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Thread: Layer Failure

  1. #1

    Layer Failure

    While I am not very experienced, this is a first for me--I printed the construct shown and the smaller "screw" broke radially (perpendicular to the axis).

    The walls are 1.2mm and I am using a 0.2mm layer---thus 6 layers for the print. THEN--I thread the assembly at 10-32 (US). No surprise that it broke. I have some recourse here and am not worried (yet) but this brings to mind-

    >>Is there a recommended number of layer-thickness-to-layer-number past which structural integrity becomes and issue?

    RegardsFritz
    Attached Files Attached Files

  2. #2
    If the model was printed vertically, the layers are the weakest possible. It's always challenging to get a strong screw thread when dealing with small diameter parts and in this case hollow internal sections. It's like a stack of pennies compressed end-to-end when the stack is pushed out of column. The layers (pennies) crack and everything goes to pieces.

    I've seen videos in which the printer operator prints the screw assembly horizontally in order to get the best strength. Unfortunately, this means that the bed is tangent to the thread, and that means very little contact with the bed. The best one I've seen is with a screw that has a segment shaved off along a chord, which provides a much flatter surface to the bed and results in the strongest possible model. For some, this option won't work, as the thread is discontinuous, but that doesn't interfere with anything that has to be attached; it merely looks unusual.

  3. #3
    Thanks Fred. Good points. I note that Fusion places the parts on the bed horizontally to begin with-I am not sure how much thought goes into that. I didn't like that orientation because of the added supports which of course make rough threads. That said I am chasing the threads with a tap and die.
    For now I have redone the parts with only to small holes down the middle to accommodate leads from a mounted LED. Probably that will work but I will also do a horizontal print and compare strength. With issues like this and warp I find myself heading for the lathe and mill more often than not. I guess the big print machines with exotic plastics handle these jobs well but for my one-offs probably 3D isn't always the best choice. I am still trying to see what the limits are. Still, I can make a lot good things for the lab with a lot less of my time so no complaints.

    Thanks again
    Fritz

  4. #4
    Technologist
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    Hi Sonnichs
    I have recently upgraded my 3d system by adding a Sapphire Pro2 to my printers and am currently "Dialing it in" for best performance. I would like to try your led holder project but can't print from the STL which are giving me scale problems! it you would like to send me the *.f3d file I will have go printing the in Rigid Nylon 6 and post the results to you if successful.

    Gambo

  5. #5
    Gambo--nice to hear from you!I am happy to hear about your upgrade and it will be interesting to learn some statistics on it.I sent a device to a professional printer recently and for $25, when it arrives, I am interested in how much better they can do than I did.A friend mentioned that sending parts out, he always gets much better looking parts. I wonder what the magic is?1) more resolution?2) different plastic?3) post finishing?Sadly the vendor I use doesn't specify.What is the resolution on your Sapphire pro2? I note some really expensive printers ($3000-$4000 US) claim resolutions of 50 and even 20 microns.Can't imagine how long the prints take.I will send you my f3d -sounds like fun and thanks!I have a sticky problem I am looking at right now. I want to print some integrating spheres. (I have used aluminum bowls but some are not quite round!)The problem with printing of course, is that the interior has to be very smooth. Obviously sanding and thick layers of primer like those that you have mentioned are key.But the print times on a large sphere (150mm) are daunting. About 25 hours for a half-sphere, 5mm thick, with 0.1mm resolution.So-I am still thinking this one over-clearly I can send them out once I see the cost. Looking back, I have never machined a half sphere on the lathe-sounds like a CNC job!I will send the f3d separately-cheersFritz

  6. #6
    Gambo-your PM space is full!I tried sending you an fd3 as you mention. For some reason the attachment rejects it--possibly it is file size?If you email me directly I can send the f3d. Just use my username on this forum plus gmail dot com.cheersFritz

  7. #7
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    I have just sent a PM with my email cheers Gambo

  8. #8
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    Hi Fritz
    The Sapphire Pro has a resolution similar to the Ender 3 but just does it better and faster!!
    We used to send all our 3d printing to a 3d print shop for printing by the SLS process the surface finish was good but still rough and it was costing us more than £100 a week hence our own printer.

    The finsh we had with the Ender was acceptable but the new printer is noticeably better. base and verticals nearly perfect but still haviing to hone the material flow to get better top surface, The Sapphire only cost me £11 more than the Ender 3 but is much more sophisticated but still has only a 220 by 220 mm bed.

    So far I have printed PLA Pet-G and Nylon PA6 all with no enclosure ( I am waiting for the Perspex panels from my laser cutting friend)

  9. #9
    Wow. The value of the sapphire was mentioned elsewhere here and it is certainly true. I may have a "fat grant" coming in and if I do we probably will want on on-site printer for the staff mechanical engineer. Depending on what negotiations I do I would consider a high end 50micron printer but if not I think the sapphire makes sense. Makes me want to replace my personal Creality!!

    I have never done Pet-G or PA6.. Does the ender handle it?

    Laser cutters are nice--I use a band saw etc here in my shop--one of my contracts has a great water jet cutter but $$ and time get in the way

    Tell us what slicer you are using!

    cheers!
    Fritz

  10. #10
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    I have been printing both PA and Pet-G on the ender! but the result with PET was disappointing due to stringing. I have printed a lot of semi pressure ( 6 Bar test) bottle tops with spectrum nylon PA6 but in an enclosure.

    I am Using the Ultimaker Cura slicer with no problems.

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