Quote Originally Posted by shakesc
I think the secret sauce is in the joining of the materials
I've found HDPE too soft if trying to tap threads into it. I know other roboteers use wood screws which can be cheap and effective.
Personally I prefer to join by using things like angle iron and bolting through the HDPE. Just about everything except the HDPE joins broke on Spur using this method
I use several systems at once to connect HDPE pannels.

Draw out the armor is as little as possible parts. CAD is my favorite here (Cardboard Aided Design)

Take the HDPE sheet, put the CAD on it, and have a go at it with the cutting instrument of choise After that, I bend the pieces using hot air so it folds together. Joints and inserts get screwed together with coarse, long narrow woodscrews (these ain't strength parts, but ease of manufacturing assists).

Then I weld up the joints with the hot air welder.
These welds tend to be brittle. So I strengthen those welds with braces I screw and weld on crosswise to the first welds.

For removable pannels, I use ali blocks I bolt inside the armor, and drill and tap thread in the ali, so the threads have enough meat to do the job. The bolting does the rest.