Small calibration panel for holes 85 x 72 mm for small printers like OneUp Tantillius Huxley Printrbot Simple etc.

thingiverse

Added an even simpler design that allows you to check your slicer settings against a known diameter. The design includes holes with diameters of 10, 10.5, 11, 11.5, and 12 mm. After printing, just stick a 10mm drill bit into it and see how far the hole size deviates from your CAD files. This is an improved version of HydraRaptor's original design at: http://hydraraptor.blogspot.de/2011/02/polyholes.html. I have reduced the dimensions by removing some holes and diameters. The polygons have 3, 4, 5, 6, 8, and 10 vertices. Their outer circle has a diameter of 3, 4, 5, 6, 7, 8, and 10 mm. Since slicing rounds the holes into polygones with a variable number of vertices, using this tool will help you control the outcome of a given diameter in CAD vs 3D print. It will tell you how much a certain diameter in CAD will be reduced when printed. You can then either scale up your model in Repetier or any other printing software, or if that would interfere with other mechanical restrictions, scale down the diameter in your CAD drawing so the outcome will be close to the final diameter as possible. Since the number of vertices that represent a circle/hole in a CAD drawing depends on the resolution you predefine in your slicer, you must be aware that results will greatly differ if you change slicer minimal resolution settings. Here is an OpenSCAD script: difference() { cube(size = [85,72,3]); for(i = [1:6]) { assign(v=[3,4,5,6,8,10][i - 1]) { assign(shrink = cos(180 / v)) { echo(v,shrink); for(d = [3:9]) { translate([d d - 4 - ((v == 3) ? 3 : 0), 11.2 i-2, 0]) cylinder(h=20, r=(d/2)/shrink, $fn=v); } } } } } Enjoy! If you like, visit my blog: http://3dptb.blogspot.com Important issue when printing: undersizing of holes. This is caused by the slicer converting circles into polygones with a variable number of vertices. This depends on the circle's diameter and the number of facets. Best thing to do is print this object and measure how much it really has after drilling. The polygons have 3,4,5,6,8, and 10 edges, while their outer circle has a diameter of 3,4,5,6,7,8,9 mm. Using the following object will allow you to determine when (and for what polygon) the printed hole's diameter corresponds with the one in CAD. The tool uses the polygones that make up each hole to give you a correction factor. This can then be used either by scaling up your model in printing software or by increasing the inner diameter in your CAD drawing. However, this is not always possible. In any case it leads to either designing correct hole diameters and afterwards reaming/drilling them or vice versa giving up holes with exact internal dimensions that make up your 3D model. But for mechanical parts this does often lead to quite big diameter variations which do then demand either an increased CAD design (that's fine but does increase material costs, since we're dealing with hollow objects) For other machining techniques it is then no problem, since the CAD holes can always be easily widened without affecting accuracy.