hdpe...

[bobthefirst1]

i saw the material hdpe on the main site of society of robots and decided to use it. how do i work with it???  cuz i want it to look as clean and precise as the many things we buy from the store.

[rbtying]

HDPE is a plastic. You can machine it with whatever tools you've got, but making it look nice and professional requires A) personal skill, B) a friend with personal skill, or C) CNC.

[Gertlex]

Not sure what rbtying means by personal skill, but my experience is that if you've got practice with a given tool, you'll be fine for shaping the plastics nicely.  I'm personally a fan of dremels... However most plastics are susceptible to melting with certain dremel operations (especially making small holes with grinding bits).  I've had good success with using delrin (teflon-related) which has a higher melting point, but also costs a bit more.

There's a few examples of stuff with delrin (and carbon fiber) that I've dremeled on my Flickr... A few of these pics are:
http://www.flickr.com/photos/gertlex/6115088582/#in/photostream
http://www.flickr.com/photos/gertlex/6115088540/#in/photostream/
http://www.flickr.com/photos/gertlex/6114544087/#in/photostream/
http://www.flickr.com/photos/gertlex/6029339033/#in/photostream
http://www.flickr.com/photos/gertlex/6029338069/#in/photostream
http://www.flickr.com/photos/gertlex/6029337895/#in/photostream

Note especially the last pic.  I tape (packing tape is great) my printed design to the material, make the holes, then cut the edges.  I use the same technique with both carbon fiber and delrin/plastic.

As for the dremel bits/accessories that you want, basically:
Diamond covered small grinding bits for holes and small details: http://www.harborfreight.com/20-piece-1-8-eighth-inch-shank-diamond-point-set-40547.html
Diamond covered cut-off discs: http://www.amazon.com/Anytime-INDUSTRIAL-DIAMOND-CUT-OFF-LAPIDARY/dp/B000FJN8LO/ref=sr_1_2?ie=UTF8&qid=1311256586&sr=8-2
Corded dremel: http://www.amazon.com/Dremel-300-1-24-Variable-Speed-Rotary/dp/B002BAHFBE/ref=sr_1_2?s=hi&ie=UTF8&qid=1315364595&sr=1-2
Right angle dremel attachment for much easier control: http://www.amazon.com/Dremel-575-Right-Attachment-Rotary/dp/B00005AXI0/ref=sr_1_1?s=hi&ie=UTF8&qid=1315364622&sr=1-1
These come with dremels, but are worth mentioning because they're so good at eating plastic: http://www.amazon.com/Dremel-438-Grit-Sanding-Bands/dp/B00004UDHG/ref=pd_cp_hi_3

Hope that helps.  Practice makes pretty.

[Conscripted]

Note especially the last pic.  I tape (packing tape is great) my printed design to the material, make the holes, then cut the edges.  I use the same technique with both carbon fiber and delrin/plastic.

What do you use to make your templates? I've had trouble in the past trying to get true 1:1 size prints.

Conscripted

[Gertlex]

I use Solidworks to design my bots, but any CAD program would be fine for such 2D parts.  I then save the drawings as PDF, and print from there... Usually there's an option in the printing dialog to the effect of "do no scale".  And of course I always take a measurement or two to make sure...

One other note is that this method works a bit better for carbon fiber where the debris (which you absolutely don't want to breathe) is small.  With plastic, the debris can bunch up under the paper, but it really wasn't a problem...