!

thanks for your thoughts!

Melzi should work with Marlin as it is based on Sanguinololu. You may have to make or change an entry in pins.h to match Melzi's pin out.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver