Sequential 4 Lock Surprise Puzzle Box

Update
If you like this design but want it to be more attractive box then check out this derivative:
https://cults3d.sitegames.net/en/3d-model/various/sequential-4-lock-surprise-gift-box-puzzle
This box was made bigger to centralise the side straps and the locking disk was simplified which resulted in more space inside.

Summary
This box needs only one key to open it and this is neatly hidden in the lower compartment so that it remains with the puzzle. When you find the key, you have to work through each lock maze in turn to reach a crank wheel which can then be turned to lift or drop a locking pin. If any of the four pins is dropped, then it prevents an internal locking ring from turning. When all locking pins have been lifted, the central drive knob can be turned 45 degrees anti-clockwise to release the lower compartment. This should easily separate from the top lock section and can be used to hold a surprise like a small bag of sweets, chocolate treat or money.

Dimensions
Overall box: 66Wx66Dx52H
Lower compartment: 62Wx52Dx28H (approximate)

Assembly instructions
Start by checking that the lock pins move freely in the holes provided in the top and bottom halves of the lock maze, filing or cutting the holes if necessary.

1. Push each lock pin through the bottom half of the lock maze so that they stick through and are ed by the side spring arms in the lower maze detents.

2. Fit each crank wheel into position with the pivot pin engaged into the lock pin at the lowest point.

3. Make sure that the top and bottom lock maze symbols line up then lower the top half of the maze onto the bottom half while adjusting the lock pins from underneath to make sure that they align with the top.

4. Clip four side straps onto the lock maze halves so that they are flush with the top and they provide stops for the locking ring at the bottom.

5. Insert the central knob with drive shaft into the maze top half and turn the assembly over.

6. Push the locking ring onto the drive shaft so that the collar goes into the bottom half of the lock maze and then fit the lock ring spring clip onto the drive shaft, ensuring that the flat side is outermost. Note that the spring clip tongue is intended to bend slightly in order to provide some 'springing' of the lock ring to the bottom of the lock maze. If the lock ring is hard to turn out of the detents in the maze base then try fitting the 2.5mm spring clip.

7. The complete lock assembly should now be in the lock position, so it's a good idea to test each lock to make sure that no printing debris is blocking the maze.

8. When the each key is inserted fully, it should push into the crank wheel and allow the associated lock pin to be raised or lowered by turning the key. Leave each lock pin in the raised position. Note that each crank wheel has a flat blade screwdriver slot at the bottom of the key hole so future assembly or lock/unlocking can be simply achieved with a screw driver (or print the cheat key, but don't tell your end s).

9. Turn the central knob 45 degrees anti-clockwise to put the lock ring into the open position and then the lock assembly should be pushed onto the lower box compartment.

10. Turn the central knob 45 degrees clock-wise so that the locking ring arms slide under the angled tabs on each wall of the lower box compartment.

11. Each lock must now be solved again to reset all four locking pins into the down (locked) position.

12. Finally, the key can be stored in the concealed compartment in the base of the lower box and the associated hatch can be slid into position. Note that the compartment door has a flat feature at one end and this should be pushed in first with the flat part facing down. This leaves a gap at one end which allows a finger nail to hook the door open.

Printing
This puzzle box has been printed in PLA.

You need to print 4 off Crank wheels, Lock pins and side straps.

The crank wheels are best printed with to properly form the screwdriver slot.

The side straps must be printed on edge to achieve bending strength and this might require 4-5 line Brim to help stick to the printing bed.

The key should be printed flat against the bed with to achieve adequate strength. Make sure the key fits easily into the keyhole, filing or cutting left over material if necessary.

There are two spring clips provided, 3mm and 2.5mm thick, These provide different levels of tension for the locking ring if it is difficult to turn out of the detents in the maze bottom. These should be printed with the flat side on the bed.

Cura Settings
Material: eSun PLA
Quality: 0.2mm or 0.28mm
Wall thickness: 0.4mm
Wall line count: 2 (minimum)
Infill: 15%
Pattern: ZigZag
Build plate adhesion: None (possibly Brim for side straps).