Machining poly lumber

[olober@ptd.net]

Does anyone have experiance in machining poly lumber on a shopbot? This is the lumber replacement made out of recycled milk jugs, etc. What I'd ideally achieve would be outdoor furniture parts cut from 3/4" and 1" thick material, with a 3/16"rad edge both top and bottom. Also having the ability to drill holes in the same setup would be a great benefit. Any practical input on the possibility of doing this and the reccomended methods will be appreciated. I am new to shopbot, what kind of speeds could be expected while producing a cut quality sufficient for lawn furniture? Thank You, LTO

[Brady Watson]

Milk Jugs are made from HDPE, which machines like butter. It puts off a nice soap-like chip. Depending on what router you are running, you can move through the material pretty aggresively. You will get some tooling lines on the part no matter how good your CNC is, a lot like acrylic when you route it. Not a big deal. Unless you have a laser, no one will cut it any better.

Personally, I would just hand-route those radiused pieces and have the bot do the drilling and profile cuts.

-Brady

[ron brown]

Good Advice Brady,

Ron

[Mayo]

I have machined a couple of different brands of recycled wood/plastic composit deck materials and they do cut very easily.

Here's an address sign sample I did a while ago:

7047
And some cut out letters:

7048

The things I've run into which you should watch out for are:

It's difficult to get paint to stick to it.
Transparent stains can work. Dry time longer than expected.
The molded in color fades.
The product is brittle - some brands more than others.
It is not to be considered "structural" strength lumber.