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Looking for suggestions - Repeatable error different print speeds

Posted by tgmorris99 
Looking for suggestions - Repeatable error different print speeds
May 27, 2017 08:38PM
I'm bringing up a new HyperCube printer and things are moving along fairly well. Calibration cubes are the right size and and look decent. However Benchy has various issues as can be seen in the attachments. One is printed at 40mm/s while the other is @ 60mm/s. One @ 100mm/s has the same basic issues. I'm still waiting on aluminum tubing for the X axis so for now I'm using steel rods, which cause some ringing in Y at higher speeds.

The errors seen in the pictures are duplicated in both prints and readily visible but they don't show up quite as well in the pictures.

The printer is a 300x300x300 build with dual Z axis steppers which are independently controlled by the RAMPS board as opposed to being wired in series. The lead screws have a flex coupler, the standard brass nut and a bearing at the top and have been lightly lubed with Super Lube. The build platform moved freely up and down the guide rods w/o binding prior to attaching the lead screws and has dual LM8UU bearings at each corner. The X axis uses bushings on the guide rod with no additional lubrication at this time. The Y axis rides on 10mm guide rods and LM10LUU bearings. The extruder feed rate has been calibrated and changing the hot end temperature doesn't seem to have any impact. The build can be seen at [www.thingiverse.com]

Looking for suggestions on where to start tracking down the cause.

ETA: I taped a laser on the bed and observed the beam on a wall 15 feet away. There was some very small vertical jitter but no movement horizontally. I'm guessing a spring-loaded anti-backlash nut or one of the Delrin anti-backlash nut blocks might help with that. The movement was about 1/10th the diameter of the beam on the wall.

Edited 1 time(s). Last edit at 05/27/2017 10:50PM by tgmorris99.
open | download - Benchy-40mm.jpg (64.4 KB)
open | download - Benchy-60mm.jpg (66.9 KB)
Re: Looking for suggestions - Repeatable error different print speeds
May 29, 2017 07:36PM
Have you tried different slicers? or maybe a different control board?

Focusing on the printer might lead you down the wrong path, It sounds like you have a good build, apart from the 2 Z motors but that's just personal preference.

A different slicer might give you better or worse results. Or a better control board might fix the issue, Yes the RAMPS is great and you are getting some great prints out of it, but if you are chasing perfection and flawless prints, maybe look and moving to the 32bit controllers.
Re: Looking for suggestions - Repeatable error different print speeds
May 29, 2017 09:01PM
Thanks for the suggestions. I also tried this on my MS V2 using the same slicer and the artifacts weren't there so that sort of rules out Cura. Since running the Benchy test I redid the Z axis alignment and calibration items still print nice. Benchy, not so much as it showed similar defects. I still have some jitter based on the laser so I'm still thinking about an anti-backlash nut as well.

I'm going to put this on hiatus until I get my anodized aluminum tubing for the X axis gantry installed so that I'm then, hopefully, only chasing a single problem.

I'd be happy to move to a newer controller but was trying, perhaps foolishly, to keep the overall cost down. However the pay once, cry once mantra may be haunting me as I need to buy a mic-6 plate for the heated bed as my MK2a aluminum bed has a warp to it. I can get most of it out in one direction but not both.
Re: Looking for suggestions - Repeatable error different print speeds
June 01, 2017 09:11AM
It looks like replacing the cheap LM10LUU bearings on the Y axis with anodized aluminum rods and lubricated bushings solves the overall quality problem. I need to rerun Benchy to see how that goes but running calibration items says things are good at the moment.

The attached images show the cylinder and square being accurate as is the 90 degree right angle. I had to fight with some binding at the extremes on Y but was finally able to get rid of that as well. These were all done at 30mm/s so I'll be doing some testing at higher print speeds as well. I need to adjust retraction settings as there's a bit too much filament at the start/stop locations.

20mm Cube & Cylinder - [i.imgur.com]
20mm Cube - [i.imgur.com]
Calibration angle - [i.imgur.com]

Fortunately there doesn't seem to be any Z banding.
Re: Looking for suggestions - Repeatable error different print speeds
June 02, 2017 09:06AM
I ran benchy again and still have issues even though the calibration stuff prints fine. I'm thinking it's something with over extrusion when moving from the flat surface to the curved bow section. The direction of travel when printing the exterior is from the stern to the bow, left to right in the picture.

This is done with a 1.75mm filament and a bowden setup. The e-steps are calibrated and the filament diameter is set properly in Cura with a multiplier of 100%.

The sample section of the hull was done at 30mm/s. Looking for suggestions as to what needs to be changed pertaining to the extruder. The cylinder was @ 60mm/s as was the upper test object. The bernchy defects also show up at 60mm/s so it doesn't seem to be speed related.
open | download - benchy-compare.jpg (171.4 KB)
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