Vinyl Wrap Magnet

I'm looking to wrap my car since I'm between jobs and would prefer to save $3500 in labor. My car really wants to be green. Tooling up for this is part of the process, but WOW does Avery Dennison charge a ridiculous amount for their wrap-pinning magnets! $55 for a pair! Most wrappers on YouTube use several pairs during a job. 

Designed with pockets to fit six 10x5mm neodymium magnets (10mm diameter x 5mm thick).

Example source, can also be found on Amazon and others:

https://www.aliexpress.us/item/3256804031184824.html

In 100pc quantities, the magnets are $0.16 (USD) each, so $0.96 total to make one of these, plus 10.5 grams of flexible PLA or TPU filament. I used FlashForge flexible orange PLA to make some. FF Flex PLA cost me $23.26 per kg including tax from Amazon. I printed these to be strong with 4 outlines and 25% infill with a 0.6mm nozzle. For a 0.4mm nozzle, you might want to go for 6 outlines, so I'm using about $0.25 of filament per piece.

Total cost, about $1.25 per finished part. That beats $30 each! 

I'm waiting for my magnets to arrive tomorrow to do a test fit and will update the model if needed. This design is 40mm diameter, the ones I'm patterning them after are 42.86mm. The magnets sit in 7mm-deep pockets with a tapered lip that was designed to have a 9mm opening and 2mm deep tapered rim to hold magnets firmly in place. It should be tight enough to not require glue but glue is an option. 

Note the magnets from Avery are shown in the video found at rvinyl.com, and those are shown as a pair to stick together face to face. This either means one is a “south” magnet and the other a “north” or possibly they alternate N-S-N-S-N-S in the ring of six? Polarity does not matter when sticking to metal but definitely will when putting two magnets together. I wonder whether there is a strength difference when attaching to metal as N-N-N-N-N-N, S-S-S-S-S-S, or N-S-N-S-N-S? I've been playing with 5x3mm magnets while waiting for the 10x5mm ones to arrive and … assembly might be “interesting”. 

Edit : got the magnets and they fit nicely in the prototype, though a little weaker than expected. I thinned the bottom to 0.5mm from 1.0mm which significantly increased the strength of the magnet's holding power. 0.5mm is also mechanically strong enough. I used 0.25mm layer height to assure 2 bottom layers in the magnet pockets. With FlashForge Flex PLA, a pair of pliers was needed to squeeze the magnets in place. No glue was needed to securely hold them in place.

Pro tip: flex PLA is similar to TPU in moisture sensitivity. The orange reel went in the dryer and I used a fresh red reel to print the new one. Much cleaner results.