Modular Case

Update 2025-05-14:

• removed unnecessary through-hole from Top Left / Right

Modular Case for AnalogSky Magic

This case was originally created for storing the "Magic" stargazing binoculars by AnalogSky. You can use it to store other things, of course. The only parameters tailored toward the binoculars are some measurements in a specific configuration.

For n = number of center pieces, the content size is:

n * 110mm x 180mm x (140 + 50)mm

The lid interior is 50mm high. 

This makes the pictured version content size 220 x 180 x 190mm 

Design goals

• modular
  • the case should be configurable depending on the users needs
  • critical parts should be replacable in case of damage
• printable without supports
• minimum print bed size: 250 x 210 x 220 mm
• assembled using screws, no glue required 
• should easily hold AnalogSky "Magic" with room to spare for padding material and some accessories.
• side recesses should function as handles

3d-printed Parts

ALL PARTS ARE ORIENTED. 
PLEASE MAKE SURE YOU UNDERSTAND THEIR FUNCTION AND ORIENTATION BEFORE ASSEMBLY.
ADDING INSERTS IN THE WRONG LOCATIONS MIGHT MAKE YOUR PART UNUSABLE.

• Lid
  • Top Left
  • Top Center  
  • Top Right 
• Bottom
  • Bottom Left
  • Bottom Center
  • Bottom Right
• Hinge
  • Hinge Upper
  • Hinge Lower
• Latch
  • Latch Upper
  • Latch Lower
  • Latch Latch

The size of the content is defined by the number of center pieces.

The configuration I chose for storing my AnalogSky "Magic" binoculars:

• side pieces (top left / right, bottom left / right) 
• 2 x top center
• 2 x bottom center

Print hinges and latches as required.

For n = number of center pieces:

Number of hinges = number of latches = n + 1

Required Materials

n = number of center pieces

A case with two center pieces amounts to about 1,5kg of PETG.

Additionally, you will need:

• M3 heat set inserts
  • I used CNC Kitchen M3 x 5.7 , but other brands will probably do as well
  • shorter inserts than 5.7 will probably work as well. Just make sure they can take the tightening force.
  • top: (n+1) * 7 inserts
  • bottom: (n+1) * 8 inserts
  • hinges: (n+1) * 4 inserts
  • latches: (n+1) * 4 inserts 
• M3 x 30 cylinder head screws and nuts for axial connections in hinges / latches
  • 2*(n + 1) M3 hex nuts
  • 2*(n + 1) M3 x 30 cylinder head screws
• M3 x 8 / 10 / 12 cylinder head screws 
  • the shortest length that will hold the parts should be 8mm. Longer screws work, but >= 14mm might protrude too much, and either look ugly or be in the way.
  • top: (n + 1) * 7 pieces
  • bottom: (n + 1) * 8 pieces
  • hinges: (n + 1) * 4 pieces
  • latches: (n + 1) * 4 pieces
• 20x10mm rectangular Magnets, < 2mm thickness. 
  • These will hold the latches closed shut
  • total: 2 * (n + 1) magnets

You can use non-cylinder head screws, but for joining multiple center pieces, cylinder heads might have the best accessibility since the access angle can get awkward.

Printing

Please take a look at the “Modular Case Print Orientations” project file to see how I printed it on my XL. 

If in doubt about the material, please use PETG. It can take slightly higher temperatures than PLA, and has better layer adhesion. This might just make the difference if the case is dropped or confronted with high temperatures in a car. 

I've printed the case in PETG on a Prusa XL, 0.4 nozzle, .2 layer height, "Speed" profile.
Standard settings were 2 perimeters, 15% infill, no supports (apart from one tiny part, see below)

You can easily reinforce it by increasing the number of perimeters and / or infill percentage.

• Print all side pieces (top left / right, bottom left / right) with the large, flat area on the print bed.
• Print all center pieces on their sides.
• Orient all hinge pieces so the side that touches the case also touches the print bed, i.e. flat on sides without screw head recess. 
• Orient all latch pieces so the largest flat sides without screw recesses are face down on the bed.
  • Slicer will warn about print stability issues for the "Latch Latch" part. Activate “supports from build plate” for this part only. Additional material usage will be minimal. 
  • Slicer will warn about print stability issues for “Latch Top”. Ignore this. It will print fine.

Assembly

ALL PARTS ARE ORIENTED. 
PLEASE MAKE SURE YOU UNDERSTAND THEIR FUNCTION AND ORIENTATION BEFORE ASSEMBLY.
ADDING INSERTS IN THE WRONG LOCATIONS MIGHT MAKE YOUR PART UNUSABLE.

This is how I assembled my case.
You can deviate from this plan as you see fit, but it's a good starting point.

• Hinge subassemblies
  • put a hex nut on a 30mm screw
  • using the 30mm screw as a lever, push the nut into the hex-shaped opening of the lower hinge part
  • unscrew the 30mm from the nut, leaving the nut in the lower hinge part
  • fasten both parts together with the 30mm screw
  • do not over tighten 
  • optional: use thread lock to prevent the screw from wiggeling out of the nut

• Latch subassemblies
  • insert the hex nut in the "latch latch" part using the same method described for the hinge part
  • attach "latch latch" to "latch top" using the 30mm screw
  • do not over tighten 
  • optional: use thread lock to prevent the screw from wiggling out of the nut
  • glue the magnets into both "latch latch" and "latch bottom", observing correct polarity
    • the magnets should attract each other and keep the latch closed

• Heat Set Inserts
  • insert heat set inserts into all front and back holes that will receive screws for hinges and latches
    • these can be found on all body parts (side and center pieces)
  • insert heat set inserts into all side holes of ONE upper and ONE lower piece
    • observing the case from the front, this part will be the left-most center piece
  • if you have only once center piece, add heat set inserts in all side holes
  •  if you have more than one center piece, insert heat set inserts into the RIGHT side of the additional center part(s), leaving the LEFT side WITHOUT INSERTS
    • OBSERVE ORIENTATION! Center pieces have a FRONT and a BACK.
      • The back side will have the hinge mounting holes close to the lip
      • The front side will have the latch mounting holes closer to the split line

• Lid assembly
  • using the M3 x 8/10/12 screws, fasten the top left piece to the center piece that has inserts on both sides
    • please maintain correct part orientation
  • observing the lid from the front (latch side), attach any additional center pieces to the right of the current assembly
  • finally attach the top right piece

• Bottom assembly
  • same process as lid

• Final Case Assembly
  • put the lid on the bottom part, then turn the whole case on its face, making sure the lid stays in place. 
    • The two parts will want to slide around. Keep them close or use some painters tape to temporarily attach them for hinge / latch mounting.
  • attach the lid to the bottom part using the prepared hinge assemblies
  • turn the case on its back and attach the latches to the front side
    • make sure you push both latch upper and lower part as far UP as possible when fastening the latch parts to the body
    • the upper latch part should have some friction against the lip when rotating. This will prevent it from flopping around too much. 
    • the lower part should be as far UP as possible, so the lip of the latch can easily engage with the slot and keep the case shut. 

Rotating the lid should be effortless. The latches should ideally have some friction so they stay open, once pulled out of the "locked" position.

Padding

Now that you have a finished case, I highly suggest you add some padding before throwing fragile valuables in it.

As you can see from the pictures, I added felt-wrapped EVA-foam pieces that were shoddily cut and partly messed up with hot glue because I was getting impatient and wanted to see it finished.

There is at least one centimetre space in all directions around the binoculars for my configuration. Unfortunately, I forgot that felt has significant volume, so I had to incorporate both 10mm and 5mm foam to accommodate for the felt volume.

Still, the result is pretty satisfying, and both the binoculars and its accessories are held snugly in place. Nothing rattles or moves.

Notes

• The pictures might show parts that are missing fillets (bottom right side) or have excessive through-holes (all side parts for the hinge mounts). These are older parts and have been fixed in the model files.
• I'm not super happy with the latch design, but I'm also neither a fan of latches integrated into the body, nor the ones that clip around a long screw in the bottom part. At least my design is flush with the surrounding lip feature, and can be replaced if needed. Feel free to come up with a better design that does not require a magnet.
• Notably, the case does not have belt mounts, grips or handles, apart from the recesses in the sides. I couldn't come up with a solution that wouldn't clash with the modularity of the case, or lead to supports and ugly cuts, so I postponed it. I hope to find a solution that can reuse the join screws as mounts.  
• the material cost is about 35eur for a case with two center pieces, including screws, inserts and magnets, excluding everything else (e.g. printer wear, energy cost, print setup, labor, design iterations). It is not cost efficient, but it is a fun project.
• An accidental stress test showed that the case can take quite a beating before it breaks.
  My case configuration also survived a 100kg adult standing on it for a brief moment.
• if in doubt, please get a professional hard-shell case for photography equipment. This case is mainly a fun experiment and learning opportunity.

I'd love to see pictures of your builds, color combinations, finishes and padding / interior variations. 

Have fun!