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June 27, 2017

M.G. Chemicals PETG

After renovating the backyard last year, I installed some solar lighting.

The lights came with a plastic spike that pushed into the ground but I didn’t use them.

One reason was because that would have either put them in the planters where the solar cells would be blocked by the fence so no charge, or on the lawn where they would have to be moved every time the lawn was mowed.

On June 24th we had a scorcher of a day and Carol pointed out that the lights seemed to be listing. Some to starboard, others to port…and at a fair angle too!

Initially I thought the 3D printed mounts I’d made last year had come loose and to some point that was true.

Ultimately what had happened was that the screw holding in the mount had reached the PLA’s glass transition point, with the stress of the heavy weight of the solar light (they have a glass lens; not plastic), it was enough to start the topple syndrome.

IMG 1172

The outside temp was 30C. When I took the mount off the post rail, the screw felt a lot hotter than that.

Of course there was no use reprinting more mounts in PLA if they were only going to last a year.

Then I remembered I had some M.G. Chemicals new improved PETG.

IMG 1174

The glass transition point is 25C higher than PLA! I redesigned the mounts to make them taller and a thicker base for the screw to sit in.

IMG 1173

I started printing and replacing the mounts. After they were all done, it was time to sit back and wait.

IMG 1177

I only needed to wait until the next day. The temp outside climbed to 31.2C, and the solar lights stood like sentries without a movement.

The new mounts worked out perfectly.

One thing I should note if you try something like this, I used a fan on one print. PETG seems to cool off quick enough anyway so really the fan is more or less to stop stringing. I found the best way to print these small mounts is slow and no fan. Excellent adhesion between layers and almost no stringing in these small items.

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