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stutter printing sphere

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I’m having some trouble printing a bowl that I’ve not been able to figure out, any help would be great. When printing the base that is just a cylinder all is fine, when the sphere portion starts printing the UM starts to stutter about a quarter around the circle of that layer and sometime pauses for a half second. At first I thought it was just the complexity of the curves I was generating but then tried a simple design out of just spheres using openscad and the problem is still there. I’ve played with the facet sizes using both $fa and $fn with a small resolution and larger and that is not solving it. Printing wall thickness matching matching model, infill 100%, … But still this things stutters and stops on these rounds. I think alignment/pot settings are all good, it seems more like the complexity is an issue. netfabb cleaned files have the same problem.

- designed with openscad

- sliced with cura

- printed with printrun

You can see the result in the picture, the base has these stutter points

 

8002472620_21ce8860b4.jpg

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Hi. I've seen this before in my prints. I think it is because at the bottom of the sides of the bowl, where the sides are thickest, the printer "fills in" each side with a wavy layer, which "sticks out" and gives the bumpy effect. You might be able to fix it by telling Cura (if you are using Cura) that you are making a vase. This should result in the sides being made of one layer thickness and get rid of the waves.

If has always intrigued me that defects like this are extremely repeatable. I've printed out a few of the vases from ThingUniverse (particularly the Roundem vase:

http://www.thingiverse.com/thing:20068

) and the lumps and bumps are always in exactly the same places.

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I did use Cura. You're right, it does repeat at the same place but it is not across the entire circumference of the sphere at that layer. Almost as if where it is being split down the middle for slicing is the problem, maybe an odd number radius works better than even?

Two concentric spheres, as this simple cup is, should not have a heaver bottom that I know of so is cura just making some assumptions? I think the vase setting on the simple interface is just a collection of presets, anybody know what the collection is?

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thanks for the pointer Daid, I orignally had the problem using an old samsung Q1 as a controller, works well otherwise. With that I found others are callin git the 'hickup'.

http://wiki.ultimaker.com/Communication_speed_improvements

I have also tried with an old laptop with not much better results. AN i7 worksation still has issues. I'll look through the link above.

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If you are still using RepG, dump it. Use Printrun (Pronterface), which does a lot better in buffering commands, solving a few issues that RepG has with sending GCode.

Stay away from Windows Vista. My laptop runs it, and I have had my share of problems with it related to USB printing.

250000 baud, the default in Cura's firmware, gives good communication results. Older firmwares where running at lower baudrates, and less baud is less messages per time, which results in a higher chance of buffering problems.

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I'm using Cura 12.08 for slicing and printrun to print both on W7 (64), XP(32) and Ubuntu 12.04(32), what else ;) The W7 box is not as bad as the others, but all have the same issue. The baudrate on linux had to be dropped with new uploaded firmware using the Cura wizard to communicate.The package dependencies/versions for running Cura/python under Ubuntu are a guess, but it runs so I don't think that is the issue. Here is the scad model if anybody else wants to give it a try:

//$fs = 2;

$fa = .5;

//$fn = 360;

module main() {

difference () {

sphere(70);

sphere(68.4);

translate ([0,0,80]) color("red") cube(150, 150, 60, center = true);

}

}

module remove() {

translate ([0,0,-140]) color("red") cube(150, 150, 60, center = true);

}

difference () {

main ();

remove();

}

translate ([0,0,-65]) cylinder(h = 8, r=40, $fa=.5);

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