Snowflake for Giants

Some friends asked us to help out on a quick project. They needed a decoration for a holiday party in 3 days. After a few emails, a delivery, file wrestling, and some machining time and we were done. They designed an 8 foot tall snowflake sculpture.

To make something that big and keep the cost reasonable, we tried a new material (for us). Coroplast is a corrugated plastic sheet material. Ours was 96”x48” in white. Using the advice of the experts at the ShopBot Forum, we used a 1/16in (0.0625”) straight end mill. Since Coroplast was only 0.17” thick, we cut it in one pass.

Things We Learned

1. Coroplast can be held down with painter’s tape around the perimeter. Using a small diameter bit barely pushes the material at all. We had double-sided carpet tape as a back up.

2. There is the risk that the dust shoe could pull the parts off the table during a move and run the router through them. In the future, we’ll set the safe Z height to 3”.

3. Machining plastic generates static. Dust of all kinds stuck to the parts even when vacuuming it. There is a trick where you rub them with dryer sheets to cancel the static, but we didn’t try it.

4. Coroplast is inexpensive, $16/sheet, but needs some structure for large projects. The snowflake will be taped together and hung. It is too flimsy to bear its own weight.

5. Coroplast edges do feather. We ran a tiny bit, 14Krpm, 2ips, counterclockwise on this job. We didn’t experiment with our settings so we’ll need to look in to this more.

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