Inside The Box
Inside The Box
3D printing a trading card storage box
A friend at work recently got me into playing Magic: The Gathering again, with the end result being the purchase of several packs of cards that I didn’t know what to do with. While I could have taken a trip down to the local card shop or amazon for a commercially made card box, it seemed like a good opportunity to make a card storage box myself with my new 3D printer. PRUSA i3 MK3 and HATCHBOX Gray PLA filament.
The printer is the kit version of the Prusa i3 MK3 and was released back in fall of 2018. Aside from waiting about 4 months for the for my order to ship, I couldn’t be happier with it. While I’ve had a few failed prints due to poor part design or slicing parameters, the printer has worked well. This project, however, was not without it’s share of poor design/use of CAD.
When I first drew the box, I had foolishly left out a Space Claim for the cards from the CAD assembly, assuming that I had thoroughly reviewed all dimensions before exporting to .STL. 24 hours later I discovered that while the two halves of the card box fit together quite snugly, I had somehow drawn the card box to be 1 inch too short, not allowing for the cards themselves to be stored in the box when closed. So in an effort to salvage a bad situation, I decided to print new bottom and top pieces to assemble to the already printed parts, resulting in two similar, but different card boxes.
CAD Design
CAD of the re-designed card box
The nice part about having to print the new pieces was that it allowed for one of the two designs to be altered to provide better protection to the cards when closing the card box. The original design left about 1 inch of the cards exposed above the bottom half of the box. While trying to assemble the smaller/failed box, it occurred to me that the cards could become damaged by catching an edge of the lid of the box on a card while trying to close the box. I wanted to be able to easily remove cards without having to shove my fat fingers into the box, so for the redesigned lower half, I raised the ends of the box to be above the top of the cards. This allows the cards in the middle to be plucked from the side, while providing a safer path for the top half of the box during assembly.
At 9 inches long, by 2.56 inches wide (outside dimensions), both boxes are intended to store a small collection of trading cards that have been sleeved in KMC Hypermat penny sleeves, without much side-to-side movement. The interfacing surfaces were drawn with .0005 [in] clearance per surface, which will essentially be an interference fit if the prints are not reworked post printing.
Wall thickness for non-mating surfaces has been set to .125 [in], and .0625 [in] for mating surfaces. This provides relatively flexible walls in the middle of the box, while the short ends remain rigid. The combination of tightly dimensioned assembly surfaces and the rigidity of either end of the box makes it very difficult for the box to come apart without manually separating the two halves from one another.
Slicing & Print Setup
My general approach to slicing settings is to promote a smooth surface finish, while avoiding settings that will lead to a failed print. As such, I generally do not optimize for print speed or material used. Fortunately, given the surface area of the base of the print, it should have difficult time becoming un-stuck from the build plate, allowing for increased infill and perimeter print speeds. If using the Prusa edition of Slic3r, I recommend reducing the External Perimeter print speed to 18 [mm/s] to support a smoother external surface. I also set infill to 5% with a 3D Honeycomb pattern to provide a uniform pattern/strength to both the bottom and side surfaces requiring infill.
Additionally, to minimize/prevent the corners of the print from lifting away from the build plate, I recommend the use of a 5 [mm] brim. Sharp corners are much more efficient at transferring heat away from a print than flat surfaces. Applying a small brim will increase the surface area of the perimeter of the print, which will help counteract some of the contracting forces as the corners of the box cool.
Post printing
The interface between the top and bottom halves of the box requires some finishing/sanding post print, since once assembled, the box is very difficult to open due to minimal assembly clearance. Additionally, due to the layer lines from the two halves being in the same orientation, a card box that has not been sanded post printing will be nearly impossible to open.
I suggest sanding with progressively finer sandpapers, starting with 100 grit, working down to about 220 grit sand paper. This will knock down the rough unfinished print surface, while slightly increasing assembly clearance. For a smoother finish, the print may be wet-sanded with the 220 grit (or finer) sandpaper. It is also recommended that a dust mask is worn during this process to prevent inhaling plastic dust created through sanding.
My plan is to make several smaller boxes for a deck of double sleeved cards, but we’ll just have to wait and see what happens. If you’re interested in printing your own copy, links to .STL, .STP and Parasolid files are provided below.
Card-Box Files
- Link to Parasolid (.x_t), Stereolithography (.stl) and .stp files on Grabcad.
- PLA is recommended for printing material.
- Print time is estimated to be 15 hours for the lower half, and 5 hours for the top half.