HuxBox - a box for the space's Rep Rap Huxley 3D printer
angusgr — Sun, 05/08/2012 - 9:53pm
I designed and made an acrylic box to hold our Rep Rap Pro Huxley 3d printer.
Why Box In a Printer?
The main reason was to ensure stable and warm temps, for tidy prints. Being a large warehouse-like space, MHV is prone to cold draughts during winter. In fact, some winter days the heated printer bed was having trouble getting up to temperature at all due to heat lost in the surrounding air!
Draughts also seem to effect the clean deposition of layers. I didn't do a complete test, but here are two prints I did on consecutive Saturdays:
Neither print is what I'd call a "success." However, the left hand print was done in open air, and the edge on it is much more ragged than the right hand print, which was done in the cardboard box prototype.
Also, dust is an enemy of printer extruders. MHV is a dusty space.
MAJOR EDIT OCTOBER 2012
So, the box may not be a net gain for the printer. In the dead of winter it certainly seemed to help. However, now that temperatures are much warmer it seems like boxing the printer in has some negative effects - layers stay warm and soft longer, so the printer is more prone to "smoosh" them around when the next layer is laid down. Leading to uneven prints. You can mitigate this by using the Cool plugin in Skeinforge (or Slow Down in Slic3r) to make sure each layer takes a minimum time. However for now - in temperate weather - we've just removed the box altogether. In fact we've been experimenting with active cooling, sending a smooth and even flow of air over the entire print gives noticably good results as well. More experimentation with different object sizes & styles would give us more information, especially once winter comes back and the workshop cools down again!
I wanted a design that matched the printer's form closely, not a square box.
I started out with some ideas about 3D printing angled brackets and drilling holes in the acrylic to hold them together. However, after lots of consultation with other MHV members I was convinced that the way to work with acrylic was to "weld" it together with chemical acrylic welder.
So I came up with this design. Lots of high school trigonometry to get the angles right!
The sections, from left to right, are: Rear panel, front door, outlined front panel (door closes against this, provides rigidity for box), left side panel, right side panel.
There is a slot on the left side panel, leading from the base up to the filament feedthrough. This allows you to lift the whole box off the printer, without disturbing the filament. Lifting the box off is very useful for changing flament or performing maintenance, but in day to day operation you can just open the front door and reach in.
The other cutout recess on the left side is for the power and USB cables to get out.
What's a cheap and plentiful prototyping material? Cardboard! This prototype was to test the fundamental idea, and to ensure the design cleared the printer on all sides:
Limited visibility meant leaving a hole in the cardboard front rather than a hinged door, though. Draughty!
Still, the printer warmed up faster and print quality seemed better. Time to make a more fireproof, less opaque, version!
The design was CNC cut in 6mm clear acrylic by a local plastics shop, Plastic Creations. 6mm acrylic is probably overkill, but I shared a sheet of acrylic with someone who was building an aquarium and needed the extra thickness.
I collected the sheets, covered in protective paper, from Plastic Creations along with a needle-tipped dispenser full of Weld-On thin acrylic welding solvent.
Important: Weld-On is easy to use and makes really powerful joins, but it's a very nasty chemical. If you're using it, read the safety information and take every precaution!
Putting the box together was a case of making a simple jig to put two pieces together, then using the needle dispenser to run Weld-On along the inside edge of the joint. Capillary action pulls the weldon into the joint itself.
After 10 minutes or so the welded joint was solid enough to move on to the next side:
Thanks to Werner for his expertise in simple jig construction, and Kim for her general assembly assistance.
I found CNC cut acrylic to be exceptionally easy to work with as a beginner! Safety concerns aside, the Weld-On solvent is near-magical!
Attaching the door was the last part. I did this a day later, so the other joints had time to cure.
I'd picked up some clear acrylic piano hinges from Plastic Creations. First I chemically welded them to the side of the box, then taped & clamped the door in place and welded them to the door:
I wouldn't do it this way again:
Piano hinges are longer and thinner than necessary, and because they're long even a small amount of flex due to the door weight causes them to sag and foul the hinge barrel at the bottom. I should have found some alternative hinges. The only thing you need to make sure of is that the hinge flanges are wide enough to reach around the door on the side, past the 6mm edge of the door to the box behind it (an "over the edge" hinge setup.)
I should have welded them to the door first with the door sitting flat, then attached the door to the frame.
As a result of my poor choices, the door hinges were very creaky and stiff until Jess noticed some parts of the flange were fouling as they turned. A delicate application of the dremel cleaned them up, but it would have been better to have avoided the whole fiasco!
If I did this over again, I would consider CNC drilling mounting holes and then screwing metal hinges into the door & side panel.
Box looks good, printer prints well and has been serving MHV nicely through a somewhat chilly & draughty winter!
My initial trepidation with acrylic is long gone, I can't wait for another excuse to build with it!