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Shapes on first layer left open and not completing


jweaver

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Posted · Shapes on first layer left open and not completing

I am using Cura (14.07 and 14.09) with a Simple Metal and love it.

But I have observed something which is causing me a major problem.

When the very first layer goes down.. And the initial outline is printed.. Sometimes, CURA doesn't close the shape.

This then leaves a little blob, which on the next pass either gets snagged on the hot end and rips up the print.. Or it just gets absorbed, which then causes a lump which takes a fair few layers to disappear.

I am doing a print now and the first layer has 4 triangles and 4 squares.. I have set the speed down to 10mm/s so that I can watch it.. And clearly it never even tries to print part of one of the triangles and one of the squares.

This has now left a blob, which is still being dragged around many layers on..

Has anyone else observed this? Is this something that the printer is doing? Or CURA?

If CURA there really needs to be an option to lay down a complete first layer and always close up shapes.

I look forwards to any thoughts that people have.

Jon

 

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    Posted · Shapes on first layer left open and not completing

    Ate you sure that your object has a flat bottom? It sounds like parts of it are hovering slightly above the bed, and so not printing on the first layer.

    A simple fix might be to use Cura's cut off bottom feature to sink the bottom of the print fractionally into the bed, so all the areas now touch on the first layer.

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    Posted · Shapes on first layer left open and not completing

    Are you sure the issue come from Cura? Is the first layer in layer view looking good? If its good in Cura but not when printing then you might print the first layer too fast, print to cold, bed too cold, head travel too fast or have bad level.

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    Posted · Shapes on first layer left open and not completing

    I can't be sure, and am certainly not saying that its a problem with CURA.

    But I have slowed it the head right down and it appears that for certain shapes it simply doesn't finsh all the edges on the very first pass.

    Take for example this:

    http://www.thingiverse.com/thing:354039

    The very first layer draws several triangles and circles.. And in my case, 2 of the triangles and 1 circle wasn't closed.. So this left a little 'blob' which then caused problems on later layers.

    When it did the 2nd pass (Still on the same layer) it drew around them and closed them up.. But the 'damage' was done by then..

    The first layer (When finished) looks exactly like CURA shows in its layer view.. BUT.. The process of drawing it appears to be a bit odd when it leaves some of the shapes open...

     

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    Posted · Shapes on first layer left open and not completing

    Perhaps you could post a photo to show what you mean? I'm finding it a bit hard to visualize the issue.

     

    Here you go.

    Some of these gaps in the shapes are just down poor extrusion..

    But some of them, the head never goes all the way around. So its leaves the shape open, and this allows it to rip off.

    I accept that the 'strands' between the shapes are just the extruder dribbling and perhaps I nee to go a bit cooler.. But you can clearly see that the start/end point of some of the triangles are not right.

    CIMG9638_small.jpg

    CIMG9641_small.jpg

    CIMG9642_small.jpg

     

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