Resin Addict Forum

I'm designing a garden seeding tool that is roughly similar to a hollow walking cane/stick. At the top is a smallish funnel and at the bottom is some assorted gear, but we can imagine it as a 2" hollow extension that slips over the end of the cane and comes into contact with the ground.

Stresses will be similar, but somewhat less than one would have with a walking cane.

I'm considering trying to cast the whole thing in resin, but it seems more attractive to cast the top funnel and bottom gear in resin using a 1" aluminum tube for the tube part.

My problem is that given this is a tool that should be expected to last a few decades, I'm not sure how to join the aluminum to the resin. I thinking some sort of glue, or perhaps a collar with bolts.

The only thing I really don't want to do is perforate the aluminum (like putting a bolt through it) since I want to keep a smooth uninterrupted tube on the inside.

I'm still in the design phase, so all options are open. What would you do? The aluminum tube would have a 1" inside diameter. If I resin cast the entire tube, it could be slightly trumpet or funnel shaped all the way down to make for easier demolding.

A related problem is how to color coordinate the aluminum and resin.

BTW, using PVC pipe or plastic electrical conduit isn't out of the question instead of aluminum. If I do that, I need to dress it up though, somehow so it looks better and make it UV resistant.

I guess you could cast the part around the pipe. Drill a few holes in the section to be cast around and the resin will 'grab' it nicely.
The resin will suffer from UV damage, btw.

Thanks for your input. I'm still working it out, and I've realized I'm going to have to switch to a harder resin than I have now.

This won't (hopefully) be left outside all the time, but UV degradation does really concern me. I have black resin now that should be somewhat UV resistant, but I really don't want to use black for the finished product since if left in the sun, it will get too hot to hold.

Luke

Unless your black resin's datasheet specifically states UV resistance then the colour means nothing. Also, something I found from an injection moulded project at work a few years back is that there are varying levels of UV resistance and for what you are describing you are after something very strong, which I'm not sure would be available in polyurethane format. There may be a UV stabiliser additive available.

In terms of fixing to the aluminium tube, just use a quality glue meant for that purpose.

Hmmm. I assumed black urethane was UV resistant. I'll double check the specs. I know the resin I have at the moment isn't tough enough. I'm planning to try another one that is harder and specs better for my purposes, but yes, it does seem like I may be pushing the envelope a bit far although I'm still thinking I have enough design flexibility to make it work.

OK yeah that's a bad assumption. It's more than likely not UV resistant

Polyurethane UV stabilisers are apparently available, but you really need to talk to a manufacturer or even a chemist for advice on it.