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Need Random Periphery Start/End-points


eldrick
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Posted · Need Random Periphery Start/End-points

I manufacture a part for sport fencing, which is basically a slightly-tapered hollow cylinder about the size and shape of a thumb.

Since there are no corners to "hide" the start/endpoints, any regularity in their placement is very obvious to the eye, and 14.03 does a lousy job of randomizing the starts. On this piece, most of the dots wind up organized into two columns spaced about 2mm apart or in short vertical segments 3-4mm long.

This is very annoying and looks even worse with the smooth surface texture that Cura provides other wise.

Could we possibly either get a Random checkbox, or really randomize the default start points so they are more-or-less evenly distributed around a rounded piece?

 

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    Posted · Need Random Periphery Start/End-points

    If the walls are .4mm thick meaning it only makes *one* pass and never goes back to the same spot on the same wall a second time and if there are no holes in the walls of the piece and no non-printing moves and no retraction then you can probably use the "spiralize" feature which adjusts the Z position very gradually along each layer so that there is no Z seam - every move includes a tiny increase in Z.

    However if your part isn't incredibly thin then you can't use spiralize and I'm not sure what you can do.

    I guess I recommend tuning the Z axis - try doubling the Z acceleration. Each doubling of acceleration means the movement is 1.4X faster (square root of 2) which means the blobs are 1.4X smaller. Increasing Z jerk also speeds things up. But if you increase acceleration too much you will lose steps and your part will be the wrong height. That's why you need to experiment - make long 10 to 50mm moves up and down and verify that the Z comes right back to the same starting point. I recommend pronterface to play with acceleration and to do the movements:

    printrun/pronterface/prontrface download:

    http://koti.kapsi.fi/~kliment/printrun/

    Another way to shrink the blobs is to print slower so that there is less pressure in the print head. Try printing at half speed and see if that makes a difference. I don't know if your reprap has marlin but if so you can do this on the fly with feed rate control. I have found that printing at 30mm/sec with .1mm layers makes the Z seem almost disappear completely due to the pressure in the nozzle being so much lower.

    Another way to shrink blobs is to lower temperature so that the PLA flows more like toothpaste and less like honey. For example 190C might give you smaller blobs than at 220C (although this also raises the pressure which could paradoxically make the blobs bigger so lowering XY speed might be better).

     

     

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    Posted · Need Random Periphery Start/End-points

    I don't have any blobbing with Cura, although I did with Kisslicer and Slic3r.

    I've got tiny pinprick pits, which is fine - I just need them more evenly distributed so they disappear as part of the texture, instead of being grouped in lines that make them obvious.

     

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