Platform Level Test Pattern

Unlike that pattern, this OpenSCAD program produces an STL file that gets sliced in the usual manner, so that the end result shows exactly how the first layer of all other objects gets laid down.

Thread Thickness Test - solid model

Thread Thickness Test - solid model

It’s two threads wide and one thread thick: customize the OpenSCAD code to match the settings in Skeinforge (or Slic3r or whatever you’re using) to make it build properly.

The two tabs mark the +X and +Y directions. The bottom surface will be wonderfully shiny from the build plate, so the symmetry along the diagonal shouldn’t pose a problem.

Should the thickness vary more-or-less linearly along any of the bars, then you know which way to level the platform. If it varies non-uniformly, then either the build plate isn’t flat or the printer has other problems.

The actual width depends on the actual thickness, of course: a too-low nozzle will create a too-wide pattern regardless of the extrusion settings. The thickness should be uniform across the entire pattern, so you can still adjust the platform leveling screws.

If you’re using a Z-minimum platform height sensor, now’s the time to adjust the switch touch-off height to make the thread thickness come out right.

When the thread thickness comes out right, then the width should match the extrusion settings: the bottom layer will be exactly like all the others. That’s the ideal situation, anyway.

A thickness snap gauge comes in handy for this sort of thing.

The OpenSCAD source code:

// Platform Level test pattern
// Ed Nisley KE4ZNU - Dec 2011

//-------
//- Extrusion parameters must match reality!

ThreadThick = 0.25;
ThreadWidth = 2.0 * ThreadThick;

//-------
// Dimensions

BoxSize = 80;

//-------

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  Range = floor(50 / Space);
  for (x=[-Range:Range])
    for (y=[-Range:Range])
      translate([x*Space,y*Space,Size/2])
        %cube(Size,center=true);
}

//-------

ShowPegGrid();

for (Index=[0:3])
  rotate(Index*90)
    translate([0,BoxSize/2,ThreadThick/2])
      cube([BoxSize,2*ThreadWidth,ThreadThick],center=true);

for (Index=[-1,1])
  rotate(Index*45)
    translate([0,0,ThreadThick/2])
      cube([sqrt(2)*BoxSize,2*ThreadWidth,ThreadThick],center=true);

translate([BoxSize/2,0,ThreadThick/2])
  cube([BoxSize/6,2*ThreadWidth,ThreadThick],center=true);

translate([0,BoxSize/2,ThreadThick/2])
  rotate(90)
    cube([BoxSize/6,2*ThreadWidth,ThreadThick],center=true);
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  1. #1 by txoof on 25-February-2012 - 17:41

    Thanks for the leveling tips!

    • #2 by Ed on 25-February-2012 - 18:56

      The absurdly heavy double-aluminum-plate platform on my printer eliminates need to pry fresh objects off the plate, leaving the lower plate in perfect alignment. You surely must pay more attention to the plate position if you’re applying more force to the X-axis stage.

      A Z-minimum switch means you never need to worry about platform height again… I like that!

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