How To Improve Outer Wall Quality.

Discussion in 'Calibration, Help, and Troubleshooting' started by Syko_Symatic, Feb 3, 2017.

  1. Syko_Symatic

    Syko_Symatic Well-Known Member

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    Just looking for some advice on how to improve the outer wall quality of my prints? It's not bad but it could be better.

    I was wondering what mechanical adjustment was needed, tightening belts and such?

    Also if anyone has any pointers on slicer changes that could improve it.
     
  2. Miasmictruth

    Miasmictruth Well-Known Member

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    Make sure you are extruding the right amout of plastic. Over or under can make blobs or holes
    I like to do this with a small single wall box,
    - Set your extrusion width to 1.5 nozzel width. So a .4 nozzel set it to .6
    - Use calipers and measure you filament as accuratly as possible, enter this into filament diameter, set extrusion mulitply to 1
    - Print the box 10mmx10mmx8mm or so, 0-1 bottom layers, 1 wall, 0 top. I usualy use vase mode
    - Measure the wall thickness a in a couple spots, stay away from the bottom few layers as if you z is not perfect they may be squished/streached
    - Adjust the extrusion muliplyer based on over/under sized wall (ex. goal .6, measured .65 -> .6/.65 = .92 set multiplier to .92)
    - reapeat this a couple times until the extrusion is the correct width.
     
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  3. Miasmictruth

    Miasmictruth Well-Known Member

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    I also like to print inside to outside,
    I slow down the outer perimeter some over the overall speed
    make sure the bed is perfectly level right now I use manual mesh bed leveling for that
    Depending on your infil% add extra top layers to eliminate holes
     
  4. mike01hu

    mike01hu Well-Known Member

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    Outer surface finish depends on so many things that it is difficult to know where to start! Mechanically, the Z axis needs to be good with better couplers for the screw rods so that the rods run true with no wobble and the corner rods are well supported with no free play. There has been a lot of dialogue during the early days on this forum regarding the bushes but I am on stock bearings that were well run-in and they run very smoothly. Screw tightness is always an issue on a well-used machine as they do work loose and need to be checked periodically, particularly the X and Y rod clamps and mounts. All the frame screws need to be checked too. All my recent bed level issues disappeared after a screw tightening session!!!

    Excessive print speed is always a contributor to poor surface finish, so if speed is not an issue I always print at a much lower speed e.g. 30mm/s. I also use three perimeters as I find that there can be patterning from the infill with fewer perimeters but this is also due to the high percentage of perimeter overlap that I use at 30%.

    Layer height with regards to nozzle diameter will also affect the finish, so always aim to keep layer height to less than 80% of nozzle diameter, so the maximum for a 0.4mm nozzle is 0.32mm but I normally print at 0.2mm as I am rarely in a hurry.

    This list is not exhaustive and there are issues around filament manufacturer, type, colour and fillers but this comes with experience.
     
  5. GrodanB

    GrodanB Well-Known Member

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    Ahh diameter of the filament... Think I measured for my first roll of filament... But have totally forgot that...

    3D printing is like peeling raw eggs... Very slow, carefull work and one simple mistake there is a huge mess...

    Need checklist for filament change soon ...

    Good advice checking the screws. With the acrylic case the screws are tightened just enough... Hopefully...

    I got a good surface finish after changing the z-axis lead screws (super careful reassembly of the z-axis to avoid any drag), updated the Y axis motor mountand,electronics. Lubrication of all axis probably help. The new electronic is very silent and the new Y motor mount made the printer smooth in all axis. I think this helped to get the moire effect from the print.

    Then I also did a mechanical bed level so all corners are measured max 70 micon different in height relative the Y and X axis... so the electrical bed level hopefully does not need to work to much...

    That I think did it for me... There are some places I try to figure out why they are not as good as the rest but that is me... Might be the diameter...
     
    #5 GrodanB, Feb 7, 2017
    Last edited: Feb 7, 2017
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  6. Miasmictruth

    Miasmictruth Well-Known Member

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    Diameter and the mulitplier change the same parameter basically. In slic3r just measuring the diameter was usually enough to calibrate my extrusion on my old printer, but for some reason that doesn't seem to work as well in S3D, so I usually modify the multiplier then. I think some filaments may expand when heated more then other which may lead to the need to calibrate each filament.
     
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  7. mike01hu

    mike01hu Well-Known Member

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    Yes, I found S3D temperamental in this area, most likely because it tries to deal with every variable in existence :eek: whereas Slic3r is happier. But, I now find that S3D was worth the initial investment. I don't think filament expansion is a factor but diameter and positon of the filament entering the hob can make a significant difference. For the latter it is important to have the PTFE tube pass through the lever right up to the hob, that is why many of us have cut a small length of the tighter PTFE tube permanently fitted it in the lever to ensure the filament only sits in one area on the hob.
     
  8. Syko_Symatic

    Syko_Symatic Well-Known Member

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    I did like this method but it ended up causing a little bit of under extrusion. Have you come across this? The wall thickness was perfect!
     
  9. Miasmictruth

    Miasmictruth Well-Known Member

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    Hmm, I usually don't get under extrusion but it has happened with certain filaments. I cant think of a specific example but if it does I would boost the multiplier a little and to a small multiwall print to double to check. I just calibrated a new filament this way, black inland PLA and it's comming out beautifully.

    IMG_20170208_063911676.jpg
     
    #9 Miasmictruth, Feb 8, 2017
    Last edited: Feb 8, 2017
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