Jump to content

Prints/Walls too thick


Maxinai

Recommended Posts

Posted · Prints/Walls too thick

Hi Ultimaker Community,

I have a problem with my 3D prints and I need your help to fix it.

 

The problem is that my prints are too big but only in X and Y axis. Its not proportional ... a 30mm cube will be 30.5 x 30.5 x 30mm when printed and a 50mm cube will be 50.5 x 50.5 x 50mm when printed. Until recently I just thought my printer was inaccurate and I made things fit by trial and error but this error is too "regular" / "reconstructable" to come from inaccuracy (...I think). I designed a test piece (unable to take&show pictures right now but will do later) that had circular as well as rectangular extrusions and holes of multiple sizes. All holes (circular and rectangular) were 0.5mm to small and all extrusions (circular and rectangular) 0.5mm to big. I don't know what is the cause of this problem (in truth, I don't even know if it has to do with Cura or if it is just my printer).

 

If some of you have any idea what is causing this or how to fix / circumvent this please tell me!

 

 

Specs:

Printer: Anet A8 (Yes... I know... shame on me for being that cheap ?)

Nozzle: 0.4mm (but I have 0.2, 0.3 and 0.5mm nozzles if that is of importance)

Filament: cheap PLA (most of the time)

Print-temperature: 205°C (extruder) + 60°C (bed) (I found 205°C to work better for me than the standard 190°C (f.e. layer adhesion))

(rest of Cura Settings in the picture)

Cura_Settings.png

  • Link to post
    Share on other sites

    Posted · Prints/Walls too thick

    So what you report is two different issues and EXTREMELY common.

     

    PLA when it cools it shrinks but stays liquid for a long time (a few milliseconds) while printing so it's basically going down as a liquid rubber band - like snot.  This is pulling inward when making those vertical holes and 0.5mm is about right.  Sometimes 0.4mm.  The most effective solution is to increase the diameter of all vertical holes (but not horizontal holes) by about 0.4 or 0.5mm.  Other people just drill the holes out later which seems silly but works quite well and you don't have to sweat what temperature you printed at or how strong the fan was and so on.  You can also set "horizontal expansion" to a negative value such as -0.4 but then the outer surfaces will also shrink (which may solve your other problem?).

     

    Regarding the exterior dimensions - this is not normal - well it's normal at corners only.  So if think of the cube as having 3 edges, 4 of the edges - the vertical ones - are likely sticking out - bulging out.  The other 4 should be fine.  If you measure the cube such that the micrometer doesn't touch any of those 4 edges you should get that the cube is perfect (within 0.1mm anyway).

    These bulging corners are caused because the printer slows down for the corners and the pressure in the print head doesn't slow fast enough so it overextrudes as it slows down and then underextrudes as it speeds up again pulling out of the corner.  You can fix these by slowing down the print speed when printing edges and shortening the time spent on corners.  The former is done by lowering the print speed (all the printing speeds).  If you want high accuracy try 30mm/sec.  There are other ways to speed up the print without losing quality - print with larger nozzles and/or print thicker layers.

    The other key thing to do is turn off "acceleration control" and "jerk control" if those are enabled.  Those 2 features reduce ringing (which can be quite visible and annoying but I don't care about it and a micrometer does not see ringing at all as it is a very tiny error) but they increase the bulges of corners on cubes.  Removing acceleration control means the printer doesn't slow down as long on corners.

  • Link to post
    Share on other sites

    Posted · Prints/Walls too thick

    First off thanks for the help!

    The first issue sounds like what i am experiencing, but where can I set the horizontal expansion (In Cura? or in my firmware? I have no idea). I haven't seen any bulging edges in my prints, maybe I just missed them ... but that wouldn't explain why the "poles" are 0.5mm to thick as well. Could it be the same problem as the holes just that this time the PLA of the walls flows outwards? Drilling out my holes works most of the time the problem was that recently i made a lot of "interior tubes" (f.e. i made a ball screw and nut) and interconnecting parts where drilling out just wasn't an option.

    Again thanks for the quick response will try the horizontal expansion thing as soon as possible!

  • Link to post
    Share on other sites

    Posted · Prints/Walls too thick

    I think of it as "buldging corners" as it's a two dimensional issue.  But it repeats on each layer.  Look for this on any cube you have printed.  Avoid those when taking measurements - or at least be aware.

     

    In cura just above the settings there is a search box.  Many people will tell you to make all settings visible.  I don't recommend that.  Instead just type "initial" in the search box and all settings (even invisible ones) will appear that have "initial" in the setting name.  Or search for "horiz".

     

    Again with the threading - add about 0.4mm or 0.5mm to any vertical holes in CAD software.  This may seem crazy to have to do but keep in mind that these same sorts of issues happen with injection molding.  You even have to change the angles of corners!  If you want a 90 degree corner I believe you have to make it 89 degrees in the mold!  Plus the whole part shrinks by 0.6% or so with injection molding.

     

    Of course usually the mold makers do this kind of thing for you (and charge you $50K).

     

  • Link to post
    Share on other sites

    Create an account or sign in to comment

    You need to be a member in order to leave a comment

    Create an account

    Sign up for a new account in our community. It's easy!

    Register a new account

    Sign in

    Already have an account? Sign in here.

    Sign In Now
    • Our picks

      • Introducing Universal Cura Projects in the UltiMaker Cura 5.7 beta
        Strap in for the first Cura release of 2024! This 5.7 beta release brings new material profiles as well as cloud printing for Method series printers, and introduces a powerful new way of sharing print settings using printer-agnostic project files! Also, if you want to download the cute dinosaur card holder featured below, it was specially designed for this release and can be found on Thingiverse! 
          • Like
        • 10 replies
      • S-Line Firmware 8.3.0 was released Nov. 20th on the "Latest" firmware branch.
        (Sorry, was out of office when this released)

        This update is for...
        All UltiMaker S series  
        New features
         
        Temperature status. During print preparation, the temperatures of the print cores and build plate will be shown on the display. This gives a better indication of the progress and remaining wait time. Save log files in paused state. It is now possible to save the printer's log files to USB if the currently active print job is paused. Previously, the Dump logs to USB option was only enabled if the printer was in idle state. Confirm print removal via Digital Factory. If the printer is connected to the Digital Factory, it is now possible to confirm the removal of a previous print job via the Digital Factory interface. This is useful in situations where the build plate is clear, but the operator forgot to select Confirm removal on the printer’s display. Visit this page for more information about this feature.
          • Like
        • 0 replies
    ×
    ×
    • Create New...