Hood for BCN3D Sigma, after Toobyy (.225" plexi) by Processaurus

Last crawled date: 2 years, 11 months ago

This is a thicker, .225" thick plexiglass version of Toobyy's well conceived enclosure for the BCN3D Sigma 3D printer (theirs was R17, mine is R19, but the version doesn't seem to affect the fit).
Why thicker? Because the material was free! Covid customer service shield from a local company.
Instructions from the original apply here. This uses most of the same parts. This version differs in a couple minor ways:
Plexiglass material is .225" (5.715mm).
Latches are thicker to accommodate the thicker plexiglass.
Latches engage further into mating part.
Door flap accommodates thicker material.
Door flap may be printed in two pieces, or optionally in one piece ("door lower combined" STL).
SAE Hardware used from the american hardware store (I couldn't find metric nuts that would fit right here):
For Brackets:
20x 4-40 pan head machine screws, .75" long
20x 4-40 nuts
20x size #4 fender washers
For hinges
8x 6-32 bolts, .75" long
8x 6-32 nuts
8x #6 washers
8x #6 lock washers
For Hinge pin
2x 4-40 screw, pan head, .75" long
2x 4-40 nut
2x #4 washer
2x #4 lock washer
note, the screw is a little small in diameter, I used some shrink tubing to make the diameter fit the hinges a little better. Room for improvement there.
Latches:
2x #4 sheet metal screw, pan head, .75" long.
Note, drill out latches to size, they were quite small diameter.
Construction notes:
I printed all brackets and latches in one batch, with disolvable PVA supports. Did PLA as the main material here, because it is easy, but extra points for printing in PETG.
I got the PDF of the pattern for the plexiglass printed at a local print shop on the big, 3' wide black and white printer, it was $4. The important bit is that it is printed TO SCALE. I taped the pattern to the sheet of plexi, and rough cut the six pieces apart with a circular saw on saw horses. Then I used the bandsaw to cut them to size with a fine tooth blade. It was awful, the plexiglass melts easily and makes this wad of melted plastic under the cut. It also gets into the saw. Apparently "extruded" plexiglass melts at a lower temperature than "cast" plexiglass. Mine was a pain to machine, must have been the extruded type.
On mine I diverged from Toobyy's advice as far as going gung ho and drilling all of the holes before putting it together. This mostly worked out, but it would be good to drill a little bit towards the corner of the plexiglass- the idea is if the hole is off a little bit in the wrong direction, it won't make the plexiglass too tight against the other plexi pieces. The 4-40 nuts had some slop in the brackets, which was good, as I could put together the enclosure loose, and the brackets could shift around a little, and then tighten them down at the end.
Door Flap. I printed the "combined" (single piece) version of the door flap, and printed it with PVA supports, doing it on end, sticking up, with the part that clamps the plexiglass facing down on the bed. Printed with a brim, which helps it being on end. It fits on the Sigma's build plate if you print it a bit diagonal. I printed the flap once I had most of the enclosure together, as long parts tend to have more of a danger of warping.