Brackets for joining wood or extrusions at various angles. A variety of sizes and angles are provided.

The FreeCAD v0.19 file is included and the parameters are set from the embedded spreadsheet. Changing a number automatically updates the shape.

Use large washers to spread the force onto the plastic for maximum strength. Use a dense and isotropic infill, e.g. 50% cubic.

I printed using ABS / ASA with 0.5mm nozzle and 0.3mm layers. The ABS needs good bed levelling and a wide 10mm brim to hold it to the bed during thermal warping.

Very shallow angles (>135deg) may need supports.

Finite-Element-Analysis

The FreeCAD file works well as a test case for the FreeCAD v0.19 FEM_Module.

To prepare the analysis:

• Make the screw holes a bit bigger to help the meshing, e.g. 5mm radius
• Start the FEM module and click the "A" button to add an Analysis
• Select the last LinearPattern element of the Part
• Select Mesh => FEM mesh from shape by GMsh and hit "Apply"
• Add a material with the yellow ball button and choose "ABS-Generic"
• Scroll down to the bottom of the materials tab and select the "solid" radio, then click "Add" and click on the bracket in the 3D view.
• Click Apply at the top of the material tab.
• Add the boundary conditions by selecting the Analysis node then Model=>Mechanical Constraints=>Fixed Constraint on the vertical surface. Then add a force boundary condition to the other mounting surface.
• Double click the SolverCxxTools node, "Write .inp file" and "Run CalculiX".
• Once the results are converged, examine the maximum von Mises stress to see if it is less than the yield strength for your plastic, e.g. ~20MPa for ABS.