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Semi-automatic HDPE welding/sanity check

Semi-automatic HDPE welding/sanity check

Semi-automatic HDPE welding/sanity check

(OP)
Hello!

I'm just getting started with plastics fabrication and was wondering if someone might be willing to sanity check my current plan.

I am trying to build a 4 wheel robot which will be operating outside for prolonged periods and potentially crashing a lot. I am building the prototype on a shoestring budget, but will be seeking to make a bunch more quickly if the prototype works out.

My current plan is to build the chassis out of .25" black HDPE sheet (cheap and weather resistant). I intend to produce the initial pieces via cnc milling and then weld them together using a hot air welder.

If the prototype is successful, I will be trying to build 5 more instances quickly and then trying to scale up to 100 or so.

Scaling up the CNC cutting should be easy, but I am concerned that the manual hot air welding could be a bottleneck and quality problem. Switching to injection molding would solve most issues, but the shot size is likely to be pretty big and it's not practical for the first 5-6. Vacuum forming is another possibility, but I'm not sure about mounting holes placement quality in that case.

If I may ask, is there a more automated option for welding HDPE if it scales up? Most if not all of the welds would be .25 sheet at right angles to each other.

Also, does right angle welded HDPE sound reasonable for this sort of application? It's cheap, weather resistant, easy to machine and relatively strong/light but I haven't really seen it used for this sort of application before. The robot's pretty much a glorified box with mounting holes for 4 hub motors and a small tower for the camera/gps.

Thanks!

RE: Semi-automatic HDPE welding/sanity check

Welding HDPE sheet does not sound reasonable to me.
Some people build large chemical tanks that way, but the product is invariably extremely expensive,
and I'd worry a lot about fatigue of bonded joints in dynamic situations, especially with sharp corners and edges.

Look into rotational molding instead.

You can use huge corner and edge radii to reduce stress raisers, and make the shell almost arbitrarily thick for strength.

Mike Halloran
Corinth, NY, USA

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