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infil artifact cut parts apart internally

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Posted · infil artifact cut parts apart internally

Greetings all;


using the latest AppImage for linux to drive a BIQU BX printer, I've designed, in the latest OprnSCAD AppImage for linux, a shelf to be bolted to the rear of a 6040 mill, intended to support a B axis drive I've made.


But I've now stopped the printer 4 times because the effects of 3 angular braces supporting this "shelf" are cutting the 10mm thick shelf into 5 pieces internally as soon as the infill starts.

I have found I can make this artifact disappear if the angular brace is thinned enough there is no infill, its all wall.


Is this a bug,  or intentional?

If its intentional, can you share the reason?


What I've found, using the preview progress slider on the right, is pretty well stopped if I make the angular braces only 4.4mm thick effectively making them solid walls. If I make them 7mm thick, I get 5 pieces with a good floor on the bottom. 3mm up in the print, I can put a probe in the slots all the way to the bottom 4 or so layers. The attached pix shows what it should look like when finished. For some reason the left edge is clipped here and the green lines are the edge of the angular angular braces. View is of the bottom of the shelf, looking up at about a 40 degree angle. One side advantage is I now have a good drill and tap template from the last false start. Those bolt holes are identical for both panels.BAxisShelf.thumb.png.be5c710ffc61b055bcd894d4353fc9ed.pngBAxisShelf.stl


I'd post the OpenSCAD.scad file here. its only 88 lines of text, but its not acceptable to the forum software


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    Posted · infil artifact cut parts apart internally

    Maybe it is because it is friday afternoon, and I have had a beer, but I am having a very hard time understanding what your problem is. Perhaps you could share one or more screenshots of the problem (as opposed to what "it" should be).

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    Posted (edited) · infil artifact cut parts apart internally

    I sliced it and there are a couple of places where you assembled and combined the model and I think you missed it.

    Here you can see that the ribs continue up through the top surface leaving 3 islands.



    In this screenshot you can see a large island across the bottom of the model.



    As for the rest of it I'm right there with @ahoeben.  I don't get it.

    More screenshots or a project file might make it clearer.  When I sliced the STL it looks exactly as I would expect.


    This image is the first skin layer over the infill.  The wall of the ribs will rest on the skins and the infill is continuous from the bottom up into the ribs.  That's the way it typically slices.


    Edited by GregValiant
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    Posted · infil artifact cut parts apart internally

    That stickup out of the side of the shelf does not exist here, in OpenSCAD, or a cura preview. The solid part of that brace only penetrates the skin of that shelf by about .2mm, So where is the stickout of a fraction of a mm I see in the top edge of your 1st shot, coming from?


    Call me puzzled.





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    Posted (edited) · infil artifact cut parts apart internally

    That screenshot is from MS 3D Builder.   

    This is the Cura preview with that surface up.



    Here I've rotated the model 90°.  This is the first layer and you can see the large island is keeping the model from actually resting on the build plate.




    This is one of the artifacts from the ribs but now they are vertical instead of on the top.  The jig-jog that the nozzle makes will definitely leave a marred surface BUT it's being sliced exactly per the model. 




    Edited by GregValiant
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    Posted · infil artifact cut parts apart internally

    So I've trimmed it so the angle brackets are touching but not actually penetrating either the shelf with the corners cut away, or the front panel, and left the brackets at 4.4mm thick at which point those 3 artifacts disappear. It's also doing the horizontal holes surprisingly well so this one may be usable. The next rendered version if I have to print another, will be my 2nd with a PCD nozzle in the printer, but will be done in Atomic's carbon fiber black PETG and will have 5 ribs for re-enforcement. Might be fun. If I can tolerate the wait.


    This is intended to be printed shelf (face with clipped corners) face down. It will hold the 4th axis supplied with a 6040 gantry style milling machine, after it has been retrofitted with a 50/1 harmonic drive and one of the brand new 3 phase stepper/servo motors.  Those are sweet.  If anyone else buys that mill, expect to use your trash trailer for target practice to see if you can hit it with ALL the electronics, its all built by lowest bidder stuff and won't do the job. You also use up the spindle motor in 10 hours, so figure on a real motor and a vfd that takes orders from decent software. I will have, when this conversion is done, about $3800 in an $1150 mill.


    Its job will be to hold and rotate an 18" long 2x2 hard maple stick, while LinuxCNC is carving a 2" diameter, 2 start, 12mm pitch buttress thread to make the screw for a woodworking vise. This drive  weighs about 15 lbs. If this PETG doesn't cold flow and sag that is.


    Many thanks for the advise showing me I need to be more precise. Thank you all.




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    Posted · infil artifact cut parts apart internally

    Congratulations.  Most FDM machines are very accurate.  Overall dimensions and any hole locations are usually spot-on.  Small holes may need help from "Hole Horizontal Expansion" but that setting can have un-anticipated consequences and the word "hole" has an odd definition in Cura.  A pin chuck is your friend - I just hand drill small holes to size.

    Precision on the CAD side and having the STL translator set to a high resolution are keys to a good model that will in turn give you a good print. 

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    Posted (edited) · infil artifact cut parts apart internally

    I thought I'd take a closer look at your Shelf5 model as something seemed "off".

    There is a gap between the ribs and the wall.  Cura will see it and you won't get good adhesion because there will be outer walls facing each other across the gap.





    Here at the other end of the rib, the tail of the rib isn't even with the back of the angle plate.



    Adding some dimensions shows up what may be other problems (unless this is exactly how you wanted the model to be).  The cyan lines are square to the world.



    If the model isn't accurate then the print won't be accurate.  Things like the gap between the rib and the wall will show up in the preview and in the print.  That gap will make the part weak.

    All those slight angles will not be noticeable in the preview but will certainly be present in the print.  Any slicer can only deal with the model that is opened.  "That's how it is so that must be what they want." is the mantra.

    Having software decide "That can't be right - I'll make an adjustment and won't tell anybody." is always a bad idea.


    Edited by GregValiant
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