Bench Answers

On a calibrated FDM printer, around 0.2–0.3 mm per side is a common starting point. Confirm it with a tolerance coupon printed in the same material and orientation as the final part.

Slicers approximate arcs with straight segments and the outer line of a hole squashes inward. Over-extrusion makes it worse. Calibrate flow first, then use hole compensation or enlarge holes in CAD.

Yes. FDM parts are weakest between layers. Orient the part so the main bending or tensile load runs along the layers rather than across them.

For most bending loads, extra perimeters add more strength than extra infill because stress concentrates near the outer surfaces. Three to four walls is a good functional baseline.

Use brass heat-set inserts or captive hex nuts for joints that will be opened repeatedly. Modelled threads work for coarse sizes, and self-tapping screws suit parts assembled once.

PETG is a sensible default for indoor brackets because it creeps less than PLA and is tougher. Use ASA for outdoor or warm locations, and nylon where wear and impact matter.

Generally not. PLA softens at roughly 55–60 °C, and a closed car in summer sun can exceed that. ASA, ABS or polycarbonate are better choices.

Use a filament dryer or a well-controlled oven at the temperature recommended by the manufacturer, then store the spool sealed with desiccant. Nylon, TPU and polycarbonate are the most moisture-sensitive.

Choose a parametric tool. FreeCAD is free and open source, Onshape runs in the browser, Autodesk Fusion offers a personal-use licence, and OpenSCAD suits people who prefer code. Check current licence terms before committing.

Three to five revisions is common. Printing small coupons for critical interfaces before the full part reduces both the number of revisions and material use.